Aim-TTi QPX600DP, QPX600D Instruction Manual

QPX600D & DP

PowerFlex+ Dual DC Power Supplies

Table of Contents

Specification 2 Safety 5 Installation 6 Connections 7 Initial Operation 9 Manual Operation – Independent Mode 11 Manual Operation – Link Modes 19 Maintenance 20 Remote Operation 21 Remote Commands (QPX600DP only) 31

Note: The latest revisions of this manual, device drivers and software tools can be downloaded from: http://www.aimtti.com/support

This manual is 48511-1460 Issue 12

General specifications apply for the tem per ature range 5°C to 40°C. Accuracy specifications apply for the temperature range 18°C to 28°C after 1 hour warm-up with no load and calibration at 23°C. Typical specifications are determined by design and are not g uar anteed.

OUTPUT SPECIFICATIONS (E ach Output)

Voltage Range: Two ranges: 0V to 60V or 0V to 80V

Specification

Current Range: 0.01A to 50A Power Range: Up to 600W Voltage Setting: Resolution: 1mV (60V Range),

2mV (80V Range) Accuracy: 0.1% of setting ± 2mV, (± 4mV on 80V range)

Current Setting: Resolution 10mA

Accuracy: 0.3% of setting ± 20mA

Operating Mode: Constant voltage or constant current

with automatic cross-over provided that the power demanded stays within the power envelope, see graph. Outside of this envelope the output becomes unregulated. CV, CC or UNREG mode indication in display.

Output Switch: Independent electronic switching, with ON indication. In addition, BOTH ON

and BOTH OFF keys permit both outputs t o be switched on/off synchronously (±10µs). Preset voltage and current displayed when off.

Output T erminals: Rear panel safety terminals accepting 6mm wire diameter, 6mm plugs or

8mm spades at 50 Amps max, or 4mm plugs at 30 Amps max.

QPX600D & DP Power Envelope (per channel)

Sensing: Switchable between local and remote. Screwless remote sense terminals on

rear panel. Sense miswiring trip and indication.

Ripple & Noise (20MHz bandwidth):

Load Regulation: Change in output for any load change within PowerFlex envelope, using

Line Regulation: Change in output for a 10% line change:

Transient Response: <2ms to within 100mV of set level for a 5% to 95% load change. Output Protection: Output will withstand an applied forward voltage of up to 90V.

Over-voltage Protection (OVP):

Over-current Pr otection (OCP):

Over-temperature Protection:

Temperatur e Coefficient: Typically <100ppm/°C

Typically <3mVrms, <20mV pk-pk at maximum load, CV mode

remote sense: Constant voltage: <0.01% ± 5mV

Constant voltage: <0.01% ± 5mV

Reverse protection by diode clamp for reverse currents up to 3A. Range 2V to 90V. Resolution 0.1V; accuracy: 0.2% ± 0.2V.

Response time typically 100µs. Range 2A to 55A. Resolution 0.1A; accuracy: 0.5% ± 0.2A.

Response time typically 100ms. The output will be tripped off if a fault c auses the internal temperature to rise

excessively.

METER SPECIFICATIONS (E ach Output)

Display Ty pe: 5-digit (Volts), 4-digit (Am ps) , black-on-white backlit LCD. Voltage

(CC Mode and Unreg): Current

(CV Mode and Unreg): V x A: Resolution 0·1W

V/A: Meter shows calculated nominal V/A value, together with uncertainty

Resolution 1mV Accuracy: 0.1% of reading ± 2 dig its

Resolution 10mA Accuracy: 0.3% of reading ± 2 dig its

Accuracy: 0·5% ± 0·1W

range; 5 digit resolution.

LOGIC CONTROL INPUT and OUTPUT (Each Output)

LOGIC IN is a rear-panel opto-isolated input with an 820Ω resistor in series that is activated at an input voltage greater than approximately 3.3V. The maximum voltage that can be applied without damaging the unit is 20V and the input should not be taken negative by more than 3V. User c an set LOGIC IN (via the keyboard) to enable the output, disable the out put , or be ignored when it is activated.

LOGIC OUT is an isolated rear-panel open-collector output that will sink up to 2mA when activated (‘switch closure’); the maximum voltage that can be applied to LOG IC OUT is 30VDC. User can set LOGIC OUT to be ‘closed’ or ‘open’ for output enabled or disabled, current limit (CC mode), power limit (UNREG mode), or for any fault trip.

