Features
- Programmable to read phase angle or power factor with two waveshapes of identical period
- Phase angle resolution of 1°, 0.° or 0.01°, accuracy of 0.03% at AC line frequency
- Power factor from 1.000 to 0.000 with sinusoidal signals
- Accepts AC signals from 1 Hz to 10 kHz at voltages up to 250 Vrms
- Transmits phase angle between two AC wave shapes of similar period
- Transmits power factor from 1.000 to 0.000 with sinusoidal signals
- For frequencies from 0.005 Hz to 10 kHz, voltages from 10 mV to 250 Vac
- 4-20 mA, 0-20 mA, 0-10V or -10V to +10V transmitter output, (isolated)
- Analog output resolution 0.0015% of span, accuracy ±0.02% of span
- RS232 or RS485 serial data, Modbus or Laurel ASCII protocol (isolated)
- Dual 120 mA solid state relays for alarm or control (isolated)
- 5V, 10V, 12V, or 24V dc transducer excitation output (isolated)
- Power 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac (isolated)
- DIN rail mount housing, 22.5 mm wide, detachable screw-clamp connectors
- Operating temperature from -40°C to 70°C (-40°F to 158°F)
- Extended allows up to 180 data points for custom curve linearization and a rate derived from consecutive readings
Certificates of Compliance
The Laureate 4-20 mA, 0-20 mA, 0-10V or -10V to +10V and RS232/RS485 output transmitter for phase angle transmits the lead or lag in degrees from 0° to 360° between two periodic signals of the same period. In the illustration to the right, phase angle is 360*P1/P. The signals are applied to the Channel A and B inputs of the Laureate dual-channel pulse input signal conditioner board. A resolution of 1°, 0.1° or 0.01° is selectable. Accuracy is 0.01% up to 100 Hz, 0.1% at 1 kHz, and 1% at 10 kHz.
Phase Angle Measurement
Phase angle in degrees indicates the phase lead or lag between two periodic signals of the same period, as determined from their zero crossings. These two signals will typically be the voltage and current applied to a load. As illustrated, the phase angle in degrees is +360*P1/P.
Power Factor Measurement
The power factor of an AC power system is the ratio of real power in watts (W) divided by apparent power in volt-amperes (VA). For sinusoidal signals, power factor is the cosine of phase angle.
The Laureate power factor transmitter computes power factor as the cosine of phase angle. Power factor readings can range from 1.000 to 0.000 with three decimal places and an accuracy of 0.1% for sinusoidal signals at 50/60 Hz power line frequency. While power factor is always positive, the transmitter artificially assigns a minus sign to power factor for negative phase angles, and it sets power factor to 0 for phase angles greater than 90°.
Designed for flexibility
Phase angle and power factor are determined by timing crystal clock pulses over a specified gate time which is selectable from 10 ms to 199.99 s. By selecting the minimum gate time of 10 ms, the update rate can be up to 20/s for 50/60 Hz AC line frequency. Improved accuracy is obtained by making the gate time long enough so that multiple cycles can be averaged.
Exceptional Accuracy and Stability. Laureate transmitters determine frequency by taking the inverse of period as measured with a calibrated quartz crystal time base. This results in extremely accurate and stable 6-digit internal readings (±999,999 counts), which are then processed in software. The analog output is generated by an ultra-linear 16-bit (65,536 step) digital-to-analog converter (DAC) for 0.02% output accuracy. The update rate of the transmitter output is a programmed gate time + 30 ms + 0-2 signal periods. For a 60 Hz signal, the update rate would be 20 per second. Such fast update rates are ideal for alarm and control.
The update rate of the transmitter output is a programmed gate time + 30 ms + 0-2 signal periods. For a 60 Hz signal, the update rate would be 20 per second. Such fast update rates are ideal for alarm and control.
