99 Washington Street Melrose, MA 02176 Fax 781-665-0780 TestEquipmentDepot.com ® 1744/1743 Power Quality Logger Users Manual PN 2560353 April 2006 Rev.1, 6/06 © 2006 Fluke Corporation, All rights reserved. Printed in USA All product names are trademarks of their respective companies.
Table of Contents Title Introduction .......................................................................................... Information and PC Software CD ..................................................... Logger Power Supply ....................................................................... Power Interruptions........................................................................... Introduction to the Logging Functions.................................................. Symbols ...............
1744/1743 Users Manual Min/Max Values........................................................................... Voltage Interruptions.................................................................... Voltage Dips and Swells .............................................................. Voltage Harmonics........................................................................... Current Harmonics ........................................................................... Mains Signaling....................
Contents (continued) Timeplot diagram.......................................................................... 60 UNIPEDE DISDIP Table.............................................................. 61 Cumulative Frequency – Harmonics.............................................
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List of Tables Table 1. 2. 3. 4. 5 6. 7. Title Symbols.............................................................................................. Standard Equipment ........................................................................... Optional Accessories.......................................................................... 1744/1743 Power Quality Logger Controls and Indicators ...................................................................... Test Lead Markings...........................
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List of Figures Figure 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Title 1743 and 1744 Power Quality Loggers .............................................. 1744/1743 Power Quality Logger - Front View................................. Supplying Operating Power to the Logger ......................................... Logging in a 3-Phase 4-Wire (Wye) System...................................... Logging in a 3-Phase 3-Wire (Delta) System.....................................
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1744/1743 Power Quality Logger Introduction The Fluke 1744 and 1743 Power Quality Loggers are sophisticated, robust, easy-to-use electrical power-recording devices for the electrician or powerquality specialist. Note This manual also refers to the 1744 or 1743 Power Quality Logger simply as “the Logger.” You’ll prepare the Logger for use with the included PQ Log software CD.
1744/1743 Users Manual Logger Power Supply The Logger does not include a power switch, but turns on automatically whenever its power supply leads are connected to a voltage in its allowed range. You can plug the Logger’s power supply leads into a standard wall outlet (using the included adapter cord), or you can connect them directly to the power network under test (in parallel with the test leads) if there is no convenient wall outlet.
Power Quality Logger Introduction to the Logging Functions • Energy, total energy • Flicker (Pst, Plt) • Voltage THD • Current THD • Current CF • Voltage harmonics to the 50th (not in P function) • Voltage interharmonics (not in P function) • Mains signaling voltage • Unbalance • Frequency CURRENT INPUT 10VRMS MAX MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45-65 Hz 100 -350V 5 VA L1/A L2/B L3/C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 1743 POWER LOGGER START STOP RS232 IN I 3
1744/1743 Users Manual Symbols Table 1 lists the symbols used on the instrument and in this manual. Table 1. Symbols Symbol W X J T F P ) ~ ; Description Important information. See the manual. Hazardous voltage. Earth ground. Double insulation. Direct current (DC). Conforms to European Union requirements. Canadian Standards Association is the certified body used for testing compliance to safety standards. Do not dispose of this product as unsorted municipal waste.
Power Quality Logger Safety Instructions W X Warnings • To avoid electrical shock, do not connect any part of the Logger to systems that have higher voltages to ground (earth) than are marked on the Logger. • Areas between the power company meter and the source of the distribution system are characterized as CAT IV areas. To avoid electrical shock or equipment damage, never connect the Logger to power in CAT IV areas if the voltage-to-earth ground is greater than 300 V.
1744/1743 Users Manual • Connect clip-on current transformers and/or Flexi Set to insulated live conductors only. • If measuring sensors are to be connected to noninsulated live conductors, additional personal protective measures must be taken as required by local government agencies.
Power Quality Logger Safety Instructions Table 2.
44/1743 Users Manual Inspect the contents of the shipping box for completeness and damage. Report any damage to the shipper. Features This section introduces the Logger’s controls, indicators, and other features. Refer to Figure 2 and Table 4. 1 6 CURRENT INPUT 10VRMS MAX 7 MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45 -65 Hz 100 -350V 5 VA L1/A L2/ B L3 /C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 3 5 1743 POWER LOGGER START STOP RS232 I N I 3 I 2 I 1 V3 V 2 V1 POWER 2 4 egb021.