ANALOG REMOTE CONTROL and MONITORING (Each Output)

Quasi-analogue inputs and outputs to set voltage and current limit and t o monitor actual output voltage and current. The control inputs are read four tim es per second by the A-D converter and the output is set according t o t he s elect ed input sc aling ; sim ilarly the monit or outputs are updated four times per s econd with values representing the actual output voltage and current. These signals each have a range of 0 t o 10V or 0 t o 5V with respect t o the shared COM return signal; the set range applies to all inputs and outputs.

Analogue Control Voltage Range: Keyboard selectable to be 0 to 10Vdc or 0 to 5Vdc for

range maximum output. Absolute maximum input 20Vdc. Analogue Control Accuracy: Voltage: 0.3% ± 4mV; Current: 0.5% ± 40m A. Analogue Control Common Mode Range: ± 2.5Vdc max to negative output. Analogue Control Input Impedance: Analogue Monitor Voltage Range: Same as set for Analogue Control Voltage Range. Analogue Monitor Accuracy: Voltage: 0.3% ± 4mV; Current: 0.5% ± 40m A. Analogue Monitor Output:

Nominally 40kΩ.

Connect to isolated measuring system with >10kΩ input

impedance. Will withstand a short-circuit.

LINK MODES

In addition to independent output operation, the inst r um ent is capable of operating in a number of different voltage tracking modes which can be activated f rom the LINK MENU. These modes include Output 2 voltage (V2) tracking Output 1 voltage (V1) by any ratio in the range 5% to 2000%, V2 and I2 set to track V1 and I 1 (1:1) with total V1 + V2 displayed (useful when Output 1 and Output 2 are series connected), V2 and I 2 set to track V1 and I1 (1:1) with total I1 + I2 displayed (useful when Output 1 and Output 2 are parallel connected).

KEYBOARD & ROTARY CONTROL

All functions, including the selection and set-up of the remote control interf ac es, c an be set from the keyboard. The rotary Jog control can be used to adjust output voltage and current settings in a quasi-analogue mode. The output to be controlled is first selected with the appropriate Control key.

DISPLAY FEATURES

The displays (one for each output) are graphic LCDs, backlit by white LEDs; contrast is softwarecontrolled and can be adjusted from t he keyboard.

The default status displays show the VOLTS (5 digits) and AMPS (4 digits) in 12mm high characters, plus output rang e and stat us. At other times, for example during store or recall of instrument set-ups, the displays show up to 7 lines of information, instructions, or prompts.

INTERFACES (QPX600DP only)

Full digital remote control facilities are available through the RS232, LAN, USB and GPI B interfaces. Setting and r eadbac k resolutions are the same as for the O ut put and Meter specifications respectively.

RS232: Standard 9-pin D-connector. Baud rate 9600. USB: Standard USB 2.0 hardware connection. LAN: Ethernet 100/10base-T hardware connection..

1.4 LXI Core2011 compliant GPIB: Conforms with IEEE488.1 and IEEE488.2. Remote Command

Processing Time:

GENERAL

AC Input: 115V – 240V AC ± 10%, 50/60Hz.

Power Consumption: 1600VA max. Operating Range: +5ºC to +40ºC, 20% t o 80% RH. Storage Range: Environmental: Indoor use at altitudes up to 2000m, Pollution Degree 2. Store/Recall: Up to 10 set-ups can be saved and recalled via the keyboard or

Safety & EMC: Complies with EN61010-1 & EN61326-1.

Size: 130mm H (3U) x 356mm W x 413mm D

Typically <100ms between receiving the command terminator for a step voltage change at the instrument and t he out put voltage beginning to change.

Installation Category II.

−40ºC to + 70ºC.

remote interfaces.

For details, request the EU Declaration of Conformity for this instrument via http://www.aimtti.com/support

(serial no. needed).

Weight: 9.2kg Options: 19-inch rack kit.

Safety

This power supply is a Safety Class I instrument according to IEC classification and has been designed to meet the requirem ents of EN61010-1 (Safety Requirements for Elect r ical Eq uipm ent for Measurement, Control and Laborator y Use). It is an Installation Category II instrument intended for operation from a nor m al sing le phase s upply.

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 um ent 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 between +5°C and –10°C without degradation of its safety. Do not operate while condensation is present.

Use of this instrument in a manner not spec ified by these instructions may impair the safety protection provided. Do not operate the instrum ent outside its rat ed 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 entional interruption 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, t er m inals m ay 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 befor e it is opened for any adjustment, replacement, m aint enance or repair.