All signal conditioner board ranges are factory-calibrated, with calibration factors for each range securely stored in an onboard EEPROM. These factors can be scaled via software to accommodate external shunts, enabling field replacement of signal conditioner boards without necessitating recalibration of the associated transmitter. For optimal accuracy, factory recalibration is recommended annually. All Laurel Electronics instruments undergo factory calibration using the industry-leading Fluke calibrators, which are recalibrated yearly and certified traceable to national standards, ensuring the highest level of precision and reliability.
Laureate Transmitters are easily programmed with Laurel’s free Instrument Setup Software, downloadable from our website and compatible with Windows PCs, requiring a data interface board for setup.
The extended Laureate computer board can display rate based on successive readings. It also allows exceptionally accurate custom curve linearization, for example to read out liquid volume or rate of flow in a horizontal cylindrical tank based on level reported by a 4-20 mA transmitter. For setup, up to 180 data points can be input into a computer spreadsheet or text file by the user. The computer then calculates spline-fit segments, which are downloaded into the transmitter.
Standard Features of Laureate LT Transmitters Include:
- Serial communications output, (isolated), RS232 or RS485 (half or full duplex), jumper selectable. Three protocols are user selectable: Modbus RTU, Modbus ASCII, or Laurel ASCII. Modbus operation is fully compliant with Modbus Over Serial Line Specification V1.0 (2002). The Laurel ASCII protocol is simpler than the Modbus protocol and is recommended when all devices are Laureates.
- 4-20 mA, 0-10V or -10V to +10V analog transmitter output, (isolated), jumper-selectable and user scalable. All selections provide 0.0015% resolution of output span and 0.02% output accuracy of a reading from -99,999 to +99,999 counts that is also transmitted digitally. Output isolation from signal and power grounds eliminates potential ground loop problems. Note that Ethernet data I/O is provided by Laurel's LTE series transmitters.
- Dual-channel pulse inputs for voltage signals, NPN or PNP proximity switches, contact closures, magnetic pickups or flow meters.
- Dual solid state relays, (isolated), for alarm or control. Rated 120 mA at 130 Vac or 170 Vdc.
- Selectable transducer excitation output, (isolated), user selectable 5V@100 mA, 10V@120 mA, 12V@100 mA, or 24V@50 mA.
- Power 85-264 Vac, (isolated), low-voltage 10-48 Vdc or 12-32 Vac power is optional.
Digital signal filtering modes can be selected to ensure stable readings in electrically noisy environments.
- An unfiltered selection provides true peak and valley readings and aids in control applications.
- A batch average filter selection averages each 16 conversions.
- An adaptive moving average filter selection provides a choice of 8 time constants from 80 ms to 9.6 seconds. When a significant change in signal level occurs, the filter adapts by briefly switching to the shortest time to follow the change, then reverts back to its selected time constant. An Auto setting selects the time constant selection based on signal noise.
Peak and valley values are automatically captured. These may be displayed via Laurel's free Instrument Setup Software, which runs on a PC under MS Windows or can be transmitted as serial data.
Two control inputs (CMOS/TTL levels, logic 0 = tied to digital ground, logic 1 = open) or dry contacts that can be set to control / activate 14 transmitter commands.
An (isolated) 5, 10, 12, or 24 Vdc excitation output is standard to power transducers or two-wire transmitters. Ratiometric operation, which automatically compensates for changes in the applied excitation, is jumper selectable for applications, such as bridges, where the signal to be measured is proportional to the excitation level.
LT series DIN rail Transmitters & signal conditioners can be interfaced to a wide range of sensors and transducers using one of seven available plug-in signal conditioner boards. The transmitters duplicate the high performance (high accuracy, high read rate) and extensive programmable features of Laureate 1/8 DIN digital panel meters, counters and timers. They utilize the same signal conditioners boards, much of the same firmware, and Laurel's free Windows-based Instrument Setup Software. They come in a compact DIN rail mount package with detachable screw-clamp connectors for easy wiring.