Power Quality Logger Safety Instructions Table 4. 1744/1743 Power Quality Logger - Controls and Indicators Item Name Description A Power supply leads and 3-phase plus neutral voltage test leads B RS232 interface port C START/STOP D Channel LEDs E Power status LED F Connector for Flexi Set or current clamps G Logging status LED Power supply voltage range: 88-660 V ac or 100-350 VDC, 50 Hz / 60 Hz, 600 V CAT III. Fixed installed voltage input cables for L1 or A, L2 or B, L3 or C, N.
1744/1743 Users Manual Power Network Configurations You can set up the Logger to work with several power network configurations: • • • • • Single-phase voltage Single-phase voltage, current, power 3-phase voltage 3-phase voltage, 3-phase current, power 3-phase voltage, 3-phase current, neutral current, power Note 3-phase logging with no neutral current can be done with appropriate optional accessories (available separately).
Power Quality Logger Using the Logger Using the Logger This section explains how to operate the 1744/1743 Power Quality Logger. A typical logging session includes four steps: 1. Preparing the Logger for use with the PQ Log software. 2. Installing the Logger at the logging site. 3. Leaving the Logger to collect data for a period. 4. Downloading and evaluating the logged data. These steps are described in the following pages.
1744/1743 Users Manual Preparing the Logger for Use Prepare the 1744/1743 Logger for use with the PQ Log software as follows (see Figure 3): 1. Connect the Logger to line power. Use the power supply cables to connect to an outlet, or to the test leads phase and neutral for Wye configurations, or any two-phase leads for delta.
Power Quality Logger Using the Logger Power in Parallel with Test Leads Power from Wall Outlet Max 660 V Voltage Test Leads Voltage Test Leads Power Supply Leads Power Supply Leads CURRENT INPUT 10VRMS MAX MEASUREMENT INPUT SUPPLY INPUT CURRENT INPUT 660V MAX 88 -660V 45-65 Hz 100 -350V 5 VA 10VRMS MAX L1/A L2/ B L3/ C N 830 VRMS MAX CAT MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45-65 Hz 100 -350V 5 VA L1/A L2/ B L3/ C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 600 V CAT 300 V CAT 1743 P
1744/1743 Users Manual 3. Run the PQ Log software as described in the PQ Log Users Manual. 4. Set up the Logging job and transfer the settings to the Logger. Test Leads – Markings The 1744/1743 Logger includes built-in, labeled test leads for voltage terminals L1 or A, L2 or B, L3 or C, and N, as well as two for the internal power supply. The Flexi Set or current clamp sets are connected by a seven-pin plug to the Logger. Color coding clips are provided for your convenience. Table 5.
Power Quality Logger Using the Logger Logging with Voltage Converters The 1744/1743 Logger includes an adjustable converter ratio that enables it to be used with voltage converters (potential transformers, or PTs). Note When logging with voltage converters, make sure the power supply cables are not connected in parallel to the voltage test leads, or the Logger’s power consumption can reduce accuracy. The converter ratio is defined using the PQ Log software.
1744/1743 Users Manual • Use only the current probes specified in this manual. If you use flexible current probes, wear suitable protective gloves or work on de-energized conductors. • Do not expose the Logger to moisture or humidity. • To prevent electrical shock, always connect power supply and voltage test leads to the Logger before connecting to the load. • All accessories must be approved for 600 V CAT III or higher.
Power Quality Logger Using the Logger Connect the Logger as follows: Note ∆ (Delta) or Υ (Wye) measurements The 1744/1743 Logger is prepared for logging in 3-phase 4-wire (Wye) systems (P-N), or 3-phase 3-wire (Delta) systems (P-P). Please note the different types of connection and configuration in the PQ Log software. 1. Connect all required measuring leads. 2. If you want to supply the Logger from an extra outlet, use the supplied line power adapter.
