Page 1 Model 931A Power System Analyzer Operation Manual Arbiter Systems, Inc. Paso Robles, California U.S.A.
Page 2 This manual is issued for reference only, at the convenience of Arbiter Systems. Arbiter Systems, Inc. has made reasonable effort to verify that all diagrams are accurate as of September 1, 2003. However, due to production changes and availability of parts, these diagrams are subject to revisions and modifications.
Page 3 Table of Contents • Section One: General Information • Section Two: Functional Description • Section Three: Operation • Section Four: Specifications • Appendix A: RS-232C Commands • Appendix B: Optional Accessories Arbiter Systems, Inc. 9/2003. All rights reserved. International copyright secured. PD0017400I...
Page 5: Table Of Contents
Table of Contents 1.0 GENERAL INFORMATION............1 1.1 S ....................1 COPE 1.2 E ................1 QUIPMENT UPPLIED 1.3 A ..............1 CCESSORIES VAILABLE 1.3 A ..........2 CCESSORIES VAILABLE ONTINUED 2.0 FUNCTIONAL DESCRIPTION............3 2.1 S ....................3 COPE 2.2 I ....................
Page 6 Table of Contents 3.3.4 Timer Control Functions...............38 3.4 F ................39 RONT ANEL ISPLAY 3.5 D ..............39 IRECT EASUREMENTS 3.5.1 AC Voltage Measurement.............40 3.5.2 AC Current Measurement .............41 3.5.3 DC Voltage Measurement.............43 3.5.4 Frequency Measurement...............44 3.5.5 Harmonic Measurement..............45 3.6 C ..............47 OMBINED EASUREMENTS 3.6.1 Connecting the Inputs ..............48...
Page 7 Table of Contents 4.2.1 Voltage and Current ..............96 4.2.2 Phase Angle.................. 96 4.2.3 Frequency..................96 4.2.4 Timer .................... 97 4.2.5 Transducer..................97 4.2.6 Harmonics ..................97 4.2.7 Power Quantities ................97 4.3 G ..............98 ENERAL PECIFICATIONS 4.3.1 Measurement Bandwidth.............. 98 4.3.2 Memory ..................
Page 8 Figure 3-7 3-Phase, 3-Wire, 2-Element ............70 Figure 3-8 3-Phase, 4-Wire, 2.5 Element .............71 Figure 3-9 3-Phase, 4-Wire, 3-Element ............72 Figure 3-10 3-Phase, 4-Wire, 3-Element ............81 Figure B-1. Model 931A Case, Side Views..........121 Showing Handle / Bail.................121 Table B-2. Custom Data Table ..............125...
Page 9: General Information
Model 931A greatly enhances the precision measurement of these AC parameters. Powered by either an internal rechargeable battery or by AC line voltage, the Model 931A is truly portable. This manual is divided into four sections and two appendices as follows: Section 1.
Page 10: Accessories Available - Continued
AS0060100 1-Phase Clamp-On CT Test Lead * Please see our Test Lead catalog, PD0026400 for additional information on other test lead accessories. A wide variety of high-quality test leads and accessories are also available. Contact Arbiter Systems for further information.
Page 11: Functional Description
These inputs share a common return, and accept signals of up to 10 volts DC, or 100 mA DC. The Model 931A can be configured to measure the voltage or current directly, or convert the signals for display of either measured input units or a percentage of full-scale or percent error.
Page 12 Section 2: Functional Description Figure 2-1. Model 931A Front Panel...
Page 13: Measurement Channels
Figure 2-2. Input Multiplexing 2.3 Measurement Channels The Model 931A incorporates two measurement channels, referred to as Channel 1 and Channel 2. Multiplexing of the voltage and current inputs makes it possible to connect them to one or both of these measurement channels, in different configurations.
Page 14 Section 2: Functional Description Configuration Measured Input Referenced To Va-b Voltage A Voltage input B Vb-c Voltage B Voltage input C Vc-a Voltage C Voltage input A Va-c Voltage A Voltage input C Vc-b Voltage C Voltage input B Vb-a Voltage B Voltage input A Va-n...
Page 15: Measurement Method
CH2 and a clean synchronous signal with the desired fundamental frequency to CH1. The Model 931A will lock on to the CH1 signal and the CH2 signal can be analyzed.
Page 16: User Interface
12.5 Ks/s, allowing accurate measurements at frequencies down to 5 Hz. The record length under these conditions is 655 ms. The Model 931A completes a measurement cycle 2 to 3 times per second. The cycle includes collecting data, processing and displaying results. A faster update rate of 4 to 5 times per second is achieved by initiating the “Fast...
Page 17: Rs-232C Interface
PC, modem, or terminal. When connecting the Model 931A to a PC, use the supplied null- modem cable. The RS-232C port may also be used to connect a printer to the instrument.
Page 18: Power Supply And Battery
The low battery state is indicated on the main display by “LOW BAT!!”, and flashes On and Off. The Model 931A will automatically shut down if the low battery condition persists for longer than several minutes. It is recommended that the unit be charged or shut off when it indicates a low battery condition.
Page 19: Start-Up Sequence
2.8 Start-Up Sequence Several tasks are performed during the power-on initialization sequence. First, the Model 931A reads calibration data from the EEPROM (installed only in units with serial numbers greater than A0194). The initial sign-on message reports any errors in the calibration data along with the calibration date. These errors are corrected using a built-in Hamming Code Algorithm.
