Model 931A Power System Analyzer

Model 931A Power System Analyzer

Full featured Model 931A goes beyond basic and power quantity measurements, supporting two way communications, transducer calibration, timer features and more.

Model 931A Manual
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Model 929A/930A/931A Data Sheet
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Model 929A/930A/931A Data Sheet Español
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Model 931A, with state-of-the-art PowerDSA Digital Signal Analysis, make more measurements, more accurately, and at a lower price than ever before. Basic accuracy of 0.05 % of reading and 0.05 ° phase, harmonic analysis, and full three-phase capability are standard. Model 931A also incorporate full two way serial communication for use in power quality trend monitoring. The model expands usability by including transducer calibration and timer features.

Model 931A, featuring PowerDSA Digital Signal Analysis, measures all of the basic quantities: true-rms voltage and current, frequency and phase angle, as well as power quantities such as watts (W), watthours (Wh), volt-amperes (VA), volt-ampere hours (VAh), volt-amperes reactive (VAR), volt-amperes reactive hours (VARh), and power factor (PF), all with 0.11 % basic accuracy.

Measure harmonics and view the results graphically on the high contrast 240x64 graphic display. The two channels are normalized to Channel 1 fundamental phase, so you can see, for example, the relationship between current waveform distortions and voltage phase.

Other key functions include a timer/counter for measuring relay operating times, elapsed test times, or for counting input rates and events. The 931A include a full three-phase input section, for automated three-phase measurement sequences, complete with multiple display modes (see Key Features tab, below)

  • Top-of-the-line Power Measurement and Analysis product
  • Measures basic and power quantities
  • High accuracy
  • Field ready
  • Multiple display options including three phase displays

Basic three-phase display - Voltage, current, phase, frequency and power quantities on one convenient display.
Vector display - view voltages, currents and phase angles with their vector representation.
Voltage/Current Sequence display - view voltage, current and phase along with positive, negative and zero sequence values.
Energy display - view voltage, current, phase, frequency and energy quantities on one convenient display.

  • Power Trend Monitor and recording system - verify phase relation, phase rotation, power direction, load balance and more
  • Transducer Calibration supported
  • CT/PT Ratios
  • Extended Measurement Ranges



Basic Inputs

Supports two main measurement channels, Channel 1 and Channel 2. Any voltage or current input signal may be selected for either channel. For basic measurements (voltage, current, frequency, phase angle) any combination of inputs may be used. For power and energy measurements (active power, apparent power, reactive power and power factor), one voltage and one current must be selected. For three-phase measurements, the input configuration is selected automatically, based on the measurement type (for example, 3-phase 4-wire 3-element).


Input Range

1.5 Vrms to 750 Vrms (underrange to 200 mV) [2 Vdc to 1000 Vdc (Model 931A Only)]


Four; A, B, C, N
Phase-to-Synthesized Neutral (A+B+C / 3)


1 megohm


< 3.5 mA per IEC348 and UL1244


Input Range

0.04 Arms to 20 Arms (underrange to < 1 mA)


Three; A, B, C, plus synthesized neutral


0.01 ohm maximum


Transformer, 1000 Vrms


Synthesized, -(A+B+C)



Two; 4 Vdc to 300 Vdc; 20 Vrms to 300 Vrms; or dry contact/thyristor output


Optical, 300 Vrms, each channel



0 to 1, 0 mAdc to 100 mAdc and 0 Vdc to 10 Vdc


Overvoltage to 120 V, both inputs


Optical, 300 Vrms


Voltage and Current


Wideband: True rms, 3 kHz Bandwidth
Narrowband: Fundamental magnitude


0.05 % of reading


< 1 % of reading, typical at 0.3 mArms

DC Voltage

0.1 % of reading + 25 mVdc, typical

Phase Angle


Channel 1 to Channel 2

A-B Range

0 ° to 360 ° or ± 180 °

A-B Accuracy

0.05 °


< 1 °, typical at 0.3 mArms



Channel 1


20 Hz to 500 Hz (underrange to 5 Hz)


0.005 % of reading



Channel 1 or Channel 2


2nd to 50th Harmonic (50 Hz or 60 Hz fundamental)


5 % of THD reading + 0.01 %


THD; K-factor; Amplitude bar graph; and individual harmonic magnitude and phase (simultaneous)

Waveform Display

Channel 1 and/or Channel 2



0 MVA or MVAh to 99999 MVA or MVAh
± 99999 MVAR or MVARh
± 99999 MW or MWh
± 1.0000 PF, lead or lag


0.11 % of VA, for VA, VAR, and W
0.001 PF



0.0001 seconds to 9999.9 seconds, or 0.01 cycles to 999999 cycles


0.005 % of reading + 1 digit

AC Trigger

Add 1 ms maximum, 0.15 ms at 120 Vrms

Transducer Accuracy

0.05 % of reading + 0.01 % range




240x64 graphic LCD with cold-cathode fluorescent lamp (CCFL) backlight


21 function keys plus On/Off


EEPROM (calibration data)
Battery backup RAM (setup and stored results)
Real-time clock


Instrument calibration data
User setups (up to six)
Logged data (15 to 200); time-tagged

