LDH400P
400W DC Electronic Loads
INSTRUCTION MANUAL
Contents
1. Introduction ................................................................................................... 4
2. Specification ................................................................................................. 5
3. Safety ............................................................................................................ 9
4. Installation ...................................................................................................10
4.1 Mains Operating Voltage .................................................................................................. 10
4.2 Mains Lead ....................................................................................................................... 10
4.3 Mounting ........................................................................................................................... 10
4.4 Ventilation ......................................................................................................................... 10
4.5 Fuses ............................................................................................................................... 11
5. Connections ..................................................................................................12
5.1 Front Panel Connections .................................................................................................. 12
5.2 Rear Panel Connections ................................................................................................... 12
5.3 Prospective Fault Current Protection ................................................................................ 13
6. Initial Operation ...........................................................................................14
6.1 Organisation of this manual .............................................................................................. 14
6.2 Load modes ...................................................................................................................... 14
6.3 Constant and Transient Operation .................................................................................... 14
6.4 Dropout voltage ................................................................................................................ 14
6.5 Slow Start ......................................................................................................................... 14
6.6 Voltage and Current Limit Conditions ............................................................................... 15
6.7 Power Limit ....................................................................................................................... 15
6.8 Input Condition Lamps ...................................................................................................... 15
6.9 Fault Conditions ................................................................................................................ 15
6.10 Connecting the Load to the Source .................................................................................. 16
6.11 Switching On .................................................................................................................... 16
7. Front Panel Operation ..................................................................................17
7.1 Keys and ∆ Adjust ............................................................................................................. 17
7.2 The Display and the Home Screen ................................................................................... 18
7.3 General Numeric Entry of Parameters .............................................................................. 20
7.4 Variation of Parameter Values using ∆ Adjust ................................................................... 20
7.5 Configuring the Load ........................................................................................................ 20
7.6 Selection of Load Mode .................................................................................................... 21
7.7 Level A and Level B Setting .............................................................................................. 21
7.8 Dropout Voltage ................................................................................................................ 21
7.9 Slow Start ......................................................................................................................... 22
7.10 Introduction to Transient Operation .................................................................................. 22
7.11 Transient Menu ................................................................................................................. 22
7.12 Transient Frequency ......................................................................................................... 23
7.13 Transient Duty Cycle ........................................................................................................ 23
7.14 Slew Rate ......................................................................................................................... 23
7.15 Voltage and Current Limits ............................................................................................... 24
7.16 Store and Recall Facilities ................................................................................................ 25
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7.17 Utilities Menu .................................................................................................................... 26
8. Analogue Remote Control ........................................................................... 27
8.1 Remote Voltage Control ................................................................................................... 27
8.2 Remote Level Select ........................................................................................................ 27
9. Application Notes ........................................................................................ 28
9.1 Sources ............................................................................................................................ 28
9.2 Stability of Source and Load Combinations ...................................................................... 29
9.3 Dynamic Behaviour in Transient Operation ...................................................................... 29
9.4 Start-up transients ............................................................................................................ 30
9.5 Characteristics of each Operat ing Mode .......................................................................... 30
9.6 Multiple Unit Operation ..................................................................................................... 32
10. Remote Interface Configuration .................................................................. 33
10.1 GPIB Interface .................................................................................................................. 33
10.2 RS232 Interface ............................................................................................................... 33
10.3 USB Interface and Device Driver Installation .................................................................... 34
10.4 LAN Interface ................................................................................................................... 34
10.5 Interface Locking .............................................................................................................. 36
11. Status Reporting .......................................................................................... 37
11.1 Input State and Input Trip Registers (ISR & ISE and ITR & ITE). ..................................... 37
11.2 Standard Event Status Registers (ESR and ESE) ............................................................ 38
11.3 Execution Error Register (EER) ........................................................................................ 39
11.4 Status Byte Register (STB) and GPIB Service Request Enable Register (SRE) .............. 39
11.5 GPIB Parallel Poll (PRE) .................................................................................................. 40
11.6 Query Error Register - GPI B I EEE Std. 488.2 Error Handling ........................................... 40
11.7 Power on Settings ............................................................................................................ 40
11.8 LDH400P Status Model .................................................................................................... 41
11.9 Register Summary ............................................................................................................ 41
12. Remote Commands ...................................................................................... 42
12.1 Remote and Local Operation ............................................................................................ 42
12.2 Remote Command Handling ............................................................................................ 42
12.3 Remote Command Formats ............................................................................................. 42
12.4 Command Timing ............................................................................................................. 43
12.5 Response Formats ........................................................................................................... 43
12.6 Command List .................................................................................................................. 43
13. Maintenance ................................................................................................ 47
13.1 Cleaning ........................................................................................................................... 47
13.2 Fuses ............................................................................................................................... 47
13.3 Calibration ........................................................................................................................ 47
13.4 Firmware Update .............................................................................................................. 47
13.5 Troubleshooting ................................................................................................................ 47
2
Full operating and programming instructions for this instrument can be found in the appropriate
product folder of the accompanying CD-ROM.
This information can also be downloaded from t he suppor t page of the Aim-TTi website,
http://www.aimtti.com/support
.
This manual is 48511-1830 Issue 1
Français
14. Sécurité ........................................................................................................48
Les instructions complètes de fonct ionnement et de programmation de cet instrument se
trouvent dans le dossier approprié du CD-ROM d’accompagnement.
Ces informations sont également t éléchar geables depuis la page de support du site Internet de
Aim-TTi, http://www.aimtti.com/support
.
Numéro du manuel 48511-1830, 1 édition.
Deutsch
15. Sicherheit .....................................................................................................49
Vollständige Betriebs- und Programmieranweisungen für dieses G er ät finden Sie im
entsprechenden Produktordner der beigefügten CD-ROM.
Diese Informationen können auch von der Support-Seite auf der Aim-TTi-Website
heruntergeladen werden, http://www.aimtti.com/support
Italiano
16. Sicurezza ......................................................................................................50
Le istruzioni complete per il funzionamento e la programm azione dello strum ent o sono
incluse nella relativa cartella del prodotto del CD-ROM fornito.
È anche possibile scaricare queste informazioni dalla pagina dell’assistenza del sito Web
Aim-TTi, http://www.aimtti.com/support
Questomanuale è la versione 48511-1830 revisione 1.
Español
17. Seguridad .....................................................................................................51
Las instrucciones completas de funcionamiento y prog r am ación de este instrumento
pueden encontrarse en la carpeta del producto correspondiente en el CD-ROM adjunto.
También es posible descargar esta información desde la página de asistencia de la web
de Aim-TTi, http://www.aimtti.com/support
.
Este manual es el 48511-1830 versión 1.
3
1. Introduction
This DC electronic load is for use in investig at ing the behaviour of many different types of high
voltage DC power sources such as PFCs, batteries, solar cells, fuel cells or wind generators, as
well as electronic power supply units.
The load inputs are rated to CAT II (300V). This allows for PFCs and mains connected power
supplies to be directly tested using the electronic load without t he need for an isolation
transformer.
The unit provides four different operating modes: constant current, constant power, constant
resistance and constant conductance.
It operates over the voltage range 10 to 500 Volts and the current range 0 to 16 Amps with a
continuous power dissipation capability of up to 400 Watts.
A low voltage dropout facility is provided to protect sources such as bat t eries from damaging
levels of discharge by reducing the load current when the source voltage falls below the dropout
threshold setting.
An internal transient generator can r epeat edly switch the load between two different oper at ing
levels, level A and level B. The frequency and duty cycle of the transients can be set over a wide
range. The transients can also be initiated by an external logic signal. The transitions between
the levels have a true linear slewing characteristic in all modes, with the slew-rate being
adjustable over a wide range.
The unit meters and displays measured values of Volts & Amps and equivalent Watts & Ohms. A
monitor output providing a voltage proportional to the cur r ent flowing allows the behaviour of a
source to be viewed on an oscilloscope or external meter.
All adjustable system parameters can be set via numeric keyboard entry or via the dig ital rem ot e
interfaces for quick and convenient instrument control.
Up to 30 non-volatile storage locations can be used to store and recall instrument parameter set
ups, ideal for test and calibration procedures.
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An external control voltage can also be used to set the level of the load. Any desired waveform
can be applied, with the internal slew rate control circuit remaining active to provide additional
control.
The unit is fully protected against excessive current , power dissipation or internal t em per ature,
and minimises audible noise by automatically controlling the fan speed according t o t he power
dissipation.
Current:
16 Amps max. through the front and rear panel terminals.
Voltage:
500 Volts max. while conducting current.
Power:
400 Watts max. up to 28ºC, derating t o 360 watts at 40º C.
Minimum Operating Voltage:
10V.
resistance:
1180kΩ to load negative).
Reverse Polarity:
Body diode will conduct; 16 Amps max.
Isolation Voltage:
CAT II (300V) either load input to chassis ground.
Rear Panel Input:
Safety terminals accepting 4mm plugs at 16 Amps max.
Front Panel Input:
Safety terminals accepting 4mm plugs at 16 Amps max.
Current Range:
0 to 16 A (1 mA resolution).
Setting Accuracy:
± 0·2% ± 30 mA.
Regulation:
< 30 mA for 90% load power change (V > 25 Volts).
Temperature Coefficient:
< (±0·02% ± 5 mA) per ºC.
Slew Rate Range:
5 Amp per s to 500 Amp per ms.
Minimum transition time:
50 µs.
Power Range:
0 to 400 Watts (100 mW resolution).
Setting Accuracy:
± 0·5% ± 2 W ± 30 mA (V > 25 Volts).
Regulation:
< 2% over 25 V to 550 V source voltage change.
Temperature Coefficient:
< (± 0·1% ± 5 mA) per ºC.
Slew Rate Range:
60 W per s t o 6000 W per ms.
Minimum transition time:
150 µs.
Resistance Range:
50 Ω to 10 kΩ (1 Ω resolution).
Setting Accuracy:
±0·5% ± 2 digits ± 30 mA (V > 25 Volts).
Regulation:
< 2% for 90% load power change (V > 25 Volts).
Temperature Coefficient:
< (±0·04% ± 5 mA) per ºC.
Slew Rate Range:
1 Ω per ms to 100 Ω per µs.
Minimum transition time:
150 µs.
2. Specification
Accuracy specifications apply for 18°C – 28ºC, using the rear panel terminals, after 30 minutes
operation at the set conditions. Setting ac cur ac ies apply with slew rate at the ‘Default ’ setting.
INPUT
Maximum Input Ratings
Minimum effective
Off State Leakage:
Input Terminals
OPERATING MODES
Constant Current Mode (CC)
(1)
(2)
1Ω .
<5 mA (including voltage sense circuit input resistance - typically
Constant Power Mode (CP)
(1)
(2)
Constant Resistance Mode (CR)
(1)
(2)
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Conductance Range:
0·001 to 1 A/V (1 mA/V resolution)
Setting Accuracy:
± 0·5% ± 2 digits ± 30 mA (V > 25 Volts).
Regulation:
< 2% for 90% load power change (V > 25 Volts).
Temperature Coefficient:
< (±0·04% ± 5 mA) per ºC.
Slew Rate Range:
0·1 A/V per s to 10 A/V per ms.
Minimum transition time:
150 µs.
Pulse Repetition Rate:
Adjustable from 0·01Hz (100 seconds) to 10k Hz.
Pulse Duty Cycle:
1% to 99% (percentage of period at Level A).
Setting Accuracy:
±1 %
Setting Accuracy:
± 10% (on linear part of slope, excluding high frequency aberrations).
Variation in Level Settings:
± 5 digits of specified setting resolution for present mode and range.
internal transient generator.
Isolation:
CATII (300V) to load negative.
Setting Accuracy:
± 2% ± 200mV.
Volts & Amps:
Measured values of current through and voltage across t he load.
Watt & Ohms:
Power and equivalent load resistance, calculated from Volts and Amps.
Volt age Accuracy:
± 0·1% ± 0.02%FS.
Current Accuracy:
± 0·2% ± 0.04%FS.
Constant Conductance Mode (CG)
(1)
(2)
TRANSIENT CONTROL
Transient Generator
Slew Rate Control
The slew rate control applies to all changes of level whether caused by manual selection, remote
control or the transient gener at or.
The level change is a linear slew between the two level settings. The range available in each
mode is shown above.
Oscillator Sync Output
Connection: Terminal block on rear panel. Lo terminal output grounded to chassis
DROPOUT VOLTAGE
The load will cease to conduct if the applied voltage falls below the Dropout Voltage setting;
active in all modes. The Dropout Voltage setting is also the t hr es hold for the Slow Start facility
and acts as an offset voltage in Constant Resistance mode.
Slow Start
If Slow Start is enabled, the load will not conduct any current until the source voltage reaches the
Dropout Voltage setting; it will then ramp the controlled variable up (in CC, CP and CG modes) or
down (in CR mode) to the Level setting at a rate determined by the Slew Rate setting .
METER SPECIFICATIONS
Display Ty pe: 256 x112 pixel graphic LCD with white LED backlight.
internally. TTL/CMOS (5V) output. High during Level B phase of
Measured Values
6
Output Terminals:
BNC (chassis ground) on front panel or ter minal block on rear panel.
Output Impedance:
600Ω nominal, for >1MΩ load (e.g. oscilloscope).
Scaling:
250mV per Amp (4 Volts full scale).
Accuracy:
± 0·5% ± 5mV.
Isolation:
CATII (300V) to load negative.
Bandwidth limit (-3dB):
40kHz.
1.4 LXI Core 2011 compliant.
USB:
Standard USB 2.0 connection. Operates as virtual COM port.
Capabilities: SH1, AH1, T6, L4, SR1, RL2, PP1, DC1, DT0, C0, E2.
RS232:
Standard 9-pin D connection. Baud rate: 9600.
internally.
Input Impedance:
10kΩ. Input prot ect ed against excess input voltages up to 50V.
Isolation:
CATII (300V) to load negative.
Operating Mode:
The applied voltage sets the operating level within the range.
Scaling:
4 Volts full scale (250mV per Amp).
Accuracy:
± 2% ± accuracy of range.
Common mode rejection:
Typically better than –76dB.
Operating Mode:
The applied signal selects between Level A and Level B settings.
Threshold:
+ 1·5V nominal. A logic high selects Level B.
Input to the LED of an opto-isolator t hr ough 1kΩ resistor.
Threshold:
Apply >+3V to disable the load input. Max. Voltage 12V.
CURRENT MONITOR OUTPUT
REMOTE CONTROL
Digital Remote Interfaces
The unit provides LAN, USB, GPIB and RS232 interfaces for full remote control.
LAN:
GPIB: Conforming to IEEE488.1 and IEEE488.2.
Ethernet 100/10base-T connection with auto cross-over detection.
External Control Input Characteristics
Connection: Terminal block on rear panel. Lo terminal input grounded to chassis
External Analogue Voltage Control
External Logic Level (TTL) Control
Remote Disable Input
Connection: Terminal block on rear panel.
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will trip into the fault state at 460 Watts.
Protection Current:
The input is disabled if the measured current exceeds a user set limit.
a protection against high power sources
reverse polarity.
Protection Voltage:
The input is disabled if the measured voltage exceeds a user set limit.
suppressors will start to conduct at typically 800V ± 20%.
safe levels.
currents that exceed 20A.
AC Input:
110V–120V or 220V–240V AC ±10%, 50/60Hz. Installation Categor y II.
Power Consumption:
40VA max. Mains lead rating: 6A minimum.
Operating Range:
+ 5ºC to + 40ºC, 20% to 80% RH.
Storage Range:
– 40ºC to + 70ºC.
Environmental:
Indoor use at altitudes up to 2000m, Pollution Degr ee 2.
Cooling:
Variable speed fan. Air exit at rear.
Safety:
Complies with EN61010-1.
EMC:
Complies with EN61326.
Size:
130mm H (3U) x 212mm W (½ rack) x 435mm D.
Weight:
5.7 kg.
Option:
19-inch rack mount kit.
PROTECTION
Excess Power: The unit will attempt to limit the power to 430 Watts; if this fails the unit
Excess Current: The unit will trip into the fault state at nominally 20 Amps.
Excess Voltage: The unit will conduct a current pulse (to absor b induct ively generated
Temperature: The unit will trip into the fault state if t he Mosfet temperature exceeds
Reverse Polarity: The unit will trip into the f ault stat e if a reverse current is drawn that
The unit is protected by fuses that pr ot ect the unit against currents that
exceed 20A. This is primarily as
with a current capability of >20A being connected to the load with
spikes) for 1ms at about 510V.
The unit will trip into the fault state at nominally 530V. Surge
exceeds 200mA. The unit is protected fuses that protect the unit against
GENERAL
Specification Notes
(1)
Slew Rate Ranges refer to the theoretical slope of the transition between two levels,
regardless of whether that t r ansit ion can be achieved when taking into account the level
difference, the set transition dur at ion, t he minimum transition time, and the characteristics of the
source.
