AimTTi 1908 Series User manual

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
Distribution in the UK & Ireland
Lambda Photometrics Limited
Lambda House Batford Mill
Harpenden Herts AL5 5BZ
United Kingdom
E: [email protected]
W: www.lambdaphoto.co.uk
T: [phone]
F: [phone]
Characterisation,
Measurement &
Analysis

Page 1
CONTENTS
1Product Description......................................................................................................4
2Safety .............................................................................................................................5
Symbols ...............................................................................................................................6
3Installation .....................................................................................................................7
3.1 Mains Operating Voltage ..........................................................................................7
3.2 Mains Lead...............................................................................................................8
3.3 Mounting...................................................................................................................8
3.4 Handle/stand ............................................................................................................8
4Getting Started ..............................................................................................................9
4.1 Using this Manual.....................................................................................................9
4.2 Installation and Safety ..............................................................................................9
4.3 AC Power and Battery Operation .............................................................................9
4.4 Switching On and Off................................................................................................9
4.4.1 On/Off operation with AC Power .............................................................................9
4.4.2 On/Off operation without AC Power ......................................................................10
4.4.3 Power-up Settings.................................................................................................10
5Measurement Connections ........................................................................................10
5.1 Input Sockets..........................................................................................................10
5.1.1 Multimeter Test Leads ..........................................................................................11
5.2 Rear Panel Connections.........................................................................................11
5.2.1 Trigger In/Out........................................................................................................11
5.2.2 Digital Interfaces ...................................................................................................11
5.2.3 AC Inlet.................................................................................................................11
5.2.4 Protective Earth Terminal .....................................................................................11
6Making Basic Measurements .....................................................................................12
6.1 Scale Length...........................................................................................................12
6.2 Measurement Parameter Selection ........................................................................12
6.3 Measurement Range Selection ..............................................................................12
6.4 Making Voltage Measurements ..............................................................................13
6.5 Making Current Measurements ..............................................................................13
6.6 Making Resistance Measurements.........................................................................13
6.6.1 Two Wire Measurements ......................................................................................13
6.6.2 Four Wire Measurements .....................................................................................14
6.7 Making Continuity and Diode Checks.....................................................................14
6.7.1 Continuity Measurement .......................................................................................14
6.7.2 Diode Checks .......................................................................................................14
6.8 Making Frequency Measurements .........................................................................14
6.9 Making Capacitance Measurements ......................................................................15
6.10 Over Voltage Protection ......................................................................................15
6.11 Measurement Hold ..............................................................................................15
6.12 Measurement Null ...............................................................................................15
6.13 The Cancel Key...................................................................................................15
7Additional Parameters and Functions.......................................................................16
7.1 Combined AC + DC Measurements .......................................................................16
7.2 Decibel Measurement (dB).....................................................................................16
7.3 Removing Test Lead Resistance (:Null) ..............................................................16

Page 2
7.4 Temperature Measurement (oC/oF) ........................................................................17
7.5 Touch and Hold (T Hold) ........................................................................................17
7.6 Measurement Speed and Measurement Filter........................................................17
7.7 Zero Re-Calibration ................................................................................................17
8Dual Measurement Mode............................................................................................18
8.1 Dual Measurement Combinations ..........................................................................18
8.2 Making Voltage and Current Dual Measurements..................................................19
8.3 Measurement Update Times ..................................................................................19
9Triggered Operation....................................................................................................20
9.1 Trigger In Signal .....................................................................................................20
9.2 Trigger Out Signal (Measurement Complete).........................................................20
10 Advanced and Programmable Functions ..............................................................21
10.1 Selecting or Cancelling a Function......................................................................21
10.2 Limits...................................................................................................................21
10.3 Ax + b ..................................................................................................................21
10.4 Min-Max ..............................................................................................................22
10.5 Delta %................................................................................................................22
10.6 Watts ...................................................................................................................23
10.7 VA .......................................................................................................................23
11 Data Logging............................................................................................................23
11.1 Setting-up the Logger..........................................................................................23
11.2 Running the Logger.............................................................................................24
11.3 Starting and Stopping the Logger........................................................................24
11.4 Recalling Logger Readings .................................................................................24
11.5 Clearing Logger Readings...................................................................................24
12 The Utilities Menu ....................................................................................................25
12.1 Beep Sound {BEEp}............................................................................................25
12.2 Measurement Speed {SPEEd} ............................................................................25
12.3 Measurement Filter {FiLt}....................................................................................25
12.4 External Trigger {E-tr}..........................................................................................25
12.5 Battery Condition {bAtt} .......................................................................................25
12.6 dB Reference Impedance {db-rEF} .....................................................................25
12.7 Temperature Probe Setup {rtd} ...........................................................................26
12.8 Set Factory Defaults {rESEt} ...............................................................................26
12.9 Switch Off on AC Power disconnection {AC OFF}...............................................26
12.10 Measurement Update Symbol {StAr}...................................................................26
12.11 GPIB Address {Addr}...........................................................................................26
13 Maintenance .............................................................................................................27
13.1 Calibration ...........................................................................................................27
13.1.1 Zero Calibration ....................................................................................................27
13.1.2 Routine Calibration ...............................................................................................27
13.2 Hard Reset ..........................................................................................................27
13.3 Fuse Replacement ..............................................................................................27
13.3.1 Current Range Fuses............................................................................................27
13.3.2 Internal AC power fuse .........................................................................................28
13.4 Cleaning ..............................................................................................................28
13.5 Firmware Updates...............................................................................................28

