Thurlby Thandar Instruments 1604 User Manual

1604

40,000 Count Digital Multimeter

Table of Contents

Introduction 2 Specifications 3 Safety 7 EMC 8 Installation 9 General Operation 10 Making Measurements 12 Further Functions 14 Maintenance & Calibration 15 Remote Operation 15

Instructions en Francais 16 Bedienungsanleitung auf Deutsch 25 Istruzioni in Italiano 34 Instrucciones en Español 43

Introduction

This true RMS multimete r is a low-cost manual/autoranging bench-top instrument with a large, bright LED display. It offers 4¾ digit ( 40,000 count) scale length and a resolution of 10µV and 10mΩ.

The key features are:

• 0.56” (14mm) high brightness LED display.

• 0.08% basic accuracy, 40,000 counts.

• Manual or autoranging.

• DC and AC Volts, DC and AC current, Resistance and Frequency measurement; Continuity

and Diode checks.

• True RMS AC measurem ent , 4,000 counts.

• Display nulling.

• Touch hold mode - holds ont o a stable reading until updated.

• Remote control and data-logging to disk using optional W indows software.

• Fully compliant with EN61010-1 Safety and EN61326 EMC standards.

TEST EQUIPMENT RISK ASSESSMENT

Recommendation from the U.K. Health and Safety Executive

Users of this equipment and or their employers are reminded that Health and Safety Legislation require them to carry out valid risk asses sments of all electrical work so as to identify potential sources of electrical danger and risk of electrical injury such as from inadvertent short circuits. Where the assessments show that the risk is significant then the use of fused test leads constructed in accordance with the HSE guidance note GS38 ‘Electrical Test Equipment’ for use by electricians’ should be used.

Range

Accuracy

Resolution

Notes

Max input 1000V

†

Range

Accuracy

Resolution

ACCURACY

Accuracies apply for 1 year 19°C to 25°C. Temper at ure coefficient outside these limits is <0.1 x quoted range accuracy per °C.

DC Volts

Specifications

400mV 0.08% ± 4 dig. 10µV

4V 0.08% ± 4 dig. 100µV

40V 0.08% ± 4 dig. 1mV DC/AC pk.

400V 0.08% ± 4 dig. 10mV

1000V 0.09% ± 4 dig. 100mV

AC Volts (True RMS)

45Hz - 400Hz 400Hz - 4kHz 4kHz - 20kHz

400mV 1% ± 4 dig. 2% ± 4 dig. 100µV

4V 1mV

40V 0.5% ± 4 dig 2% ± 4 dig 5% ± 4 dig. 10mV 400V - - 100mV 750V 1% ± 4 dig. - - 1V

Accuracies apply for readings between 400 and 4,000 counts. Additional error at crest factor = 3 is typically 1%. Input impedance = 10MΩ nominal. 1kΩ unbalanced CMR = >60dB at DC/50Hz/60Hz

265V DC/AC rms max

†

Input impedance 10MΩ nominal

NMR:>60dB @ 50/60Hz

CMR:>90dB @ DC/50Hz/60Hz†

Max. input = 750V rms, 1kV pk. (265Vrms on 400mV range).

Resistance

Range Accuracy Resolution Notes

400Ω 0.15% ± 6 dig.∗ 10mΩ

4kΩ

40kΩ

400kΩ

4MΩ 40MΩ (up to 20MΩ) 40MΩ (up to 40MΩ)

0.1% ± 4 dig.

0.15% ± 4 dig.

0.3% ± 6 dig.

1.0% ± 10 dig.

2.0% ± 10 dig ∗ after Null

100mΩ

1Ω

10Ω

100Ω

1kΩ 1kΩ

Max. input 265V DC or ACrms any r ange.

Max. open circuit voltage 4V.

†

60Hz rejection is a factory option.

Range

Accuracy

Resolution

Notes

4mA

0.1% ± 4 dig.

0.1µA

Max. input 1A, 250V, f use pr otected

400mA

0.1% ± 4 dig.

10µA

Voltage burden <500mV

10A (up to 1A)

0.3% ± 4 dig.

