908 5½ Digit Dual Measurement Multimeter
CONTENTS 1 2 3 4 5 6 7 Product Description ......................................................................................................4 Safety .............................................................................................................................5 Symbols ...............................................................................................................................6 Installation ............................................................................
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 8 Dual Measurement Mode ................................
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 .................
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: • Operation from AC line or built-in rechargeable batteries. • 0.02% basic accuracy, 120,000 counts. • Manual or Auto-ranging.
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.
Symbols The following symbols are used on the instrument and in this manual: WARNING - risk of electric shock. CAT II CAT III mains earth (ground) CAUTION - refer to accompanying documentation; incorrect operation may damage the meter. Protective Earth terminal Measurement Category II. Inputs may be connected to AC mains power under Category II overvoltage conditions direct current Measurement Category III.
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.
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.
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.
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.
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 GPIB (1908P only) Protective Warning! This instrument must be Conductor earthed.
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.
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.
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.
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.
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.
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 [<] / [>].
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.
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.
Main Secondary Measurement Time (4SPS) Measurement Time (20SPS) Any Dual Function None .25s .05s Vac, dB, Iac Hz* .25s .05s Hz* Vac, Iac .25s .05s Vac, dB, Iac Vdc, Idc .5s .1s Vdc, Idc Vac, Iac .5s .1s Vac, dB Iac 6s 3s Iac Vac 6s 3s Vdc + Vac Vdc, Vac, Hz .5s .1s Idc + Iac Idc, Iac, Hz .5s .1s Measurement Time (4SPS) Measurement Time (20SPS) .25s .125s *Any Hz dual measurement Frequency measurements have a fixed measurement time (gate time) of 0.25s or 0.
10 Advanced and Programmable Functions A number of additional functions are available via the Functions menu, accessed by pressing the [Function] key. These include: Limits, Min/Max, Ax+b, Delta%, Watts and VA. An additional function of Logging is described in the next section. All functions are mutually exclusive and use the secondary display to show the result. Consequently they cannot be used with any measurement that requires the secondary display such as dual measurements and dB.
To select Ax + b, press [Function] and use the Navigator keys to choose {Ax+b} as the flashing symbol. Confirm with [OK]; the secondary display will flash the word {run}. To view or edit the A or b values, press [<] or [>] to select {Edit} and confirm with [OK]. The existing A value will be displayed and can be changed using the Navigator keys ([<] / [>] to select the digit and [ᴧ] / [v] to change the value).
confirmed with [OK], the display will return to {run}. Pressing [OK] at this point will start the function running. The reference value is can be number variable over the range ±000000 to ±999999; the decimal point position is set by the range in use during edit. The reference default value of 10000 (decimal point determined by range) can be entered by pressing the shifted key Clear [Shift] [Auto]. The latest meter reading can be entered by pressing the shifted key Copy Rdg [Shift] [Stop]. 10.
Logging Every reading (All) With the period set to All {ALL}, the timer is inoperative and readings are stored after every measurement, i.e. at the measurement rate of 4 readings/sec or 20 readings/sec dependant on mode and measurement speed setting. To select All, first set the period to Off (using the shifted key Clear [Shift] [Auto]) and press [v]. Confirm with [OK]. Logging from the Timer To engage the timer starting from Off or All, press the Navigator Up key once or twice respectively.
12 The Utilities Menu A number of options can be set via the Utilities menu. Pressing [Utilities] will cause the main display to show {–Util–} with the currently selected menu item flashing in the secondary display. Use the Navigator keys to select the required item and select it with [OK]. When selected the item name will appear in the main display with the current status flashing in the secondary display. Use the Navigator keys to change the status or value, and confirm it with [OK].
12.7 Temperature Probe Setup {rtd} The temperature measurement function can be set to use a two wire {2W} or four wire {4W} connection - the latter using the SENSE sockets in addition to the HI and LO INPUT sockets. The default value is four wire {4 W}. 12.8 Set Factory Defaults {rESEt} The instrument can be returned to factory defaults. This will return all values to their defaults and clear any stored data. When [OK] is pressed, the display will show Accept? {ACCEPt}.