Page 20: Operation
This terminal is connected to the instrument chassis, and also to the safety ground lead of the AC power connector. When the Model 931A is operated with the power line cord connected, the chassis of the instrument will be connected to the safety ground for the ac outlet. However, when operated from the internal battery with the power cord disconnected, the chassis will be floating.
Page 21: Voltage Inputs
A transducer can be tested “live” in a circuit, or using an external source. The transducer inputs are connected to the Model 931A voltage or current measurement channels, and the transducer output is connected to the Model...
Page 22: Timer Inputs
Section 3: Operation 931A transducer measurement input, except for Custom Pulse, which uses the Timer Input. For details on transducer testing, refer to paragraph 3.8. 3.2.5 Timer Inputs Two timer inputs are provided via two pairs of insulated banana jacks, with...
Page 23 Section 3: Operation Make amplitude measurements with the instrument in either the narrow-band mode (fundamental only), or wide-band mode (true rms). In wide-band mode, the square root of the average of the squared instantaneous sampled values determines the true rms amplitude. It includes harmonics up to 3.05 kHz and removes DC prior to calculation.
Page 24 Section 3: Operation To use the POWER/VARS function, Channel 1 must be set to measure AC voltage, and Channel 2 must be set to measure AC current. In wide-band mode, active power (watts) is measured by taking the average of the products of the instantaneous values of voltage and current, and includes the effects of harmonics.
Page 25 W = +0.707 • VA Phase = +90º PF = 0 Lead Vars = -1.0 • VA W = 0 Current Leads Voltage Conventions Used in the 931A θ Where: (Theta) = Phase Angle between voltage NARROW-BAND: and current. A negative number θ...
Page 26 Section 3: Operation Reactive Power (VARS) Delivered QUADRANT QUADRANT Power Factor Power Factor -LAG +LAG Reactive Power Reactive Power Delivered Delivered (+VARS) (+ VARS) (inductive load, (inductive load) synchronous) Active Power Received Active Power Delivered (-Watts) (+Watts) Active Power Active Power (Watts) (Watts) Received...
Page 27 Section 3: Operation 3.3.1.4 VA/PF Press the VA/PF key to display the apparent power and power factor for signals routed to Channels 1 and 2. The input multiplexing circuitry determines which input signals are Setup 4 connected to the measurement channels, according to selections made by the operator (refer to paragraph 2.3).
Page 28 Section 3: Operation measurements, Fast Fourier Transform analysis determines the residual. Dividing the rms of the residual by the wide-band rms amplitude determines the Total Harmonic Distortion (THD). With these techniques, harmonic measurement accuracy is not dependent upon fundamental frequency. Select any harmonic with the movable cursor found in the graphic display using the arrow keys.
Page 29: Measure Hold
Section 3: Operation 3.3.1.7 Channel 1 Select Press the CHANNEL 1 SELECT key to view the input configu- ration menu for Channel 1. Always connect the lowest distortion input signal to Channel 1 CHANNEL 1 SELECT since it is used as the internal reference. For most power systems the voltage has lower distortion than the current.
Page 30 Section 3: Operation 3.3.1.10 CH2 Range Press the CH2 RANGE key to select the operating voltage or current range for Channel 2. The ranges are only approximate and vary from unit to unit. Press the CH2 RANGE key to view CH2 RANGE a range selection.
Page 31 (based on the input and output ranges). Prior to initiation of Transducer measurements, the Model 931A automatically performs a self-calibration.
Page 32 (refer to paragraph 3.3.2.13 for a discussion of scaling factors). CH1/CH2 is useful for checking the amplitude and phase angle accuracy of current transformers. Connect the primary in series with a Model 931A current...
Page 33: Secondary Functions
Section 3: Operation input and set that input to Channel 1. Connect the transformer secondary to another current input and set that input to Channel 2. Set the scale factor for the CT input (refer to paragraph 3.3.2.13) and press CH1/CH2. Using an external source, supply the appropriate level current.
Page 34 To select the appropriate measurement mode, move the cursor to the desired mode and press ENTER. The input pairs shown in parenthesis are those used for the TABULAR display. The Model 931A displays the following display selection menu when you press ENTER:...
Page 35: Tabular Display
Tabular Display The 931A makes a sequence of measurements as shown in the 3-Phase Measurement Selection menu. Amplitude, power and phase quantities for the individual phases are shown along with the totals for the system. In the right column, the screen identifies totals by a ‘T’, energy readings by ‘H’...
Page 36 ‘Vb’ is internally generated using the synthesized neutral circuit, and the accuracy of all results depends on the symmetry of the phase voltages. In all three-phase modes, the Model 931A also measures and displays phase the sequence, ‘ABC’ or ‘CBA’. (see Figures 3-2 and 3-3). A phase measurement of ‘Vab to Vac’...
Page 37 The bottom half of the display shows the positive (V1, I1), negative (V2, I2) and zero (V0,I0) sequence values. The Model 931A defines the positive sequence as the values in the ‘ABC’ direction and negative sequence as values in the ‘CBA’...
Page 38 Section 3: Operation Figure 3-2. Three-Phase Displays for an ABC System...
Page 39 Section 3: Operation Figure 3-3. Three-Phase Displays for a CBA System...