1mA

10A (up to 5A)

1.0% ± 4 dig.

1mA

Max. input 10A, 250V, f us e pr ot ec t ed

10A (up to 10A)

3% ± 10 dig

1mA

Voltage burden <500mV

Range

Accuracy (45Hz - 10kHz)

Resolution

Notes

4mA

0.5% ± 4 dig.

1µA

Max. input 1A, 250V, f use pr otected

400mA

0.5% ± 4 dig.

100µA

Voltage burden <500mV

10A (up to 1A)

0.8% ± 4 dig.

10mA

10A (up to 5A)

1.5% ± 4 dig

10mA

Max. input 10A, 250V, f us e pr ot ec t ed

10A (up to 10A)

3% ± 4 dig.

10mA

Voltage burden <500mV

Range

Accuracy

Resolution

Gate

Notes

4kHz

0.01% ± 1 dig.

0.01Hz

Sensitivity set by

40kHz

0.01% ± 1 dig.

0.1Hz

10s

AC range setting

Continuity:

4kΩ range select ed; audible t one sounds for impedance <10Ω.

Diode Test:

Test curr ent approximately 1mA at 1V; displays voltages up to 3V.

Voltage:

Maximum Input:

265V DC or AC rms.

Hold:

Reading is frozen

T-Hold (Touch & Hold):

Reading is frozen when stable.

Min/Max:

Minimum and maximum readings stored.

shows in the display when the measurement range is exceeded.

DC Current

AC Current (True RMS)

Accuracies apply for readings between 400 and 4,000 counts. Additional error at crest factor = 3 is typically 1%.

Frequency

Continuity and Diode Test

Maximum Open Circuit

FURTHER FUNCTIONS

Null (Relative): Stores current reading and subtracts it from future readings. Up to

±1,000 counts can be nulled without restricting the measur em ent range. Counts greater than ± 1,000 can be nulled to give a Relative reading but the measurement range is correspondingly reduced; OFL

Display Ty pe:

High brightness LED. Height 0.56” ( 14m m ) .

Scale Length:

4¾ digits (40,000 counts); AC ranges 4,000 counts.

Annunciators:

For all ranges, functions and program modes.

Reading Rate:

2.5 readings/sec.

Overrange:

Display shows OFL if input too great for range.

3VA max. Installation Category II. 60Hz operation is a factory option.

optional Windows software.

Operating Range:

+5°C to + 40°C, 20% to 80% RH.

Storage Range:

−40°C to + 70°C.

Environmental:

Indoor use at altitudes up to 2000m, Pollution Degr ee 1.

Safety:

Complies with EN61010-1.

EMC:

Complies with EN61326.

Size:

260(W) x 88(H) x 235(D)m m, excluding handle and feet.

Weight:

2.0kg.

DISPLAY

GENERAL

Power: 110V-120V or 220V-240V AC ±10%, 50/60Hz, adjustable internally;

RS232 Interface: Baud Rate 9600. Permits remot e c ont r ol and data-logging to disk using

Performance levels achieved are detailed in the user manual.

EC Declaration of Conf ormity

We Thurlby Thandar Instruments Ltd Glebe Road Huntingdon Cambridgeshire PE29 7DR England

declare that the

Model 1604 Digital Multimeter

meets the intent of the EMC Directive 2004/108/EC and the Low Voltage Directive 2006/95/EC. Compliance was demonstrated by conformance to the following specifications which have been listed in the Official Journal of the European Comm unit ies.

EMC

Emissions: a) EN61326-1 (2006) Radiated, Class B

b) EN61326-1 (2006) Conducted, Class B c) EN61326-1 (2006) Har m onics, referring to EN61000-3-2 ( 2006)

Immunity: EN61326-1 (2006) Immunity Table 1, referring to:

a) EN61000-4-2 (2009) Electrostatic Discharge b) EN61000-4-3 (2006) Electromagnetic Field c) EN61000-4-11 (2004) Voltage Interrupt d) EN61000-4-4 (2004) Fast Transient e) EN61000-4-5 (2006) Surge f) EN61000-4-6 (2009) Conducted RF

Safety Multimeter: EN61010-1 Installation Category I measurements to 1000V,

Installation Category II measurements to 600V, Pollution Degree 1.