Capacitors inside the power supply may still be charged even if the power supply has been disconnected from all voltage sources but will be safely discharged about 10 m inut es af ter switching off power.

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 def ec t ive, has been subject to mechanical damage, excessive moisture or chemical corrosion the safety protec t ion m ay be impaired and the apparatus should be withdrawn from use and returned for checking and repair.

Make sure that only fuses with the required rat ed cur r ent and of the specified type are used for replacement. The use of makeshift fuses and the short-circuiting of fuse holders is prohibited.

Do not wet the instrument when cleaning it. The following symbols are used on the instrument and in this m anual:-

Earth (ground) terminal.

mains supply OFF.

mains supply ON. alternating current (ac)

direct current (dc)

Caution – risk of danger. Refer to the documentation (this manual) to find

out the nature of the potential hazard and any act ions which have to be taken.

Mains Operating Voltage

This instrument has a universal input range and will operate fr om a nominal 115V or 230V mains supply without adjustment. Check that the local supply meets the AC Input requirement given in the Specification.

Mains Lead

Connect the instrument to the AC supply using the mains lead provided. Should a mains plug be required for a different mains outlet socket, a suitably rated and approved mains lead set should be used which is fitted with the required wall plug and an IEC60320 C13 connector for the instrument end. To deter m ine t he m inimum c ur r ent rating of the lead-set f or t he int ended AC supply, r efer to the power rating information on the equipment or in the Specification.

Any interruption of the mains earth conduct or inside or outside t he inst r um ent will make the instrument dangerous. Int entional interruption is prohibited.

Mounting

Installation

WARNING! THIS INSTRUMENT MUST BE EARTHED.

This instrument is suitable both for bench us e and r ac k mounting. It is delivered with feet for bench mounting. The front f eet include a tilt mechanism for optimal panel angle.

A rack kit for mounting in a 19” rack is available from the Manufacturers or their overseas agents.

Ventilation

The power supply is cooled by intelligent multi-speed fans which vent at the rear. Take care not to restrict the air inlets at the front (top, bottom & side panels) or the exit at the rear. In rack-mounted situations allow adequate space around the instrument and/or use a fan tray for forced cooling.

be taken when using the power supply at voltages above this level.

applied between LOGIC OUT and LOGIC COMmon is 30VDC.

Rear Panel Connections

Output Terminals (each output)

The load should be connected to the positive (red) and negat ive (black ) terminals marked OUTPUT. The term inals accept 4mm plugs into the end (but note that 4m m plugs will only support 30 Amps), 6mm diameter wire or plugs into t he cr os s -hole or 8mm spade connections (with a maximum blade width of 16mm). The wiring and connectors must be capable of support ing the current required; f or 50 Amps, 6mm

Remote sense connections to the load, if r equired, are made from the positive (+) and negative (−) REMOTE SENSE terminals. Remote sense operation is select ed from the keyboard or via a remote control interface; R/SNS (Rem ot e Sense) shows in the display beside the output status ( OFF, CV, CC or UNREG ) when remote sense is selected and goes off when remote sense is deselected.

cable is needed.

Connections

The M4 threaded opening marked

Warning! Voltages above 70Vdc are hazardous live according t o EN 61010-1 and great care must

Always ensure that connections to the terminals are only made in a manner t hat does not compromise the protection provided by the terminal s t hem sel ves.

Ensure that the contact parts of all connecting wires are fully inserted and inaccessible to the touch.

Always make connections to the instrument w i th the OUTPUT off.

Logic Input (each output)

LOGIC IN is connected to the input of an isolating opto-coupler via an 820Ω resistor in series. The input is activated by an input voltage greater than approximately 3.3V between LOGIC IN and LOGIC COMMON; up to 20V may be applied to the input but it should not be taken negative by more than 3V. The active input current will be between 2mA and 25mA, depending on applied input voltage. The function of LOGIC IN is set from the keyboard.

Do not apply a voltage to LOGIC IN / LOGIC COMMON exceeding 50V with respect to

Logic Output (each output)

LOGIC OUT is the open-collector output of an opt o-isolated NPN transistor that will sink up to 2mA when active (‘switch closure’). The function of LOGIC OUT is set f r om the keyboard.

provides a connection point to safety earth gr ound.

The maximum voltage that can be Do not apply external voltages between the terminals exceeding 30VDC.