13 Maintenance Routine maintenance is limited to re-calibration, resetting and cleaning. The only repair maintenance that can be carried out by the user is current range fuse replacement. 13.1 Calibration 13.1.1 Zero Calibration 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, meter accuracy may be affected as the meter’s temperature changes.
13.3.2 Internal AC power fuse The AC supply transformer on the Main PCB is protected against an internal fault by a nonresettable thermal fuse. To avoid the thermal fuse being accidentally tripped by connecting to a 230V supply when the instrument set for 115V operation, a standard 500mA (T) 250V fuse is fitted in position FS3 on the main PCB. Should this fuse need replacing, following such an event, remove the case upper and replace the fuse following the instructions and diagrams of Section 3. 13.
14 Remote Operation The 1908P model can be remotely controlled via its RS232, USB, GPIB or LAN interfaces. The 1908 (non ‘P’) can only be controlled via USB. In order to remotely control the instrument via RS232, GPIB or LAN, mains power must be applied. USB however can function with or without mains power applied as it is host powered. As such the USB interface can be used when powered from the batteries. The GPIB interface provides full facilities as described in IEEE Std. 488 parts 1 and 2.
The Baud Rate for this instrument is fixed at 9600; the other parameters are 8 data bits, no parity and one stop bit. Flow control uses the XON/XOFF protocol, but because of the low volume of data associated with this instrument it is very unlikely that flow control will actually be invoked. 14.3 USB Interface and Device Driver Installation The instrument firmware can be updated in the field through the USB port. This does not need the driver described here.
Since it is possible to misconfigure the LAN interface, making it impossible to communicate with the instrument over LAN, a LAN Configuration Initialise (LCI) mechanism is provided via a push switch (marked LAN reset) accessible through a small hole in the rear panel. This restores the default configuration with DHCP enabled, so the unit will then follow the sequence described in the previous paragraph. Note that resetting the LAN interface removes any password protection.
14.4.6 LXI Discovery Tool This tool can be used to display the IP addresses and other associated information of all connected devices that comply with the VXI-11 discovery protocol. It is a Windows PC application, which is provided on the supplied CD-ROM,that can be installed and run on the controlling PC, with the unit either connected directly to the PC network connector or via a router.
Error register. A summary is reported in the Status Byte Register, as selected by two masking registers – the Input Trip Enable register and the Standard Event Status Enable Register. Two further mask registers, the Service Request Enable register and the Parallel Poll Response Enable register, control operation of the GPIB hardware Service Request and Parallel Poll (and the associated ist message) respectively.
The Standard Event Status Register is read and cleared by the *ESR? query, which returns a decimal number corresponding to the contents. On power-up or initialisation after standby it is set to 128, to report the power-on bit. The Standard Event Status Enable Register provides a mask between the Event Status Register and the Status Byte Register. If any bit becomes ‘1’ in both registers, then the ESB bit will be set in the Status Byte Register.
15.5 GPIB Parallel Poll (PRE) Complete Parallel Poll capabilities are offered by this instrument as defined in IEEE Std. 488.1. The Parallel Poll Enable Register (which is set by the *PRE command and read by the *PRE? query) specifies which bits in the Status Byte Register are to be used to form the ist local message. If any bit is ‘1’ in both the STB and the PRE then ist is ‘1’, otherwise it is ‘0’. The state of the ist message can also be read directly by the *IST? query.
15.8 1908 Status Model 15.9 Register Summary Set Query Name † ITR? Input Trip Register ITE ITE? Input Trip Enable Register † EER? Execution Error Register † QER? Query Error Register † *ESR? Standard Event Status Register *ESE *ESE? Standard Event Status Enable Register *STB? Status Byte Register *SRE *SRE? Status Byte Enable Register *PRE *PRE? Parallel Poll Response Enable Register † These registers are cleared after being queried, or by the *CLS command.