Probes: IEC1010-2-031 Rated to 1000V, Installation Category III.

CHRIS W ILDING TECHNICAL DIRECTOR

2 January 2013

incorrect operation may damage the met er.

Safety

This multimeter is a Safety Class I instr um ent according to IEC classification and has been designed to meet the requirem ents of EN61010-1 (Safety Requirements f or Elect r ical Eq uipment for Measurement, Control and Laborator y Use). It is an Installation Category II instrument int ended for operation from a nor m al single phase supply.

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 protect ive conductor.

The test leads supplied with this instrument meet t he r equirements of IEC1010-2-031 and are rated to 1000V Category III; use only these test leads with the m et er or a set of equivalent perfor m anc e.

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 1 environment (no pollution, or only dry non-conductive pollution) in the temperature range 5°C to 40°C, 20% - 80% RH (non-condensing). It m ay occasionally be subjected t o t emperatures between +5° and −10°C without degradation of its safety. It has been designed for Installation Category II m easur em ent use to 600VDC/ACrms and Installation Category I measurement us e t o 1000VDC/750VACrms. The full definitions of Categories I and I I can be found in IEC664, but the f ollowing can be taken as a guide:

Installation Category I is signal level e.g. telecommunicat ion, elect r onic equipment, with smaller transient overvoltages than Installation Category II.

Installation Category II is local domestic supply level, e.g. portable equipment and appliances. In particular, Category II does not include distribution level supplies, e.g. three phase installations which are classified as Installation Category III.

For this equipment 2500V is the maximum peak transient overvoltage that can be tolerated by any terminal with respect to earth ground 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 instrum ent outside its rat ed supply voltages or environmental range. In particular excessive moisture may impair safety.

When the instrument is connected to its supply or its inputs are connected to live voltages, terminals may be live and opening the covers or removal of parts (except those t o 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 adjust m ent, replacement, maintenance or repair.

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 rated current 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 and in particular use only a soft dry cloth to clean the display window. The following symbols are used on the instrument and in this manual:

WARNING - risk of electric shock.

CAUTION - refer to accompanying documentation;

mains earth (ground)

direct current

alternating current

This instrument has been designed to meet the requirements of the EMC Directive 2004/108/EC. Compliance was demonstrated by meeting the test limits of t he following standards:

Emissions

EN61326-1 (2006) EMC product standard for Electrical Equipment for Measurement, Control and Laboratory Use. Test limits used were:

a) Radiated: Class B b) Conducted: Class B c) Har m onics: EN61000-3-2 (2006) Class A; the instrument is Class A by product category.

Immunity

EN61326-1 (2006) EMC product standard for Electrical Equipment for Measurement, Control and Laboratory Use.

Test met hods, limits and performance achieved are shown below (requirement shown in brackets):

a) EN61000-4-2 (2009) Electrostatic Discharge : 4kV air, 4kV contact, Performance B (B).

EMC

b) EN61000-4-3 (2006) Electromagnetic Field:

c) EN61000-4-11 ( 2004) Voltage Interrupt: ½ cycle and 1 cycle, 0% : Performance A (B);

d) EN61000-4-4 (2004) Fast Transient, 1kV peak (AC line), 0·5kV peak (signal connections), Performance B (B).

e) EN61000-4-5 (2006) Surge, 0·5k V ( line to line), 1kV (line to ground), Performance A (B). f) EN61000-4-6 (2009) Conducted RF, 3V, 80% AM at 1kHz (AC line only; signal

connections <3m, therefor e not tested), Perform ance A (A). According to EN61326-1 the definitions of performance criteria are:

Performance criterion A: ‘During test normal performance within the specification limits.’ Performance criterion B: ‘During t est, temporary degradation, or loss of function or

performance which is self-recovering’. Performance criterion C: ‘During t est, temporary degradation, or loss of function or

performance which requires operator int er vention or s ystem r eset occurs.’