(2)
Minimum Transition Time specification is an indication of the f ast es t available transition using
a benign source and low inductance connections, with a minimum terminal voltage of 25V and a
minimum current of 200m A. The actual performance attainable with electronically regulated
power supplies depends on the combination of source and load loop bandwidths and
interconnection inductance.
8
instrument.
l
3. Safety
This instrument is Safety Class I accor ding to IEC classification and has been designed to meet
the requirements of EN61010−1 (Safety Requirements for Electrical Equipment for
Measurement, Control and Laboratory Use). It is an Ins tallation Category II instrument intended
for operation from a nor m al single phase supply.
This instrument has been tested in accordanc e with EN61010−1 and has been supplied in a safe
condition. This instruction manual contains some information and warnings which have to be
followed by the user to ensure safe operation and to r etain the inst r ument in a safe condition.
This instrument has been designed f or indoor use in a Pollution Degree 2 environment in the
temperature range 5°C to 40°C, 20% −80% RH (non−condensing). It may occasionally be
subjected to temperatures bet ween +5° and −10°C without degradation of its safety. Do not
operate while condensation is present.
It has been designed for CAT II (Measurement and Overvoltage Category II) use to 300Vrms.
CAT II is local domestic supply level, e.g. portable equipment and appliances.
For this equipment 2500V is the maximum peak t r ans ient overvoltage that can be tolerated by
any load input terminal with respect to earth gr ound without impairing s afety.
Use of this instrument in a manner not spec ified by these instructions may impair the safety
protection provided.
Do not operate the instrument outside its rated supply voltages or environmental range.
WARNING! THIS INSTRUMENT MUST BE EARTHED
Any interruption of the mains earth conduct or inside or outside t he inst r um ent will make the
instrument dangerous. Int ent ional inter ruption is prohibited. The protective action must not be
negated by the use of an extension cord without a protective conductor.
When the instrument is connected to its supply, terminals may be live and opening the covers or
removal of parts (except those to which access can be gained by hand) is likely to expose live
parts. The apparatus shall be disconnected from all voltage sources before it is opened for any
adjustment, replacement, m aint enance or r epair.
Any adjustment, maintenance and repair of the opened instrument under voltage shall be
avoided as far as possible and, if inevitable, shall be carried out only by a skilled person who is
aware of the hazard involved.
If the instrument is clearly defective, has been subject to mechanical damage, excessive
moisture or chemical corrosion the safety protection may be impaired and the apparatus should
be withdrawn from use and returned for checking and repair.
The instrument contains both encapsulated fuses and non-resetting thermal fuses; t hese ar e not
replaceable by the user. The short-circuiting of these protective devices is prohibited.
Do not wet the instrument when cleaning it.
The following symbols are used on the instrument and in this m anual:−
Caution Refer to t he accompanying
Alternating Current.
Mains supply OFF.
9
documentation, incorrect
operation may damage the
CAT II
Measurement and Overvoltage
Category II (300V)
Chassis ground.
Mains supply ON.
4. Installation
4.1 Mains Operating Voltage
The operating voltage of the instrument is shown on the rear panel. Should it be necessary to
change the operating voltage from 230V to 115V or vice-versa, proceed as f ollows:
1. Disconnect the instrument fr om all voltage sources , including the mains and all inputs.
2. Remove the screws which hold the case upper to the chassis and lift off.
3. Unplug all cable connectors from t he power supply PCB (don’t pull on the wires).
4. Remove the five nuts which hold the power supply PCB in place, and lift it off the studs.
5. Fit the soldered links (alongside the transformers) for t he required operating voltage:-
For 230V fit only LK2 and LK5
For 115V fit only LK1, LK3, LK4 and LK6.
These links may be either tinned copper wire or zero-ohm resist or s.
6. Refit the power supply PCB, ensuring that no wires are t rapped. Check that all cables are
correctly connected and that all five nuts are suff icient ly tightened.
7. Refit the case upper.
8. To comply with safety standard requirements the operating voltage marked on t he r ear
panel must be changed to clearly show the new voltage setting.
4.2 Mains Lead
Connect the instrument to the AC supply using the mains lead provided. Should a mains plug be
required for a differ ent t ype of mains outlet socket, use a suitably rated and approved 3-core
mains lead set which is fitted with the required wall plug and an IEC60320 C13 connector f or the
instrument end. This instrument req uires a lead rated at 6A for all mains supply voltages.
Any interruption of the mains earth conduct or inside or outside t he inst r um ent will make the
instrument dangerous. Int ent ional inter ruption is prohibited.
4.3 Mounting
This instrument is suitable both for bench us e and r ack mounting. It is delivered with feet for
bench mounting. The front feet include a tilt mechanism for optimal panel angle.
A rack kit for mounting one or two of these half-width 3U high units is available from the
Manufacturers or their overseas agents; a blanking piece is also available for unused positions in
the rack.
4.4 Ventilation
The unit is cooled by a variable speed fan which vents at the rear. Take car e not t o restrict the air
inlets at the top, side and bottom panels or the exit at the rear. In rack-mounted s it uat ions allow
adequate space around the instrument and/or use a fan tray for forced cooling. If ducting is
applied to the air outlet, additional extraction is required.
WARNING! THIS INSTRUMENT MUST BE EARTHED
10
4.5 Fuses
4.5.1 Current Range Fuses
The unit is protected by two 10A fuses that protect the unit against currents t hat exceed 20A.
This is primarily as a protection against high power sources with a current capability of >20A
being connected to the load with reverse polarity.
The replacement fuse must be a 10x38mm 10A 1kVdc rated HRC fuse. To replace a fuse:
1. Disconnect the instrument from all voltage sources.
2. Remove the screws retaining the fan guard.
3. Replace the fuse with one of identical specification and size.
4. Refit the fan guard securely.
4.5.2 Inte r nal AC Power Fuse
The AC supply transformers on the PSU PCB is protected against an internal fault by a nonresettable thermal fuse. To avoid the thermal fuse being accidentally tripped by connecting to a
230V supply when the instrument set for 115V operation, a standard 500mA (T) 250V fuse is
fitted in position FS6 on the PSU PCB. Should this fus e need r eplacing , following such an event,
remove the case upper and replace the fuse following the instructions of ‘Mains Operating
Voltage’ section 4.1.
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5. Connections
5.1 Front Panel Connec tions
5.1.1 Load Input
The INPUT terminals for t he load cir cuit on t he front panel accept 4mm plugs. Their maximum
current rating is 16 Amps.
Do not use both the front panel and rear panel terminals simultaneously.
The wiring and connection arrangement mus t be capable of s uppor t ing the current required.
The load circuit is isolated from g r ound, with a rat ing of CATII (300V), but it is essential to
observe safe insulation practice.
Ensure that the source is connected with the correct polarity.
The maximum current throug h t hes e t er m inals is 16 Amps.
The maximum voltage allowed across the load is 500 Volts.
The unit contains a fuse in the load circuit, see section 4.5.
5.1.2 Current Monitor Output
The Current Monitor terminals provide a voltage proportional to the load current flowing with a
scaling factor of 250 mV per Amp (4 Volts for 16 Amps full scale). The output impedance is
nominally 600Ω and the calibration assumes a high impedance load such as an oscilloscope.
The current monitor circuit is referenced to chassis ground, as such is isolated from
the load circuit with a rating of CATII (300V).
5.2 Rear Panel Connections
5.2.1 Load Input
The INPUT terminals for the load circuit on the r ear panel accept 4mm plugs. Their maximum
current rating is 16 Amps.
Do not use both the front panel and rear panel terminals simultaneously.
The wiring and connection arrangement mus t be capable of s uppor t ing the current required.
The load circuit is isolated from g r ound, with a rat ing of CATII (300V), but it is essent ial t o
observe safe insulation practice.
Ensure that the source is connected with the correct polarity.
The maximum current throug h t hes e t er m inals is 16 Amps.
The maximum voltage allowed across the load is 500 Volts.
The unit contains a fuse in the load circuit, see section 4.5.
5.2.2 Terminal Blocks
All other rear panel connections are made via the screw-less terminal blocks. To make
connections to the terminal blocks, use a flat screwdriver to press the spring-loaded orang e
actuator inwards to open the wire clamp; insert the wire end f ully into the hole and release t he
actuator. Ensure the wire is properly gripped. Take care to observe the marked polarity.
5.2.2.1 Remote Disable Input
Apply greater than +3V (preferably +5V) to the DISABLE INPUT terminals to disable t he load
input; these are the input to an opto-coupler, through 1kΩ, and are galvanically isolated from all
other terminals. The input current is less than 2· 5m A at 5V.
The maximum input voltage is +12Vdc. Avoid reverse polarity.
12
protected against excess input voltages up to 50V.
5.2.2.2 Oscillator Sync Output
The SYNC OUTPUT is a TTL/CMOS (5V) output driven by the signal from the internal oscillator ;
this output is chassis ground ref er enc ed. There is a 1kΩ series protection resistor.
5.2.2.3 Remote Control Voltage Input
The CONTROL VOLTAGE terminals are used in two operating modes of the instrument:
In EXTERNAL VOLTAGE mode an analogue signal applied here sets the level of the load; the
scaling is 4 Volts full scale.
In EXTERNAL TTL mode, a logic signal applied here selects either the LEVEL A setting (logic
low) or the LEVEL B setting (logic high). The switching threshold is nominally +1·5V.
These terminals are refer enced to chassis ground. Input impedance 10kΩ. Inputs are
5.2.2.4 Current Monitor Output
The top pair of terminals, mar ked CURRENT MONITOR, provide the current monitor output.
They are wired in parallel with the front panel Current Monitor BNC and the same requirements
apply.
5.2.3 Digital Remote Control Connections
The LDH400P model provides full remote control capabilities through standard LAN, USB, GPIB
and RS232 interfaces. All of these are isolated from the load input term inals of the unit. The USB,
GPIB and RS232 interfaces are connect ed t o c hassis ground, and care must be taken to avoid
introducing ground loops. The LAN interface is isolated by standard network t r ans formers.
Full details are given in the ‘Remote Interface Configuration’ section 10.
5.3 Prospective Fault C urrent Protection
This unit is not intended to act as an overcurrent fault protection device for the source being
tested. However the instrument does contain two 10A, 1000V, HRC fuses that prot ect the unit
against currents that exceed 20A. This is primarily as a protection against high power sources
with a current capability of >20A being connected to the load with reverse polarity, but will also
provide protection against any other prospective fault c ur r ent >20A.
13
6. Initial Operation
This instrument provides a controllable DC load (a power sink) intended for testing all forms of
DC power supply including PFCs, batteries, photo-voltaic cells , fuel cells, turbines and generators
as well as electronic power supply units.
6.1 Organisation of this manual
The paragraphs below are intended to briefly introduce the particular features of this instrument
and the terminology used in this manual. More technical details are given in later chapter s of the
manual.
The next chapter describes the gener al oper at ion of the front panel and its display, followed by
full instructions for setting each parameter. A short chapter then describes the Analogue Remote
Control facilities, including level selection by a logic level signal.
Following that there is a chapter giving som e application not es and implementation details, which
gives more information on some practical difficulties which may occasionally be encountered in
each operating mode, together with some advice on mitigating strategies.
Finally the digital remote control interfaces and comm and s et of the LDH400P.
6.2 Load modes
The power dissipating stage in this load is fundam entally an adjustable current s ink, which
conducts a current that does not depend on the voltage presently applied from the source being
investigated. This is known as Constant Current operation.
An analogue multiplier is used to offer other oper at ing modes in which the current does depend
on the applied voltage in a known way, providing a choice of Constant Power, Constant
Resistance, or Constant Conductance characteristics.
6.3 Constant and Transient Operation
The load offers two independent level settings, referred to as Level A and Level B. Two keys
marked A and B in the
active.
Transient changes in the magnitude of the load are generated by switching between the two
levels. The transition between the two is a straight line at a slew rate that is specified by the user.
The switching between the two levels can be controlled either by an internal transient oscillator,
which has adjustable frequency and duty cycle, or an external logic (TTL level) signal.
There is no restriction on which of the two levels is the larger.
LEVEL SELECT area of the front panel allow the choice of which level is
6.4 Dropout voltage
The primary purpose of the dropout facility is to protect batteries from being excessively
discharged. When the source voltage falls below the Dropout threshold voltage setting, the load
will reduce the current it draws, eventually to zero. This is a dynamic limit, not a latched state, so
if the source voltage recovers above the threshold (as batt eries often do) then the load will
conduct current again.
6.5 Slow Start
The slow start facility causes the current taken by the load to r ise gently, at the rate
determined by the slew rate setting, when the load is enabled or when the source
voltage rises above the Dropout Voltage threshold setting. It also causes the current to
fall at the same rate when the load input is disabled. This facility is particularly useful in
Constant Power mode, to avoid a latch-up condition when the source is started; see the
‘Application Notes’ section 9.
14
6.6 Voltage and Current Limit Conditions
The unit has provision for the user to specify limits on the permitted measured value of voltage or
current. If either of these limits is exceeded then the input will be disabled.
6.7 Power Lim it
The unit continuously monitors the internal power dissipation and varies the speed of the fan
accordingly. If the dissipation rises above about 430 Watts, a hardware power limit circuit will
come into operation and attempt to constrain the load current to control the dissipation. The unit
is then operating in a non-linear mode, which will change the stability conditions. If the power limit
circuit fails to prevent the power rising above a slightly higher fault threshold ( per haps because of
instability) then the fault detector will be tripped and the load will cease to conduct.
6.8 Input Condition Lamps
Two lamps above the Input Enable switch indicate the operating stat e of the unit. They are both
off when the input is disabled. The green lamp lights when the input is enabled, and if t he load is
operating normally then the yellow lamp will not be lit.
The yellow lamps lights if the load cannot conduct the required current, with a message on the
status line at the top right of the display distinguishing between the three possible reasons:
• Power Limit: the power limit circuit is operating as described above.
• Dropout: the voltage applied from t he sour c e is below the sett ing of the Dropout voltage.
• Low Voltage: the power stage is in the minimum resistance condition, because the
voltage available from the source is insufficient to maintain the curr ent level req uir ed.
The minimum resistance condition will occur either if t he sour c e is switched off and is not
providing any voltage at all, or if the voltage drop across the connection leads is causing the
actual input voltage at the load to be below its minimum operating level. Note that if the source
voltage is suddenly applied while the load circuit is in this state, then a current t ransient will
probably occur.
If only the yellow lamp is lit, with the green lamp off, then a persistent fault condition exists.
6.9 Fault Conditions
The unit detects (in hardware) the following fault conditions:
• Current above about 20 Amps.
• Power in excess of about 450 Watts (that the power limit circuit has not succeeded in
controlling to the lower threshold as described above).
• Voltage above about 530 Volts.
• Reverse Polarity (current exceeding 200mA) .
• Excessive heatsink temperat ur e.
• Fan failure.
The fault detectors for excess current, power and voltage have filter networks with a
time-constant of a few milliseconds to allow brief transients to be handled.
When any of thes e fault conditions occurs, the input is disabled, so the unit will cease to conduct
current and a fault messag e will be displayed. An excessive current or power condition will
disappear as soon as the input is disabled, but any of the other c onditions will cause t he yellow
lamp only to remain lit, and the message Fault to show on the status line, until it is cleared.
15
6.10 Connecting the Loa d to the Source
The INPUT terminals of the load must be connect ed t o t he s our ce to be tested using sufficiently
low resistance and low inductance connections. Inductance in the interconnection can have a
significant adverse impact on the stability of the source and load com binat ion. The wiring should
be as short and as thick as possible. It is es sent ial t hat t he voltage dr op acr os s t he c onnec ting
leads is sufficiently less than the source voltage to leave enough working voltage across the load.
The load input terminals of t he inst rument are floating from ground, and are rated to CATII 300V.
Connection to an AC mains circuit, primary side DC or non isolated bridge rectifier is permitted on
the negative input terminal with a voltage limit o f 500Vdc between the positive input terminal and
the negative input terminal.
Reverse polarity of the inputs is not permitted.
The maximum permissible voltage between the negative input terminal and earth ground
425V (peak of CAT II 300V).
Ensure that all wiring is safely insulated for the working voltage involved.
PFC safe test and operation area diagram
is
6.10.1 Prospective Fault Current
The instrument detects any fault condit ion and r esponds by disabling t he load by turning off the
power devices. As a last resort there ar e internal fuses in the load circuit, so that if the external
source applies a condition so far beyond the current rating of the unit, the f us es will protect the
instrument against dangerously high currents.
6.10.2 Remote Input Disable
This input is provided for remote override of the INPUT ENABLE function of t he load, poss ibly for
safety reasons. It is available in all operating modes of the instrument. It is a fully floating input to
an opto-isolator: apply 3 to 12 volts (observing polarity) to disable the load. The load is only
enabled if this signal is absent and the input has been enabled with the front panel controls.
6.11 Switching On
The line POWER ( ) switch is at the bottom left of the front panel. Before switching on ( l ),
check that the line operating voltage of the unit (marked on the rear panel) is suitable for the local
supply. After switching the power on (
information. Avoid turning off the power until the instrument is fully initialised and the home
screen is displayed.