Page 40 Pressing RESTART will also reset Energy values to zero. 3.3.2.8 Config Press SHIFT then the CONFIG key to set the transducer input CONFIG and output ranges; it affects the testing of transducers. The TRANSDUCER Model 931A can be set to automatically calculate and display...
Page 41 Section 3: Operation transducer error as percent of full scale, when the same input signal is applied to the transducer under test and the Model 931A. Any calibrator or load box with source may be used, or transducers may be calibrated in-circuit.
Page 42: Print Log
Use the SCALE key to apply individual Scale Factors to each SCALE AC measurement input function. Scale Factor corrections can adapt the Model 931A for use with current or potential CH1 / CH2 transformers. These adjustments can compensate for phase or amplitude error, and account for the ratio of a CT or PT.
Page 43 For example, a magnitude scale factor of 100, with 10 volts applied to the Model 931A input, displays 1000 volts. Therefore, if the Model 931A was used to measure the voltage at the output of a 100:1 PT, and the magnitude scale factor was set to 100, the display would show the actual voltage value present at the PT input (compensating for the 100:1 reduction of the PT).
Page 44: Data Entry Functions
Section 3: Operation offsets equal the offset at the fundamental frequency multiplied by the chosen harmonic number. Enable or disable individual scale corrections globally using the SCALE menu (see Scale Factor Screen above), bottom line. Measurements made in wide-band mode use digital true-rms detection. Phase corrections are applied for power quantities by using complex multiplication.
Page 45: Right Arrow
Section 3: Operation Use the up arrow key to move the display cursor up. The cursor movement function associated with this key is automatically enabled when required. After making a menu selection, this key Setup 4 will return to its primary function. 3.3.3.4 Right Arrow( ) Use the right arrow key to move the display cursor right.
Page 46: Timer Control Functions
Section 3: Operation 3.3.4 Timer Control Functions Three keys, located left of the timer connection terminals, control operation of the internal timer. The functions of these keys are described below. 3.3.4.1 Display Use the DISPLAY key to view the main display for the timer; this includes the time measurement, the timer function and trigger DISPLAY modes.
Page 47: Front Panel Display
ARM/RESET function may also be used to manually stop the timer during a measurement cycle. 3.4 Front Panel Display The Model 931A uses a supertwist liquid-crystal display with a resolution of 240 horizontal pixels by 64 vertical pixels. In most cases, both measurement channels simultaneously display information from measurements and some instrument configuration.
Page 48: Ac Voltage Measurement
Section 3: Operation 3.5.1 AC Voltage Measurement The Model 931A can measure and display AC voltages of up to 750 Vrms. 3.5.1.1 Input Connections Four inputs, labeled ‘A’, ‘B’, ‘C’, and ‘N’ are available for measuring AC voltage, and each uses identical circuitry. Input multiplexing circuitry allows measurement of the value at inputs ‘A’, ‘B’, or ‘C’, relative to any other input.
Page 49: Performing The Measurement
Channel 2 for the current. 3.5.2 AC Current Measurement The Model 931A can directly measure and display AC currents of up to 20 Arms. It can measure higher currents using a current transformer (CT) and with direct readout using the scaling feature (see paragraph 3.3.2.13).
Page 50: Configuring The Channel
Section 3: Operation The Model 931A provides three sets of input connectors for measuring AC current: labeled ‘A’, ‘B’, and ‘C’. All three inputs use identical circuitry and are electrically isolated from all others: the voltage inputs, and chassis ground.
Page 51: Dc Voltage Measurement
Model 931A displays dashes for both Channel 1 and Channel 2. 3.5.3 DC Voltage Measurement The Model 931A can directly measure and display DC voltages of up to 1000 Vdc. 3.5.3.1 Input Connections The Model 931A provides three inputs for measuring dc voltage. Labeled ‘A’, ‘B’, ‘C’, and ‘N’, all four inputs use identical circuitry.
Page 52: Frequency Measurement
Frequency measurements. 3.5.4.1 Input Connections The Model 931A can measure the frequency of AC voltages or currents connected only on Channel 1. Make connections in the same manner as for magnitude measurements (refer to paragraphs 3.2.2 for AC voltages and 3.2.3...
Page 53: Harmonic Measurement
3.5.5 Harmonic Measurement The Model 931A can measure harmonic content up to the 50th harmonic for fundamental signals of 50 or 60 Hz. Either Channel 1 or 2 may be used to...
Page 54 AC Input connections. 3.5.5.2 Configuring the Channel(s) To configure the Model 931A for harmonic measurement, press either the CHANNEL 1 SELECT or CHANNEL 2 SELECT keys and select the measurement quantity from the channel menu. The Model 931A measures harmonics on signals processed by either channel.
Page 55: Combined Measurements
The top line of text shows THD and K-factor, which relate to the overall input signal, and do not change when the cursor is moved. The Model 931A analyzes harmonics by first determining the AC fundamental and the DC components of the signal. It then removes them algebraically from the digitized waveform.
Page 56: Connecting The Inputs
Channel 1, and the current signal to Channel 2. Since the voltage in a power system is usually more stable and less distorted than the current, the Model 931A uses Channel 1 as a reference for phase measurements. Both a voltage and current input signal are required to measure all power quantities.