1744/1743 Users Manual Connections in 3-Phase 4-Wire (Wye) Systems The following figure shows the connections for logging 3-phase 4-wire (Wye) systems: L1 L2 L3 N CURRENT INPUT 10VRMS MAX MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45 -65 Hz 100 -350 V 5 VA L1/A L2 / B L3 / C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 1743 POWER LOGGER START STOP RS232 IN I 3 I 2 I1 V3 V2 V1 POWER egb003.eps Figure 4.
Power Quality Logger Using the Logger Connections in 3-Phase 3-Wire (Delta) Systems Figure 5 shows the connections for logging 3-phase 3-wire (Delta) systems. L1 L2 L3 L4 CURRENT INPUT 10VRMS MAX MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45 -65 Hz 100 -350V 5 VA L1/A L2 / B L3 / C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 1743 POWER LOGGER START STOP RS232 IN I 3 I 2 I1 V3 V2 V1 POWER IP65 egb004.eps Figure 5.
1744/1743 Users Manual Connections for Single-Phase Logging Figure 6 shows the connections for logging single-phase systems. L1 N L3 L2 CURRENT INPUT 10VRMS MAX MEASUREMENT INPUT SUPPLY INPUT 660V MAX 88 -660V 45-65 Hz 100 -350V 5 VA L1/A L2/ B L3/ C N 830 VRMS MAX CAT 600 V CAT 300 V CAT 1743 POWER LOGGER START STOP RS232 IN I 3 I 2 I1 V3 V2 V1 POWER egb005.eps Figure 6.
Power Quality Logger Using the Logger Connections for Medium-Voltage Networks In a 3-phase 3-wire (Delta) system with three separate voltage converters and three current transformers, the Logger can measure phase-phase (P-P, Delta) or phase-N (P-N, Wye). See Figure 7.
1744/1743 Users Manual Phase-Phase Delta Logging Figure 7 shows the connections for phase-phase Delta logging. 1. Connect the voltage test leads to the outputs of the voltage transformers (VTs). 2. In PQ Log, select the measuring range with the matching nominal voltage and P-P logging. 3. Enter the correct converter/transformer ratio for current and voltage. egb007.bmp Figure 8.
Power Quality Logger Using the Logger Phase-Ground, Wye-Logging Figure 7 shows the Phase-Ground, Wye-Logging. Figure 9 shows typical PQ Log settings for using potential transformers (PTs) and current transformers (CTs) with a 16 kV network. egb010.bmp Figure 9.
1744/1743 Users Manual 1. Connect the voltage test leads to the outputs of the voltage transformers (VTs). 2. In PQ Log, select the measuring range with P-N logging and matching nominal voltage. 3. Enter the correct converter/transformer ratio for current and voltage. Note Current clamp sets are available for 1 A current transformers.
Power Quality Logger Using the Logger 1. Connect the voltage test leads L2 or B and N to the common ground point. 2. In PQ Log, select the measuring range with P-P logging and matching nominal voltage. 3. Enter the correct converter/transformer ratio for current and voltage. egb007.bmp Figure 11. PQ Log Settings for a 16 kV Network Note Current clamp sets are available for 1 A current transformer.
1744/1743 Users Manual • Time-activated job: The Logger starts logging as soon as the preprogrammed start time is reached, and stops at the defined end time. • Immediate job: The Logger starts logging as soon as power is on. Note the following about logging jobs: • The connection can be verified using the logging channel LEDs. If all three LEDs are lit continuously, the connection and the signal levels are within nominal range. For details, see Table 4 in the Features section.
Power Quality Logger Methods of Logging Evaluating the Logged Data You’ll use PQ Log to evaluate the logged data. Data can be read out during logging as well as at the end. 1. Connect the Logger to line power. 2. Connect the RS232 interface cable to your PC’s serial port, then to the Logger. 3. Start the PQ Log software. 4. Use PQ Log to transfer the data from the Logger to the PC. 5. Once the data is transferred, remove the RS232 interface cable and operating power from the Logger. 6.
1744/1743 Users Manual egb015.bmp Figure 12. Selecting Voltage Input Ranges During Job Processing Note For P-P logging, the P-P voltage must be entered as the nominal voltage (e.g. 400 V for 230 V systems). Signal Sampling Input signals (up to three voltages and four currents) are filtered with an antialiasing filter, and digitized with a 16-bit A/D converter. The sampling rate is 10.24 kHz. All parameters are calculated from this data.