16
l ) the LCD should light and display firmware version
7. Front Panel Operation
In this manual, front panel labels are shown as they appear, in capitals, e.g. LEVEL SELECT.
Individual key names are shown in bold, e.g.
their present function, as labelled on the bottom line of the display, shown in bold italics, e.g.
Limits. Text or messages displayed on the LCD are shown in bold, e.g
Transient, and the blue soft-keys are referred to by
. Enabled, Utilities.
7.1 Keys and ∆ Adjust
The front panel keys are divided into four areas:
① The numeric keys.
② The blue keys below the display - Used to configure the instrument t hrough the menu
structure described in section 7.2.4.
③ The
selection and returns to the home scr een. The
request from digital remote control.
④ The three
settings is active, or engage t he transient mode which switches between them. The associated
lamps indicate the presently active state; these keys are also used to retur n from external
analogue control to manual selection.
⑤ The
choose and modify the existing value of any one of t he num eric parameters of the instrument.
⑥ The
load, with alternate presses switching between the conducting and non-conducting conditions.
The green lamp shows if the input is enabled; t he yellow lamp reports if t he power stag e is
saturated, as described in the paragraph ‘Input Condition Lamps’ in the ‘Initial Operation’ section
6.8.
CE key - Cancels the last numeric keystroke while the Home key cancels an entire menu
LEVEL SELECT keys (A, B and Transient) - Determine which of the two level
∆ ADJUST k nob and its three associated keys (Levels, Off and Transient) - Used to
ENABLE key in the INPUT section (referred to as the INPUT ENABLE key) - Controls the
Home key is also used for the ‘return to local’
17
7.2 The Display and the Home Screen
All parameter settings and meter readings are shown on the backlit liquid crystal display (LCD).
At power up the instrument initialises to the home scr een, which is the nor mal display during
operation of the unit. This screen displays all of t he load m et er readings and the most important
load parameter settings as described below, and is also the top level of the soft-key driven menu
structure. The display changes to show other sc r eens as select ions ar e m ade to enter parameter
values and then returns to the home screen when entry is complete.
7.2.1 [A] Status Line
The status line of the instrument is visible along the top of the display at all times except when
one of the store, recall or ut ilities menus is being shown. It indicates the current status of the
instrument as follows (in order, from left to rig ht across the display):
• The load mode field indicates the present load mode – CC, CP, CR, or CG.
• Slow is displayed when slow start operation has been enabled.
• Slew is displayed as a warning when the present slew rate setting is too slow with
regards to the level difference, tr ansient frequency and duty cycle, see ‘Slew Rate’ section
7.14.
• Lim is displayed when either of the user defined current or voltage limits is enabled.
• The level select field (in the centre) indicates which input level or control method is
currently selected – Level A, Level B, Transient, Ext V or Ext TTL.
• The LAN field indicates the status of the Local Area Network (if fitted) . When there is no
LAN connection the field displays
indicator will flash between
See the ‘Remote Interface Configuration’ chapter for more infor m ation.
• The input status field (at t he right hand end) indicates the instrument’s present load input
condition – Disabled, Enabled, Low Voltage, Dropout, Power Limit or Fault, as
described in the paragraph on ‘Input Condition Lamps’ section 6.8.
7.2.2 [B] Home Screen Data
Below the status line are the meter displays which show the actual measured source voltage and,
once the load is enabled, the load current.
7.2.3 [C] S ettings Data
The screen is divided into three areas. On the left , under the heading METERS, the display
shows the present power in the load and the equivalent resistance; these values are comput ed
from the measured voltage and current readings. Any of these meter displays will show
MAX for power) if the measur ed value is beyond the capabilities of the unit.
In the centre, under the heading
Level B (the units depend on the operating mode) and the Dropout Voltage setting.
On the right, under the heading
and Duty cycle of the internal oscillator, and the Slew Rate of the transit ions.
. While a connect ion is being established the
and , and then while connected the field will show .
HIGH (or
LEVELS, the display shows the present settings for Level A and
TRANSIENT, the display shows the settings for the Frequency
18
All six of these parameters can be m odified either by direct numeric entry or by using the k nob to
increment or decrement the present value.
Mode
To select the operating mode.
Limits
To impose cut-off limits on the applied voltage or current values.
Level
To enter numeric values for Level A and Level B.
Dropout
To enter a numeric value for the Dropout Voltage.
Transient
To access a second level to set-up the transient functionality.
Store & Recall
To setup, review and use saved settings of the unit.
‘Analogue Remote Control’.
parameters of the remote int er faces.
Freq
To enter a numeric value for the Frequency of the internal oscillator.
Duty
To enter a numeric value for the Duty cycle of the internal oscillator.
Slew
To enter a numeric value for the S lew Rate of the transitions.
Slow
To enable or disable the Slow start and stop facility.
7.2.4 [D] Soft-Keys
The soft-keys are the six blue keys found dir ectly below the LCD. The function of each of these
keys changes as the instrument is operated. The available function is shown on the bottom line
of the display in a tab above each key. If any of the keys have no functionality in a particular
menu then the tab is lowered to show it is inactive.
On the home screen there are two sets of soft-key functions available; the right hand key,
alternately labelled More > or More < switches between the two. All additional menus are
accessed through the soft-keys in one of these sets.
The major parameters accessible in the first set are:
The second set includes:
Extern
Utilities
The Transient second level menu (when selected from the first set above) includes:
On most of the lower level menus, the left hand key, labelled Back or Cancel, can be used to
return to the previous menu. This allows exploration of the various menus without risk of putting
the unit into unexpected configurations. Back returns to the previous menu, keeping any
changes that have been made in the current menu, while Cancel (if offered) will undo any
change made before reverting t o t he pr evious menu. The
screen and the top level of the menu structure (also abandoning any incomplete value entry).
To enable or disable analogue remote control of the level, or logic (TTL)
level selection between the two levels, as described in the chapter on
To configure some secondary facilities of t he inst rument and to set
Home key reverts directly to the home
19
7.3 General Numeric Entry of Parameters
All user modifiable load parameters can be set using the numeric keypad. The desired parameter
is first selected from the menu using the soft-keys. The display then changes t o show the
parameter entry screen which indicates the name of t he paramet er, its present value prior to
editing, and in most cases the entry limits and resolution. A message prompting for the entry of
the new value is shown. When any number k ey is pressed this prompt is removed and replaced
by the new value being constructed, and the soft-key labels change to show a list of units
applicable to the parameter being edited. The
the entire entry may be cancelled by pressing either the
Once the number entry is complete it must be terminated by pressing the required units soft-key
(choosing A or mA, for example). The value is then checked against the parameter lim its and, if it
falls within the allowed range, it is accepted and immediately implemented as the new value for
that parameter. If the value does not fall within the permitted range t hen an error message is
displayed and the buzzer will sound. If applicable the entry may be rounded to fit within the
specified parameter resolution.
Paragraphs below describe particular features associat ed with each parameter.
CE key deletes individual keystrokes; alternatively
Home key or the Cancel soft-key.
7.4 Variation of Parameter Values using ∆ Adjust
The level and transient parameters of t he load can be adjusted by incrementing or decrementing
the present value using either the knob or sof t-keys.
Note: this adjustment mechanism is only available whilst the instrument is on the hom e sc r een.
Two keys above the knob, labelled
and initiate the adjustment. Press ing the
selects Level B and a third press selects the Dropout Voltage setting. The cycle can be repeated
if required. Similarly, multiple presses of the
and Slew Rate. A lamp above each of these keys blinks whilst adjustment is enabled and four
cursor soft-keys are shown.
The display of the selected parameter value is expanded to fill its edit box, with an adjustment
indicator (
which digit position will be adjusted, and then either the knob or the ▲and ▼ soft-keys can be
used to increment or decrement the value at that position. Digits to the left of the one being
varied are automatically incremented or decrem ent ed when the decade overflow or underflow
point is reached. Digits to the right of the one being varied always remain unchanged unless a
point of decade resolution change is reached, in which case digits to t he r ight may be lost
through truncation. If the least significant digit is being increm ented and a decade resolution
change is reached, the new least significant digit becomes the one being adjusted.
Each change made is applied immediately, so long as the value remains within the permitted
limits of that parameter. If an increment or dec r em ent of the current position would exceed a
range limit then the parameter value remains unchanged; partial adj ustments are not made.
Pressing the Off soft-key or the Off key above the k nob ( or the
retaining the new value, and returns the display to the home screen. Pressing the Cancel softkey ends the adjustment and r est ores the last parameter to the value it had when it was selected
for adjustment.
) positioned under the digit to be varied. The ◄ and ► soft-keys can be used to select
Levels and Transient, select the parameter to be modified
Levels key initially selects Level A; a second press
Transient key select between Frequency, Duty Cycle
Home key) ends the adjustment,
7.5 Configuring the Load
The normal sequence of operat ion is t o s elect t he load Mode, set t he required operating Level
and Dropout Voltage, and then Enable the input. If transient operation is required, the second
Level setting and the Slew Rate parameter s m us t be s et , as well as the f r equency and duty cycle
of the internal oscillator if it is t o be us ed.
The home screen shows all the parameter settings , which can be viewed before the input is
enabled. All parameters except load Mode can be adjusted as req uir ed while the input is enabled.
20
CC
Constant Current
The current is the Level setting, independent of voltage.
CP
Constant Power
Implements I = W / V where W is the Level setting.
CG
Constant Conductance
Implements I = V * G where G is the Level setting.
and V
dropout
is the Dropout Voltage setting.
Changing the load mode while the input is enabled will trip a fault detector and cause the input to
be disabled before the change is implemented.
7.6 Selection of Load Mode
The first action in conf iguring the unit for a particular application is to choose the load mode,
which determines how the current drawn by the load varies with the applied voltage (V). The
Mode soft-key on the home screen opens a m enu offering the various modes listed in the table
below. More detailed descriptions of the properties of each mode are given in the ‘Application
Notes’ section 9.
Changing the mode requires the load input to be disabled, which will be done automatically if not
already done by the user. The display returns to the home screen as s oon as a m ode is s elect ed.
The available operating modes are:
Constant Resistance
CR
Implements I = (V – V
7.7 Level A and Level B Sett ing
Pressing the Level soft-key on the home screen initially opens the level setting prompt for either
Level A or Level B, depending on which was altered last. The right hand soft-keys, labelled
A SET and B SET, can be used to switch the prompt to the other level. If the level being edited is
not currently active in controlling the load, a Select soft-key will appear allowing it to be made the
active selection if required. A new numeric value can be entered as described above. Separate
settings for bot h level values are retained f or each operating mode.
The level setting menu remains on screen, allowing f ur t her c hanges to be made, until either the
Back soft-key or the
Home key is pressed to return t o the home screen.
7.8 Dropout Voltage
Pressing the Dropout soft-key on the home screen opens the Dropout Voltage setting prompt. In
the usual way this displays the present Dropout Voltage setting, the range in which the new value
can be set, and the maximum resolution of t he s et t ing. After entry of the num ber pr es s eit her t he
mV or V soft-key to implement t he set ting. Either the Back soft-key or the
display to the home screen.
The primary purpose of the dropout voltage set t ing is to protect batteries from excessive
discharge. The load will cease to conduct current when the applied voltage from the sourc e falls
below this setting. Note that this is a dynamic limit, not a lat ching condition, so if there is any
wiring resistance between the source and the voltage sensing point of the load then there will be
a soft entry into the dropout condition – the s er ies voltage drop will reduce as the cur r ent star ts t o
fall, so raising the voltage measured by the load. Batteries may also recover as the load is
reduced, raising the voltage back above the dropout t hr eshold so the load resumes conduction.
There is a possibility of hunting or instability in this operating condition. The front panel lamp will
show yellow and the status line report Dropout when the dropout circuit becomes active.
) / R where R is the Level setting
dropout
Home key returns the
The Dropout Voltage setting has a special effect in Constant Resistance (CR) mode, when it
provides a starting point for the constant r esistance char ac t er ist ic (see the description in the
‘Application Notes‘ chapter for more detail).
The Dropout Voltage setting is also used as the threshold for the Slow Start circuit (see below).
If the dropout f acility is not required, set the Dropout Voltage to 0 Volts. The status line will show
Dropout as a warning whenever this setting is above 0V and no current is being drawn.
21
7.9 Slow Start
The purpose of the slow start circuit is to r am p t he demand of the load up slowly from zero to the
final value. The rate of rise is determined by the Slew Rate setting. The ramp starts either when
the Input is Enabled, or when the voltage from the attached sour ce passes the level of the
Dropout Voltage setting. When the Input is Disabled the demand will ramp back down to provide
a slow stop (assuming, of course, that the source voltage remains active).
The setting for t h is facility is on the Transient menu, so first press the Trans soft-key on the
home screen to enter the Transient menu, and then press the Slow soft-key on that menu to
access a soft-key to alternately enable or disable slow start. While it is enabled, Slow will appear
on the status line of the instrument. Pr ess t he Back soft-key to return to the transient m enu or
the Home key to return dir ec t ly to the hom e s cr een.
In CP (constant power) mode the slow start facility will almost always be needed, to avoid the
lock-up condition that will occur at low voltages (when attaining the desired power requires a high
current) if the sour ce does not have suff icient current capability to reach the power level
demanded. See the ‘Application Notes’ chapter later for a discussion of some of the implications
of the fact that c onstant power mode caus es the load to act as a negative resistance.
In CR (constant resistance) mode the load will start at the maximum O hm s level of t he active
range and ramp down to the final Ohms value. Becaus e t he initial r esistance is not infinite there
will be an initial current step before the ramp starts when the load becomes active. Note also that
a linear slew in Ohms is not a linear slew in Amps if the source voltage is constant.
7.10 Introduction to Transient Operation
The unit includes the capability of generating load tr ansients, which are intended t o help in
testing the transient response of a source. Transient operation is available in all operating modes.
A transient is an alternation between the Level A and Level B settings, with the transition between
the two levels being a straight line (in the controlled variable of the act ive mode) whose slope is
determined by the Slew Rate setting. Note that the transient is specified by setting the two
absolute levels, not the difference between them (as is the case with some electr onic loads) .
There is no limitation on which of the two levels is the larger.
Transients can be timed either by an internal oscillator or by an external TTL signal (see the
description of the Extern menu, section 8 ). Transient operation controlled by the internal
oscillator always starts with the Level A setting, including a transition from Level B if r equired. The
oscillator starts when the last of the three required conditions occurs: either when the input is
Enabled, or when the Transient level control key is selected, or (if the slow start circuit is active)
when the source voltage rises above the Dropout Voltage threshold.
It is also possible to use the External Analogue Voltage control mode to g ener at e transients of
any required shape by using an external generator to produce the required waveform. This is
also controlled by the Extern menu, section 8 ). Note t hat t he exter nal signal still passes through
the internal slew rate control circuits, so appropriate Slew Rate set tings need to be made.
To end Transient operation (whether internal or external) and return to a constant level press
either the A or B key (in the
LEVEL SELECT section) as required.
7.11 Transient Menu
Press the Trans soft-key on the home screen to enter the Transient menu which gives access to
the controls for the Fr equency and Duty Cycle of the internal oscillator and the Slew Rate
settings which apply to all changes in level, however caused.
These parameters can also be changed using t he
do this the unit must be on the home screen not the Transient menu.
Note that changes to the transient frequency or duty cycle do not take effect until the end of t he
present cycle, at the return to Level A. This is particularly noticeable at very low frequencies.
Disabling and then re-enabling the load input will also immediately start a new cycle.
22
∆ ADJUST facilities described previously, but to
7.12 Transient Frequency
The repetition rate of t he internally timed transients can be set in terms of f r equency or period.
Pressing the Freq or Period soft-key on the Transient menu opens the Frequency and Period
setting menu. A new value can be entered, in the present representation, in the usual manner.
Two soft-keys labelled Freq and Period allow the alternative representation to be chosen. Press
the Back soft-key to retur n to the transient menu or the
The soft-key label on the transient menu will show either Freq or Period to reflect the most
recent choice of representation.
7.13 Transient Duty Cycle
Pressing the Duty soft-key on the Transient menu opens the Duty cycle setting menu. This
setting specifies the percentag e of each repetition spent at the Level A setting, including the
transition from Level B to Level A; the transition back to Level B and the time stable at that
setting occupies the remainder of the cycle.
The available duty cycle range is 1% to 99%, but note that the t im e duration of each portion of
the cycle must be sufficient for t he t r ans it ion defined by the Slew Rate and Level settings to
occur; otherwise the load will never reach the steady state at the set value before t he next
transition in the opposite direction starts. This error condition is discuss ed below. Press the Back
soft-key to return to t he Transient menu or the
Home key to return to t he home screen.
Home key to return to t he home screen.