Page 57 Section 3: Operation Select AC current at current input ‘A’ by moving the cursor to ‘Ia’ in the top row, then press ENTER to confirm. 3.6.2.2 Performing the Measurement Press the PHASE/FREQUENCY key to produce a display similar to the one shown below: The large number at the top of the display shows the phase angle of the signal routed to Channel 2, relative to that of Channel 1.
Page 58 Section 3: Operation Figure 3.4 Phase Angle Example Range Resultant Setting Polarity Setting Reading ±180º (-) for Channel 2 lagging Channel 1 -60º ±180º (+) for Channel 2 lagging Channel 1 +60º 0 – 360 (-) for Channel 2 lagging Channel 1 300º...
Page 59: Active Power - Reactive Power
Section 3: Operation 3.6.3 Active Power – Reactive Power The Model 931A can measure the active power (rms watts) and reactive power (vars) from the combination of an AC voltage routed to measurement Channel 1 and an AC current routed to Channel 2.
Page 60: Apparent Power - Power Factor
Reactive Power = Vfund * Ifund * sin(-θ) 3.6.4 Apparent Power – Power Factor The Model 931A can measure the apparent power (volt-amps, or VA) and power factor from the combination of an AC voltage routed to Channel 1 and an AC current routed to Channel 2.
Page 61 Section 3: Operation 3.6.4.1 Configuring the Channels Configure the chosen measurement channels after connecting the voltage and current to the appropriate input terminals (see figure 2-1 for instrument locations). Press CHANNEL 1 SELECT to configure measurement channel 1 and to view the following menu: Arrows form the cursor, which highlight one of the selections.
Page 62: Waveform Display
CHANNEL 2 SELECT. Press the WAVE- FORM key again to display both waveshapes simultaneously. The Model 931A Waveform Display includes a text display showing the rms magnitudes for the two signals and the frequency of the signal at Channel 1.
Page 63: Timer Measurements
Section 3: Operation 3.7 Timer Measurements The Model 931A includes a Timer for measuring events such as relay contact timing. The timer has two channels, which are optically isolated from the instrument common and from each other. Both inputs can accept various...
Page 64 Section 3: Operation 3.7.2 1 Function Select Function from the Timer Configuration Menu and press the ENTER key to view the following display: “Time A to B” configures the timer circuitry to display the time elapsed between a valid trigger for the ‘A’ input and a valid trigger for the ‘B’ input.
Page 65 Section 3: Operation the data may be based on 50 Hz, 60 Hz, or the fundamental frequency of the signal present at measurement Channel 1 (Ch 1 Hz). Select Display Choice from the Timer Configuration Menu to view the following display: Seconds sets the timer to display measurement results in seconds.
Page 66 Section 3: Operation 3.7.2.4 Trigger A Select Trigger A from the Timer Configuration Menu and press ENTER to view the following display: This sub-menu allows selection of the type of input to be used for the trigger for timer ‘Channel A’. The following are descriptions of each of the choices: “DC Applied”...
Page 67: Measurement Categories
‘A’. Refer to paragraph 3.7.2.4. 3.7.3 Measurement Categories All measurements performed by the timer section of the Model 931A can be classified as either time or count measurements. The following paragraphs describe both categories.
Page 68: Time Measurements
Testing transducers with the Model 931A is straightforward using an external source, such as a calibrator or source and load box. Also perform live, in- circuit tests. Prior to starting a transducer test the Model 931A automatically makes a self-calibration.
Page 69: Configuring The Transducer
Transducer Testing. “1Ph 2Wire 1E” sets the Model 931A to measure values in a single- phase circuit, having a hot wire and a neutral wire. Since sequential...
Page 70 ‘b’ with current ‘B’, and voltage ‘C’ to ‘N’ with current ‘C’). To create voltage ‘b’, connect the ‘B’ voltage input to the ‘N’ voltage input. “3Ph 4 Wire 3E” sets the Model 931A to measure values on a 3-phase Y circuit, for comparison to a 3-element transducer. See Figure 3-8.
Page 71: Input Type
See paragraph 3.2.2 for a description of AC voltage measurements. “Phase” sets the Model 931A to measure the Phase Angle between the voltage and current at the predefined inputs, for comparison to a phase angle transducer. For 3-Phase configurations, the display shows average phase angle.
Page 72: Input Range
See section 3.5.4 for a description of frequency measurements. “Vars” sets the Model 931A to calculate reactive power (vars) based on voltage, current, and phase measurements from the predefined inputs. The results are compared to a reactive power transducer. For three-phase configurations, the display shows the total reactive power.
Page 73: Output Range
Custom mA allows the user to enter a current range within the limits of 0 to 100 milliamperes DC. Custom Pulse allows the user to setup the Model 931A to accept a calibrated pulse from the transducer that is proportional to the measured transducer value.
Page 74: Connecting The Inputs
4 mA at the output. 3.8.2 Connecting the Inputs If needed, use the main measurement inputs on the Model 931A as the input for transducer tests at any value up to their rated maximum (see Specifications, Section 4).
Page 75 Section 3: Operation for voltage and channel 2 for current, as channel 1 is used as a reference channel, as the voltage signal is typically the most stable signal.
Page 76 Section 3: Operation Figure 3-5 Single-Phase, 2-Wire, 1-Element Transducer Test...
Page 77 Section 3: Operation Figure 3-6 Single-Phase, 3-Wire, 2-Element Transducer Test...