Page 3
14 Remote Operation....................................................................................................29
14.1 GPIB Interface.....................................................................................................29
14.2 RS232 Interface ..................................................................................................29
14.3 USB Interface and Device Driver Installation ......................................................30
14.4 LAN Interface ......................................................................................................30
14.4.1 LAN IP Address and Hostname ............................................................................31
14.4.2 mDNS and DNS-SD Support ................................................................................31
14.4.3 ICMP Ping Server .................................................................................................31
14.4.4 Web Server and Configuration Password Protection ............................................31
14.4.5 LAN Identify ..........................................................................................................31
14.4.6 LXI Discovery Tool................................................................................................32
14.4.7 VXI-11 Discovery Protocol ....................................................................................32
14.4.8 VISA Resource Name...........................................................................................32
14.4.9 XML Identification Document URL ........................................................................32
14.4.10 TCP Sockets .....................................................................................................32
15 Status Reporting......................................................................................................32
15.1 Input Trip Registers (ITR & ITE)..........................................................................33
15.1.1 Input Trip Register (ITR) .......................................................................................33
15.2 Standard Event Status Registers (ESR and ESE) ..............................................33
15.3 Execution Error Register (EER)...........................................................................34
15.4 Status Byte Register (STB) and GPIB Service Request Enable Register (SRE) 34
15.5 GPIB Parallel Poll (PRE) .....................................................................................35
15.6 Query Error Register - GPIB IEEE Std. 488.2 Error Handling .............................35
15.7 Power on Settings ...............................................................................................35
15.8 1908 Status Model ..............................................................................................36
15.9 Register Summary...............................................................................................36
16 Remote Commands .................................................................................................37
16.1 General ...............................................................................................................37
16.1.1 Remote and Local Operation ................................................................................37
16.1.2 Remote Command Handling.................................................................................37
16.1.3 Remote Command Formats..................................................................................37
16.1.4 Command Timing..................................................................................................38
16.1.5 Response Formats................................................................................................38
16.2 Command List .....................................................................................................39
16.2.1 General Commands..............................................................................................39
16.2.2 Main Display Commands ......................................................................................40
16.2.3 Dual Measurement Mode Commands...................................................................42
16.2.4 First Level Modifier Commands ............................................................................42
16.2.5 Second Level Modifier Commands .......................................................................43
16.2.6 Data Logging Commands .....................................................................................44
16.2.7 Common Commands ............................................................................................45
16.2.8 Status Commands ................................................................................................45
16.2.9 Interface Management Commands.......................................................................46
17 Default Settings........................................................................................................47
18 Graphical Interface PC software.............................................................................48
19 Specifications ..........................................................................................................49
Note: This manual is 48581-1470 Issue 3

Page 4
1 Product Description
This precision bench-top/portable multimeter has dual measurement capability and a dual
display which can show either two independent measurements, a measurement together with
its range value, or a measurement with one of the many programmable functions available.
The key features are:
xOperation from AC line or built-in rechargeable batteries.
x0.02% basic accuracy, 120,000 counts.
xManual or Auto-ranging.
xDC and AC Volts, DC and AC current, Resistance, Capacitance, Frequency, and
Temperature measurement; Continuity and Diode checks.
xTrue RMS AC and AC+DC measurement.
xTwo or Four wire selectable ohms measurement.
xDisplay nulling and Ohms null.
xSelectable measurement speed.
xTouch hold mode - holds onto a stable reading until updated.
x500 point data logger with timer.
xTemperature measurement for PT100 or PT1000 sensors.
xMeasurement post-processing to give:
dB and power measurement with settable reference impedances
percentage deviation from a user-entered reference
linear scaling with offset
limits comparison for go/no go testing
automatic storage of minimum and maximum readings.
xRemote control via USB interface (1908)
xRemote control via USB, RS232, GPIB and LAN (LXI) interfaces (1908P)
xExternal input/output remote triggering.
x1908-PC Link software providing:
Remote control of main functions
Logging function with graphical & tabular displays
Logged data can be exported to a CSV file
xClosed case calibration.
xFully compliant with EN61010-1, EN61010-2-030 & EN61010-2-033 Safety, and
EN61326-1 EMC standards.