7.14 Slew Rate
Pressing the Slew soft-key on the Transient menu opens the Slew Rate setting menu. This Slew
Rate setting sets the slope of the t r ansit ions bet ween the two level settings. It applies to all
changes in level whether caused by manual setting, adjustment using the knob, the internal
transient generator or external voltage contr ol. It is also used to determine the rate of rise and fall
when the Slow Start circuit is triggered.
The slew control circuit introduces a small additional error int o t he ac cur ac y of the level settings,
which varies depending on the actual Slew Rate setting . I f the dynamic facilities of the load are
not being used, then the Default soft-key sets the circuit to the calibrated state f or best accuracy.
The circuit provides a linear transition in the control value of t he ac t ive mode, s o, for example, in
Constant Power (CP) mode the slew rate is expressed in Watts per microsecond, Watts per
millisecond or (at very slow rates) Watts per second. The shape of t he c ur r ent transition is
therefore not necessarily linear in any mode other than Constant Current (CC).
In addition to the usual numeric prompt t his m enu also shows the calculated theoretical transition
time considering the present Slew Rate setting and the differenc e bet ween Level A and Level B.
This theoretical value takes no account of any dependency of t he actual transition time on the
source and load characteristics, impedances and interconnection inductance which may occur,
particularly at f ast s lew rates. The user m ust ensure that the transition time which results from the
values entered is not shorter than the minimum at tainable trans it ion tim e in t he pr esent mode,
which is documented in the Specification. It is emphasised that severe overshoots can occur if
the slew rate is set faster than the combination of source and load is capable of supporting
(which may be slower than the value in the Specification, which applies to optimal conditions) ,
see the section on ‘Fast Slew Rate Limitations’ section 7.14.2.
To set the slew rate to the minimum attainable transition time in the pres ent m ode as
documented in the Specification, press the Optimum soft-key.
Pressing the Range soft-key produces a display of the limits of available slew rate for the present
operating mode. If a slew rate value is entered that falls outside the parameter limit range, an
error message is displayed, followed also by a display of these ra n ge limits.
23
The bandwidth of the power stages of the load is reduced (by changing the compensation
networks) when the slew rate is set to less than 0·1% of the maximum slew rate for the given
load mode. For example, in constant current mode, the maximum slew rate sett ing is 500A/ms,
so the bandwidth is reduced when the slew rate is set < 500A/s. This change is made even if the
transient facilities are not being used, and alters the dynamic behaviour of the unit. This may
improve stability with some difficult combinations of source and load characteristics.
Upon completion of the slew rate setting update, press the Back soft-key to return t o t he
transient menu or the
Home key to return to t he hom e s cr een.
7.14.1 Slow Slew Rate Limitations
There is a lower limit to the slew rate value that can be used, wh ich is determined by the
combination of slew rate, fr equency, duty cycle, and t he difference between the two levels. If the
requested transition time ( which is the diff er ence between the level settings divided by the slew
rate) is longer than the available time (which is the oscillator period m ult iplied by the smaller duty
factor), then the transition will not complete before the oscillator initiat es a r eturn to the other
level. As a result, the intended level setting will never be reached. In this case, Slew is displayed
in the status line as a warning.
7.14.2 Fast Slew Rate Limitations
In practice there are a number of limitations on the fastest slew rate actually attainable. O ne is
the minimum transition time of t he power stages of the load (which depends on the operating
mode – see the Specification). If a combination of a fast slew rate and a small change in level
imply a transition time shorter than this, t hen the settling time of the power stage will dominate.
The dynamic behaviour of a source and load combination at high slew rates depends on many
factors, particularly interconnection inductance and the dam ping factor of feedback loops. In
addition, the response of the power stages of the load is slower when operated at very low or
high currents, or at low voltages. In many circumstances, a lower slew rate setting will be needed
to avoid aberrations.
If an attempt is made t o set a slew rate faster than is possible in the circumstances, then
significant overshoots and extended settling times can arise. When configuring fast transitions
approaching the limits of the capabilities of the unit , it is st rongly recommended that the current
monitor output be viewed on an oscilloscope to verify the results actually obtained. Particular
care should be taken to avoid a fast transition down to a low current, as t his m ay result in t he
power stage entering the cut-off stat e, which incurs a long recovery time and possibly multiple
current pulses.
In CR (constant resistance) mode, where the cur r ent is inversely related to the resistance
transition, it is particularly difficult to predict the m aximum us eful slew rate setting.
7.15 Voltage and Current Limits
These limits specify values of sour c e voltage and load curr ent which will cause the load to
automatically disable its input if the actual measured voltage or current exceeds the set limit. This
is not an independent hardware trip, but a simple comparison against t he m et er m eas ur em ents.
To access the Limits menu, press the Limits soft-key on the home screen.
The V / I soft-key toggles the menu between setting up the two limits, allowing a numeric value
for each to be entered in the usual way. Pressing the None soft-key (or entering a value of zero)
disables that particular limit. Press the Back soft-key or the
screen.
Home key to return to t he home
24
While a value is specif ied for either limit, Lim appear s on t he stat us line of the display. Then, if
either of the limits is exceeded a fault messag e is displayed and the load input is disabled.
7.16 Store and Recall Facilities
The instrument is able to store and rec all up to 30 user defined sets of load parameters in
non-volatile memory. Each memory location holds all the parameter set tings – load Mode, active
level, Level A value, Level B value, Dropout Voltage level, transient Frequency, Duty and Slew
Rate and the state of Slow start.
Both the store and recall menus display a preview of the parameters that ar e alr eady stor ed
within each memory location. If a memory location is empty then ( ---) is displayed. A memory
location can be selected either by using the ▲ or ▼ soft-keys or the knob to step t hr ough the
locations in sequence, or by entering the location number dir ectly using the numeric keypad (with
a leading zero if required). The currently selected m em or y location number (and user-specified
name) is highlighted on t he display, and the location number is also displayed above the table of
previewed parameters (this copy of the location number also updates during num eric entry).
Note: the store and recall menus look almost ident ical, see the menu name in the top left corner
to distinguish between the two.
7.16.1 Store Menu
To access the Store menu, press the Store soft-key on the home scr een. There are three
available options that can be applied to each memory location – store the pr esent settings to the
memory location, delete the contents of the memory location and rename the memor y location.
To store the present load configuration and sett ings to a memory location, select the desired
location and then press either the Confirm soft-key (if the location is presently empty) or the
Replace soft-key to overwrite the existing contents. O nce s t or ed, the parameters will be shown in
the preview table. If the location was empty prior to the store operation, then the location will
initially be given a default name of Store_nn, where nn is the location number.
To rename a memory location, press the Rename soft-key which opens the character entry
screen. Select a character using t he knob, or alternatively the digits 0 to 9 and the decimal point
can be entered using the numeric keys. To enter the selected character, press the Enter soft-key.
To delete the previously entered character press either the CE soft-key or the CE hard-key.
Use the ◄ and ► soft-keys to select the character position. The maximum number of charac t er s
in a memory location name is limited to 10. Upon completion of t he c har act er string entry, press
the Confirm soft-key to accept the changes and return to the store menu where the memory
location name will automatically be updated. Alternatively press the Cancel soft-key to reject any
changes and leave the memory location name unchanged.
To delete the contents of a memory location, select the desired location and pr ess t he Delete
soft-key. Delete will then be shown in the top left cor ner of the display and the soft-keys will list
the options of either Cancel (canc el t he deletion) or Confirm (confirm that the location contents
are to be deleted). The contents of the memory location are not erased until the Confirm soft-key
is pressed. Pressing the Cancel soft-key will return to the store menu without deleting the
contents of the memory location. As soon as the deletion is confirmed the load parameters and
location name will be replaced with (---).
7.16.2 Recall Menu
To access the Recall menu, press the Recall soft-key on the home screen. To recall the load
parameters from a memor y location, s elect t he des ired m emory location using the ▲ or ▼ softkeys or the knob, and then press t he Confirm soft-key. The instrument will then return directly to
the home screen with all the recalled load parameters updated, but the load input will be disabled
to avoid unexpected results. Alternatively press the Back soft-key or
home screen without recalling the stored load parameters.
Home key to return to t he
25
Load Mode:
Constant Current.
Level A & Level B:
Zero for all modes, except maximum resistance for CR mode.
Dropout Voltage:
0V.
Slow Start:
Off.
Transient generator:
1 Hz at 50% duty cycle.
Slew rate:
The Default setting for best calibration of the Level settings.
Protection Limits:
Set to None.
7.17 Utilities Menu
Pressing the Utilities soft-key on the hom e screen gives access to four sub-menus to configur e
various instrument settings and preferences. Instruments fitted with Digital Remote Cont r ol
interfaces have a fifth sub-menu. The selection can be made using either the ▲ or ▼ soft-keys
or the knob. Press the OK soft-key to initiate the selection and enter the sub-menu, or press the
Back soft-key or the
7.17.1 Optional Settings
There are two preferences that can be c hanged: the state of the input enable at power up and
whether the buzzer is enabled. Each preference has two mutually exclusive options, with the
active selection indicated by a
the knob and press the Confirm soft-key to initiate the selection.
7.17.2 Reset to Factory Defaults
Selecting this sub-menu opens a furt her s ub-menu to determine whether to reset just the present
load configuration and parameters (which is useful if a problem is encountered), or just to clear
the contents of every store and recall memory location, or to r es et everything .
Proceed with caution before confirming as this process cannot be undone. Press the Confirm
soft-key to accept the res et and r et urn to the utilities menu. Alternatively, to abandon the reset,
press either the Cancel soft-key to return to the utilities menu or the
to the home screen.
Home key to return to t he home screen.
. Select the required option using either the ▲ or ▼ soft-keys or
Home key to return directly
The default settings (which are also set by the *RST remote command) are:
7.17.3 Screen Contrast A djustm ent
This sub-menu offers the choice of white-on-black or black-on-white display by using the Invert
soft-key. The screen contrast setting then allows the display to be optimised for viewing angle
and ambient temperature. Use the knob to change the setting, watching the scr een pr eview.
Press Confirm to retain the new settings or Cancel to revert to the previous settings and return
to the Utilities menu, or
Home to revert and return dir ect ly to t he hom e sc r een.
7.17.4 Calibration
The calibration menu allows for the existing calibration sett ings to be adjusted and should only be
carried out by qualified personnel with access to the necess ar y calibrated t es t equipment. Entry
to the calibration menu requires a password which is published in the Service Guide, along with
details of the calibration procedure. Please contact your supplier if you require a copy.
7.17.5 Interface Settings
The interface setting s menu only appears on the programmable version of the instrum ent. It
allows the setting of the GPIB address and gives an overview of the LAN connection status and
shows the IP address obtained by the unit once the connection is established.
The GPIB address can be adjusted by using the knob, and can be set to any value between
0 and 30, but must be unique on the bus. The unit does not offer a Listen Only capability. The
address is only changed when the Confirm soft-k ey is pressed; alt er natively the address can be
left at its previous value by pressing the Cancel soft-key.
26
protected against excess input voltages up to 50V.
8. Analogue Remote Control
Two forms of voltage controlled rem ot e oper at ion ar e available: External Voltage Control, where
an analogue voltage fully defines the demanded level of the chosen operat ing mode, and
External TTL Control where an external logic voltage selects between the two levels set as
Level A and Level B. The same rear panel control voltage input is used for both of these modes.
These terminals are refer ence to chassis ground. Input impedance 10kΩ. Inputs are
Pressing the Extern soft-key on the home screen opens the external selection menu, where
either the knob or the ▲ and ▼ soft-keys can be used to highlight the desired external control
method. Pressing the Enable soft-key switches to the highlighted method; alternat ively pressing
either the Back soft-key or Home key returns the instrument to the home s cr een leaving t he level
select unchanged.
To return from external to internal control, us e one of the three
8.1 Remote Voltage Control
When External Voltage Control is enabled, the Ext lamp will illuminate and Ext V will be
displayed in the status line. The internal Level A and Level B parameters no longer have any
effect. The load mode and full scale range can still be changed in the usual way if required. The
Dropout Voltage setting remains active, if it is set above zero.
The
CONTROL VOLTAGE input has a scaling factor of 4 Volts full-scale. The conversion factors for
each mode and range are:
Operating Range Scale Factor
400 Watts 150 Watts per Volt
10 kOhms 2500 Ohms per Volt
1 A/V (Siemens) 0·25 A/V (Siemens) per Volt
The slew rate circuit and setting remains in circuit and the required transient wave shape can be
obtained by adjusting these settings in combination with the shape of the signal applied to the
remote input, subject to t he t r ans ition t im e limitations of the load circuit.
8.2 Remote Level Select
LEVEL SELECT keys.
16 Amps 4 Amps per Volt
When External TTL Control is enabled, the Ext lamp will illumina te and Ext TTL will be displayed
in the status line. If the external signal applied to the
threshold (nominally + 1·5 V) then the level set by the Level A control is active; if the signal is
above the threshold then the level set by the Level B control applies. Any logic signal (TTL or
other) which crosses the 1·5V threshold is satisfactory. The transitions are defined by the setting
of the slew rate. All parameters can be changed as required in the usual way.
27
CONTROL VOLTAGE input is below the logic
9. Application Notes
This chapter is intended to give helpful inform at ion conc er ning practical applications of the unit.
All electronic loads are subject to the impact of s our ce c har acteristics, interconnection inductance
and feedback loop characteristics, which can give rise to unexpected instability or poor dynamic
behaviour. The information given here will assist in understanding the factors involved. The initial
sections below cover general considerations, while later sections provide greater detail on the
particular characteristics of each operating mode.
9.1 Sources
Batteries are a low impedance source and, apart f r om t he pos sibility of inductance in the
interconnecting leads, they are generally easy to use in conjunction with an electronic load. The
dropout facility should be used to protect batteries from being damaged by excessive discharge.
Electronic supplies have active feedback networks whose dynamic characteristics of ten interact
with the load. When that load (like this instrument) also includes an active feedback contr olled
network, whose dynamic characteristics in turn depend on the nature of the source, it will be
apparent that the behaviour of the resulting system can be im pos sible to pr edict.
9.1.1 Source resistance
If a source has signif icant r es istance ( including the resistance of the connecting leads), so that
the voltage falls as the current rises, it is important to ensure that the voltage across the load
terminals remains at all times above the minimum permissible operating voltage.
The particular considerations concerning source r esistance which apply in Constant Power mode
are discussed in the section covering that mode below.
9.1.2 Sour ce inductance
Source and interconnection inductance has a major impact on the behaviour of t he load: the
fundamental characteristic of an inductance is that it generates an emf to oppose any change in
current. As the current rises, the emf gener at ed by the inductance reduces t he voltage acr oss t he
load terminals, perhaps to the point where the load saturat es . Whenever the voltage falls below
about 25V the transconductance of the power stage c hanges considerably; this changes the
damping factor of the feedback loop and alters its dynamic behaviour, possibly giving rise to
overshoots or even oscillation.
Whenever the load curr ent falls, the inductor will generate a voltage transient which might exceed
the voltage rating of the load. The unit is f it t ed with gas dischar ge tubes designed to absorb nonrepetitive transients. Even if the overvoltage detector disables the load input, these GDTs remain
connected, so if large energy levels are likely then some form of external protection must be
added, such as a catching diode across the inductor in the source.
9.1.3 Shunt capacitance
The load can only sink current, so it can only pull the voltage at its term inals down. The source
must pull the voltage up, including providing charging cur r ent to any capacitance across the
terminals. If the total current available is more than sufficient to charge this capacitance at the
slew rate required, then the load will continue to conduct the excess current during the transition
and the behaviour will be as expected. However, if the source cannot charge t he c apacitor at the
required slew rate, then the load will cut-off until the final voltage is reached. There will then be
an overshoot as it starts to conduct, f ollowed by a ringing as t he sour c e r esponds .
28
9.2 Stability of Source and Load Combinations
This instrument is opt im ised for accuracy under constant load conditions by using a high gain
feedback loop. Because of t his, the possibility exists for combinations of source, interconnection
and load characteristics to give rise to instability. There are three major potential causes:
inductance in the wiring between source and load (or an inductive output impedance of the
source), capacitance in parallel with the connection between source and load (including an output
capacitor within the source) and the characteristics of active feedback circuits within the source.
In Constant Power, Conductance and Resistance modes, the system includes an analogue
multiplier used by the load to derive the current requirement from the instantaneous voltage. This
reduces the bandwidth of the loop and adds additional phase shift. In g eneral, Constant Current
mode is the most likely to be stable, but in some cases instability can be avoided by using a
different mode. The conditions that affect the dynamic behaviour of the load in transient operation
also lead to instability, and some of the suggest ions in the s ect ions below may be found helpf ul.
Many supplies have L-C output filters to reduce noise; these introduce extra phase shif t int o t he
overall source and load combination and can increase the possibility of instability. If there is no
damping across the inductor, a resonant circuit can be formed which allows oscillations to build
up to significant amplitude.
9.2.1 Remedial Actions
The compensation networks of t he power stages in the load ar e c hanged when the Slew Rate is
set to less than 0.001 times the maximum slew rate for the given load mode and range. For
example if constant current mode is selected, t he m aximum s lew rate set ting is 500A/ms, hence
the compensation networks are changed at s lew rates set tings below 500A/s. Even if the
transient facilities are not being used, this change in compensation reduces the bandwidth and
may make the source and load combination stable.