Analogue Control (each output)

V CONTROL and I CONTROL inputs provide quasi-analogue control of the Output Voltage and Current Limit respectively. The inputs are read 4 times per second by the A-to-D converter and the output is set according to the select ed input s caling . The input scaling for both can be set as 0 to 10 Volts or 0 to 5 Volts for range maximum output. The Analogue Control functions and scaling are both selected from the k eyboard. The V CONTROL and I CONTROL inputs are differential, with a limited common mode range of ± 2.5Vdc with respect to the negative output. They should be driven from a ‘floating’ source such as another power supply.

Do not apply external voltages between the terminals exceeding 20Vdc.

Pin Name

Description

RXD

Received data to instrument

DSR

No internal connection

Analogue Monitor (each output)

The output terminal voltage and output curr ent m ay be monitored on V MONITOR and I MONITOR respectively. The output s caling for both is the same as that set for V CONTROL and I CONTROL, see previous section.

The Analogue Monitor outputs should be connected to a measuring system with ‘floating’ inputs such as a DMM.

Do not apply external voltages to these terminals.

RS232 (QPX600DP only)

9−pin female D−connector with pin connections as shown below. Can be connected to a standard PC port using a fully wired 1:1 male-female cable without any cross-over connect ions.

1 RI 2 TXD Transmitted data from instrument

4 CTS 5 GND Signal ground 6 RTS

Passively asserted (+V through 10kΩ)

8 DTR 9 CD No internal connection

Signal ground is connected to instrument ground.

USB (QPX600DP only)

The USB port is connected to instrument ground. It conforms with USB 2.0 (Full Speed) and accepts a standard USB cable. The Windows plug-and-play funct ions should aut om at ically recognise that the instrument has been connected. If the correct driver is not found, follow the Windows on-screen prompts and install the required files from the CD supplied.

LAN (QPX600DP only)

The LAN interface is designed to meet 1.4 LXI ( Lan eXtensions for Instrumentation) Core 2011. Remote control using the LAN interf ace is poss ible using a TCP/IP Socket prot ocol. The instrument also contains a basic Web server which provides information on the unit and allows it to be configured. Since it is possible to misconfigure the LAN interface, mak i ng it impossible to communicate with the instrument over LAN, a LAN Configur ation Initialise (LCI) mechanism is provided via a recessed switch on the rear panel (marked LAN RESET) to reset the unit t o the factory default.

Further details are given in the Remote Operation chapter. For more information on LXI standards refer to www.lxistandard.org/home

GPIB (QPX600DP only)

The GPIB signal grounds are connect ed to the instrument ground. The implemented subsets ar e:

The GPIB address is set fr om t he front panel.

SH1 AH1 T6 L4 LEO SR1 RL2 PP1 DC1 DT0 C0 E2

This section of the manual is a gener al intr oduction to the controls and operation of the instrument and is intended to be read before using t he power supply for t he first time. In this manual f r ont panel keys, connections and indicators are shown in capitals, e.g. ESCAPE, JOG SET, OUTPUT, ON. Messages shown on the display are printed in a different type-font, e.g.

Limits, CV, Store.

Switching On, Output On/Off

The power switch is located at the bottom left of the front panel. At power-up the default behaviour is for the instr ument's settings to be restored to those

automatically saved when it was switched off, but with the outputs in independent mode and always off (

can change this default setting such that the power-down status of the individual outputs and of the tracking mode are rest or ed at power-up, see the Extra Functions section.

Each DC Output is switched on and off electronically with alternate presses of its key; the ON lamp illuminates when the Output is on. At the same time the message above the VOLTS and AMPS display changes from

the present operating mode; should t he load cause t he inst rument to operate outside its guaranteed power range the display will instead show

BOTH ON or BOTH OFF keys can be used to switch both outputs on or off together; the outputs switch synchronously within <10µs of each other. Note that, if one output is already on and the other off, BOTH ON will turn the off output on and BOTH OFF will turn the on output off.

OFF is shown at the top right-hand side of each output ’s display). However, the user

Select Output

The output to be adjusted is selected by pressing CO NTROL 1 or CONTROL 2; the corresponding LED lamp will light to show which output is currently under the control of the numeric k eypad or

rotary control. Note that the individual OFF keys, will always operate regardless of which output is currently selected by the CONTROL keys. Control of Output 1 is t he default setting at power-up.