†

Note: The 1604 is a sensitive measuring instrument and, if s ubj ec t ed to a sufficiently large radiated RF field, measurements may deviate beyond the accuracy specification at c er t ain frequencies up to 1GHz. However, possible deviations will be small and infrequent and are not deemed to be a problem in practice. In all other res pects t he inst r ument will operate normally (Performance A) in fields up to 3V/m.

Cautions

To ensure continued com pliance with the EMC directive the following precautions should be observed:

a) Only use screened cables and connectors to connect between the mult im et er’s RS232

interface and other equipment .

b) After opening the case f or any reason ensur e that all signal and ground connections are

remade correctly before replacing the cover. Always ensure all case screws are correctly refitted and tightened.

c) In the event of part replacement becoming neces sar y, only use components of an

identical type, see the Service manual.

†

3V/m, 80% AM at 1kHz, 80MHz – 1GHz: Performance B Performance A (A); 1V/m, 2.0GHz to 2.7GHz: Performance A (A).

25 cycles, 70% : Performance B (C); 250 cycles, 0% : Per formance C(C).

(A) and 1.4GHz to 2GHz:

Mains Operating Voltage

Check that the instrument oper ating voltage marked on the rear panel is suitable for the local supply. Should it be neces sar y to change the operating voltage, proceed as follows:

1) Disconnect the instrument from all voltage sources.

2) Unclip the front bezel by gently pulling the centre of each long edg e up and forward. The case halves are held together by 4 plastic push-rivets. Use the blade of a s m all

screwdriver in the slot beside each rivet to first ease out t he r ivet head and t hen fully remove the rivet body. Separate the case halves. Visit www.tti-test.com for further details.

3) Remove the 3 scr ews securing the pcb to the case lower and lift out the pcb with front and rear panels attached.

4) Change the voltage settings by changing the soldered links as shown below:

Installation

5) Reassemble in the reverse order.

6) To comply with safety standard requirements t he oper ating voltage marked on the rear panel must be changed to clearly show the new voltage setting.

Note: The transfor mer primary is protected by an integral thermal fuse which remains unchanged when the operating voltage is altered.

Mains Lead

When a three c or e m ains lead with bare ends is provided it should be connected as follows:-

WARNING! THIS INSTRUMENT MUST BE EARTHED WHEN OPERATED FROM AN AC LINE SUPPLY

Any interruption of the mains earth conduct or inside or outside t he inst r ument 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.

Brown - Mains Live

Blue - Mains Neutral

Green / Yellow - Mains Earth

600V (Category II) and 10A current capability.

Name

Description

DCD

Linked to DTR

TXD

Transmitted data from instrument

RXD

Received data to instrument

DTR

DTR from host PC must be set t o + 9V ( logic 0)

GND

Signal ground

DSR

Linked to DTR

RTS

RTS from host PC must be set to -9V (log ic 1)

CTS

Linked to RTS

This section is a general introduction to t he features and organisation of t he multimeter intended to be read before using the instr ument for the first time. Detailed operation is covered in the Making Measurements section.

Connections

Input Sockets

The input sockets are 4mm safety sockets on a 19mm pitch designed to accept 4m m safety plugs with fixed or retractable shrouds. The sockets are all rated t o 1000V ( Cat egory I)/600V (Category II) with respect to eart h ground.

The input impedance between V/Ω and COM is nominally 10MΩ. The black COM socket is considered less positive than the red socket.

The mA/10A current sockets are low impedance; the voltage burden between mA/10A and COM at full scale is <500mV. The black COM socket is considered less positive than the white mA/10A sockets.

Multimeter Test Leads

General Operation

RS232

The test leads supplied meet the requir em ents of IEC1010-2-031 and are rated to 1000V Category III. Use only the test leads provided, or a set of similar performance, to ensure safe operation. Alternative test leads should be rated to at least 1000V (Category I),

The RS232 interface permits remot e cont r ol and data-logging to disk using optional Windows software. The interface is fully opto-isolated from the measurement system; t he hos t computer provides power (via the DTR and RTS lines) to the TXD opto output and drives the RXD opto input directly. The 9-way D-type on the meter m ust be connected to the 9-way D-type of the PC’s serial port via a 9-way cable (all connections made); the PC is nulled out at the multimeter interface as shown below:

9 GND Signal ground

Signal grounds are connected to instrum ent safety ground. To ensure compliance with EMC legislation use only screened cable assemblies with screened

connectors when connecting to other equipment .