If instability arises, observe the voltage waveform across the load with a scope: if at any point t he
voltage rises above the open circuit emf of the s our ce, then there must be an inductive element
present to form a resonant c ir cuit . Som e m eans must be found to insert damping into this circuit .
One technique is to use a network consisting of a capacitor and a resistor in series (sometimes
called a Zobel network), across the input term inals of the load. Many electronic loads have such
a network built-in; it is omitted f r om t his load t o m aximise its versatility by offering t he lowest
possible input capacitance. It can be added externally: values around 2·2µF and 5Ω are
common, but note that this mus t be a non-inductive power resistor capable of dissipating a few
watts. A flat film type is best – wire wound resistors are not suitable.
9.3 Dynamic Behaviour in Transient Operation
When the transient capabilities of the load are used, the dynamic behaviour of the source and
load combination during the transitions depends on similar consider at ions t o those affecting
stability: series inductance, shunt capacitance and feedback loop characterist ics. Pr oper
operation depends on the load neither saturating nor cutting off at any point in the cycle. The
faster the slew rate sought, t he more likely it is that aberrations will occur on the transitions.
Because of changes in the transconductance of the FETs, the dynamic behaviour of the power
stages changes at both low and high currents, and also at low voltages when the inter-electrode
capacitance increases considerably. In general, behaviour is optimum at the lower end of the
current range (100mA to 4A) and at voltages > 25V.
Attempting to achieve a slew rate beyond the capabilities of a source and load combination can
result in substantial overshoot and ringing. Reducing t he slew rate, som et im es by jus t a small
amount, will often improve the response considerably.
29
9.3.1 Source Characteristics
The purpose of transient t est ing is to examine the behaviour of any feedback loops within the
source. If the response of the source is under-damped, then in general the use of an active load
will accentuate the effect. This is particularly true in the modes where the load responds to
changes in voltage. At particular transient frequencies (particularly higher fr equencies) the load
may excite resonances in L-C filters or match t he nat ur al frequency of a feedback loop. This can
result in considerable reaction from t he s our ce, possibly to the extent of causing damage.
Mechanical generators have substantial inductance, mechanical inertia and slow response times.
Transient response testing of such sources should only be attem pted at low slew rates.
9.4 Start-up transients
There are two different start-up condit ions t o cons ider depending on whether the source or the
load is switched on first.
If the source is switched on first and the load enabled afterwards then the start-up may have a
small transient, but this will not g ener ally exceed the mag nit ude of the Level setting, except at
very low current settings. This transient can be controlled by selecting Slow Start and setting a
gentle Slew Rate.
In the other case, when the load is enabled before the sour ce is switched on, much larger
transients can be generated. The reason for t his is t hat as soon as the load is enabled the
internal feedback loop will attempt to conduct t he c ur r ent demanded by the level setting. In the
absence of a source voltage this will result in the gate drivers applying maximum bias voltage to
the power FETs, reducing their resistance to minimum (<500mΩ) in an attempt to force a current
to flow. This is the condition that produces t he Low Voltage warning on the status line of the
display. When the sour ce is s witched on and starts to pr oduce a voltage it will initially see this
500mΩ load, which will cause a significant current trans ient unt il the feedback loop has time to
respond and reduce the bias on the FETs. There are two means to reduce this. One is t o use the
Slow Start facility with a non-zero setting of the Dropout Voltage to ensure that the load does not
attempt to conduct until the sourc e voltage is present, and then set the Slew Rate to control the
initial transient. The second is to use Constant Resistance (CR) mode, when zero source voltage
should cause zero current to flow. Because of the tolerance on internal offset voltages it m ay be
necessary to set the Dropout Voltage to a small value (a few tens of mV) to ensure that t he unit
does not enter the Low Voltage saturation condition (the yellow lamp also indicates this).
If it is desired to test t he start-up behaviour of a power supply, the best approach is to use a small
auxiliary supply to pre-bias the load into conduction, together with series isolating diodes to
cause the load current to transfer from this bias supply to the supply under test when it starts to
produce its output voltage.
9.5 Characteristics of each Operating Mode
The following sections give a brief descript ion of the way each mode is implemented, and give
some guidance of the effect that has on the application of the load.
The unit has two power stages (each a large FET) in parallel. Local current feedback around
each stage ensures equal power sharing, with overall current feedback to an earlier stage used
to enhance accuracy. This architecture provides fundamentally a constant current sink. Ideally
the operation of the power stages would be independent of the applied voltage, but in pr actice,
both the gain and the inter-electrode capacitance of t he FETs vary with operating point,
particularly at low voltages (below about 25V) and at either low or hig h c ur r ents. This results in
slower response and different stability conditions and dynamic behaviour in these regions,
whatever the operating mode.
The other operating modes first derive the current required according t o the instantaneous
source voltage applied and then use the power stages to conduct that curr ent .
30
9.5.1 Constant Current Mode
As described above, this is the fundamental operating m ode of the power stages of this
instrument, so it has the simplest feedback loop and the widest bandwidth. The sensed voltage
signal is only used for the meters and pr ot ection. Constant current mode is normally used in
conjunction with low impedance power supplies, and will be quite stable unless there is significant
inductance in either the interconnections or the source. Becaus e of the wider bandwidth it is
particularly critical to have low inductance connections in this mode.
Note that the load cannot be used in constant current m ode t o t es t a c onstant c ur r ent power
supply, as this combination has only two stable conditions: if the load setting is below the supply
limit then the supply will not be in constant current operation and will deliver its maximum output
voltage, whereas if the load setting is above the limit of t he s upply then the load will saturate at
its minimum operating resistance with the supply delivering its designed current. The best way to
test a constant current supply is to us e the load in constant resistance mode, with a suitable
setting of the Dropout Voltage offset, as described below.
9.5.2 Constant Powe r Mode
Constant Power mode is implemented by using an analogue divider to divide the specified power
setting by the actual sensed voltage to calculate the nec ess ar y curr ent . The power stages then
adjust their conductivity in order to obtain this current. If the source voltage falls then the load will
seek to keep the same power level by reducing its resistance to raise the current. The fact that
the current rises as the voltage falls means t hat the load is acting as a negative resistance. This
behaviour is also exhibited by most switch-mode power supply circuits.
This characteristic raises the possibility of a latch-up condition if the source has a significant
output impedance. To explain this, consider the possibility that the source voltage falls slightly
(perhaps because of noise) – the load responds by increasing the current to maintain the power
level. This causes a further reduc t ion in the terminal voltage of the source (because of its internal
impedance), so the increase in power is less than expected. The load responds to this by
reducing its resistance even more, in an attempt to incr eas e t he cur rent and obtain the required
power . A cross-over point is reached when the fall in voltage outweighs the increase in current
and the load cannot draw the required power. This leads to the latch-up condition, with the load at
its minimum resistance (nearly a short-circuit), the voltage across it almost zero, and the source
is delivering its maximum current into the almost short-circuit load. The status line of the display
will be showing the Low Voltage warning.
If the source impedance is purely resistive then this condition will be triggered when the source
terminal voltage falls to half its open circuit voltage (this is t he m aximum power tr ansfer condition
of classical electrical theory). More co m monly, it will also be triggered imm ediat ely if t he s our ce
reaches a current limit, or enter s c onstant cur r ent operation.
The only way to recover from this situation is to disable either the load input or t he sour c e out put .
The vast majority of electronic sour ces will start in a current and power limited state at power-up,
so, to avoid immediately entering the latch-up condition, it is necessary to use the slow start
facilities of the load to constr ain t he power demand while the source builds up its output voltage.
As Constant Power mode has the characteristics of a negative resistance, the possibility always
exists of forming a negat ive resistance oscillator in com binat ion with the output impedance of the
source. In practice, constant power mode norm ally operates well in conjunction with sources
designed to supply such a load.
In transient operation, if the source is constant voltage (with low source impedance), then t he
current will follow the changes in power demand and the response will be very similar to constant
current mode. If t he s our ce voltage falls as the power demand increases, then (as described
above) the current has to increase more t han pr oportionally and the current slew rate rises; this
will limit the maximum useful power slew rate.
31
9.5.3 Constant Conductance and Resistance Modes
In both these modes, the analogue m ult iplier-divider is used to derive the current required from
the sensed voltage. In Conductance mode the current required is calculated by multiplying the
sensed voltage by the specified conductance; in Resistance mode the cur r ent required is
calculated by dividing the difference between the sensed voltage and the dropout voltage setting
by the specified resistance.
In both cases, the current rises as t he applied voltage rises. At equivalent resistance and
conductance settings, the path from the voltage sense input through to the power stage is the
same, so the two modes will exhibit similar stability characteristics.
In transient operation, the two modes are very different. In Conductance mode, the current
required linearly follows the changing conductance value and the behaviour is fundamentally
similar to constant current mode. In Resistance mode, the required current is inversely
proportional to the linearly changing resistance value, so the resulting current waveform is very
non-linear, changing rapidly at the low resistance part of the cycle. This rapid change
accentuates the effect of inductance in t he interconnecting leads and can easily lead to
bottoming and overshoots. Resistance mode is best used at higher voltages and m odest
currents.
9.5.4 Dropout Voltage and Resistance Mode
The use of the Dropout voltage setting as an offset in Constant Resistance mode allows flexibility
in constructing load characteristics for particular circumstances. For example, setting a low value
of resistance and a significant value of dropout voltage yields a characteristic similar to a string of
LEDs or a Zener diode and provides an alternative to a Constant Voltage mode but without the
extreme stability problems of that mode.
9.6 Multiple Unit Operation
It is possible to operate two loads in parallel in Constant Current mode, which will double both the
current handling and power dissipation capability of a single unit. The connections to the source
should be matched as well as possible.
Note that additional stability issues may arise, because of phase response diff er enc es between
the units; the use of more than two units in parallel is not recommended. Multiple unit operation
should not be attempted in any operating mode ot her than Constant Current.
32
10. Remote Interface Configuration
The LDH400P model can be remotely controlled via its RS232, USB, GPIB or LAN interfaces.
The GPIB interface provides f ull facilities as described in IEEE Std. 488 parts 1 and 2.
The RS232 interface communicates dir ect ly with a standard COM port.
The USB interface enumerates as a Communications Class device and interacts with application
software through a standard virtual COM port device driver on the PC. The instrument firmware
can be updated in the field via the USB port; see the ‘Maintenance’ chapter for details.
The LAN interface is designed to meet LXI (Lan eXtensions for Instrum entat ion) version
1.4 LXI Core 2011. Remote control using the LAN interface is possible using the TCP/IP Sockets
protocol. The instrument also contains a basic Web ser ver which provides infor m ation on the
unit and allows it to be configured from a web browser. Simple command line control from the
browser is also possible.
10.1 GPIB Interface
The standard GPIB interface 24-way connector is located on the instrument rear panel. The pin
connections are as specified in IEEE Std. 488.1-1987 and the instrument complies with both
IEEE Std. 488.1-1987 and IEEE Std. 488.2-1987.
It provides full talker, listener, service request, serial poll and parallel poll capabilities. There are
no device trigger or controller capabilities. The IEEE Std.488.1 interface subsets provided are:
SH1, AH1, T6, L4, SR1, RL2, PP1, DC1, DT0, C0, E2.
The GPIB address of the unit is set from the front panel: fr om the Home screen select the
Utilities menu then Interface Settings. The present GPIB addr ess is displayed. I f it needs to be
changed, use the rotary knob to set t he desir ed addr ess and t hen pr es s t he Confirm soft-key.
The interface will operate with any commercial GPIB interface card, using the device drivers and
support software provided by the manufacturer of that card.
10.2 RS232 Interface
The 9-way D-type serial interface connector is located on the instrument rear panel. It should be
connected to a standard PC port preferably using a fully wired 9-way 1:1 male-female cable
without any cross-over connections. Alternatively, a 3-way cable can be used, connecting only
pins 2, 3 and 5 to the PC, but with links made in the connector at t he PC end between pins 1, 4
and 6 and between pins 7 and 8, as shown in the diagram:
Most commercial cables provide these connections.
In addition to the transmit and receive data lines, the instrum ent passively asserts pins 1 (DCD)
and 6 (DSR), actively drives pin 8 (CTS) and monitors pin 4 (DTR) fr om the PC. This allows the
use of a fully wired 9-way cable.
The Baud Rate for this instrument is fixed at 9600; the other parameters are 8 data bits, no parity
and one stop bit. Flow control uses the XON/XO FF pr ot ocol, but because of the low volume of
data associated with this instrument it is very unlikely that flow control will actually be invoked.
33
10.3 USB Interface and Device Driver Installation
The instrument firm ware can be updated in t he field through the USB port. This does not need
the driver described here. It requir es a PC sof t ware utility provided by the manuf acturer, and uses
a HID driver that will already be installed on the PC. If that is the only USB functionality required,
download the package containing the fir m ware update t ogether with the PC utility from the
manufacturer, and follow the instructions included.
Using the USB interface for r em ot e c ont r ol r equires a Communications Device Class driver on
the PC to provide a virtual COM port instance. In Windows a suitable driver is provided by
Microsoft, but it is not installed by default. The data (.INF) f ile to control the installation is provided
on the Product Documentation CD delivered with the unit; however the same driver is also used
by many other instruments from this manufacturer and may already be known to the PC.
To install the driver for the first time, first switch the unit on, and then connect the USB port to the
PC. The Windows plug and play functions should automat ically recog nise t he attachment of new
hardware to the USB interface and (possibly after sear c hing the internet for some time) prompt
for the location of a suitable driver. Follow the Windows prompts and point to the CD, then the
sub-directory for this product, and then to the USB Driver sub-directory below that. The file is
named USB_ARM_VCP_xxx.INF, where xxx is a version number. (A readme.pdf file will also be
found in that directory if further assistance is needed.)
In some cases Windows will not complete this procedure (especially recent versions which
search the internet first , looking for the unique Vendor ID and Product ID), in which case the
instrument will show in Device Manager as “not working properly”. If this happens, s elect t his
device, right click and choose “update driver soft ware.. . ” and then “browse this computer for
driver software...” and then locate the . I NF file on the CD as described above.
Once Windows has installed the device driver it will assign a COM port number to this particular
unit. This number will depend on previous COM port assignments on this PC, and it may be
necessary to use Device Manager to discover it. Each instrument has a unique USB identif ier
which is remembered by the system, so it will receive the same COM port number whenever it is
attached to the same PC (regardless of the physical interface socket used), even though t he
COM port will disappear while the instrument is disconnected or switched off. Other instrum ents
will receive different COM port numbers. Note that a different PC will not necessarily assign the
same COM port number to a particular instrument ( it depends on t he hist or y of installations),
however Device Manager can be used to change the assignments given.
This virtual COM port can be driven by Windows applications (including a term inal emulat or ) in
exactly the same way as any standard COM port, except that the Baud rate and other settings
are unnecessary and are ignored. Some old applications might not function with COM port
numbers 3 or 4, or above 9. In this case, use Device Manager to chang e the allocation given.
Once it is installed, the driver will be maintained by Windows Update in the usual way.
10.4 LAN Interface
The LAN interface is designed to comply with the LXI standard version 1. 4 LXI Core 2011 and
contains the interfaces and protocols described below. For more information on LXI standards
refer to www.lxistandard.org
When powered up and attached t o a net work , the unit will by default attempt to obtain IP address
and netmask settings via DHCP, or, if DHCP tim e s ou t (after 30 seconds), via Auto-IP. In the
very unlikely event that an Auto-IP address cannot be found a st atic IP address is assigned; the
default is 192.168.0.100, but t his can be changed on the web page. Connecting via a router is
recommended as this is significantly quicker to assign an IP address; connecting directly to a PC
will only begin to assign an Auto-IP address after the 30 second DHCP timeout.
.
34
Since it is possible to misconfigure the LAN interface, making it impossible to communicate with
the instrument over LAN, a LAN Configur at ion I nit ialise (LCI ) m echanism is pr ovided via a push
switch (marked LAN reset) accessible throug h a sm all hole in the r ear panel. This restores the
then the LAN status indicator is .
for DHCP. The LAN status indicator is animated, flashing between and
display becomes
use by another device. Communication is not possible and the display shows
default configur at ion with DHCP enabled, so the unit will then follow the sequence described in
the previous paragraph. Note that reset t ing the LAN interface removes any password protection.
The progress of establishing a LAN connect ion can be viewed either by inspecting the I nterface
Settings menu (from t he home screen press Utilities then Interface Settings) or by interpreting
the symbol shown on the status line of the home screen, which has four poss ible indications:
No LAN If the unit cannot detect any connection t o a LAN, e. g. the cable is unplugged,
Configuring The unit has detected a LAN connection but is not yet configured, e.g. is waiting
LAN OK The LAN connection is now configured and the unit can communicate. The
LAN FAULT The unit has detected a problem with LAN connection, e.g. Its IP address is in
10.4.1 LAN IP Address and Hostname
To communicate with the instrument through the LAN interface, the IP address (which was
allocated during the connection procedure described above) must be known. Once connected
and correctly configured, the IP address of the unit is displayed within the interface setting s m enu
(press Home, then select t he Utilities menu then Interface Settings). Alternatively the address
can be obtained from the DHCP server, or by using the LXI Discovery Tool described below.