16 Remote Commands 16.1 General 16.1.1 Remote and Local Operation At power-on the instrument will be in the local state, with normal keyboard operation possible. All remote interfaces are active and listening for a remote command. When any command is received from any interface the instrument will enter the remote state. In this state the keyboard is locked out, the display switches to the home screen, with the REM indicator displayed.
16.1.4 Command Timing There are no dependent parameters, coupled parameters, overlapping commands, expression program data elements or compound command program headers. All commands are separate and sequential, and are executed when parsed and immediately considered complete. To provide useful functionality, the Operation Complete bit (bit 0) in the Standard Event Status Register is only ever set by the *OPC command.
16.2 Command List This section lists all the commands and queries implemented in this instrument. All numeric parameters are shown as and may be sent as , or as described above. 16.2.1 General Commands READ? READ2? MODE? Returns the next reading from the main display immediately after the command has been parsed. The syntax of the response is: Where is a character string divided into 11-character plus up to 8-character fields.
MODE2? Returns the state of the secondary display, including the mode, range and whether the range is locked (manual) or autoranging. The syntax of the response is: ,,, The response includes three ASCII data fields. The first field contains the secondary display Mode which includes: VDC, VAC, IDC, IAC, FREQ. The second field contains the range e.g. 1000mV.
IAC Sets the main display to ac Amps and optionally sets the range; if no range is specified the display defaults to mA autorange. The following can be used to set the range: <1MA>,<100MA>,<1000MA>,<10A> IACDC Sets the main display to ac+dc Amps and optionally sets the range; if no range is specified the display defaults to mA autorange.
16.2.3 Dual Measurement Mode Commands VDC2 Sets the secondary display to dc Volts (autoranging). VAC2 Sets the secondary display to ac Volts (autoranging). IDC2 Sets the secondary display to dc Amps and optionally selects mA (autoranging) or the 10A range; if no range is specified the existing range is used. The following can be used: <1MA>,<100MA>,<1000MA>,<10A> If the main display is set to ac Amps the secondary range will be the same as the main display range.
16.2.5 Second Level Modifier Commands DELTA DELTA? Selects the Delta % function and optionally sets the reference value; if no reference value is specified the existing value is used. The percentage deviation shows in the secondary display. Returns the Delta % value. The syntax of the response is: Where is a character string divided into two fields (value followed by %) exactly as for the standard READ? Response; see that command section for details.
VA Sets the VA function; Vac or Vdc must first have been selected in the main display and the meter must be connected for both voltage and current measurement. VA shows in the secondary display. VA? Returns the result of the VA calculation. The syntax of the response is: Where is a character string divided into two fields (value followed by units) exactly as for the standard READ? response; see that command section for details.
16.2.7 16.2.8 Common Commands *IDN? Returns the instrument identification. The response is in the form , , , where is the manufacturer's name, is the instrument type, is the interface serial number and is the revision level of the firmware installed. *RST Resets the functional parameters of the instrument to the default settings as listed in the Factory Default Settings section. Does not affect any remote interface settings.
16.2.9 Interface Management Commands LOCAL Go to local. Any subsequent command will restore the remote state. ADDRESS? Returns the GPIB bus Address. The response is . IPADDR? Returns the present IP address of the LAN interface, provided it is connected. If it is not connected, the response will be the static IP if configured to always use that static IP, otherwise it will be 0.0.0.0 if waiting for DHCP or Auto-IP. The response is nnn.nnn.nnn.nnn, where each nnn is 0 to 255.
17 Default Settings As supplied, all conditions are set to defaults as in the listing below. The meter is returned to default settings by the system reset command from the Utilities menu (see section 12.8) or by the ∗RST remote command. Defaults: Measurement parameter set to DC Volts, single measurement mode. Auto-ranging mode set. All first level modifiers cancelled, including Ohms Null. All second level modifiers cancelled. Ax + b factors set to A = 1.0000 and b = 00000 Limits set to 0.