The LT series Transmitters accessible from this page include a 4-20 mA, 0-20 mA, 0-10V, or -10V to +10V analog output (isolated, user selectable), an RS232 or RS485 serial data interface (isolated, user selectable), and dual 120 mA solid state AC/DC relays (isolated). An (isolated) 5, 10, 12, or 24 Vdc transducer excitation output is included with all models other than those with a temperature or AC RMS signal conditioner.
Connecting Laureate LT Transmitters to a Local Area Network (LAN)
Up to 30 Laureate LT Transmitters and/or Digital Panel Meters can be configured for RS485 and daisy-chained to an LT Transmitter for seamless LAN integration. Alternatively, Laurel LTE series Ethernet transmitters can connect directly to a LAN via an Ethernet cable. Setup for both configurations is streamlined using Laurel’s free Instrument Setup Software, which simplifies node discovery and transmitter configuration.
Flexible Communication Options for LT Transmitters
Laureate Transmitters can be equipped with Laurel communication boards to support various interfaces and protocols. These include serial interfaces with ASCII or Modbus RTU protocols, and Ethernet interfaces with web access, ASCII, or Modbus TCP/IP protocols, ensuring versatile connectivity for your commercial applications.
| LT Transmitter Signal Input & Function | Model Series | Analog Output | RS232 & RS485 | Dual Relays | |
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| 1 | DC Input Voltage and Current | LT-DC |  |
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| 2 | AC RMS Voltage or Current | LT-RMS | |
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| 3 | Process Voltage or Current | LT-P | |
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| 4 | Weighing Applications | LT-WA | |
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| 5 | Load Cell & Microvolt Signals | LT-WM | |
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| 6 | Thermocouple (Types J, K, T, E, N, R, S) | LT-TC | |
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| 7 | RTD Temperature | LT-RTD | |
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| 8 | Resistance in Ohms | LT-R | |
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| 9 | Frequency, Rate, Speed | LT-FR | |
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| 10 | Pulse Input Totalizer | LT-FR | |
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| 11 | Process Signal Totalizer | LT-VF | |
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| 12 | Sum, Difference, Ratio, Product of 2 Inputs | LT-FR | |
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| 13 | Batch Controller Pulse Input | LT-FR | |
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| 14 | Batch Controller Analog Input | LT-FR | |
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| 15 | On/Off Duty Cycle | LT-FR | |
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| 16 | Stopwatch Timing for Single Events | LT-FR | |
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| 17 | Average Time of Periodic Events | LT-FR | |
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| 18 | AC Phase Angle and Power Factor | LT-FR | |
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| 19 | Quadrature Position or Rate | LT-QD | |
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4-20 mA & Serial Data Transmitter for AC Phase Angle & Power Factor
| Phase Angle Mode | ||||
|---|---|---|---|---|
| Item Transmitted | Phase angle difference between two waves of same period | |||
| Transmitted Units | 1°, 0.1°, 0.01° | |||
| Frequency Range | .005 Hz to 10 kHz | |||
| Resution | .01°, .005 Hz to 100 Hz, 0.1° at 1 kHz, 1° at 10 kHz | |||
| Accuracy | 0.03° at 50 or 60 Hz | |||
| Maximum Timing Interval | 200 sec | |||
| Recalibration: All ranges are calibrated at the factory. Recalibration is recommended every 12 months. | ||||
| Power Factor Mode | ||||
| Item Transmitted | Power factor between two sine waves of same period | |||
| Transmitted Units | 1.000 to 0.000, 1.00 to 0.00, or 1.0 to 1.0 | |||
| Polarity | Negative sign indicates negative phase angle | |||
| Frequency Range | 0.005 Hz to 10 kHz | |||
| Accuracy | 0.1% at power line frequencies | |||
| Inputs | ||||
| Signal Types | Sinusoidal AC and square waves | |||
| Signal Ranges | 10 mV to 250 Vac | |||