10.4.2 mDNS and DNS-SD Support
The instrument supports these multicas t nam e r es olut ion prot oc ols, which allow a meaningful
host name to be assigned to the unit without needing an ent r y in the database of a central
nameserver. The desired hostname can be entered on the webpage (which will have to be
accessed by IP address the first time); spaces are not allowed. The name then appears in t he
.local domain (e.g. myLDH400.local), if t he ac ces sing device is configured to support the protocol
(which is the case with most modern PCs). The default name is t followed by the serial number.
10.4.3 ICMP Ping Server
The unit contains an ICMP server allowing the instrument to be ‘pinged’ using its IP address as a
basic communication check, or by its host name if name resolution is working.
10.4.4 Web Server and Configuration Password Protection
The unit contains a basic web server. This provides information on the inst rument and allows it to
be configured. The Configure and Instrument Control pages can be password protected to deter
unauthorised changes to the remote oper ation configuration; the default configuration is ‘no
password’. The Configure page itself explains how to set the password. The password can be up
to 15 characters long; note that the User Name should be left blank. The password and
hostname will, however, be reset to the def ault ( no password) if the rear panel LAN reset switch
is used to reset all the LAN parameters to their factory default.
10.4.5 LAN Identify
The instrument's main web page has an 'Identify' function which allows the user to send a
command to the instrument which causes its display to flash until the command is cancelled.
10.4.6 LXI Discovery Tool
This tool can be used to display the IP addresses and other associated information of all
connected devices that comply with the VXI-11 discovery protocol. It is a Windows PC
application, which is provided on the supplied CD-ROM, that can be installed and run on the
controlling PC, with the unit either connected directly to the PC network connec t or or via a router.
Double clicking on any entry in the list of discovered devices will open the PC's web browser and
display the Home page of that device. For a later version of t he tool that supports discovery by
both VXI-11 and mDNS visit www.lxistandard.org
35
. There are also tools f or LAN discovery
included as part of the National Instrum ent s Measurement and Automation Explorer package and
the Keysight Vee application.
10.4.7 VXI-11 Discovery Protocol
The instrument has very limited support of VX I-11 which is sufficient for the discovery protocol
and no more.
It implements a Sun RPC Port-mapper on TCP port 111 and UDP port 111 as defined in
RFC1183. The calls supported are:
NULL, GET PORT and DUMP.
On TCP port 1024 a very simple VXI-11 protocol is implemented, sufficient only for instrument
discovery. This implements the following calls:
CREATE LINK, DEVICE_WRITE, DEVICE_READ and DESTROY_LINK.
Once a link has been created anything written to the device is ignored and any att em pt to read
from the device returns the sam e ident ification string as the *IDN? query.
10.4.8 VISA Resource Name
Because of the limited support f or VXI-11 (Discovery Protocol only), the instrument must be
referred to by its raw socket infor mation when used with software packages which communicate
using a VISA resource name. For example, an instrument at IP address 192.168.0.100 would
normally have a VISA resource name of "TCPIP0::192.168.0.100::inst0::INST R" but for this
instrument the name must be modified to read "TCPIP0::192.168.0.100:: 9221::SOCKET" where
9221 is the TCP port used by this instrument for control and monitoring , see below.
10.4.9 XML Identification Document URL
As required by the LXI standard, the instr um ent provides an XML identification document that
can be queried via a GET at “http://IPaddress:80/lxi/identification” that conforms t o t he LXI XSD
Schema (available at http://www.lxistandard.org/InstrumentIdentification/1.0
Schema Standards ( http://www.w3.org/XML/Schema ). This document describes the instrument.
The hostname can be used instead of the IP address if name resolution is working.
10.4.10 TCP Sockets
The instrument uses 2 sockets on TCP port 9221 for instr um ent control and monitoring. Text
commands are sent to this port as defined in ‘Remote Commands’ and any replies are returned
via the same port. Any command string must contain one or more complete commands. Multiple
commands may be separated with either semicolons “;” or line feeds . No final terminator is
required, since the TCP frame implies a terminator, but one may be sent if desired.
10.5 Interface Locking
All the remote interf ac es ar e live at all times, to remove any need to select the active interface
and to ensure that the LAN interface is always available (as demanded by the LXI standard). To
reduce the risk of the inst r um ent being inadvertently under the control of two interfaces at onc e a
simple lock and release mechanism is provided in the instruction set. The lock is automatically
released where it is possible to detect disconnection, or when the
to the interfaces may also be restr ict ed using the web pages.
Any interface may request to have exclusive control of the inst r um ent by sending an “IFLOCK 1”
command. The lock may only be released by sending an “IFLOCK 0” com m and from the
interface instance that currently has the lock, and may be queried from any interfac e by sending
an “IFLOCK?” command. The reply to this query will be “ -1” if the lock is owned by another
interface instance, “0” if the interface is free and “1” if t he lock is owned by the requesting
interface instance. Sending any command f r om an int er face without control privileges that
attempts to change the instrum ent stat us will set bit 4 of the Standard Event Status Register and
put 200 into the Execution Error Register to indicate that there are not sufficient privileges f or t he
required action.
) and the W 3C XML
Local key is pressed. Access
36
Note: it is also possible to configure t he pr ivileges for a particular interface to either ‘read only’ or
‘no access’ from the Web page interface.
Bit 7
Fault trip: the input has been disabled by one of t he har dware fault detectors.
Bits 6-3
Not used, permanently 0.
limit specified by the user.
exceeded the limit specified by the user.
Bit 0
Not used, permanently 0.
11. Status Reporting
The standard status and error reporting model described in IEEE Std. 488.2 was designed for the
GPIB interface and contains some f eat ur es intended for use with the Service Request and
Parallel Poll hardware capabilities of that interface, and to accom m odate its semi-duplex
operation. Although those facilities are of little use with other interf aces , t his inst rument makes
the full set of capabilities available to all of the interfaces. A separate set of many of the status
and error registers is m aintained f or eac h pot ent ial inter face instance. The GPIB, USB and
RS232 interfaces each provide a single instance, while the LAN interface provides three: one for
the Web page and one each for t he two TCP socket interfaces . Having a separat e s tatus m odel
for each interface instance ensures t hat data does not get lost, as some status query commands
(e.g. ‘*ESR?’) clear the contents of a register after reading the pr esent value.
The full set of err or and stat us r egisters and the individual bits they contain is shown in the Status
Model Diagram and described in detail below, but in brief the status is maintained using four
primary registers, the Input State Register, the Input Trip Register, the Standard Event Status
Register and the Execution Error regist er. A summary is reported in the Status Byte Register, as
selected by three masking regist er s – the Input State Enable Register, the Input Trip Enable
register and the Standard Event Status Enable Register. Two further mask registers, the Service
Request Enable register and the Parallel Poll Response Enable register, control operation of t he
GPIB hardware Service Request and Parallel Poll (and the associated ist mes sage) respectively.
It is recommended that, when controlling t he unit t hr ough any interface other than GPIB, the
controller program should simply read the primary status registers directly.
The instrument specific Input State and Input Trip Registers record events related to the electrical
function of the load and its interaction with the sour ce under test.
The Standard Event Status Register, supported by the Execution Error and Query Error registers,
records events concerned with command parsing and execution, and the flow of com m ands,
queries and responses across the interface. These are mainly of use during software
development, as a production test procedure should never gener ate any of these errors.
11.1 Input State and Input Trip Registers (ISR & ISE and ITR & ITE).
These two registers report elect r ical conditions that have arisen during the operation of the load.
By their nature they are common to all interfaces .
The Input Trip Register reports events that have resulted in the unit unexpectedly disabling the
load input.
The Input State Register reports the present state of t he power stage of the load in the same way
as the green and yellow lamps on the front panel and the status line of the display.
Each of these registers has a s um m ar y bit in the Status Byte Register, with an associated Enable
Register to determine which, if any, bits contribute to that summary. All these registers are bit
fields, where each bit is independent (so more than one may be set simultaneously) and has the
significance detailed below.
11.1.1 Input Trip Register (ITR)
Bit 2
Bit 1
The bits in the Input Trip register are set when the event they report occurs, and then r em ain set
until read by the ITR? query. After the Response Message is sent any bits reporting conditions
37
Over Current protect: the input has been disabled because the current exceeded the
Over Voltage protect: the input has been disabled because the applied voltage
difference, or fan failure.
Bits 6-5
Not used, permanently 0.
Bit 4
Not used, permanently 0.
Corresponds to the Dropout warning in the display.
Corresponds to the Power Limit warning in the display.
Corresponds to the Low Voltage warning in the display.
Bit 0
Input Disabled: Reports the present state of the input enable setting.
Bit 7
Power On. Set when power is first applied t o t he inst r ument.
Bits 6, 3 & 1: Not used, permanently 0.
The parser is reset and parsing continues at the next byte in the input s t r eam .
register, if a syntactically correct command cannot be executed for any reason.
commands and read response messages in the c or r ect sequence.
Bit 0
Operation Complete. Set in response t o the ‘*OPC’ command.
that no longer apply will be cleared; any bit reporting a condition that remains t r ue will remain set.
The Input Trip Enable Register provides the mask between the Input Trip Register and the Status
Byte Register. If any bit becomes ‘1’ in both registers, then the INTR bit (bit 1) will be set in the
Status Byte Register. This enable register is set by the ITE <NRF> command to a value 0 - 255,
and read back by the ITE? query (which will always return the value last set by the controller). On
power-up the ITE register is set t o 0 and ITR is cleared (but bits it contains may be set after
initialisation in the unusual case of any of the conditions report ed being true).
11.1.2 Input State Register
Bit 7
Bit 3
Bit 2
Bit 1
The bits in the Input State Register continually reflect the present state of the condition they
report. The register can be read by the ISR? q uer y, but this does not change the state of the
contents. On power-up it is normally set to 1 (input disabled), unless t he power up option on the
Utilities menu has been set to retain the previous state.
The Input Status Enable register provides a mask between the Input Status Register and the
Status Byte Register. If any bit becomes ‘1’ in both registers, then the INST bit (bit 0) will be set in
the Status Byte Register. This enable register is set by the ISE
0 - 255, and read back by the ISE? query (which will always return the value last set by the
controller). On power-up it is set to 0.
Fault condition: One or more of the hardware detectors is reporting a fault condition.
Caused by excess temperature, input voltage, internal to external sense voltage
Voltage below Dropout: the load is not conducting cur rent because the source
voltage is below the dropout voltage setting.
Input nonlinearity: the load is not conducting the current expected because the
power limit circuit is restricting it.
Input saturation: the load cannot conduc t t he c ur r ent required because there is
insufficient voltage from the source.
<NRF> command to a value
11.2 Standard Event Status Regis ters (ESR and ESE)
The Standard Event Status Register is defined by the IEEE Std. 488.2 GPIB standard. It is a bit
field, where each bit is independent and has the following signif icance:
Bit 5
Bit 4
Bit 2
The Standard Event Status Register is read and cleared by the *ESR? query, which returns a
decimal number corresponding to the cont ents. On power-up it is set to 128, to report the
power-on bit.
38
Command Error. Set when a syntax error is detected in a command or parameter.
Execution Error. Set when a non-zero value is written to the Execution Error
Query Error. Set when a query error occurs, because the controller has not issued
0
No error has occurred since this regist er was last read.
cause can be determined by reading the Input Trip and State Registers.
command in the present circumstances.
This error can be avoided by turning the input O FF before sending the command.
103
Recall Error: the store specified in a RECALL command does not contain valid data.
interface which is locked out of write privileges by a lock held by another int er face.
Bits 7, 3 & 2: Not used, permanently 0.
as the condition is true.
Register correspond to bits set in the Standard Event Status Enable Register.
The bit will be cleared after the Response Message Terminator has been sent.
correspond to bits set in the Input Trip Enable Register.
correspond to bits set in the Input Status Enable Register.
The Standard Event Status Enable Register provides a mask between the Event Status Register
and the Status Byte Register. If any bit becomes ‘1’ in both registers, then the ESB bit will be set
in the Status Byte Register. This enable register is set by the *ESE
0 - 255, and read back by the *ESE? query (which will always return the value last set by the
controller). On power-up it is set to 0.
11.3 Execution Error Register (EER)
This instrument specific register contains a number representing the last comm and pr oces sing
error encountered over this interf ace. The error numbers have the following meaning:
<NRF> command to a value
100
101
102
200
The Execution Error Register is read and cleared using t he ‘EER?’ command. On power up this
register is set to 0 f or all inter face instances.
There is no corresponding mask r egister: if any of these errors occ ur s, then bit 4 of the Standard
Event Status Register will be set. This bit can be masked from any further consequences by
clearing bit 4 of the Standard Event Status Enable Register.
Enable Error: For some reason, the input enable command cannot be executed. The
Numeric Error: the parameter value sent was outside the permitted range for the
Interruption Error: the input has been disabled in order to execute a command (e.g.
a mode or range change) which cannot be performed while the input is enabled.
Access Denied: an attempt was made to change the instrument’s settings from an
11.4 Status Byte Register (STB) and GPIB Service Request Enable Register ( SRE)
These two registers are implemented as r equired by the IEEE Std. 488.2.
Any bits set in the Status Byte Register which correspond to bits set in the Service Request
Enable Register will cause the RQS/MSS bit to be set in the Status Byte Register, thus
generating a Service Request on the bus.
The Status Byte Register is read either by the *STB? query, which will return MSS in bit 6, or by a
Serial Poll which will return RQS in bit 6. The Service Request Enable register is set by the *SRE
<NRF> command and read by the *SRE? query.
Bit 6
Bit 5
Bit 4
Bit 1
Bit 0
39
MSS/RQS. This bit (as defined by IEEE Std. 488.2) contains alternatively the
Master Status Summary message returned in response to the *STB? query, or the
Requesting Service message returned in r es ponse t o a Ser ial Poll.
The RQS message is cleared when polled, but the MSS bit remains set f or as long
ESB. The Event Status Bit. This bit is set if any bits set in the Standard Event Status
MAV. The Message Available Bit. This will be set when the instrument has a
response message form at t ed and r eady to send to the controller.
INTR. The Input Trip Bit. This bit is set if any bits set in the Input Trip Register
INST. The I nput State Bit. This bit is set if any bits set in the Input State Register
ISE
Input Status Enable Register
= 0
ITE
Input Trip Enable Register
= 0
EER
Execution Error Register
= 0
ESR
Standard Event Status Register
= 128 (pon bit set)
QER
Query Error Register †
= 0
ESE
Standard Event Status Enable Register †
= 0
STB
Status Byte Register
= 0
SRE
Service Request Enable Register †
= 0
PRE
Parallel Poll Response Enable Register †
= 0
† Registers marked thus are normally only used thr ough t he GPIB interface.
11.5 GPIB Parallel Poll (PRE)
Complete Parallel Poll capabilities are offered by this instrument as defined in IEEE Std. 488.1.
The Parallel Poll Enable Register (which is set by the *PRE
<NRF> command and read by the
*PRE? query) specifies which bits in the Status Byte Register are to be used to form the ist local
message. If any bit is ‘1’ in both the STB and the PRE then ist is ‘1’, ot her wise it is ‘0’. The state
of the ist messag e can also be read directly by the *IST? query.
The physical layer protocol of the Parallel Poll (determining which data line is to be driven and its
logic sense) is configured by the PPC and PPE commands and released by the PPU and PPD
commands in the manner defined by the standard. The instrum ent im plements passive pull-up on
the DIO lines during Parallel Poll.
11.6 Query Error Register - GPIB IEEE Std. 488.2 Error Handling
These errors are much more likely to occur on the semi-duplex GPIB interface, which requires
the instrument to hold a response until addressed t o talk by the cont roller. All the other interfaces
provide full duplex communication, with buffering in the physical layer which will usually hold a
response from the instrum ent until the controlling software reads it; there is no equivalent of the
GPIB state ‘addressed to talk’, so the instrument is not aware of the actions of the cont r oller
The IEEE 488.2
UNTERMINATED error arises if the instrument is addressed to talk and has nothing
to say, because the response format ter is inactive and the input queue is empty. This will cause
the Query Error bit to be set in the Standard Event Status Register, a value of 3 to be placed in
the Query Error Register and the parser to be reset.
The IEEE 488.2
DEADLOCK error arises if t he r espons e formatter is waiting to send a response
message and the input queue becom es full. This will cause the Query Error bit to be set in the
Standard Event Status Register, a value of 2 to be placed in the Query Error Register and the
response formatter t o be reset, discarding the waiting response message. The parser will then
start parsing the next
The IEEE 488.2
message and a
<PROGRAM MESSAGE UNIT> from the input queue.