18 Graphical Interface PC software 1908-PC Link is a PC application that can be found in the 1908 folder on the CD-ROM provided with this instrument. It is an application that provides a graphical user interface (GUI) for remote control of the multimeter from a PC. Connection can be via USB, RS232, or LAN (Ethernet). The GUI provides remote access to the instrument using a point-and-click interface arranged similarly to the actual instrument.
19 Specifications ACCURACY Accuracies apply for 1 year 19°C to 25°C. Temperature coefficient outside these limits is <0.1 x quoted range accuracy per °C. DC Volts Range Accuracy Resolution Input Impedance 100mV 0.02% ± 3 dig. (after null) 1uV 10.11MΩ 1000mV 0.02% ± 3 dig. 10uV 10.11MΩ 10V 0.02% ± 3 dig. 100uV 10.0MΩ 100V 0.02% ± 3 dig. 1mV 10.1MΩ 1000V 0.02% ± 3 dig. 10mV 10.
Resistance 2-wire or 4-wire measurement. Range Accuracy Resolution 100Ω 0.05% ± 8 dig. 1mΩ 1000Ω 0.05% ± 5 dig. 10mΩ 10kΩ 0.05% ± 5 dig. 100mΩ 100kΩ 0.05% ± 5 dig. 1Ω 1000kΩ 0.05% ± 5 dig. 10Ω 10MΩ 0.3% ± 2 dig. 100Ω Maximum Input: 1000V DC or AC rms, any range. Maximum Open Circuit Voltage: 3.5V DC Current Range Accuracy Resolution 10mA 0.05% ± 5 dig. 100nA 100mA 0.05% ± 5 dig. 1uA 1A 0.2% ± 5 dig. 10uA 10A 0.2% ± 5 dig to 5A 100uA 10A 0.
Frequency Range Accuracy 100Hz 1000Hz Resolution 0.01Hz 0.01% ± 1 dig. 0.1Hz 10kHz 1Hz 100kHz 10Hz Accuracy specifications for 100Hz range apply only at slow measurement speed of 4 readings per second. Range: Input sensitivity: 10Hz to 100kHz Better than 30mVrms (100mV range); better than 10% of range for all other Vac and Iac ranges. Capacitance Scale length: Range 1200 counts Accuracy 10nF 100nF Resolution 10pF 2% ± 5 dig. 100pF 1uF 1nF 10uF 10nF 100uF 5% ± 5 dig.
DISPLAY Display Type: High contrast backlit LCD. Main display 5½ digits 16mm high, secondary display 6 digits 10mm high. Scale Length: 5¼ digits (120,000 counts) in most modes. Annunciators: LCD annunciators for all ranges, functions and program modes. Reading Rate: Varies with function, selectable between 4 SPS and 20 SPS. Overrange: Displays OFL if input too great for range. Overflow: Displays -Or- if calculated result overflows display.
Operating Range: +5°C to + 40°C, 20% to 80% RH Storage Range: −20°C to + 60°C Environmental: Safety & EMC: Indoor use at altitudes up to 2000m, Pollution Degree 2. Complies with EN61010-1, EN61010-2-030, EN61010-2-033 & EN61326-1. For details, request the EU Declaration of Conformity for this instrument via http://www.aimtti.com/support (serial no. needed). 250(W) x 97(H) x 295(D)mm in bench-top configuration 213.5(W) x 86.5(H) x 269(D)mm ( 2U/ ½ - rack) in rack-mount format Size: Weight: 3.2kg.
Thurlby Thandar Instruments Ltd. Glebe Road • Huntingdon • Cambridgeshire • PE29 7DR • England (United Kingdom) Telephone: +44 (0)1480 412451 • Fax: +44 (0)1480 450409 International web site: www.aimtti.com • UK web site: www.aimtti.co.uk Email: info@aimtti.