Switching On

Power Switch

The multimeter is switched on and off with alternate press es of the Operate key. This key only switches the DC power to the measurement circuits; it does not switch the AC power which means that the isolated RS232 circuit continues to be powered. Disconnect from the AC supply by unplugging the mains cord from the back of the instrum ent or by switching off at the AC supply outlet; make sure that the means of disconnection is readily accessible. Disconnect f r om t he AC supply when not in use.

Power-up Settings

At power-up using the Operate key the default action is to restore power-down settings; t he power-down settings are not retained if AC power is removed.

To restor e t he default settings (Volts, DC, Autorange) press SHIFT then Reset. Turning the meter on at the AC supply whilst any key is held down initiates a buzzer and display

test (all segments and annunciators should be lit); when the key is released the revision of the installed firmware is shown in the display as x.x. Pressing the Operate key switches on the meter as normal.

Buzzer

A short beep is sounded whenever an invalid key is pressed, e.g. pressing Hz when an AC range is not selected; such keystrokes ar e not accepted. The buzzer is also used to indicate a resistance <10Ω in Continuity mode.

Keyboard

Selection of the primary function is made dir ectly by pressing the appropriate keys e.g. V and DC for DC Volts; the primary function is showing beside the key. The meter is switched between autoranging and manual with alternate presses of the Auto/Man key; alternatively using the arrowed up and down keys changes the range and sets manual ranging.

The further f unc t ions ( Null, Hold, Min-Max etc.) are all selected by pressing SHI FT f ollowed by the appropriate key; the shifted function is shown in blue above the key. When SHIFT is pressed the annunciators for all the shifted functions are lit; when the function is selected with the appropriate key only the associated annunciator remains lit.

is exceeded.

Scale Length

The scale length is always ± 40,000 counts, except AC ranges which are ± 4,000.

Function Selection

All functions are directly selected by pressing the appropriat e function keys (e.g. V followed by DC to set DC Volts). Changing function sets autorange when there is more than one range; providing the appropriate function has been selected ( e.g. Ω f or r esistance m easurement) and the parameter to be measured is within the range of the meter, a valid reading should always be shown.

Making Measurements

The units and function are shown in the display (e.g. to indicate autorange.

Continuity and Diode Test and selected by pressing SHIFT followed by the appropriate key. The associated annunciator confirms the s elect ion. Continuit y sets the meter to the 4kΩ r ange and buzzes for values below approximately 10Ω.

Range Selection

Selecting a new function always sets autorange to ensure an in-range reading is made with maximum resolution whenever possible; the meter ranges up at 40, 000 counts ( 4, 000 on AC ranges) and ranges down at 3,840 counts (V and Ω) or 255 counts (mA); AC ranges range down at 384 counts and 25 counts respectively.

There are, however, situations when it is desirable to lock the range; for example, to stop the meter autoranging to t he 40MΩ range and back between successive resistance measurements of lower resistance values, or to set a lower resolution range when an unstable parameter is being monitored. To lock t he r ange, change from auto to manual ranging, see below.

Manual range changing is selected either by alternate presses of the Auto/Man key, which locks the meter in its present range, or by using the arrowed up/down keys which both change the range and lock the meter in that new range. The Auto annunciator is off in Manual mode. Overrange is indicated by OFL in the display; overrange is shown when the count exceeds 40,000 in a manually locked range (1024V/768V on the 1000VDC/750VAC ranges respectively). Autoranging can be restored by pressing t he Auto/Man key again.

and V for DC Volts) together with Auto

Making Voltage Measurements

Voltage measurements are made using t he r ed V/Ω socket and the black CO M socket having selected the appropriate function and range as described above.

The meter will show a minus sign (on dc measurements) when the voltage applied to the red socket is more negative than that applied to t he black socket.