INTERRUPTED error arises if the response formatter is waiting to send a response
<PROGRAM MESSAGE TERMINATOR> has been read by the parser, or the input
queue contains more than one END message. This will cause the Query Error bit to be set in t he
Standard Event Status Register, a value of 1 to be placed in the Query Error Register and the
response formatter t o be reset, discarding the waiting response message. The parser will then
start parsing the next
<PROGRAM MESSAGE UNIT> from the input queue.
11.7 Power on Se ttings
The following instrument status values are set at power on:
The Input State (ISR) and Trip (ITR) Reg ist er s will report any conditions which presently apply.
The instrument will be in local state with the keyboard active. The instrument parameters at
power on are the same as at the last switch off, except for possibly the input enable state, which
by default is always off at power on, but may be configured by the user to be t he s am e at power
on as at the last switch off.
40
Set
Query
Name
†
*ESR?
Standard Event Status Register
11.8 LDH400P Status Model
11.9 Register Summary
† ITR? Input T rip Register
ITE ITE? Input Trip Enable Register
ISR? Input State Register
ISE ISE? Input State Enable Register
† EER? Execution Error Register
† QER? Query Error Register
*ESE *ESE? Standard Event Status Enable Register
*STB? Status Byte Register
*SRE *SRE? Status Byte Enable Register
*PRE *PRE? Parallel Poll Response Enable Register
† These registers are cleared after being queried, or by the *CLS command.
41
12. Remote Commands
12.1 Remote and Local Operation
At power-on the instrument will be in the local state, with normal keyboard operation possible. All
remote interfaces are act ive and listening for a remote command. When any command is
received from any interface the inst r um ent will enter the r em ote state. In this state the keyboard
is locked out, the display switches to the home screen, with R E M O T E displayed in place of
the soft-key tabs. The instrument may be retur ned t o the local state by pressing the
however the remote state will be immediately re-entered if the instrum ent is addressed again or
receives another command from any interface. It is the responsibility of the user to avoid any
conflict if parameters are c hanged from the front panel while in the Local state.
12.2 Remote Command Handling
Each remote control interface has a separate input queue which is filled, under interrupt, in a
manner transparent to all other instrument operations. The RS232 interface implements flow
control by sending XOFF when the queue contains approximately 200 character s , and then XON
when about 100 free spaces become available. All the other interfaces have standard automatic
flow control mechanisms built into their physical layer communication protocol.
Commands are taken from t he input queues by the parser as available. Commands and queries
from each queue are executed in order, but the order of execution of commands from different
interfaces is not defined and should not be r elied upon. It is strongly recommended that use
should be made of the interface locking facilities described above. The parser will not start a new
command until any previous command or query is complete. Responses are s ent t o t he int er face
which issued the query. There is no internal output queue, so on t he GPIB interface the response
formatter will wait, indefinitely if necessary, until the complete response message has been read
by the controller, before the parser is allowed to start the next command in the input queue. On
all other interfaces the response m ess age is immediately sent into buffers in the physical layer.
Local key;
12.3 Remote Command Formats
Commands are sent as <PROGRAM MESSAGES> by the controller, each consisting of zero or more
<PROGRAM MESSAGE UNIT> elements, separated (if there is more than one such element) by
<PROGRAM MESSAGE UNIT SEPARATOR> elements, and finally a <PROGRAM MESSAGE TERMINATOR>.
<PROGRAM MESSAGE UNIT SEPARATOR> is the semi-colon character '; ' ( 3BH).
The
<PROGRAM MESSAGE TERMINATOR>, which separates or terminates <PROGRAM MESSAGES>, is
The
the new line character (0A
may also be used, either with the last character of t he message or with the new line. In the case
of the LAN interface, com m ands m ay not be split acr os s TCP/IP packet boundaries.
A <PROGRAM MESSAGE UNIT> is any of the commands in the remote commands list, which must be
sent in full as specified. A command must be separated fr om any parameters by
(which is defined as the character codes 00H to 20H inclusive, excluding the new line character
0A
H). No <WHITE SPACE> is permitted within any command identifier or parameter, but any other
additional
<WHITE SPACE>, so it cannot be used to delete incorrect characters, and will not hide the error.
<WHITE SPACE> is ignored. Note that the Backspace character (07H) is treat ed as
The high bit of all characters is ignored and all commands are case insensitive. Commands that
require a numeric a parameter accept t he free form
as Character Program Data <
<NRF> numbers must be in basic units, may have a decimal point and fr ac t ional part, and can
include an exponent part if helpful. They are rounded to the precision supported, so (for transient
frequency) the numbers 10000, 10e3 or 9999. 99 all res ult in 10. 00kHz.
H), but in the case of the GPIB int er face the hardware END message
CPD> as specified.
<WHITE SPACE>
<NRF> format; t ext parameters must be sent
42
the Default value, which gives the best accuracy of the level settings.
The response is: MODE <CRD><RMT> where <CRD> can be C, P, R or G.
A <NRF>
Set Level A to <NRF>. The units are implied by the present load mode.
B <NRF>
Set Level B to <NRF>. The units are implied by the present load mode.
12.4 Command Timing
There are no dependent parameters, coupled parameter s , overlapping com mands, expression
program data elements or compound command program headers. Note, however, that the
MODE command sets standard values for Level A, Level B, Range and the Slew Rate, so these
must be explicitly set afterwards. Alternatively it is possible to use the store and recall facilities of
the instrument to quick ly retr ieve a complete s et-up of an operating mode and its values.
All commands are separate and sequential, and are executed when parsed and immediately
considered complete. To provide useful functionality, the Operation Complete bit ( bit 0) in the
Standard Event Status Register is only ever set by the *OPC command. Either the *OPC
command or the *OPC? query can be used f or device synchronisation due to the sequential
nature of remote operat ions.
The actual electrical response to changes in load settings is subject to the present slew rate
setting, but that is considered t o be an as pect of normal operation and not part of the command
execution time. If a slow slew rate is in use the V? and I? queries can be used to c heck progress.
12.5 Response Formats
Responses from the instrument to the controller are sent as <RESPONSE MESSAGES>, which
consist of one
which is the carriage return character ( 0D
case of GPIB only, the
<RESPONSE MESSAGE UNIT> followed by a <RESPONSE MESSAGE TERMINATOR>,
END message NL^END. This is shown as <RMT> in the descriptions below.
H) followed by the new line character (0AH) with, in the
Each query produces a specific
<RESPONSE MESSAGE> which is described in the entry for the
query command in the remote commands list below. Most responses consist of a keyword
followed by either text or a number in one of the f ollowing f or m ats:
<NR1> An integer without a decimal point or a unit.
<NR2> A fixed point number with a fractional part but no exponent part.
<NR3> A floating point number with both a fract ional part and an exponent part .
<
CRD> Charact er Respons e Data, consist ing of the text characters listed.
When helpful, num ber s ar e followed by a units indication (which depends on the present load
mode) to provide confirmation. The units used are: A, V, W, OHM, SIE & HZ (SIE is conductance
in Siemens, or A/V .) Slew rates are expressed the basic unit (of the active mode) per s econd,
with an exponent (which is always positive, with E+03 representing kUnits/s or Units/m s , and
E+06 representing MUnits/s or Units/us).
12.6 Command List
This section lists all the commands and q uer ies im plemented in this instrument. All numeric
parameters are shown as
Command parameters (unlike respons es) ar e not followed by a units indication.
12.6.1 Instrument Function Commands
MODE <CPD> Set the load mode to <CPD>.
Where
resistance, conductance or voltage.
<NRF> and may be sent as <NR1>, <NR2> or <NR3> as described above.
<CPD> can be C, P, R, or G, corresponding to constant current, power,
The input will be automatically disabled if not previously done.
This command also sets both the Level A and Level B settings to 0 for all
modes except CR, when they are both set to 10kΩ, and sets the Slew Rate to
MODE? Returns the load mode selected.
43
where the <NR2> is followed by a unit’s suffix determined by the load mode.
where the <NR2> is followed by a unit’s suffix determined by the load mode.
DROP <NRF>
Set the Dropout Voltage level to <NRF>, in Volts.
The response is: DROP <NR2>V<RMT> where <NR2> is in Volts.
exponent as required.
determined by the present load mode and an exponent part as required.
SLOW <NRF>
Set Slow Start facility on or off, where <NRF> has the meaning: 0=Off, 1=On.
The response is: SLOW <NR1><RMT> where <NR1> is either 0 (=Off) or 1 (= On)
corresponding to Level A, Level B, Transient, Ext Voltage and Ext TTL.
corresponding to Level A, Level B, Transient, Ext Voltage and Ext TTL.
FREQ <NRF>
Set the Transient Frequency to <NRF>, in Hz.
The response is: FREQ <NR2> HZ <RMT> where <NR2> is in Hz.
DUTY <NRF>
Set the Transient Duty Cycle (%A) to <NRF>, in percent (rounded to integer).
The response is: DUTY <NR1>%<RMT> where <NR1> is a percentage.
VLIM <CPD>
VLIM NONE disables and removes any voltage limit.
VLIM 0V<RMT> if no voltage limit is set.
ILIM <CPD>
ILIM NONE disables and removes any current limit.
ILIM 0A<RMT> if no current limit is set.
INP <NRF>
Set the input on or off where <NRF> has the meaning: 0=Off, 1=On.
The response is INP <NR1><RMT> where <NR1> is either 0 (=Off) or 1 (= On).
The response is <NR2>V<RMT> where <NR2> is in Volts.
The response is <NR2>A<RMT> where <NR2> is in Amps.
A? Return the s et Level of Level A.
The response is: A
<NR2>U<RMT>
B? Return the s et Level of Level B.
The response is: B
<NR2>U<RMT>
DROP? Returns the set Dropout Voltage level.
SLEW <NRF> Set the Slew rate to <NRF>, in unit/s (units of the present Load Mode) using an
SLEW? Returns t he s et Slew rate.
The response is: SLEW
<NR3>U<RMT> where <NR3> is in Unit/s with the Unit
SLOW? Returns the setting of the Slow Start facility.
LVLSEL <CPD> Set the Active Level Select to <CPD> Where <CPD> can be A, B, T, V or E
LVLSEL? Returns the Level Select state.
The response is: LVLSEL
<CRD><RMT> Where <CRD> can be A, B, T, V or E
FREQ? Returns the set Transient Frequency.
DUTY? Returns the set Transient Duty Cycle (%A).
VLIM <NRF>
Set the Voltage Limit to <NRF>. Either VLIM 0 or alternatively
VLIM? Returns the Voltage limit. The response is:
VLIM
<NR2>V<RMT> where <NR2> is in Volts, or
ILIM <NRF>
Set the Current limit to <NRF>. Either I LI M 0 or alternatively
ILIM? Returns the Current Limit. The response is either:
ILIM
<NR2>A<RMT> where <NR2> is in Amps, or
INP? Returns t he input state.
V? Returns t he measured source input voltage.
I? Returns the measured load current
44
firmware installed.
Does not affect any remote interf ac e settings.
*SAV <NRF>
Save the present set-up to the store specified by <NRF>, where <NRF> is 1-30.
Recalling an empty or invalid store is an execution error.
sequential nature of all operations.
executed because all commands are sequential.
This command does nothing because all operations are sequential.
*TST?
The Load has no self-test capability and the response is always 0<RMT>.
*TRG
The Load has no trigger capability. The command is ignored in this instrument.
Does not clear any Enable Registers.
Does not change the value, which continues to reflect the inst rument condition.
ISE <NRF>
Set the Input State Enable Register to <NRF>
The response is: <NR1><RMT>.
Clears any bits that no longer apply.
ITE <NRF>
Set the Input Trip Enable Register to <NRF>
The response is: <NR1><RMT>.
EER?
Query and clear Execution Error Register. The response format is <NR1><RMT>.
QER?
Query and clear Query Error Register. The response format is <NR1><RMT>.
not by this query, as any previous message must have already been sent.
*SRE <NRF>
Sets the Service Request Enable Register to <NRF>
The response is <NR1><RMT>.
12.6.2 Common Commands
*IDN? Returns the instrument identif icat ion.
The response is in the form < NAME>, <model>, <serial>, <version>
where <NAME> is the manufacturer's name, <m odel> is the instrument type,
<serial> is the interface serial number and <version> is the revision level of the
*RST Resets the functional parameters of t he inst r ument to the default settings as
listed in the Factory Default Settings sect ion.
Does not affect the contents of t he Save and Recall stores.
*RCL <NRF> Recall a set-up from the st or e spec ified by <NRF>, where <NRF> is 1-30.
*OPC Sets the Operation Complete bit (bit 0) in the Standard Event Status Registe r.
This will happen immediately the command is executed because of the
*OPC? Query Operation Complete status.
The response is always 1
<RMT>
<RMT> and is available immediately the command is
*WAI Wait for Operation Complete tr ue.
12.6.3 Status Commands
*CLS Clear Status. Clears all status indications, including the Status Byte.
ISR? Query the I nput State Register. The response is: <NR1><RMT>.
ISE? Returns the value in the value in the Input State Enable Register.
ITR? Query the Input Trip Register. The response form at is <NR1><RMT>.
ITE? Returns the value in the value in the Input Status Enable Register.
*STB? Report the value of the Status Byte. The response is: <NR1><RMT>.
Because there is no output queue, MAV can only be read by a GPIB serial poll,
*SRE? Report the value in the Service Request Enable Register.
45
*PRE <NRF>
Set the Parallel Poll Enable Register to the value <NRF>.
The response is <NR1><RMT>.
The response is 0<RMT> if the local message is false, or 1<RMT> if true.
LOCAL
Go to local. Any subsequent command will restore the remote state.
interface from taking control using the web interface.
the user has disabled this interface from taking control (via the web interface).
ADDRESS?
Returns the GPIB bus Address. The response is <NR1><RMT>.
The response is nnn.nnn.nnn.nnn<RMT>, where each nnn is 0 to 255.
The response is nnn.nnn.nnn.nnn<RMT>, where each nnn is 0 to 255.
The response is <CRD><RMT> where <CRD> is DHCP, AUTO or STATIC.
<CPD>
<CPD> must be one of DHCP, AUTO or STATIC.
address part an <NR1> in the range 0 to 255, (e.g. 192.168.1.101).
an <NR1> in the range 0 to 255, ( e. g. 255.255.255.0).
*PRE? Report the value in the Parallel Poll Enable Register.
*IST?
Returns the state of the ist local message as defined by IEEE Std. 488.2.
12.6.4 Interface Management Commands
IFLOCK <NRF> Set or Clear t he lock requiring the instrument to res pond only to t his int er face,
where
It is an Execution Error (number 200) if the request is denied either because of
conflict with a lock on this or another interface, or the user has disabled this
IFLOCK? Q uer y the status of the interface lock.
The response is:
= 0 if there is no active lock,
= 1 if this interface instance owns the lock or
= -1 if the lock is unavailable either because it is in use by another inter face or
IPADDR? Returns the present IP address of the LAN interfac e, provided it is connected.
If it is not connected, the r es ponse will be the static IP if conf igured to always
use that static IP, otherwise it will be 0.0.0.0 if waiting for DHCP or Auto-IP.
<NRF> has the meaning: 0 = clear and 1 = set the lock.
<NR1><RMT> where <NR1> is
NETMASK? Returns the present netmask of the LAN interface, provided it is connected.
NETCONFIG? Returns the first means by which an IP address will be sought.
The following commands specify the parameter s t o be used by the LAN inter face. Note: a power cycle is
required after these comm ands ar e s ent before the new settings are used (or returned in respons e t o
the queries listed above). The instrument does not attempt to check the validity of the IP address or
netmask in way other than checking that eac h part fits in 8 bits. The rear panel LAN reset switch will
override these commands and restore the defaults as described earlier.
NETCONFIG
IPADDR
<QUAD>
NETMASK
<QUAD>
Specifies the first means by which an IP address will be sought.
Sets the potential static IP address of the LAN interface ( as on t he webpage).
The parameter must be strict ly a dotted quad for the IP address, with each
Sets the netmask to accompany the static IP address of the LAN interface.
The parameter must be strictly a dott ed quad for the netmask, with each part
46
13. Maintenance
The Manufacturers or their ag ents overseas will provide a repair service for any unit developing a
fault. Where owners wish to undertake their own maintenance work, this should only be done by
skilled personnel in conjunction with the Service Guide, which may be obtained directly from the
Manufacturers or their agents overseas.
13.1 Cleaning
If the instrument r equires cleaning use a cloth that is only lightly dampened with water or a mild
detergent.
WARNING! TO AVOID ELECTRIC SHO CK, OR DAMAGE TO THE INSTRUMENT, NEVER
ALLOW WATER TO GET INSIDE THE CASE. TO AVOID DAMAGE TO THE CASE
NEVER CLEAN WITH SOLVENTS.
13.2 Fuses
See section 4.5.