Page 78 Section 3: Operation Figure 3-7 3-Phase, 3-Wire, 2-Element Transducer Test...
Page 79 Section 3: Operation Figure 3-8 3-Phase, 4-Wire, 2.5 Element Transducer Test...
Page 80 Section 3: Operation Figure 3-9 3-Phase, 4-Wire, 3-Element Transducer Test...
Page 81: Connecting The Outputs
(left) and common (middle). Note: Be certain to configure the Model 931A to accept the type of transducer signal and range, whether voltage or current output. Paragraph 3.8.1.4 describes available Output Ranges.
Page 82 Most transducers with contact (or pulse) outputs use either an electrome- chanical or a solid-state relay. If the transducer has an electromechanical relay at the output, it is important to use the Debounce feature on the Model 931A. Otherwise, do not use it.
Page 83 Section 3: Operation 6. Display Output As–select either Measured Quantity or Percent Error. Although the menu choices include Percent Full Scale, only Measured Quantity and Percent Error pertain to Custom Pulse. The sample Transducer Configuration Menu shown below illustrates settings for a different transducer using the “Rate of A”...
Page 84: Contact Closures
Any time X is set to a value greater than “1”, in the “Time A to X Counts” function, the Model 931A computes average output values, or the % error. It does this by measuring the overall time for multiple contacts (defined by X)
Page 85: Equipment Setup
Section 3: Operation the Model 931A displays and holds the Input and Output values until pressing ARM/RESET, which begins a new test. 3.8.5.4.2 Contact Closures > 1 / second “Rate of A” is generally used for calibration standards (transducers) with output rates normally much greater than 1Hz.
Page 86: Performing A Test
3.8.5.6.1 For Contact Closures < 1 / Second Use Time A For X Counts. After setting up the test and configuring the Model 931A, apply the input power source to the transducer and Model 931A. Refer to Figure 3-10. Press the TRANSDUCER key to view the standard measurement screen.
Page 87 (transducer) or CONFIG (timer) to change the measurement settings. After re-configuring the test parameters, press TRANSDUCER and the Model 931A is ready for another test. To start the next test, press the ARM/RESET key twice. 3.8.5.6.2 For Contact Closures > 1 / Second After setting up the test and configuring the Model 931A, apply the input power source to the transducer and Model 931A.
Page 88 Section 3: Operation 3. Using the “Rate of A” Function, the Model 931A should continually update the measurement values. The Model 931A also cycles between each measured phase indicated in the lower left corner of the display. 4. The Transducer Input value indicates the total input, in this case three- phase power.
Page 89 Section 3: Operation Figure 3-10 3-Phase, 4-Wire, 3-Element Custom Pulse Transducer Test...
Page 90: Using External Pt's & Ct's
1. As an example, measure the ratio of a PT by performing the following steps: 2. Use Channel 1 to configure the Model 931A to measure the voltage at the input of the PT. 3. Use Channel 2 to configure the Model 931A to measure the output of the Apply the operating voltage to the input of the PT, and press the CH1/CH2 key.
Page 91: Reviewing Data
3 phase data includes all the data presently on the 3-phase display.hen the Model 931A captures a data record, it displays a momentary message in the lower right-hand corner. The message confirms that the data was saved and shows the assigned record number.
Page 92: Printing / Data Export
3.11 Printing / Data Export The Model 931A can print or export data, in several formats, directly over the RS-232C communications port. Refer to paragraph 2.6 for information on using the RS-232 port. Print or export data at the time the measurement is performed, or store it for later printing or exporting (using the LOG DATA key).
Page 93: Ascii Format
Procomm and Windows HyperTerminal. The procedure for capturing bitmap files is as follows: 1. Set the Model 931A to make the desired measurement, or select a stored data record and configure the Model 931A to display the desired data. 2. Connect the Model 931A to the host computer, using a 9-pin RS-232C cable.
Page 94: Spreadsheet
Section 3: Operation It takes several seconds for the Model 931A and the host computer to establish communication and begin the transfer. 3.11.5 Spreadsheet Using this mode import data directly into spreadsheet programs. Data is comma and quote-delimited; commas separate all data fields (number and text), with text enclosed in quotes.
Page 95 Section 3: Operation 1/1/95 = 34700 12/31/3199 = 474,816 As a decimal fraction of 1, corresponds to the time of Time: day, and is the standard format for time in spreadsheet applications. This number is determined by the formula: n=S/86400 where: S = number of seconds elapsed since midnight.
Page 96 Section 3: Operation 3.11.5.2 3-Phase Data The Model 931A exports 3-phase data when executing the print operation. This occurs in one of the 3-phase tabular display operating modes. The 3- phase data is exported with the following format: log data #, date, time, “min/max/normal”, “3 phase mode”, “ABC/CBA”, V,...
Page 97 Section 3: Operation Average current for all phases. Phase: Average phase angle between current and voltage for all phases. Frequency: The frequency of the measured signals. Power: The total active power of all of the phases. VARS: The total reactive power of all of the phases. The total apparent power of all of the phases.
Page 98 Section 3: Operation 3.11.5.3 Timer Data The Model 931A exports timer data when executing the print operation. This occurs while performing measurements or reviewing stored data in the timer mode of operation. Timer data is exported with the following format: log data #, date, time, “min/max/normal”, “function”, “trigger A”, “trigger B”,...