Note that when AC voltage ranges are selected with the meter inputs open circuit a non-zero reading will usually show because stray AC sig nals couple into the meter’s high impedance input. This is perfectly normal and will not affect the accur acy of practical voltage measurements where source impedance is generally low.

The maximum voltage that can be applied between V/Ω and COM is 1000V DC or 750V AC (265V DC/AC rms on 400mV range), Categ or y I; dam age to the instrument may result if this limit

WARNING! The maximum input voltage to ground must not exceed 1000V (Category I) or 600V (Category II) dc or ac rms . Safety will be impaired if these ratings are exceeded, see Safety section at the beginning of t he m anual.

Making Current Measurements

Having selected the appropriate current function (mA for 4mA and 400mA range, A for 10A range), current measur ements up to 400mA are made using the white mA socket and the black COM socket; current measurements up t o 10A are made using the 10A and COM socket. The meter will show a minus sign (on dc measurements) when the polarity of the current is out of the mA or 10A sockets.

Current measurements using the mA socket can be autoranged between the 4mA and 400mA ranges; measurements up to 10A can be made using the 10A socket having selected the 10A range with the A key.

The 4mA and 400mA ranges, using the mA socket, are protected by a 1A (F) HBC fuse and the 10A range, using the 10A socket, is protected by a 10A (F) HBC fuse. Both fuses are fitted inside the instrument and replacement is described in the Maintenance sect ion later in t he m anual.

Note: After measuring high current using the 10A input, thermal voltages are generated that may create errors when making measur em ents on t he m ost sensitive dc voltage, current or Ohms ranges immediately afterwards. To ensure that the specified accuracy is maintained, allow 10 minutes for the therm al effects to fade before mak ing sensitive measurements.

Making Resistance Measurements

Resistance measurements are made using the V/Ω and COM sockets. Null can be used to null out residual test lead resistance, see Further Functions sec t ion.

Making Continuity and Diode Checks

Continuity and diode checks are made using the V/Ω and COM sockets. Select Continuity mode by pressing SHIFT followed by Continuity; the continuity indicator is

shown in the display. The 4kΩ range is selected and readings below approximately 10Ω sound the continuity buzzer.

Select Diode Test by pressing SHIFT followed by Diode Test; the diode annunciator is shown in the display. The 4V rang e is select ed and the diode voltage at approximately 1mA is shown (3V maximum). Reverse diode connection will show overload (OFL).

Making Frequency Measurements

Frequency measurements are made using either the V/Ω and COM sockets (f or AC voltages) or mA/10A and COM (for AC curr ents) .

First set the input sensitivity by selecting the appropriate AC volts or current range to give an inrange measurement of at least 2,000 counts; then press the Hz key to select frequency mode. Two ranges (4kHz and 40kHz) are available giving resolutions of .1Hz and 1Hz respectively over an operating frequency rang e of 10Hz to 40kHz.

The default frequency range is 40kHz which has a 1s gate time. To select the 4kHz range (10s gate time) use the arrowed down key; the Hz annunciator flashes slowly to indicate that the 4kHz range has been selected. The 40kHz range can be reselected with the arr owed up key.

At low signal levels use a screened lead and an adaptor (BNC to 4mm plugs, 19mm pitch) t o preserve signal quality and avoid spurious readings from st ray pick-up.

Note that the further functions of Null, Hold, T-Hold and Min-Max (next section) do not operate with frequency measurement.

Null

Hold

Further Functions

The further f unc t ions of Null, Hold, T-Hold and Min-Max are all selected by pressing SHIFT followed by the appropriate key; the shifted func t ion is shown in blue above the key.

Selecting Null stores the current reading and subtracts it from all the following readings. The meter range is locked and Null shows in the display. Hold, T-Hold and Min-Max can all be subsequently selected but changing f unction or range (or selecting Auto) will automatically cancel Null. Null can also be cancelled by pressing SHIFT followed by Null.

Null can be used to null out the effect of r esidual t est lead r esistance on t he lower Ohm s r anges. Select the appropriate Ohms range us ing the arrowed up/down keys. Connect the test leads together, wait for the reading to settle and select Null. Make the Ohm s m eas ur em ents in the usual way but note that if Auto is reselected or if the range is changed then Null will be cancelled. Null cannot be used with Hz.