Page 5
2 Safety
This multimeter has been designed to meet the requirements of EN61010-1, EN61010-2-030 &
EN61010-2-033 (relevant parts of the ‘Safety Requirements for Electrical Equipment for
Measurement, Control and Laboratory Use’ standards). It can be operated from its built-in
rechargeable battery or from a standard AC mains supply (Overvoltage Category II). When
connected to AC mains, it is a Safety Class I instrument.
WARNING! THIS INSTRUMENT MUST BE EARTHED
Any interruption of the mains earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited. The protective action must not be
negated by the use of an extension cord without a protective conductor.
When operated from the internal battery, without an AC mains connection, the multimeter should be
earthed by connecting the rear panel Chassis Earth terminal to an external protective earth system.
Without this connection, ‘leakage’ current from any accessible part may exceed the Normal (safe)
limit of 0.5mArms under some extreme measurement conditions, e.g. high voltage, high frequency,
AC volts measurement. Measurements to 300VACrms, 50/60Hz, for example, would not require this
protective earth connection.
The test leads supplied with this instrument meet the requirements of EN61010-031 and are rated to
1000V Cat III; use only these test leads with the meter or a set of equivalent performance.
This instrument has been tested in accordance 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 retain the instrument in a safe condition.
This instrument has been designed for indoor use in a Pollution Degree 2 environment (only dry
non-conductive pollution occurs except that occasionally a temporary conductivity caused by
condensation is expected) in the temperature range 5qC to 40qC, 20% - 80% RH (non-condensing).
It may occasionally be subjected to temperatures between +5° and 10°C without degradation of its
safety.
It has been designed for measurement use to 1000VDC/750VACrms in circuits isolated from AC
mains power (derived secondary circuits within an equipment) with occasional transient over-
voltages up to 1500Vpeak. It can also be used for CAT II (Measurement Category II) use to
600VDC/ACrms, and CAT III use to 300V DC/ACrms. CAT II is local domestic supply level, e.g.
portable equipment and appliances; CAT III is mains distribution parts of a building.
For this equipment 4000V is the maximum peak transient overvoltage that can be tolerated by any
terminal with respect to earth ground without impairing safety.
Use of this instrument in a manner not specified by these instructions may impair the safety
protection provided. Do not operate the instrument outside its rated 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 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, maintenance or repair, including the
replacement of the current range protection fuses. 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. 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.

Page 6
Symbols
The following symbols are used on the instrument and in this manual:
WARNING - risk of electric shock. mains earth (ground)
CAUTION - refer to accompanying
documentation; incorrect operation may
damage the meter.
Protective Earth terminal
CAT II Measurement Category II. Inputs may be
connected to AC mains power under
Category II overvoltage conditions
direct current
alternating current
CAT III Measurement Category III. Inputs may be
connected to AC mains power under
Category III overvoltage conditions
Standby supply. Instrument is
not disconnected from AC
mains power when switch is off.

Page 7
3 Installation
3.1 Mains Operating Voltage
Check that the instrument operating voltage marked on the rear panel is suitable for the local
supply. Should it be necessary to change the operating voltage, proceed as follows:
1. Warning! Disconnect the instrument from all voltage sources before beginning this
procedure.
2. Pull out both sides of the handle at the case pivot points, to free the position locking
pegs, and rotate the handle from the stowed position to the position shown below. Then
pull the sides of the handle outwards fully, one at a time, to remove the handle
completely.
3. Remove the two screws on the rear panel that retain the top cover and slide the top
cover towards the rear, with the soft bezel still in place, until it can be lifted clear.
Note: To avoid contaminating or damaging the PCB assembly, take care not to touch
any components other than the two shorting connectors described in the next step.
4. Remove the shorting connector in position PJ4 on the PCB beside the mains
transformer (TX1) and replace it with the alternative shorting connector from the
‘parking’ position PJ8; align pin1 of the connector with the pin 1 corner marker of the
header. ‘Park’ the unused connector on PJ8, see the diagrams below.
For 230V operation PJ4 should be fitted with the connector which has a single red wire
between its centre pins (pins 2 & 3).
For 115V operation PJ4 should be fitted with the connector which has a blue wire
between pins 1 & 3, and a brown wire between pins 2 & 4.
Note that the value of fuse FS3 (500mA) is the same for both AC voltage settings, see
Maintenance, section 13.
5. Reassemble in the reverse order.
6. To comply with safety standard requirements the operating voltage marked on the rear
panel must be changed to clearly show the new voltage setting.

Page 8
3.2 Mains Lead
For AC mains operation, connect the instrument to the AC supply using the mains lead provided.
Should a power plug be required for a different power 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 determine the minimum current rating of the lead-set for the
intended AC supply, refer to the power rating information on the equipment or in the Specification.
WARNING! THIS INSTRUMENT MUST BE EARTHED.
Any interruption of the power earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited.
3.3 Mounting
This instrument is suitable both for bench use and rack mounting. It is delivered with soft protective
front and rear bezels which have integral moulded feet; this is the most suitable configuration for
bench use.
For rack mounting the protective bezels and handle/stand can be removed such that the instrument
can be fitted beside any other standard 2U half-rack instrument in a 19” rack. A suitable 2U 19”
rack kit is available from the Manufacturers or their overseas agents; full details of how to remove
the handle and bezels are included with the kit.
3.4 Handle/stand
The instrument is fitted with a 4-position handle/stand. Pull out both sides of the handle at the case
pivot points, to free the position locking pegs, and rotate the handle from the stowed position to the
required stand or handle position. Release the sides of the handle to lock it in the new position.