| Signal Ground | Common ground for channels A & B | |||
| Noise Filter | 1 MHz, 30 kHz, 250 Hz (selectable) | |||
| Update Rate | ||||
| Conversion Interval | Gate time + 30 ms + 0-2 signal periods | |||
| Gate Time | Selectable 10 ms to 199.99 s | |||
| Time Before Zero Output | Selectable 10 ms to 199.99 s | |||
| Analog Output (standard) | ||||
| Output Levels | 4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10Vdc (user selectable) | |||
| Compliance, 4-20 mA | 10V (0-500 ohm load) | |||
| Compliance, 0-10V | 2 mA ( kOhm load) | |||
| Output Resolution | 16 bits (65,536 steps) | |||
| Output Accuracy | 0.02% of output span plus conversion accuracy | |||
| Output Isolation | 250V rms working, 2.3 kV rms per 1 minute test | |||
| Serial Data Output (standard) | ||||
| Signal Types | RS232 or RS485 (half or full duplex), jumper selectable | |||
| Data Rates | 300, 600, 1200, 2400, 4800, 9600, 19200 baud | |||
| Output Isolation | 250V rms working, 2.3 kV rms per 1 min test | |||
| Serial Protocols | Modbus RTU, Modbus ASCII, Laurel ASCII | |||
| Modbus Compliance | Modbus over Serial Line Specification V1.0 (2002) | |||
| RS232/485 Connector | Screw terminals for easy daisy chaining | |||
| Digital Addresses | 247 for Modbus, 31 for Laurel ASCII | |||
| Dual Relay Output (standard) | ||||
| Relay Type | Two solid state relays, SPST, normally open, Form A | |||
| Load Rating | 120 mA at 140 Vac or 180 Vdc | |||
| Excitation Output (standard) | ||||
| 5 Vdc | 5 Vdc ± 5%, 100 mA (jumper selectable) | |||
| 10 Vdc | 10 Vdc ± 5%, 120 mA (jumper selectable) | |||
| 12 Vdc | 12 Vdc ± 5%, 100 mA (jumper selectable) | |||
| 24 Vdc | 24 Vdc ± 5%, 50 mA (jumper selectable) | |||
| Output Isolation | 50 Vdc from signal ground | |||
| Power Input | ||||
| Standard Power | 85-264 Vac or 90-300 Vdc | |||
| Low Power Option | 10-48 Vdc or 12-32 Vac | |||
| Power Frequency | DC or 47-63 Hz | |||
| Power Isolation | 250V rms working, 2.3 kV rms per 1 min test | |||
| Power Consumption at 24V | 1.5W typical, 3W with max excitation output | |||
| Environmental | ||||
| Operating Temperature | -40°C to 70°C (-40°F to 158°F) | |||
| Storage Temperature | -40°C to 85°C (-40°F to 185°F) | |||
| Relative Humidity | 95% at 40°C, non-condensing | |||
| Cooling Required | Mount transmitters with ventilation holes at top and bottom. Leave 6 mm (1/4") between transmitters, or force air with a fan. | |||
| Mechanical | ||||
| Enclosure | Rugged black polycarbonate housing material | |||
| Mounting | 35 mm rail per DIN EN 50022 | |||
| Dimensions | 129 x 104 x 22.5 mm case | |||
| Connectors | Detachable screw clamp connectors meet VDE / IEC / UL / CSA standards. RJ45 jack for Ethernet | |||
| Tightening Torque | Screw terminal connectors: 5 lb-in (0.56 Nm) | |||
| Weight | Complete transmitter: 183 g (6.5 oz) | |||
| Replacement Case Screws | ||||
| Size | 6 | |||
| Thread Pitch | 6-19 | |||
| Length | 1/2" | |||
| Head Style | Pan Head | |||
| Drive Style | Phillips | |||
| Head Diameter | 0.256-0.270 | |||
| Head Height | 0.087-0.097 | |||
| Full/Partial Thread | Full | |||
| Drive Size | 2 | |||
| Material | Steel | |||
| Finished | Black Oxide | |||
| General | ||||
| Programming | Utilize Laurel's free Instrument Setup Software, which runs on a PC under MS Windows. | |||
| Security | Lockout options available using Laurel's free Instrument Setup Software. | |||
| Warranty | 3 years parts & labor | Recalibration: All ranges are calibrated at the factory. Recalibration is recommended every 12 months. | ||
Transmitter Pinout
Free Instrument Setup Software for Series 2 Laureates
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| 1/8 DIN Digital Panel Meters | DIN Rail Transmitters |
Free Downloadable Windows-based Instrument Setup (IS) software (Data Interface Board Required) for use with our programmable Digital Panel Meters, Scale Meters, Counters, Timers, Remote Displays, and Transmitters, are an easy method to set up Laureate 1/8 DIN digital panel meters, counters, timers, remote displays, and DIN-rail transmitters, as explained in the Instrument Setup Software Manual. Laureate 1/8 DIN instruments can also be set up from the front panel, as explained in their respective Owners Manuals. Instrument Setup software is of benefit whether or not the PC is connected to the instrument.