Page 99 The time value for the current measurement or record. 3.11.5.4 Transducer Data The Model 931A exports transducer data when executing the print operation. This occurs while performing measurements or reviewing stored data in the transducer mode of operation. Transducer data is exported with the following format: log data #, date, time, input value, “input units”, output value, “output units”...
Page 100: Harmonic Data
Output Units: value. 3.11.5.5 Harmonic Data The Model 931A exports harmonic data when the print operation is executed. This occurs while performing measurements in the harmonic display mode, or reviewing stored data while in that mode. Harmonic data differs from most of the other data types, in that it is a tabular format consisting of 49 records.
Page 101: Waveform Data
Harmonic Phase: respect to the fundamental. 3.11.5.6 Waveform Data The Model 931A will export waveform data while the print operation is executed. This occurs when performing measurements in the waveform display mode, or reviewing stored data while in that mode.
Page 102: Initiating Printing / Exporting
Section 3: Operation A decimal fraction of 1, corresponding to the time of Time: day, which is the standard format for time in spreadsheet applications. This number is determined by the formula: N = S/86400 where: S = number of seconds elapsed since midnight. Data point for Channel 1 Waveform.
Page 103: Specifications
4.0 Specifications 4.1 Inputs 4.1.1 Voltage Inputs: Four: A, B, C, and N. Phase-to-Phase. Phase-to-Neutral. Phase-to-Synthesized Neutral. Input Range: 1.5-750 Vrms (under range to 200 mV), 2-1000 Vdc (under range to 300mV). Impedance: 1 megohm. Leakage: <3.5 mA, per IEC348 and UL1244. 4.1.2 Current Inputs: Three: A, B, and C.
Page 104: Timer
Section 4: Specifications 4.1.4 Timer Inputs: Two. Maximum: 300 Vrms or dc. Isolation: 300 Vrms. Threshold : Contact open 2.9 Volts. Threshold : Contact closed 2.6 Volts. Voltage Input Impedance: 1 megohm. ≈25 Kohm. Source Impedance (for dry contact): 4.2 Measurements 4.2.1 Voltage and Current Method: Wideband: True RMS, 3 kHz BW...
Page 105: Timer
Section 4: Specifications 4.2.4 Timer Inputs: Two, voltage or dry contact. Input Ranges: 4 to 300 Vdc, 20 to 300 Vrms. Isolation: 300 Vrms (each channel) optical. Range: 0.0001 to 9999.9 seconds, 0.01 to 999999 cycles. Accuracy: 0.005% of reading + 1 digit. Trigger Error (for AC 1 millisecond maximum, Trigger):...
Page 106: General Specifications
Section 4: Specifications 4.3 General Specifications 4.3.1 Measurement Bandwidth Wideband Mode: 3.05 kHz. Narrowband Mode: 20-500 Hz, fundamental only (determined by DSP). 4.3.2 Memory Type: Non-volatile (battery-backed RAM). Data stored: User setups, measurement results; Time and date tagged. 4.3.3 Display Type: Supertwist Liquid Crystal.
Page 107: Input Power
Section 4: Specifications 4.3.6 Input Power Line Voltage: 85-264 Vac (47 - 440 Hz), 110-250 Vdc. Power: 15 W/15 VA, max. Battery: Internal, 8 hours. Charger: Automatic, multimodal. Charge time: 8 hours, fast + float. Auto-Shutdown: 10 minutes with no activity or input. 4.3.7 Serial Port Port Type: RS-232C.
Page 108: Appendix A. Rs-232C Commands
5.0 Appendix A. RS-232C Commands The following appendix contains a listing of commands, definitions and examples that may be used to control and communicate with the Model 931A via the RS-232C serial interface Commands that request information from the instrument return either current or previously logged data.
Page 109: Serial Port Examples
Appendix A. RS-232C Commands Serial Port Examples This section contains examples of controlling the Model 931A with serial commands from a computer, or terminal, to access its various features. In each example the left-hand column gives the example command. The right-hand column gives a brief description of the result after entering the command.
Page 110: Command Summary
Appendix A. RS-232 Commands 5.2 Command Summary Battery Charging Status Returns Battery and charging status Return Value Meaning Nothing Low Battery Charging Backlight Set #BLT Controls the front panel LCD backlight. Response Backlight OFF Backlight ON Backlight AUTO. The backlight remains on for approximately 20 seconds after the last keystroke Channel Calibrate ch#,ac/dc#,range#,gain#,ph/off#,s/r#CCH...
Page 111: Calibrate Input
Appendix A. RS-232C Commands Ratio CH1/CH2 Displays (on the Model 931A) the measured results as the magnitude and phase angle of the ratio of Channel 1 divided by Channel 2. Depending on the input signals selected, the display units for magnitude will be ohms, mhos, or p/u.
Page 112 Appendix A. RS-232 Commands gain# Corrected gain = uncorrected gain * (1 + gain# /1000) Ph/off# Corrected phase = uncorrected phase + (ph/off# * freq) Offset = ph / off# ÷ 1000 (DC) s/r# Action Writes calibration to memory Returns stored calibration value Return format: gain <cr><lf>...
Page 113 Appendix A. RS-232C Commands Daylight Saving Time-Set #DAY Sets the daylight saving time mode for the real time clock. Designation Daylight saving time OFF Daylight saving time ON; adds one hour to the standard time. AUTO daylight saving time; automatically adjusts the time for USA standard daylight saving time (2:00 AM on the first Sunday in April to 2:00 AM on the last Sunday in October).