Page 9
4 Getting Started
4.1 Using this Manual
In this manual front panel keys are shown in bold square brackets, e.g. [Vdc],[Function].
Sockets are shown in bold capitals, e.g. INPUT HI. LCD display data is show in bold curly
brackets, e.g. {SPEEd},{AUTO}.
The manual is available in printed form and as an electronic document in PDF format. The
manual includes cross references which are underlined within the text. These are hyperlinks
within the PDF document. The Table of Contents is also fully hyperlinked.
Hyperlinks enable the user to jump rapidly to the section referred to and then jump back to
continue reading the original section. (N.B. for hyperlink navigation within Acrobat Reader,
enable “show all page navigation tools” or use the keyboard shortcuts Alt+Left_Arrow and
Alt+Right_Arrow).
4.2 Installation and Safety
Before first use, all users should read the Safety Information in section 2 .
Before connecting AC power, check that the instrument operating voltage marked on the rear
panel is suitable for the local supply. Should a change be required, read section 3.1
Connect the instrument to the AC supply using the mains lead provided. Should a power plug
be required for a different power outlet socket, refer to section 3.2.
4.3 AC Power and Battery Operation
The instrument can be operated from AC power or from internal rechargeable batteries which
are recharged as required when AC power is connected. A red LED is illuminated whenever
AC power is connected and a yellow LED is illuminated whilst charging is taking place.
Battery Life from fully charged is approximately 20 hours with the backlight on, and up to 35
hours with the backlight off. Under battery operation a battery symbol will appear on the display
if the charge level falls below about 10%. The approximate charge level can be checked from
the Utilities menu – see section 12.5.
For the 1908P, operation of the remote interfaces (excluding USB) is only possible with AC
power connected.
4.4 Switching On and Off
The instrument behaves differently depending upon whether or not AC power is connected.
4.4.1 On/Off operation with AC Power
If required, AC power can be switched on or off using the POWER switch mounted on the rear
panel. When the AC power is switched off the default setting is for the instrument to turn off. This
ensures appropriate behaviour when used as part of a group of equipment for which AC power is
turned on or off simultaneously.
Note: To fully disconnect from the AC supply unplug the mains cord from the back of the
instrument or switch off at the AC supply outlet; make sure that the means of disconnection is
readily accessible. Disconnect from the AC supply when not in use.
The green front panel button marked [OPERATE] can be used to place the instrument into
Standby if required. Successive presses will alternate between On and Standby.
Alternative AC Power Switching Options
The response of the instrument to AC power being connected or disconnected can be altered if
required. The actions described above are the default conditions, and can be changed from the
Utilities menu – see section 12.9.

Page 10
4.4.2 On/Off operation without AC Power
With no AC power connected, operation is from the internal rechargeable batteries and the
instrument is turned on or off by successive presses of the green [OPERATE] button. The rear
panel POWER switch has no function.
4.4.3 Power-up Settings
At power up the display briefly shows the installed software revision; the instrument is then restored
to the same measurement conditions as at power down, including any advanced functions that were
running. However, if the instrument was showing a menu at power down, the menu will be
cancelled when powered up.
5 Measurement Connections
5.1 Input Sockets
The input sockets are 4mm safety sockets on a 19mm pitch designed to accept 4mm safety
plugs with fixed or retractable shrouds. All sockets are rated to 1000Vpeak with respect to earth
ground. Safety will be maintained if voltages up to 1000Vpeak are accidentally applied between
inappropriate terminals in excess of their marked ratings, but restoration of normal operation
may require replacement of protection devices (e.g. current range fuses).
The input impedance between INPUT HI and INPUT LO is nominally 10M:on dc ranges and
1M:on ac ranges. The black LO socket is considered less positive than the red socket. The
maximum voltage that can be applied between HI &LO is 1000Vdc, 750Vrms (1000Vpeak).
The sockets are rated to 600V CAT II, 300V CAT III.
The mA/10A current sockets are low impedance; the voltage burden between mA/10A and LO
at full scale is <100mV for the 10mA range and <600mV for the 100mA, 1A and 10A ranges.
The black LO socket is considered less positive than the white mA/10A sockets. The mA/1A
socket is protected with a 1.6A 1kV HRC fuse, and the 10A socket with a 10A 1kV fuse; see
Maintenance, section 14, for replacement details.
The SENSE HI & LO sockets are only used in 4-wire Ohms and RTD temperature
measurements; refer to those sections for details. When used, the maximum differential
between SENSE LO and INPUT LO should be < 0.5Vpeak. The SENSE terminals are
protected against accidental connection of up to 200Vpeak between HI &LO.
Display
Measurement
terminals
Measurement keys
Navigation
keys
Function keys
Power
Function keys