Power Quality Logger Methods of Logging Technical Specifications” on page 46. Voltage Variations The interval value of the voltage is defined as the mean value of the RMS values over the interval length defined in PQ Log. Averaging intervals can be set in PQ Log to the following: • 1, 3, 5, 10, or 30 seconds • 1, 5, 10, 15, or 60 minutes 1 Interval V N Time Measuring period egb016.eps Figure 13.
1744/1743 Users Manual Min/Max Values Logging detects the highest and lowest voltage RMS values and the highest current RMS value during the test interval, using a minimum resolution of 10 ms. The response time can be set in PQ Log to the following: • 0.5 or 1 line power period • 200 ms • 1, 3, or 5 seconds. U Max. Value Min. Value t Measuring Interval egb017.jpg Figure 14.
Power Quality Logger Methods of Logging Voltage Interruptions The Logger records two types of interruptions: • All measured RMS values of input voltages that are < 1% of the nominal voltage. (This threshold can be adjusted in PQ Log.) • Interruptions > 10 ms (0.5 line power periods). The start time and duration of each interruption are registered. 110% Un 100% Un 90% Un 1% Duration Time egb018.eps Figure 15.
1744/1743 Users Manual Voltage Dips and Swells If the voltage passes the upper limit (VN + 10%) or lower limit (VN – 10%), the event is registered as a voltage swell or dip, respectively (thresholds are adjustable in PQ Log). The duration, time, and extreme value of the dip or swell is also recorded. Heigth 110% Un 100% Un 90% Un Depth Duration Duration Time Zeit egb019.eps Figure 16.
Power Quality Logger Methods of Logging Current Harmonics Current harmonics are defined as current components that have a frequency that is an integer multiple of the fundamental frequency of the line power current. Logging function A records each individual harmonic of the phase currents and the neutral current, up to the 50th order, and presents the harmonics as absolute values. The values are averaged over the interval length defined in PQ Log.
1744/1743 Users Manual THDV – In Function A 50 Function A: ∑V n=2 THDV = 2 n V1 Vn: RMS value of harmonic frequency #n. V1: RMS value of the fundamental frequency. THDV: total contents of harmonics of the line power voltage as a percentage of the fundamental. This algorithm is according to EN 61000-4-7. THD of currents: 50 THDI = Function A: ∑I n=2 I1 2 n and THDI ( A) = 50 ∑I n=2 2 n In: RMS value of harmonic frequency #n. I1: RMS value of the fundamental frequency.
Power Quality Logger Methods of Logging Calculation of THD in Measuring Function P THD – Measuring Function P Function P does not measure harmonic values. 2 Voltages: THDV = VRMS − V1 2 V1 VRMS: RMS value of total signal V1: RMS value of the fundamental 2 Currents: THDI = I RMS − I 1 2 I1 IRMS: RMS value of the total signal. I1: RMS value of the fundamental. Note THDI for currents < 5% of IE (measuring range) can have additional uncertainties, or can be suppressed.
1744/1743 Users Manual Formula for Plt Function Plt = 3 Pst 3 ∑ i =1 12 12 Flicker [%] 12 x interval length => 1 flicker value Plt Time Interval length => 1 Pst egb020.eps Figure 17. Measuring Flicker Values Unbalance The ratio of negative-to-positive sequence harmonics is calculated, with the angles and magnitudes of the phase voltages taken into account. These values are averaged over the interval length defined in PQ Log.
Power Quality Logger Methods of Logging Current Logging The maximum values of the currents (L1 or A, L2 or B, L3 or C, and N) are measured, and the interval value of the current is calculated using the mean value over the RMS values of the interval defined in PQ Log. Logging Function A If a 3-phase current sensor is connected, the neutral current is calculated on a sample basis from the phase currents.
1744/1743 Users Manual Logger Parameters with Function P The following are the parameters of the 1744/1743 Logger with function P. RMS value of voltage and current. Basic values on 200 ms per phase.