Keypad

Only the principles of operation are outlined here; the setting of individual parameters is given in detail in later sections. The paramount consideration in designing the user inter face has been to make changing setting s as ' s afe' as possible (i.e. with minimal risk of accidentally applying excessive voltages to a load) whilst achieving ease of use. This has been achieved by requiring the user to confirm (O K) new numeric set t ings, with the option to ESCAPE at any point or even to simply pause until the operation times-out and the instrument r et ur ns t o its original settings. In addition, display messages and LED indicators prompt, g uide or warn the user such that entry or control errors are minimised. Where some of these features (e.g. beeps) are considered unnecessary by regular users, the option exists to disable them, see t he Extr a Funct ions s ect ion.

Press CONTROL 1 or 2 to select the output to be adjusted. Under nor m al condit ions t he num eric keypad is disabled; any numeric key presses will simply be ignored. To set a voltage with the keypad first press the V NUMERIC SET key; the VOLTS display changes to show the present set value in a smaller font, with the message Enter V or ESC below it, and the OK lamp starts flashing. The new value is then entered from the k eyboard; as it is entered it is displayed directly below the present setting, replacing the pr om pt m es sage. At any time during entry the new setting can be confirmed with the OK key, e.g. it is sufficient to key in 1, OK to change the s et t ing to 1Volt. When OK is pressed the display reverts to show just the new setting in the f ull-s ize f ont and the OK lamp stops flashing; if OK is not pressed within 10s of the last numeric key the entry is cancelled and the display returns to its original setting. If ESCAPE is pressed anytime in the entry procedure, entry is cancelled and the display returns to its original sett ing. The current limit is set in exactly the same way after first pressing I NUMERIC SET.

The OK key is used to confirm m ost keypad entries. At all other times it becomes the VIEW V/I LIMITS key and pressing it will cause the display to show preset output voltage and current limit for 3 seconds; during this period the

Initial Operation

Enter V,

OFF to CV (constant voltage) or CC (constant cur r ent) to indicate

UNREG (unregulated). Alternatively, the

ON keys, as well as the BOTH ON and BOTH

Limits message shows in the display.

Pressing SHIFT illuminates the ▲ lamp and gives the numeric keys the functions marked above them, e.g. STR (Store), RCL (Recall), etc. When a shift function is selected SHIFT is cancelled (the ▲ lamp is no longer lit). The fur t her key presses required to complete the selected function are described in detail in the sections that follow; if no key is pressed within 10 seconds to complete the function, the function will terminate as if ESCAPE has been pressed. SHIFT is a toggle key; pressing SHIFT again when it has been selected will cancel SHIFT. SHIFT is also cancelled by ESCAPE, or by pressing SET V or SET I.

Jog Control

The rotary 'jog' control per m its the output voltage or current limit to be incremented or decremented in steps with a resolution set by the JOG SET keys; the output immediately follows the setting, i.e. no OK is required.

Press CONTROL 1 or 2 to select the output to be adjusted. At power-up jog is always off. To jog the voltage or current setting pres s t he V or I JOG SET key; the associated lamp will illuminate and the appropriate parameter display now changes to two lines. With the output ON the top line continues to show the actual output, but the additional lower display now shows the present

Limits value; in the lower display, the JO G indicator ( ) is positioned under the digit that was last

jogged. Whilst the V or I JOG SET indicator is lit, each f ur ther press of the V or I key moves the JOG indicator one digit to the left ; the selection 'wraps-round' such that when the largest value of jog increment has been reached the next pr ess returns it to the lowest. The default position at power-up is under the LSD, i.e. the lowest jog increment is selected.

Turning the rotary jog control clockwise/anti-clock wise increments/decr ements the selected digit; digits to the left of the one being j ogged are automatically incremented/decremented when the decade overflow/underflow point is reached. Digits to the right of the one being jogged remain unchanged unless the jog step overf lows/underflows the maximum/minimum settings in which case they are set to zero. For example, 59·861V goes to 59· 961V goes to 60·000V for a 0.1V jog increment; 1.60A goes to 0·60A goes to 0·01A for a 1A jog decrement.

The jog steps that can be selected are 1mV, 10mV, 100mV and 10mA, 100mA, 1A. To disable the jog r otar y contr ol pres s the JOG SET OFF key; reselecting JOG SET V or I will

enable jog on the last used digit position. Jog is not cancelled by using numeric entry or any of the SHIFT functions but it is disabled whilst that function is enabled. Jog is disabled when control is switched to the other output using the CONT RO L 1 or 2 keys but is automat ically enabled again when control is switched back.