- When the PC is connected to the instrument, Instrument Setup software can retrieve the setup file from the instrument or open a default setup file or previously saved setup file from disk View Setup, then provides graphical user interface (GUI) screens with pull-down menus applicable to input, display, scaling, filtering, alarms, communications, analog output, and front panel lockouts. Fields that are not applicable to the instrument as configured are either left out or grayed out. Clicking on any item will bring up a detailed Help screen for that item. After editing, the setup file can be downloaded, uploaded to the instrument, or saved to a disk. The same setup file can then be downloaded into multiple instruments.
- When the PC is not connected to the instrument, the above GUI screens can be used to set up a virtual instrument. The setup file can then be saved to disk. Switching toView Menu then brings up a screen with the required front panel programming steps. This view can be printed out for use at the instrument site and to serve as a hard copy record.
Download Free Instrument Setup Software
Installation
Set User Account Control (UAC) of MS Windows to "Never notifiy me" so that Instrument Setup Software can create directories. The UAC change screen can be reached as follows:
- Under Windows 7, click on the Windows Start button in the lower left of the desktop and enter "UAC" in the search field.
- Under Windows 8, navigate to Control Panel, then to the "User Accounts and Family Safety" section, and click on "Change User Account Control Settings."
- Under Windows 10, click on the Windows Start button in the lower left of the desktop, then on "Settings", and enter "UAC" in the search field.
- Reboot your computer for the changed UAC setting to take effect.
RJ11-to-DB9 cable with rear view of DB9 connector to PC
RS232 cable, meter to PC, P/N CBL01
Laureate 1/8 DIN Laureate instruments must be equipped with a serial communications board and be connected to the computer via a serial communications cable. The connection can be via RS232, RS485, USB or Ethernet. Following setup, the serial communications board may be removed from the instrument if desired. The wiring of the RS232 cable is illustrated above with end views of the two connectors.
Laureate LT Series transmitters come standard with a 3-wire serial interface, which can be jumpered for RS232 or RS485.
Laureate LTE Series transmitters come standard with an Ethernet interface.
Meter Setup Screens
Click on any of the reduced screens below for a full-size screen view, then click on the Back button of your browser to return to this page. The screens examples below are for a fully-loaded Series 2 Digital Panel Meter (DPM), which is connected to the PC via RS232. If the meter is a Series 1 meter (pre-2007), this is sensed by the software, and somewhat different screens are brought up. Please see Series 1 setup screens.
Welcome Screen
From the computer desktop, click on Start > Programs > IS2 > IS2. Or click on the IS icon on your desktop. This splash screen will be displayed for three seconds. The software revision number is in the lower right.
Communications Selection Screen
Specify your desired communication protocol and the serial communications bus type, which should match the jumper setup of the instrument. Select None if the PC is not connected to the instrument.