Page 11
5.1.1 Multimeter Test Leads
The test leads supplied meet the requirements of IEC1010-031 and are rated to 1000V Cat
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, 600V (Cat II) and 10A
current capability.
5.2 Rear Panel Connections
5.2.1 Trigger In/Out
Screw-less connectors are provided on the rear panel for the connection of an external trigger
signal, and a trigger out signal. See section 9 for full details.
5.2.2 Digital Interfaces
Depending upon model, rear panel connectors are provided for USB only (1908) or USB,
RS232, LAN and GPIB (1908P). Refer to Remote Operation, section 14, for full details.
5.2.3 AC Inlet
The instrument can be connected to AC mains using the power lead supplied or a suitable
alternative, see Installation section 3.2. When the power lead is connected this lead provides the
necessary protective earth connection to an external protective earth system.
5.2.4 Protective Earth Terminal
For battery only operation, without an AC power lead connected, the M4 threaded chassis
connection marked must be connected to an external protective earth system via a
green/yellow insulated cable, with a cross-section of at least 0.75mm2, fitted with a M4 terminal.
Without this connection, ‘leakage’ current from any accessible part may exceed 0.5mArms, the
Normal (safe) limit specified by EN61010-1, under some extreme measurement conditions, e.g. high
voltage, high frequency, AC volts measurement.
. WARNING! THIS INSTRUMENT MUST BE EARTHED.
TTL/CMOS
External Trigger
Warning! This instrument must be
earthed. Connect terminal to an external
protective earth system when instrument
is used without an AC mains connection.
Kensington
Lock
USBRS232LAN
Power
switch
AC power
connection
Protective
Conductor
Terminal
(
1
908
P
)
GPIB
(1908P
only)

Page 12
6 Making Basic Measurements
This section describes how basic measurements are made, i.e. single measurement mode
without post-processing of the results.
6.1 Scale Length
The scale length is ±120,000 for all measurements except frequency (full scale 12,000) and
capacitance (full scale 1200). {OFL} is displayed when the range maximum is exceeded.
Note, however, that safety considerations limit the maximum voltage and current that can be
measured to below the scale length maximum.
6.2 Measurement Parameter Selection
Refer to the front panel diagram in section 5.1
The two rows of darker grey keys below the display directly select the measurement
parameters for either the primary or secondary display. When pressed alone the parameter
keys select the measurement parameter for the primary display, cancel any secondary
functions, and set the range to auto-range.
Pressing [2nd] followed by a parameter key selects the parameter for the secondary display;
this is explained fully in Dual Measurement Mode, section 8, which also details the
combinations of parameters that can be used.
Additional parameters marked in blue above certain keys are selected by first pressing [SHIFT].
Whilst shift is operational a {SHIFT} symbol appears on the left side of the display.
See section 7 for full details.
6.3 Measurement Range Selection
Refer to the front panel diagram in section 5.1, and to the display diagram below.
When a parameter is first selected, auto-ranging is enabled and an {AUTO} symbol is
displayed. Pressing either of the [ଢ଼]/[v] arrow keys (Range+/Range-) cancels auto-ranging
whilst leaving the range set to its existing value. The {MAN} symbol is displayed and further
presses then change the range upwards or downwards. Pressing [OK] returns the instrument
to auto-ranging operation.
The units appropriate to the function and range (e.g. {mV ac}) are shown to the right of the
display. When the secondary display is not being used to show measurement values, the
selected range is shown there.
Note that the 10A range, which uses a different input socket from mA measurements, can only
be selected manually. Once 10A has been selected, however, this setting will be retained for
current measurement until it is returned to mA.
Note that the {AUTO} and {MAN} symbols apply only to the primary display.
Primar
y
measurement
ected auto
ranging is
Range or
2nd measurement
Functions
2
Remote
communications
Status
Range
Mode

Page 13
6.4 Making Voltage Measurements
Having selected Vdc or Vac, voltage measurements are made using the red INPUT HI socket
and the black INPUT LO socket within the yellow area of the panel. Five measurement ranges
(auto or manual) are available from 100mV to 1000V (dc) or 750V (ac).
The meter will show a minus sign {-} (on dc measurements) when the voltage applied to the
INPUT HI socket is more negative than that applied to the INPUT LO socket.
The maximum voltage that can be applied between INPUT HI and LO is 1000V DC or 750V
AC; damage to the instrument may result if this limit is exceeded.
WARNING! The maximum input voltage to ground must not exceed 1000V peak. Safety will be
impaired if these ratings are exceeded, see Safety section at the beginning of the manual.
6.5 Making Current Measurements
Having selected Idc or Iac, current measurements up to 1.2A (1200.00mA) are made using the
white mA socket and the black INPUT LO socket; current measurements up to 10A are made
using the 10A and LO sockets. The meter will show a minus sign {-} (on dc measurements)
when the polarity of the current is such that it flows out of the mA or 10A sockets rather than
into it.
Using the mA socket three measurement ranges (auto or manual) are available from 10mA to
1000mA. Measurements up to 10A can be made using the 10A socket having manually ranged
to 10A with [ଢ଼@.
The 10mA, 100mA and 1000mA ranges, using the mA socket, are protected by a 1.6A (F) HRC
fuse. The 10A range, using the 10A socket, is protected by a 10A (F) HRC fuse. Both fuses are
accessed via a panel on the base of the instrument.
The input test leads and AC power lead must be disconnected before opening the fuse
access panel.
Note: After measuring high currents (i.e. above half scale) using the 1A or 10A ranges, thermal
voltages are generated that may create errors when making measurements on the most
sensitive dc voltage, current or Ohms ranges immediately afterwards. To ensure that the
specified accuracy is maintained, allow 10 minutes for the thermal effects to reduce before
making sensitive measurements.
6.6 Making Resistance Measurements
Pressing [:
:
2/4] selects resistance measurement in either 2 wire or 4 wire mode. Successive
presses alternate between the modes as indicated by {2W
:`
or {4W
:`
appearing briefly in the
secondary display. Six measurement ranges (auto or manual) are available from 100:to
10M:.
6.6.1 Two Wire Measurements
Normal (2 wire) resistance measurements are made using the INPUT HI and LO sockets within
the yellow area of the panel. This measurement mode is appropriate for higher resistance
measurements, and for lower resistance measurements where high precision is not required.
The effects of test lead resistance can be removed using :Null if required – see section 7.3.