Page 114 Appendix A. RS-232 Commands DSP Frequency-Return c#,s/r#FRD Sets or returns the Calibration Constant to correct the DSP frequency. 1 plus (c# ÷ 1,000,000) multiply the frequency measurements made by the DSP. Frequency Calibration Constant s/r# Action Set Calibration Constant Return Calibration Constant Return format: Numeric ASCII string.
Page 115 Appendix A. RS-232C Commands Harmonics Display harm#,ch#HAR Displays the selected harmonic (with others) for the selected channel. Shows magnitude, phase and frequency data for the harmonic number specified as harm#. To select Channel 1 Channel 2 Harmonic Magnitude-Return harm#,ch#HMA Returns individual harmonic magnitudes for the selected channel. Set the unit to measure harmonics, on the selected channel using the HAR command, prior to issuing the HMA command.
Page 116 Appendix A. RS-232 Commands Log Data Stores the current measurement data (using current date, time and instrument settings) in the next available location of the non-volatile data memory. Stores all data with current data type (standard data, standard with harmonic data, or standard with harmonic and waveform data).
Page 117: Min-Max-Display
Appendix A. RS-232C Commands MIN-MAX-Display #MMN Displays the minimum, maximum, average or present values for each parameter. Updates minimum, maximum and average continuously. Use the RST command to restart the accumulation process. Response Displays present values Displays minimum values Displays maximum values Displays average value Bandwidth-Narrow Changes the measurement mode for amplitude and power quantities to...
Page 118 Appendix A. RS-232 Commands Power Factor-Return Returns the power factor of Channel 1 and 2 together. Channel 1 must be set to measure AC voltage and Channel 2 AC current. In 3 phase mode, returns the average of the individual power factors. Response: Numeric ASCII string.
Page 119: Logged Data-Review
Store data records manually using the log data key, or via RS-232C using the LOG command. Use 0RLD to clear all logged data. When issuing this command, the specified record is written to the Model 931A display, overwriting current measurement data and placing the Model 931A in Measurement Hold Mode.
Page 120: Flash Log
Appendix A. RS-232 Commands calibrates the 0 to 1 mA DC current ranges. s/r# To store reference and resistance values. To send reference and resistance values. Serial Number serial#,s/r#SER Sets or returns instrument Serial Number. Serial# ASCII number (5 digits) s/r# To enter serial number To return serial number...
Page 121 Appendix A. RS-232C Commands To select All scale factors OFF All scale factors ON DSP Speed #1,s/r#SPD To select Slow mode Fast mode s/r# To set speed To return speed Phase Preference Set #SPH Specify the format for phase display. Phase Format ±180 degrees leading (negative display means Channel 2 lagging Channel 1)
Page 122: Setup-Recall
Appendix A. RS-232 Commands 384 – 750 10.24 – 20.0 543 – 1000 To Select Channel 1 Channel 2 Scale Factors-Set or Return in#,m#,p#,s/r#SSC Set or return calibration factors to be applied to each input function, such as for CT or PT corrections. Scale factors consist of a magnitude correction, which is a ratio (or p/u) number;...
Page 123 Appendix A. RS-232C Commands Timer Configuration Set or Return d#,f#,h#,at#,bt#,s/r#TCF Returns or sets the parameters necessary for timer operation. Display Function Seconds Time A to B Cycles (50Hz) Time A for X Counts Cycles (60Hz) Time width of A Cycles (Ch1 Hz) Frequency of A Count A Events Hold mode on stop...
Page 124: Timer Display
Timer Display Displays the Timer results in seconds, cycles, counts, or Hertz on the Model 931A, according to the timer function. The Timer must be configured using the TCF command. Once the Timer has been configured, it may be armed using the TAM command.
Page 125 Appendix A. RS-232C Commands VA/PF Display #V_P Result (or # absent) Displays the apparent power and power factor of the signals on Channels 1 and 2. Channel 1 must be set to measure AC voltage and Channel 2 AC current. VA hours Volt Amps Return #VAM...
Page 126 Appendix A. RS-232 Commands Waveform Display ch#WAV Enables the waveform display of channel 1 and channel 2. To select Channel 1 Channel 2 Both Channel 1 and 2 Bandwidth Wide Changes the measurement mode for amplitude and power quantities to wide- band including all harmonics up to 3.05 kHz.
Page 127: Appendix B. Optional Accessories
6.1.2 Input Connections Connect a high-current source as follows: 1. Slip the transformer output spade lugs into one set of the Model 931A current input binding posts (A, B, or C), and tighten securely. 2. Connect the high-current source to the 5/16-18 bolts at the top of the transformer, using a 1/2”...
Page 128: Handle/Bail
Appendix B 6.2 Handle/Bail This section contains information and procedures for installing the optional handle/bail onto the Model 931A case. 6.2.1 Parts and Accessories Included with the installation kit are the following components: Description Arbiter P/N Mounting Bracket HD0049800A Handle/Bail...
Page 129 Appendix B Figure B-1. Model 931A Case, Side Views Showing Handle / Bail...
Page 130: Extended Memory
To record measurements to extended memory, press the LOG DATA key in the same manner as with standard memory. Data recorded with extended memory is identical to that stored when the Model 931A is equipped with standard memory, however the record structure is more elaborate.