Selecting Hold freezes the reading in the display and flashes the Hold annunciator. Hold can be used with the Null already selected but Null and Min-Max cannot be selected once Hold is set. Selecting any other function (including range change, Auto/Man and T-Hold) will set that function and cancel Hold. Hold cannot be used with Hz.

T-Hold

In T-Hold (Touch and Hold) mode the meter will hold a reading until a new non-zero measurement has been detected; this allows the user to touch-probe the measurement point, remove the probes and read the meter aft er wards. Care s hould be tak en, however, when using T-Hold with the most sensitive voltage ranges; when the probes ar e lift ed from the circuit being measured their high impedance means that s t r ay pick-up might generate another ‘valid’ reading and the true T-Hold reading may be lost. Selecting T-Hold locks the meter range and shows the T-Hold annunciator in the display. When T-Hold is initially selected it is automatically ‘armed’ and the first valid (non-zero) reading will cause the display to update with a beep and the T-Hold annunciator to flash.

The meter will re-arm (2 beeps) when it subsequently sees a near-zero reading ( bec ause, for example, the probes have been removed from the measurement) but the original reading is held in the display. After the 2 beeps the T-Hold annunciator stops flashing to confirm that the m et er is armed and a new reading is taken when the probes next make a non-zero measurement. Wit h Ohms and continuity measurements, overflow, associated with the probes being open-circuit, rearms the meter. For all functions a measurement change of more than 1000 counts will also initiate a re-arm/new measurement cycle. T-Hold can be used with Null already selected but Null and Min-Max cannot be selected once T-Hold is set . Select ing any other function (including range change, Auto and Hold) will set that function and cancel T-Hold. T-Hold cannot be used with Hz.

Min-Max

While Min-Max is selected the minimum (m os t negative) and maximum (most positive) readings are stored. The Min and Max readings can be displayed, while Min-Max is running, by using the Review function (SHIFT followed by Review). The first SHIFT/Review displays the Minimum, indicated by flashing the Min annunciator; the second SHIFT/Review displays the Maximum (Max flashes); the third SHIFT/Review returns the display to normal with Min-Max still running.

Min-Max can be turned off by pressing SHIFT/Min-Max again. Selecting another function or range or Auto also cancels Min-Max. Null, Hold and T-Hold cannot be selected with Min-Max running. Min-max cannot be used with Hz. Review cannot be used with Min-Max turned off.

Routine maintenance is limited to re-calibration and cleaning. The only repair maintenance that can be carried out by the user is current rang e fuse replacement.

Calibration

Calibration is guaranteed as in the specification. The manufacturers provide a re-calibration service, as do most of their agents overseas. Where owners wish to carry out re-calibration themselves, this should only be done by skilled personnel with access to precision equipment working in conjunction with the service manual which may be purchased directly from the manufacturers or their agents overseas.

Current Range Fuses

The mA socket is protected by a 1A (F) HBC fuse and the 10A socket by a 10A (F) HBC fuse, both mounted internally. To replace a fus e, proceed as follows:

1. Disconnect the instrument fr om all voltage sources.

2. Unclip the front bezel by gently pulling the centre of each long edge up and forward.

The case halves are held together by 4 plastic push-rivets. Use the blade of a s m all screwdriver in the slot beside each rivet to first ease out t he r ivet head and then fully remove the rivet body. Separate the case halves. Visit www.tti-test.com for further details.

Maintenance & Calibration

3. Replace the fuse with one of an identical rating using t he diagram below as a guide.

4. Reassemble in the reverse order.

Mains Fuse

The transformer pr imary is protected by an integral thermal fuse which is not user replaceable. Should a fault develop which causes the thermal fuse to blow, the meter must be returned to t he manufacturer or ag ent for service.

Remote Operation

The RS232 interface permits remot e cont r ol and data-logging to disk using optional Windows software; operation is controlled by clicking with the mouse on the keys of the virtual front panel displayed on the PC.

Connection between the RS232 port and the PC’s serial port is made using a 9-way D -type to D-type cable with all connections made, see Connections section under General Operation.

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