Page 14
6.6.2 Four Wire Measurements
4 wire measurements are appropriate for precision measurement of low resistances where the
effects of the connecting leads and contact resistances are significant. 4 wire measurement
uses the HI and LO SENSE sockets in addition to the HI and LO INPUT sockets.
Connections are made as shown below.
Two Wire Measurement Four Wire Measurement
Because no significant current is flowing through the SENSE connections when utilising 4 wire
measurement, contact resistance does not affect the measurement result.
6.7 Making Continuity and Diode Checks
Pressing []selects either continuity measurement or diode test. Successive presses
alternate between the two as indicated by symbols on the left side of the display. Continuity
and diode checks are made using the INPUT HI and LO sockets within the yellow area of the
panel.
6.7.1 Continuity Measurement
Setting continuity causes the 1000:range to be selected such that readings below
approximately 10:will sound the continuity buzzer. Readings above the range maximum will
show {OPEn}.
6.7.2 Diode Checks
Setting diode check causes the 1000mV range to be selected and a current of approximately
1mA to flow out of the INPUT HI socket. With the anode of the diode connected to this terminal
the diode forward voltage will be shown. Reverse diode connection will show {OFL}.
6.8 Making Frequency Measurements
Pressing [Hz] selects frequency measurement. Measurements are made using the INPUT HI
and LO sockets within the yellow area of the panel. Four ranges (100Hz to 100kHz) are
available, giving resolutions of 10mHz to 10Hz respectively over an operating frequency range
of <10Hz to 120kHz. Reciprocal counting techniques ensure fast reading updates
(4 readings/second) even on the lowest range.This can be increased to 8 readings/second in
fast speed mode see section 12.2; however the slow speed mode should always be used when
measuring low frequencies in the 100Hz range to ensure accurate readings.
Measurements are made using the ac Volts input circuitry which is auto-ranged to provide
suitable sensitivity. At low signal levels use a screened lead and an adaptor (BNC to 4mm
plugs, 19mm pitch) to preserve signal quality and avoid spurious readings from stray pick-up.
The minimum measurable signal is <30mV rms across the frequency range (100mV range) or
<10% of range maximum for other ac voltage and current ranges.
Frequency can also be measured in dual measurement mode, see section 8.1.

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6.9 Making Capacitance Measurements
Pressing []selects capacitance measurement. Measurements are made using the INPUT
HI and LO sockets within the yellow area of the panel. Five ranges (10nF to 100µF) are
available with 1200 count full scale giving resolutions of 10pF to 100nF respectively.
Zero calibration at the factory is carried out with no test leads connected; ideally, capacitors to
be measured should be connected directly to the sockets. Test leads, if used, should be kept as
short as possible to minimise stray capacitance but nevertheless a non-zero reading will
generally be present when the lowest ranges are selected. To eliminate this offset it is
recommended that the meter reading is nulled, once the required range has been selected, with
the test leads in their measurement positions but no capacitor connected.
It is also recommended that battery operation is used when making capacitance
measurements, to minimise reading jitter. Note that, because the capacitor is discharged
between each measurement, the reading rate on the 100µF range is slower.
6.10 Over Voltage Protection
When making measurements of Resistance, Capacitance, Temperature, Continuity or Diode
checks an internal protection circuit protects the current source from source voltages applied to
the INPUT HI and LO sockets. If a voltage of greater than typically 10V is applied to the INPUT
HI and LO sockets the protection circuit will be engaged, the buzzer will sound and {trIP} will be
displayed. After completion of the trip event, the measurement mode is set to Vdc to show the
over-voltage that is being applied to the input sockets. BIT 0 of the Input Trip Register (ITR) is
set to 1 (over voltage protect) see section 15.1.
6.11 Measurement Hold
Hold operates only on the primary display. Pressing [Hold] causes the measurement to be
frozen on the display along with a {HOLD} symbol. Provided that the meter is not in dual
measurement mode and not measuring capacitance, the normal, updated, reading will be
shown in the secondary display.
Hold only operates on the primary display, any measurement being shown on the secondary
display will continue to update normally.
Hold is cancelled by pressing [Hold] again, or by changing range or function.
6.12 Measurement Null
Null operates only on the primary display. Pressing [Null] causes the measurement to be
stored and subtracted from all future readings. Pressing [Null] locks the meter in the selected
range and shows {NULL} (and {MAN}) symbols. Provided that the meter is not in dual
measurement mode and not measuring capacitance, the normal, un-nulled, reading will be
shown in the secondary display.
Null is cancel by pressing [Null] again, or by changing range or function.
6.13 The Cancel Key
[Cancel] can be used to return the meter to a basic measurement mode. It cancels dual
measurement mode, dB, Null, Hold and T-Hold, and any programmable functions including the
Logger. It does not cancel :Null.
Consequently [Cancel] should not be used to cancel a single function, such as Hold, if other
functions need to be maintained.