Page 131 Each record stored as normal data contains enough information to completely restore the Model 931A to its state when the record was logged. The type of data stored depends on the active instrument display at the time the record was logged.
Page 132 See paragraph 6.3.4 for details on setting up the custom data feature. Unless the Model 931A has an extended memory option installed, there will not be an opportunity to setup custom data, as the Auto-Log Setup is added as a...
Page 133 Appendix B ID Bit# Decimal Weight Name #Bytes Time Frequency Phase Power Ch1 DC Ch1 RMS (wide-band) Ch1 MAG(narrow-band) 1024 Ch1 Residual 2048 Ch1 Phase reference 4096 Ch1 Min 8192 Ch1 Max 16,384 Ch2 DC 32,768 Ch2 RMS (wide-band) 65,536 Ch2 MAG (narrow-band) 131,072 Ch2 Residual...
Page 134: Computing The Number Of Files And Records
RS232 LOG command, a valid Timer-A event, or on a programmed time interval. Press the LOG DATA key and the Model 931A will record the data type selected on the display. Send the RS232 LOG command to the Model 931A serial port to accomplish the same thing.
Page 135 Appendix B MENU key and select “Auto-Log Setup” and the following display will appear. First, select a trigger condition. If Time Interval is selected set the Start Log and Stop Log date and time. Next choose the Log Data category, either Normal or Custom.
Page 136: Remote Operation
Appendix B number of records that may be stored, refer to paragraph 6.3.2. As the number of records increases, the available AUX MEM will decrease. Use the up and down arrow keys to select individual logged data files. Press the ENTER key to recall the selected file. Press the left arrow key to erase the selected file.
Page 137 Appendix B #6=0 thru 59 minute of hour. #7=0 thru 59 seconds of minute. 6.3.6.1 Examples using SLO Command Command Action A new extended log file is started. If time interval data storage is selected the start time must be later than the present time.
Page 138: Review Of Logged Data
Appendix B parameter. The following example shows how to compute the custom data word for logging time and channels 1 and 2 magnitude data. Parameter Decimal weight Time Channel 1 rms Channel 2 rms 32768 Custom configuration value 33281 6.3.7 Review of Logged Data #1,#2RLD selects a log record for review or removal.
Page 139: Trigger Remote Data Logging
Appendix B 6.3.7.1 Examples using RLD Command Command Action Returns a list of the logged data files, as shown in the following example of a returned message. LOG SPACE 87% AUX MEM 98% FILES 6 9 Dec 1996 13:37:54 9 Waveform 9 Dec 1996 13:38:05 4 Harmonic 9 Dec 1996 13:38:37 15 Custom...
Page 140: Index
Appendix B 7.0 Index Battery Commands charging status, BAT, 102 AC Measurement Configurations, 6 Accessories, 1, 120 Accuracy Cable checking amplitude and phase, 25 null-modem, 2, 9 CT, 1 Calibration Commands Fast Mode vs. Slow Mode, 8 input, CIN, 103 General, 98 Store data in EEPROM, EEP, 105 harmonic measurement, 20...
Page 141 Index Review (View), 33 return DSP constant, FRD, 106 Standard String, 86 return input frequency, FRQ, 106 Timer String, 90 Frequency Range, 7 Transducer String, 91 Frequency-Return, FRQ, 106 Triggering log feature, 126 Front Panel Connections, 12 Waveform String, 93 Front Panel Display, 39 Data Dump Commands Front Panel Drawing, 4...
Page 142 Index Input Power, 99 Inputs Current, 13 Magnitude Return Command, Timer, 14 MAG, 108 Transducer, 13 Main Functions, 14 Voltage, 13 Harmonics, 19 Instrument Power Command Phase/Frequency, 15 turn unit off, KIL, 107 Power/Vars, 15 Isolation, Voltage Terminals, 3 VA/PF, 19 Volts/Amps, 14 Waveform, 20 Maximum Ratings, 3...
Page 143 Index Restart Key, 16 Review Data. See Data, Review Overload Status Command, OVD, Reviewing Data, 83 RS-232 Interface, 9 Port Pin Configuration, 9 RS-232 Commands Examples, 101 PCMCIA, 122 Introduction, 100 Phase Angle Example, 50 Phase Convention, 49 Phase Mode Set Command, PHM, Phase Preference, 19 Sampling and Filtering, 7 Scale Factor Commands, SSC, 114...
Page 144 Index Store Setup Command, SST, 114 Measurement Units, 3 Output Range, 65 Transducer Commands Channel, SCC, 111 configure, COT, 104 THD, Total Harmonic Distortion, 47 display quantities, TDU, 116 determining, 20 Transducer Connection Drawing Maximum Input, 7 Single-Phase, 2-Wire, 1-Element, Measuring greater than 30%, 7 Three-Phase Display Single-Phase, 3-Wire, 2-Element,...
Page 145: Limited Warranty
The responsibility of Arbiter Systems under this warranty is limited to repair or replacement, at Arbiter Systems’ option, of any product found to be defective. Arbiter systems shall have no liability...
Page 146 The remedies provided herein are the Buyer’s sole and exclusive remedies. In no event shall Arbiter Systems be liable for direct, indirect, incidental or consequential damages (including loss of profits), whether based on contract, tort, or other legal theory.

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