Power Requirements

Internal Battery


Sealed lead-acid


8 hours typical

Charging Time

8 hours typical; fast + float charge



85 Vac to 264 Vac, 47 Hz to 440 Hz, 15 VA maximum
110 Vdc to 250 Vdc, 15 W maximum


Designed to meet UL, CSA, VDE




205 mm x 305 mm x 225 mm (8 in x 12 in x 8.75 in)
483 mm x 483 mm x 483 mm (16 in x 16 in x 16 in), shipping


5.8 kg (12.8 lbs), net
8.2 kg (18 lbs), shipping



Operating: 0 °C to + 50 °C
Nonoperating: - 40 °C to + 75 °C



931Aopt01 16 MB memory
812H-8 Safety Ground Lead
AS0094000 Operation Manual (931A)
CA0019806 RS-232 Null Modem Cable, DB9F-DB9F, 2 m (6 ft) length
P09R Power Cord, North America, Right Angle
09311A 400 A 20:1 Precision CT, 0.1 % Accuracy
811AT-8 3-Phase Univ. Test Plug Current Lead Set
813AT-8 3-Phase Safety Voltage Lead Set
815AT-8 Model 815 Fused Safety Voltage Probe Lead Set
816AT-8 3-Phase Spade-Lug Current Lead Set
817AA-8 1-Phase Clamp-On CT Test Lead
817AT-8 3-Phase Clamp-On CT Lead Set
818AT-8 3-Phase Safety C-Hook Current Lead Set
819xyz-8 Modified Safety Clip Lead Set
841A Series Test Jack Isolator Paddle
842A Three - Series Test Jack Isolator Paddles with 60 cm Nylon Cord
842B Four - Series Test Jack Isolator Paddles with 60 cm Nylon Cord
AP0001300 1000:1 Clamp-on CT, 1000 A (Current Output)
AP0010300 100:1, 600 A rms, Clamp-On, CT (Current Output)
AP0012800 1000:1, 200 A rms, Clamp-on CT
AP0012900 250:5, 500:5, 1000:5, 1000 A rms, Clamp-on CT
AS0035901 Adjustable Tilt Handle/Bail Assembly
AS0036000 400 A CT Bracket (each)
AS0060000 1 PowerCSV Application Software for Models 931A and 930A
AS0079001 Universal Test Plug Current Shunt, A Phase Red
AS0079002 Universal Test Plug Current Shunt, B Phase Yellow
AS0079003 Universal Test Plug Current Shunt, C Phase Blue
AS0079030 Universal Test Plug Current Shunt, Set of Three
CN0030500 Adaptor Banana Shielded - Red
CN0030501 Adaptor Banana Shielded - Black
P01R-P10R Country specific power cord with right angle female end

1  Available via download only

Click to Download Latest Version of Software
930/31_PowerCSV_14Oct2010_2002 For Models 930 and 931 - requires memory option
Tera Term_01Jan2010_23 This is a very good HyperTerminal replacement. Able to capture data from Models 930A and 931A. Also able to program the GPS Satellite Controlled Clocks via serial commands.


Software Version and Related Information

Common Controls Update for PowerCSV



PowerCSV for Models 930 and 931 (930/31_PowerCSV)

VersionRev LevelVersion Notes
14Oct2010 2.002
  1. Fixes downloading of Standard Data Log issue
  2. Increments version to 2.002
  3. Updates copyright 2010
  4. Uses new Installer to ensure consistency across Arbiter product installers
28Apr2009 2.001
  1. Current release

Terminal Emulation Program (Tera Term)

Free software terminal emulator (communications program) for Microsoft Windows.

  • Tera Term (Pro) is a free software terminal emulator (communication program) for MS-Windows.
  • Supports VT100 emulation, telnet connection, serial port connection, etc.
  • Compatible with Windows 98, Windows NT, Windows 2000, Windows XP, Vista, Windows 7
Firmware Information (EPROM based firmware is not available for download)
929/30/31_Firmware_08Dec2010 Requires an EPROM update from Arbiter. The same update works for Models 929, 930 and 931.


Firmware Version and Related Information

EPROM update (929/30/31_Firmware)

VersionRev LevelVersion Notes
  1. Fixed: CT/PT scale factors were enabled upon setting factory defaults. (Reference BZ642)
  1. Problems erasing single log file. (BZ 599)
  2. Update RS232 output to replace Null (0x00) bytes with space (0x20)

App Note 110: Measuring Low-Level Signals w/Model 931A
Download application_note_110.pdf (25 kB) »

App Note 113: Using Clamp-On Current Transfomers (CTs) with Arbiter Power Analyzers
Download application_note_113.pdf (89 kB) »

Logging Files from the Model 931A Power System Analyzer
Download pd0044600_logging_931_930_data_with_teraterm.pdf (142 kB) »

Model 09311A 400 Amp Auxiliary Current Transformer
Download 09311a.pdf (156 kB) »

Model 09311A 400 Amp Auxiliary Current Transformer Español
Download 09311a_ct_espanol.pdf (73 kB) »

Overview Presentation of Model 931A Power System Analyzer
Download 931a_seminar.pdf (732 kB) »

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