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7 Additional Parameters and Functions
A number of additional capabilities can be accessed using the measurement parameter keys,
as described below. Further functions also can be selected from the Functions menu key – see
section 10.1
7.1 Combined AC + DC Measurements
Vdc+Vac or Idc+Iac measurements are made by pressing both keys together. The reading
displayed is the RMS sum (dc2+ ac2) and ac+dc is shown on the display.
Both ac and dc measurements are made on the same range: the instrument will auto-range to a
range which gives an in-range reading for both the ac and dc component of the parameter.
Clearresult to be shown as an in-range reading.
Note that this is a special case of Dual Measurement mode (see section 8.3) and the
measurement update rate is slowed accordingly.
7.2 Decibel Measurement (dB)
dB (deciBel) can be selected only when Vac is already in the main display. Pressing [Shift]
followed by [Vac] shows the dB value of the Vac measurement (referred to the chosen
impedance setting) and displays the {dB} symbol. If no secondary function is selected the
normal reading in volts will be shown in the secondary display.
dBs are shown in a fixed format with 0.1dB resolution, whatever range the Vac measurement is
being made on. The value displayed is in dBm and is calculated from the formula:
dB = 10 log10 (1000 x V2/R), where R is the selected reference impedance.
The default reference impedance is 600:but a different value can be selected within the
Utilities menu. Press [Utilities], use the Navigator keys to select {rEF} and confirm with [OK].
The existing reference value will flash. Alternative values can be selected using the Navigator
keys and confirmed with [OK].
Available values are 50, 75, 93, 110, 124, 125, 135, 150, 250, 300, 500, 600, 900, 1000, 1200,
and 8000:. Pressing [Shift] followed by [Auto] (Clear is the shifted function of Auto) returns
the value to 600:. Press [Utilities] again to exit the Utilities menu.
dB is cancelled by pressing [Vac], or by selecting any other measurement parameter or
function.
7.3 Removing Test Lead Resistance (:
:
Null)
Residual test lead resistance can be nulled out using the Ohms Null facility as follows:
Connect the test leads together and press [Shift] followed by [
:
2/4] (:Null is the shifted
function of :). The 100:range is set automatically and the {NULL} symbol flashes; the meter
stores the reading that it detects after 5 seconds provided that it is less than 1.000:(1000
counts). A beep sounds when the null is completed and the display should show zero Ohms
and no {NULL} symbol.
If the reading cannot be nulled, because the offset is too large, the reading will not change and
the buzzer will not sound.
The Ohms null is stored as a floating point value which is used on all ranges; it is not lost when
the function is changed or when the instrument is turned off. Ohms null can be cancelled by
selecting Ohms Null and not generating a sub 1.000:reading within the next 5 seconds, or by
restoring the instrument to factory defaults – see section 12.8.
Normal Null can be used together with Ohms Null.

Page 17
7.4 Temperature Measurement (oC/oF)
The instrument incorporates linearised measurements for PT100 and PT1000 platinum
resistance temperature detectors (RTDs).
The temperature function is selected by pressing the shifted function marked °C/°F [Shift]
[]. The default measurement is in degrees centigrade. To change to degrees fahrenheit
select the function again.
The default probe type is PT100. To change to PT1000 use [<] /[>].
The measurement can use either a 2 wire or 4 wire connection, the latter using the HI and LO
SENSE terminals in addition to the HI and LO INPUT terminals. The selection is made from the
Utilities menu – see section 12.7.
7.5 Touch and Hold (T Hold)
T-Hold causes the meter to “hold” a reading on the display 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 afterwards. It is not available for Ohms, Continuity, or Diode Test
measurements.
T Hold is selected by the shifted key marked T-Hold [Shift] [Hold].The{T-HOLD} symbol is
displayed, and each new reading is indicated by a beep sound. Measurement update is slow,
and small changes to the signal that occur after the probes have been connected will not be
shown.
Note that care should be taken when using T-Hold with the most sensitive voltage ranges; when
the probes are lifted from the circuit being measured, their high impedance means that stray
pick-up might generate another ‘valid’ reading and the true T-Hold reading may be lost.
T-Hold operates only on the primary display in both manual and auto-range modes; it is
cancelled by pressing T-Hold again [Shift] [Hold] or by changing the measurement parameter
or range.
7.6 Measurement Speed and Measurement Filter
The normal measurement speed is 4 readings/sec for most single measurement parameters.
For voltage, current and resistance measurements, the speed can be increased to 20
readings/sec at the expense of resolution which reduces to 12,000 counts. This is done from
the Utilities menu, see section 12.2.
In order to minimise jitter for sensitive measurements, an analogue filter is incorporated that
provides high rejection of 50Hz or 60Hz noise. Where the user requires quicker response to
signal changes, the filter can be switched off. This is particular relevant when the measurement
speed is set to 20 readings/sec. The filter is controlled from the Utilities menu, see section
12.3.
7.7 Zero Re-Calibration
An automatic zero calibration of the basic DC measurement circuitry is performed every time
that the instrument is switched on. However, if the meter has been stored at a temperature
outside the specified operating range, and is switched on before it has fully acclimatised to the
working environment, accuracy may be affected as the meter’s temperature changes. To
ensure optimum accuracy, particularly on the 100mV and mA current ranges, zero calibration
can be repeated when the meter has acclimatised by using the Null key as follows:
Press [Null] and continue to hold it down until {nULL} shows in the main display (about 3
seconds later). {nULL} continues to show whilst the auto-zero is being performed (typically 5
seconds); on completion the display returns to its previous mode.
Auto-zeroing in this way cancels Null if this was already selected; press [Null] again to re-select
if required.