13.3 Calibration
To ensure that the accuracy of the instrument r em ains within specification the calibration must be
checked (and if necessary adjusted) annually. The procedure is detailed in the Service Guide,
which also lists the calibrated test equipment required.
13.4 Firmware Update
The firmware of the instrument can be updated through the USB port using a PC software utility
available from the manufacturer. This uses a HID (human interface device) USB class driver
which will already be installed on any PC with a USB port. Instructions f or t he update procedure
are provided with the PC utility and the firmware file.
13.5 Troubleshooting
If the instrument does not s eem t o be oper ating as expected, check the following before
suspecting a fault.
1. Check that the voltage drop across the int er c onnect ing cables between source and load is
not excessive. The actual voltage at the input terminals of the load must m eet the minimum
operating voltage requirement for the current level expected. Use a DVM to measure the
actual voltage at the terminals.
2. If using a mode other than Constant Current (especially Constant Power) consult the
‘Application Notes’ chapter of this manual for guidance, especially concerning star t-up
conditions and stability considerations.
3. If the Input trips as soon as it is enabled, this is often an indication of instability.
4. If the Dropout facility is not r equired, check that the Dropout Voltage is set to zero.
5. Enter the Utilities menu, perform Restore Factor y Defaults and re-configure fr om s cr atch.
6. Read the whole of this manual carefully, as operation of the load, and its interactions with the
source, can be quite complex.
47
14. Sécurité
Cet instrument est confor m e à la classe de s écur it é 1 de la classification CEI et il a été
conçu pour satisfaire aux exigences de la norme EN61010-1 (Exigences de séc ur it é
pour les équipements électriques de mesure, de cont r ôle et d'utilisation en laboratoire).
Il s'agit d'un instrument de c at égorie II d'installation prévu pour un fonctionnement à
partir d’une alimentation monophasée standard.
Cet instrument a été testé conformément à la norme EN61010-1 et il a été fourni en état de
sécurité d’utilisation. Le présent manuel d'instruc t ions contient des informations et des
avertissements que l'utilisateur doit suivre afin d'as sur er une utilisation sans danger et de
conserver l'appareil dans un parfait état de sécurité d’utilisation.
Cet instrument a été conçu pour être ut ilisé en intér ieur, en environnement de pollution de
deuxième degré à des plages de températures allant de 5 à 40 °C, et à des taux d'humidité
compris entre 20 et 80 % (sans condensat ion) . Il peut être soumis de temps à autre à des
températures comprises entr e + 5 et -10 °C sans dégradation de sa sécurité. Ne pas le faire
fonctionner en présence de condensation.
Il a été conçu pour une utilisation de CAT II (Catégorie de m esure et surtension II) jusqu’à 300 V
CAT II correspond au niveau d’alimentation domestique locale, et se rapporte aux équipements
et appareils portatifs.
Pour ce type d’équipements, 2 500 V est la surtension tr ans it oir e de cr ête maximum pouvant être
tolérée par toute borne d’entrée de charge isolée de la masse sans affecter la sécurité de
l’appareil.
L’utilisation de cet appareil d’une manière non spécifiée par les présentes instructions risque
d'affecter la protection de sécur it é fournie.
Ne pas utiliser l'instrument hors des plages de tension d'alimentation nom inale rec om m andées ni
hors de ses tolérances d'environnement.
AVERTISSEMENT ! CET INSTRUMENT DOIT ÊTRE RELIÉ À LA TERRE
Toute interruption du conducteur de terre du secteur à l' intérieur ou à l'extérieur de l'instrument
rendra l'instrument dangereux. Une inter r upt ion int ent ionnelle est int er dit e. La s écur it é de
l'instrument ne doit pas être annulée par l'utilisation de rallonge sans conduct eur de protection.
Lorsque l'instrument est r elié au sect eur, il est possible que les bornes soient sous tension :
l'ouverture des couvercles ou la dépose de pièces (à l'exception des pièces accessibles
manuellement) risque de mettr e à découvert des pièces s ous tension. L'instrument doit être
débranché de toute source d'alimentation avant d’être ouvert pour un r églage, un remplacement,
des travaux d'entretien ou de réparations quelconque(s) .
Éviter dans la mesure du possible d'effectuer des rég lages, des travaux de réparations ou
d'entretien lorsque l'instrum ent ouvert est branché au secteur. Si cela s'avère toutefois
indispensable, seul un technicien compétent connaissant les risques encour us doit effectuer ce
genre de travaux.
S'il est évident que l'instrument est défectueux, qu'il a été soumis à des dommages mécaniq ues
ou exposé à une humidité excessive ou à une corrosion chimique, la protection de sécurité en
sera affaiblie, et l'instrument ne doit pas êtr e ut ilisé et renvoyé pour être vérifié et réparé.
L’instrument contient à la fois des fusibles encapsulés et des fusibles thermiques s ans
réenclenchement; ceux-ci ne peuvent pas être remplacés par l’utilisateur. Le court-circuitage de
ces dispositifs de protection est inter dit .
Ne pas mouiller l'instrument lors de son nettoyage.
48
Les symboles suivants figurent sur l'instrument ainsi que dans le présent manuel. –
Avertissement se reporter à la docum entat ion j oint e,
une mauvaise utilisation peut endommager l'instrument .
Courant alternatif.
Alimentation secteur OFF (arrêt)
CAT II
l
Catégorie de mesure
et surtension II (300 V)
Masse du châssis.
Alimentation secteur
ON (marche)
Schaden am Gerät verursachen!
l
15. Sicherheit
Dieses Gerät wurde nach der Sicherheitsklasse (Schutzart) I der IEC-Klassifikation und gemäß
den europäischen Vorschriften EN61010-1 (Sicherheitsvorschriften für elektrische Mess-, Steue-,
Regel- und Laboranlagen) entwickelt. Es handelt sich um ein G er ät der Installationskategorie II,
das für den Betrieb von einer normalen einphasigen Versorgung vorgesehen ist.
Das Gerät wurde gemäß den Vorschriften EN61010-1 geprüft und in sicherem Zustand gelief er t.
Die vorliegende Anleitung enthält vom Benutzer zu beachtende Inf or mationen und Warnungen,
die den sicheren Betrieb und den sicheren Zustand des Gerätes gewährleisten.
Dieses Gerät ist für den Betrieb in Innenr äumen der Umgebungsklasse 2 , für einen
Temperaturbereich von +5°C bis +40°C und 20 - 80 % relative Feuchtigkeit ( nicht kondensierend)
vorgesehen. Gelegentlich kann es Temperaturen zwischen −10°C und +5°C ausgesetzt sein,
ohne dass seine Sicherheit dadurch beeinträchtigt wird. Betreiben Sie das G er ät jedoch auf
keinen Fall, solange Kondensation vorhanden ist.
Es wurde für CAT II (Mess- und Überspannungskategor ie I I ) für 300 V-RMS konzipiert. CAT II
bezieht sich auf Messungen an Stromkreisen, die eine direkte Verbindung mit dem
Niederspannungsnetz haben, z. B. Haushaltsgeräte und tragbare Elektrogeräte.
Bei diesem Gerät sind 2500 V die maximale Stoßspannung, die von einer Eingangsklemme in
Bezug auf Erde ohne Beeinträchtigung der Sicherheit toleriert werden kann.
Ein Einsatz dieses Gerätes in einer Weise, die für diese Anlage nicht vorgesehen ist, kann die
vorgesehene Sicherheit beeinträchtigen
Auf keinen Fall das Gerät außerhalb der ang egebenen Nennversorgungsspannungen oder
Umgebungsbedingungen betreiben.
WARNUNG! - DIESES GERÄT MUSS GEERDET WERDEN!
Jede Unterbrechung des Netzschutzleiters innerhalb oder außerhalb des Ger ät es m acht das
Gerät gefährlich. Eine absicht liche Unter br echung ist verboten. Die Schutzwirkung darf durch
Verwendung eines Verlängerungskabels ohne Schutzleiter nicht aufgehoben werden.
Ist das Gerät an die elektrische Versorgung angeschlossen, so können die Klemmen unter
Spannung stehen, was bedeutet, daß beim Entfernen von Verkleidungs- oder sonstigen T eilen
(mit Ausnahme der Teile, zu denen Zugang mit der Hand möglich ist) höchstwahrscheinlich
spannungsführende Teile bloßgelegt weden. Vor jeglichem Öffnen des Gerätes zu Nachstell-,
Auswechsel-, Wartungs- oder Reparatur zwecken, dieses s t ets von sämt lichen Spannungsquellen
abklemmen.
Jegliche Nachstellung, Wartung und Reparatur am geöffneten, unter Spannung stehenden
Gerät, ist nach Möglichkeit zu vermeiden. Falls unvermeidlich, sollten solche Arbeiten nur von
qualifiziertem Per sonal ausgeführt werden, das sich der Gefahren bewusst ist.
Ist das Gerät eindeutig fehlerbehaftet bzw. wurde es mechanisch beschädigt, übermäßig er
Feuchtigkeit oder chemischer Korrosion ausgesetzt, so können die Schutzeinrichtungen
beeinträchtigt sein, weshalb das Gerät aus dem Verkehr zurückgezogen und zur Überprüfung
und Reparatur eingesandt werden sollte.
Das Gerät enthält sowohl eingekapselte Sicherungen als auch eine nicht rückstellbare
thermische Sicherung; diese Sicherungen können vom Benutzer nicht ausgetauscht werden. Es
ist verboten, diese Schutzeinrichtungen kurzzuschließen.
Beim Reinigen darauf achten, dass das Ger ät nicht nas s wird.
Am Gerät werden folgende Symbole verwendet:
Vorsicht! Bitte beachten Sie die beigefügten
Unterlagen. Falsche Bedienung kann
CAT II
Mess- und Überspannungskategorie
II (300V)
Wechselstrom
Netz OFF (aus)
49
Gehäusemasse
Netz ON (ein)
l
16. Sicurezza
Questo strumento appartiene alla Categoria di Sicurezza 1 secondo la classif ica IEC ed è stato
progettato in modo da soddisfare i crit er i EN61010-1 (requisiti di Sicurezza per Apparecchiature
di misura, controllo e per uso in laboratorio). E’ uno strumento di Categor ia I I di installazione e
inteso per funzionamento con un’alimentazione normale monofase.
Questo strumento ha superato le prove previste da EN61010-1 e viene fornito in uno stato di
sicurezza normale. Questo manuale contiene informazioni e avvertenze che devono essere
seguite per assicurarsi di un’operazione sicura e mantenere lo str umento in condizioni di
sicurezza.
Questo strumento è progettato per uso all’interno e in un ambiente d’inquinamento Grado 2,
entro la gamma di temperatur a da 5° C a 40C°, con um idit à r elat iva (non condensant e) di
20% - 80%. Può occasionalmente essere assoggettato a temperature fra + 5° C e −10°C senza
comprometterne la sicurezza. Non usare in presenza di condensazione.
È stato progettato per l’uso CAT II (Misurazione e sovratensione categoria II) a 300Vrms. CAT II
è un livello di alimentazione domestica locale, ad esempio per apparecchi e dispositivi portatili.
Per questo apparecchio, 2500V rappresenta la sovratensione transitor ia di picco mas sim a
tollerabile da ciascun terminale di ingresso del carico in relazione alla messa a terra senza
compromettere la sicurezza.
L’uso dello strumento in maniera non conforme a quanto specificato in q ues t e ist r uzioni potrebbe
pregiudicare la protezione di cui è dotato.
Non usare lo strumento per misurare tens ioni al di sopra dei valori nominali o in condizioni
ambientali al di fuori di quelle specificate.
ATTENZIONE! QUESTO STRUMENTO DEVE ESSERE COLLEGATO A TERRA
Una qualsiasi interruzione sia interna che esterna del collegamento a terra lo rende pericoloso.
E’ proibito interrompere questo collegamento deliberatamente. La protezione non deve essere
negata attraverso l’uso di un cavo di estensione privo del filo di collegamento a terra.
Quando lo strumento è alimentato, alcuni morsett i sono s ot t o tensione e l’apertura dei coperchi o
la rimozione di parti (eccetto quei componenti accessibili senza l’uso di attrezzi) può lasciare
scoperti dei morsetti sotto tensione. L’apparecchiatura deve essere staccata da tutte le sorgenti
di tensione prima di aprirla per regolazioni, manutenzione o riparazioni.
E’ consigliabile evitare, per quanto possibile, qualsiasi operazione di regolazione e di riparazione
dello strumento sotto tensione e, q ualora fosse inevitabile, dette operazioni devono essere
eseguite da una persona specializzata in materia, che sia pienamente conscia del pericolo
presente.
Quando sia chiaro che lo strumento è difettoso, o che ha subito un danno meccanico, un
eccesso di umidità, o corrosione a mezzo di agenti chimici, la sicurezza potrebbe essere stata
compromessa e lo strumento deve essere ritir at o dall’uso e rim andat o indiet r o per le pr ove e le
riparazioni del caso.
Lo strumento contiene sia fusibili di tipo incapsulato che di tipo termico s enza riprist ino; questi
non possono essere sostituiti dall’utente. È vietato cortocircuitare q uesti dispositivi di protezione.
Evitare di bagnare lo strumento quando lo si pulisce.
Sullo strumento e in questo manuale si fa uso dei seguenti simboli.
50
Attenzione - vedere i documenti allegati.
L’uso errato può danneggiare lo strumento.
Corrente Alternata Fondo dello chassis.
Alimentazione OFF (spenta)
CAT II
Misurazione e sovratensione
Categoria II (300V)
alimentazione ON (accesa)
17. Seguridad
Este es un instrumento de Clase Seguridad I seg ún la clasificación del IEC y ha sido diseñado
para cumplir con los requisitos del EN61010-1 (Requisitos de Segur idad para Eq uipos Eléct r icos
para la Medición, Control y Uso en Laboratorio). Es un equipo de Categoría de Instalación II que
debe ser usado con suministro monofásico normal.
Este instrumento se suministra habiendo sido compr obado según la norma EN61010-1. El
manual de instrucciones tiene información y advertencias que deben aplicars e para g ar ant izar la
seguridad del usuario durante su empleo.
Este instrumento ha sido diseñado para ser utilizado en un ambiente Grado 2 de Polución a
temperaturas de entre 5ºC y 40ºC y humedad relativa de entre el 20% y el 80% (sin
condensación). De manera ocasional puede someterse a temper aturas de entre −10ºC y +5ºC
sin que ello afecte a su seguridad. No hay que poner lo en funcionamiento mientras haya
condensación.
Está ideado para su empleo como un equipo CAT II (categoría II de medición y sobretensión)
con tensiones de hasta 300 VRMS. La denominación CAT II se corresponde con la categoría del
suministro eléctrico doméstico (por ej em plo, equipos y aparatos portátiles).
En el presente equipo, el pico de sobretensión máxima transit or ia t olerable por cualquier terminal
con carga de entrada con respecto a la tom a de t ier r a, s in poner en peligro la seguridad, es de
2500 V.
El uso de este instrumento de forma no es pecificada por estas instrucciones puede afectar a su
seguridad.
El instrumento no debe ser utilizado fuera de su rang o de voltaje o de su g am a am biental.
ADVERTENCIA! ESTE INSTRUMENTO DEBE CONECTARSE A TIERRA
Cualquier interrupción del conductor a tierra dent r o o fuera del instrumento implicaría que el
instrumento resultara peligroso. Está pr ohibida cualq uier int er r upc ión intencionada de la
conexión a tierra. No debe utilizarse con un cable de tensión sin tierra.
Mientras el instrumento esté conectado es posible que queden sin prot ec ción elementos bajo
tensión y la obertura de tapas o el retiro de piezas (salvo las accesibles por la mano) puede dejar
expuestos a elementos bajo tensión. Si se tuviera que ef ectuar alguna operación de ajuste,
cambio, mantenimiento o reparación es necesario desconectar el instr um ent o de todas las
fuentes de tensión.
Todo ajuste, mantenimiento o reparación del instrumento abierto baj o t ens ión debe ser evitado
en lo posible, pero si fuera ineludible, estos trabajos deben s er r ealizados exclusivamente por un
personal cualificado consciente del riesgo que implica.
Si el instrumento fuera claramente defectuoso, hubiera sido sometido a un daño mecánico, a
humedad excesiva o a corrosión química, su protección de seguridad puede f allar y el aparato
debe sacarse de uso y devolverse para comprobación y reparación.
Este instrumento contiene fusibles encapsulados y fusibles t ér m icos no r es et eables, los c uales
no podrán ser recambiados por el usuario. Está prohibido cort oc irc uitar est os disposit ivos de
protección.
El instrumento no debe humedecerse al ser limpiado.
Los símbolos a continuación son utilizados en el instrumento y en este manual:
Advertencia - Remitirse a los documentos adjuntos,
el uso incorrecto puede dañar al instrumento.
corriente alterna (CA)
51
(desconectada)
alimentación principal OFF
l
CAT II
Medición y sobretensión
Categoría II (300 V)
Masa del chasis
alimentación principal ON
(conectada)
52
Book Part No. 48511-1830 Issue 1
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