Power Quality Logger Logger Parameters with Function P Pk: Active power of the phase k: Phase (k = 1, 2, 3) Absolute value of the active power per interval per phase. Parameter in PQ Log: |P|. Pbetr = 1 M ⋅ ∑ Pbas j M j =1 M: Number of 200 ms intervals per logging interval Sum of the absolute value of the total active power on all three phases. PQ Log parameter: |P|total.
1744/1743 Users Manual Tangent φ total on all three phases tan ϕ total = Active energy per phase and total Qtotal Ptotal Active power accumulated on each logging interval Note The sign of the active power P gives the direction of the power flow (positive: from generator to load), and the sign of the power factor distinguishes between inductive load (positive) and capacitive load (negative).
Power Quality Logger Logger Parameters with Function A Logger Parameters with Function A The following are the parameters of the 1744/1743 Logger with function A. TRMS value of voltage and current. Basic values on 200 ms per phase. Vbas = 1 N 2 .∑ V i N i =1 I bas = 1 N 2 ⋅ ∑ Ii N i =1 N: Number of samples in 200 ms intervals (2048) RMS value of voltage and current per logging interval per phase V RMS = 1 M 2 .
1744/1743 Users Manual Active power of logging interval per phase P= 1 M ⋅ ∑ Pbas j M j =1 Pbas j to 200 ms value M: Number of 200 ms intervals per logging interval Total active power on all three phases 3 Ptotal = ∑ Pk k =1 Pk: Active power of the phase k: Phase (k = 1, 2, 3) Absolute value of the active power per interval per phase Pbetr = Sum of the absolute values of the active power on all three phases Pbetr total = Apparent power based on RMS values of voltage and current.
Power Quality Logger Logger Parameters with Function A Distortion power.
1744/1743 Users Manual Total active power of the fundamental for three phases Ph1total = ⋅∑ Ph1k Apparent power of the fundamental per phase. Basic value for 200 ms. Sh1bas = V1 .
Power Quality Logger Maintenance Maintenance W Caution Maintenance work on the Logger can be done only by trained and qualified personnel at a company-approved service center within the warranty period. For locations of Fluke Service Centers worldwide and contact information, see the Fluke website: www.fluke.com. With proper use, the Logger does not require special maintenance other than periodic calibration at a Fluke calibration center.
1744/1743 Users Manual Technical Specifications Logging Parameters – Overview The following table gives an overview of the logging parameters. Table 7.
Power Quality Logger Technical Specifications Maximum Number of Intervals for Logging Function P The maximum recording period can be calculated by multiplying the interval time defined in PQ Log with the maximum number of intervals in the following table. Version P, V+I A, V+I Averaged periods > 24,000 > 10,000 General Information Intrinsic uncertainty Valid for reference conditions, and guaranteed for two years. Quality system Developed, designed, and manufactured according to DIN ISO 9001.
1744/1743 Users Manual Environmental Specifications Working temperature range –10 °C to +55 °C Operating temperature range 0 °C to +35 °C Storage temperature range –20 °C to +60 °C Reference temperature range 23 °C ± 2 K Relative humidity 10 to 90%, no condensation Housing Robust, compact housing of CYCOLOY Protection IP65 per EN 60529 Safety EN 61010-1 600 V CAT III, 300 V CAT IV pollution degree 2, double insulation Type test voltage 5.
Power Quality Logger Technical Specifications Power Supply Functional range 88 to 660 V RMS ac absolute, 50 Hz / 60 Hz Safety EN 61010-1 600 V CAT III, 300 V CAT IV, pollution degree 2, double insulation Fuse Power supply fuse can be replaced only in service facility. Supply can be connected in parallel to measuring inputs (up to 660 V RMS ac). Power consumption 5W Memory capacity 8 MB Flash-EPROM Intervals > 5.600 intervals, > 39 days with 10-min intervals Events > 13.
1744/1743 Users Manual Input Voltage Input range VI P-N: 69, 115, 230, or 480 V ac Input range VI P-P 120, 200, 400, or 830 V ac Max overload voltage 1.2 VI Input range selection By job programming Connections P-P or P-N, 1- or 3-phase Nominal voltage VN ≤ 999 kV (using PTs and ratios) Input resistance Approx. 820 ke per channel. Lx-N Single phase (L1 or A, L2 or B, L3 or C connected): app. 300 ke Intrinsic uncertainty 0.