Note that the dual display of the parameter being j ogged is primarily of use if the output is O N ; with the output off both lines of t he display show the

parameter is jogged.

Display

At power-up the display briefly shows the instrument model number and installed firmware revision in the left-hand display before both displays revert to the standard status display.

The standard status display shows the voltage range and output voltage on the left (above the front panel VOLTS marking) and the current on the right (above the front panel AMPS marking) together with the present output stat us, i.e. OFF, CV, CI, or UNREG; if the output is off then

Limits is also shown in the display above the V and I values. The status of the LAN connection

is also shown in the top left corner of the display, as required for LXI compliance. Refer to the 'LAN Status Indication' paragraph in the LAN Interface section for details. Dur ing other operations, however, the display capabilities are used more extensively to show, for example, prompts during function settings, e. g. memory store and recall operations or the extra functions accessed via the shift function; details are given in the relevant sections of this manual.

Limits value and change simultaneously as the

The display contrast is set at the f act ory but can be adjusted from the keyboard to optimise it for particular ambient operating conditions. Press SHIFT, # , select Extra Function 90, and follow the on-screen prompts. Contrast can be adj ust ed independent ly f or the two displays.

Manual Operation – Independent Mode

New users should first read the Initial Operation chapter which describes the operating principles of the keypad and rotary jog control.

The default mode at power-up is ‘Tracking Off’, i.e. the two outputs are fully independent. The following sections describe operation of either output in this mode. See the later ‘Manual Operation – Link Menu’ chapter for details of the various track ing modes that can be set.

Set Voltage Range

There are two voltage ranges for each out put – a low range (0 to 60V) and a high range (0 to 80V). To select the r ange press SHIFT followed by RANGE. Changing to the higher range is always possible and the display will show Select 0 to 80V range: 2mV resolution. OK to confirm, ESC to cancel; pressing OK accepts the change. Because t he r esolut ion of the 80V range is 2mV the set-point will rounded down, if necessary, to the nearest 2mV figure (e.g. if output is set to 59.997 it will be changed to 59.996).

When changing to the low range the display will show Select 0 to 60V range: 1mV resolution. OK to confirm, ESC to cancel unless the output is set above 60V in which case the display will show to cancel. The output must firs t be set to <60V before the low range can be selected.

Set Voltage

Can’t select 0 to 60V range. Set point too high. Esc

With the output off, the standard status display shows the set voltage; Limits shows as a reminder beside (constant voltage) or CC (constant current), depending on the set current limit and load conditions,

and the display shows the actual output voltage (measured at the sense point); note that in CC mode the actual output voltage will be less than the set voltage. Both the set and actual voltage are shown to a resolution of 1mV (0-60V range) or 2mV (0-80V range). If t he set voltage and load conditions cause the instrument to operat e outside its guar ant eed power range the display will show

The voltage can be set directly from the num er ic keypad: press the NUMERIC SET V key, enter the new value using the numeric keys and confirm by pressing OK. The broad principles of keypad entry are explained in the Initial Operation chapter, which should be read by new users.

When SET V is pressed the VOLTS display changes to show the present set value in a smaller font, with the message Enter V or ESC below it, and the O K lamp star ts flashing. The new

voltage is then entered from the k eyboard, e. g. 12·345V is entered as 1, 2, ·, 3, 4, 5. As it is entered it is displayed directly below the present setting, replacing the prompt message.

The minimum voltage setting is 0·000V; the maximum setting is 60· 000V (0-60V range) or

80.000V (0-80V range). Pressing OK at any point will set the voltage entered with any remaining digits set to zero,

e.g. 1, 2, ·, 3, O K will set 12·300V; 1, OK will set 1·000V. When OK is pr ess ed t he s et voltage is changed and the display reverts to the standard status mode.

Pressing ESCAPE at any time during the sequence, or m aking no further key press within 10 seconds of the previous one will cause the display to return to its original reading before SET V was pressed.

Entering a voltage outside the range maximum (including tr ying t o ent er 3 digits before the decimal point) or trying to enter more than 5 digits will cause the buzzer to beep; the last key entry will be ignored.

The voltage can also be set using the Jog control. Pr ess ing J O G SET V will illuminate the V JOG SET lamp and the VOLTS display will again change to two lines. With the output O N t he t op line continues to show the actual output, but the additional lower display now shows the present

UNREG (unregulated) and the actual output voltage will again be less than the set voltage.

OFF in the top line of the display. With the output ON the mode changes to CV