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8 Dual Measurement Mode
In Dual Measurement mode a completely independent but complementary measurement can be
made and displayed on the secondary display. The two independent measurements are actually
made alternately, not simultaneously, and the display update rate for each measurement is
consequently reduced.
Note that this is not the same as dual display mode, where both a measurement and a modified
version of that measurement are displayed, e.g. ac Volts and the dB equivalent. In this case only a
single measurement is being made and the measurement rate is unchanged; further information is
given later in this section.
8.1 Dual Measurement Combinations
The full list of dual measurement functions is as follows:
Main Measurement Secondary Measurement
Vdc Vac, Idc, Iac
Vac Vdc, Idc, Iac, Hz
Vdc + Vac Vdc, Vac, Hz
dB Vdc, Idc, Iac, Hz
Idc Vdc, Vac, Iac
Iac Vdc, Vac, Idc, Hz
Idc + Iac Idc, Iac, Hz
Hz Vac, Iac
The parameter for the secondary display is selected by pressing [2nd] followed by the chosen
measurement parameter. The secondary display parameter must be selected after the main
parameter has been set. Pressing an illegal parameter will cause a warning double beep and
the key entry will be ignored
Capacitance, :, and Continuity/Diode check cannot meaningfully be combined with other
measurements and are therefore always excluded from the secondary display. Vac+Vdc and
Iac+Idc are also excluded because they already involve dual measurements; when they are
being used no secondary display can be set.
The secondary measurement, with the exception of the 10A current ranges, always auto-
ranges. The 10A current ranges are set by first selecting the function ([2nd] followed by [Iac] or
[Idc]) then pressing [2nd] followed by [ଢ଼]. To return to the mA measurement select [2nd]
followed by [v]. However, if both main and secondary displays are making current
measurements, the range of the secondary measurement is always that of the main display.
If Vdc and Vac are the two measurement functions, auto-ranging of the secondary display is
restricted such that the dc measurement range is not lower than the ac range; this ensures that
the dc measurement is not affected by a high ac signal, see the table within the Specification
section 19.
For example, if the main display is set to 10Vdc the secondary display can auto-range between
the 100mV, 1000mV and 10Vac ranges. In this example, low levels of ripple could be measured
(on the 100mV range) on a 10Vdc supply rail, but an ac input >12V will cause the secondary
display to show Overload {OFL} warning the user to select a higher main display dc range such
that the secondary ac measurement is in range. Similarly, if the main display is set to 100Vac
then the secondary display will not auto-range below 100Vdc, even for small dc inputs.
When frequency is selected for the secondary display the measurement is made using the ac
range set in the main display. This presents no problems if the main display is in auto-range but
if a higher range has been set manually, such that the reading is less than 5% of the range
maximum, the signal level may not be adequate for frequency measurement.

Page 19
8.2 Making Voltage and Current Dual Measurements
Measuring ac and dc Volts, or ac Volts and frequency, etc. still only require two measurement
probes because both parameters of the dual measurement are made at the same physical
point. Simultaneous measurement of voltage and current on the same circuit will however
require a third connection, see the diagram:
Note that the voltage measured at the multimeter terminals is that across the load plus the
voltage drop in the common lead which is now carrying the whole circuit current. Even if the
resistance of the lead is very low, errors may arise at high currents and low voltages (i.e. low
load resistance) because the lead resistance becomes significant compared with the load.
8.3 Measurement Update Times
As discussed at the beginning of this section, the reading update rate is reduced in Dual
Measurement Mode because the two readings are made alternately. However, the reading rate
is not simply halved because enough time must be allowed for each measurement to fully settle
to the different conditions before the display is updated; unless this is done neither display will
reliably show the true measurement value. The settling time depends on the differences
between the main and secondary measurement range, function, and signal level; the delay is
longest when both displays show an ac measurement. Note that the settling times allowed
assume a steady state signal; varying signals, or signals that exceed the range maximum on
either measurement, will give unpredictable readings.
The following table summarises the measurement time (i.e. the time for the measurement to settle
and the display to be updated) for each parameter in all the permitted display combinations.