Power Quality Logger Technical Specifications Current Input for Clamp Input signal: 0.5 V ac nominal (for II) 1.4 V peak Intrinsic uncertainty < 0.3% of II Max. overload 10 V ac Input resistance App. 8.
1744/1743 Users Manual General Specifications RMS Logging Slow Voltage Variations Logging values: Mean value RMS values averaged over interval length Min, Max values Averaging with selectable averaging time from 0.
Power Quality Logger Technical Specifications Power (Logging Functions A, P only) P, S, |P| Active power P As per EN 61036, class 2 Distorting power D As per EN 61268, class 2 (A-version only) Max value Highest value per interval Min value Smallest value per interval Phase uncertainty < 0.3 degrees Conditions Conductor centered within clamp jaws or Flexi Set Harmonics Vm, Im, THDV, THDI per IEC/EN 61000-4-7, class B Voltage harmonics (function A) intrinsic uncertainty: For Vm < 3% VN: < 0.
1744/1743 Users Manual Logging Function P Logging Values Voltage L1 or A, L2 or B, L3 or C: phase-phase or phase-neutral: • Voltage (mean, min, and max values) • THDV (mean, and max values) • Flicker Pst, Plt • Voltage events (dips, swells, interruptions) Current L1 or A, L2 or B, L3 or C, and N: • Current (mean, max values), THDI Power: • Active power P (mean, min, and max values) • Absolute values active power |P| (mean, min, and max values) • Apparent power S (mean, min, and max values)
Power Quality Logger Technical Specifications Logging Function A – “All” parameters Logging Values All parameters for voltage quality per EN 50160: Voltage L1 or A, L2 or B, L3 or C: phase-phase or phase-neutral: • Voltage (mean, max, min values) • Voltage harmonics 1st to 50th order • THDV (harmonic contents of voltage) • Interharmonics 5 to 2500 Hz (in steps of 0.
1744/1743 Users Manual Total power: • Total power P, |P|, D, S • 3-wattmeter method • 2-wattmeter method (Aron circuitry) • 2 ½ wattmeter method Applications Power quality: • Voltage quality analysis according to EN 50160 over a 1-week period (time-activated job) • Examination of measurement quantities per standards Disturbance analysis: • Long-term analysis of line power voltage • Examination of voltage dips, swells, and harmonic problems • Flicker measurement • Examination of ripple co
Power Quality Logger PQ Log PC Application Software PQ Log PC Application Software PQ Log software for Windows® PCs is the application for use with the 1744/1743 Power Quality Logger. The data are also available in ASCII format.
1744/1743 Users Manual Online Test The following figure shows the online test display. egb024.bmp Figure 18.
Power Quality Logger PQ Log PC Application Software ASCII Export The following figure illustrates the ASCII export display: egb025.bmp Figure 19.
1744/1743 Users Manual Timeplot diagram The following figure shows a typical Timeplot diagram: egb026.bmp Figure 20.
Power Quality Logger PQ Log PC Application Software UNIPEDE DISDIP Table The following figure shows a typical UNIPEDE DISDIP table: egb027.bmp Figure 21.
1744/1743 Users Manual Cumulative Frequency – Harmonics The following figure shows a typical display of cumulative frequencies for current and voltage harmonics: egb028.bmp Figure 22.
Index —A— Anti aliasing filter, 28 Apparent Power, 37 —C— Completing the Logging, 26 Connecting the clip on probes, 14 Connection modes, 27 Connections for Medium Voltage Networks, 21 Crest Factor, 37 Current, 37 Current Harmonics, 33 —D— Disposal, 45 —E— Energy, 40 Evaluation, 27 Extreme values, 29 —F— Logging Configurations, 10 Logging input for voltages, 9 Logging segments, 11 Logging with two voltage converters and two current transformers, 24 —M— Maximum nominal voltages, 6, 16 Memory model, 11
1744/1743 Users Manual Voltage Harmonics, 32 Voltage interruptions, 31 Voltage variations, 28 Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 64 FAX 781.665.0780 - TestEquipmentDepot.