Establish Communications Screen
If you selected RS-232, you will be asked to specify the PC Com Port and Baud Rate, which should match the jumper setup of the instrument. Click on Establish. With the right settings, the Communications Established field will light up in green, and the Meter Type will be recognized. If so, click onMain Menu.
Main Menu Screen
Click on File > Default Setup to retrieve the default setup file from disk for your type of meter. Click on File > Open Setupto retrieve a previously saved setup file from disk or on File > Save Setup to save your edited setup file to disk. Click onDPM > Get Setup to retrieve the setup file from your meter or on DPM > Put Setup to download your edited setup file into the meter.
DPM Input + Display Setup Screen
From the Main Menu, click on View > Setup, then on theInput+Display tab. You can now specify the meter hardware, signal type, display mode, and functions of control inputs A and B. Clicking on any item brings up a pull-down menu with the available choices.
DPM Scaling Setup Screen
Click on the Scaling tab, which provides three scaling methods to relate the signal to the displayed reading: 1) Scale and Offset method, 2) Coordinates of two points method, and 3) Reading Coordinates of Two Points method. The last method uses actual high and low signals, and the computer will prompt you.
DPM Filter Setup Screen
Click on the Filter tab, which allows you to specify the digital filter time constant (if any), the adaptive filter threshold, and whether Peak / Valley values are filtered or unfiltered. As for all setup screens, clicking on the F1 key while an item is highlighted brings up a Help screen for that item, as illustrated.
DPM Relay Alarms Setup Screen
Click on the Relay Alarms tab, which allows you to set up Alarms 1 and 2 for the optional dual relay output board. Clicking on any of the four numeric fields changes these to green and brings up a special field to enter the desired numeric value, which is tied to the displayed reading.
DPM Communications Setup Screen
Click on the Communications tab so set up serial communications. In particular, you can special the Serial Protocol and the meter address if multiple meters are to be addressed on the same serial data line.
DPM Analog Output Setup Screen
Click on the Analog Out tab so set up the optional analog output board. Three output ranges are selectable, the endpoints of which can be tied to user-specified High and Low readings.
DPM Lockouts Setup Screen
Click on the Lockouts tab to check off menu items which will no longer be accessible from the front panel of the meter. This will simplify meter operation and prevent unintended setup changes.
Meter Setup Utilities
DPM Front Panel Setup Screen
As an aid to programming the meter from the front panel when a serial connection is not available, you can return to the Main Menu and click on View > Menu. The required sequence of front panel screens will then be displayed. Click on any step in the sequence for the meaning of each digit, as illustrated for the FILtEr step. For a hardcopy, simply press on Print.
DPM Jumper Setup Screen
Specify your desired communication protocol and the serial communications bus type, which should match the jumper setup of the instrument. Select None if the PC is not connected to the instrument.
DPM Jumper Setup Screens
Click on any of the displayed plug-in boards, and you will be presented with the jumper positions and electrical connections for your selected board. This minimizes the need to refer to the printed manual.
DPM Commands Screen
This page allows you set up external input, serial communications, an analog output proportional to the display (optional), and lockouts for Laureate digital counters. The grayed out area at the top right of the screen applies to Laureate remote displays.
Graphical Output Screens (not available with Ethernet)
From the Main Menu, click on Readings if your PC is connected to the meter. A pull-down menu then offers three choices: List, Plot and Graph.
- List presents the latest readings in a 20-row by 10-column table. Press Pause at any time to freeze the display. This is one method to capture peak readings.
- Plot generates a plot of readings vs. time in seconds. It effectively turns the DPM-PC combination into a printing digital oscilloscope.
- Graph generates a histogram where the horizontal axis is the reading and the vertical axis is the number of occurrences of readings. The display continually resizes itself as the number of readings increases.
DPM Calibration Screens
Click on the Scaling tab, which provides three scalClick on the Scaling tab, which provides three scaling methods to relate the signal to the displayed reading: 1) Scale and Offset method, 2) Coordinates of two points method, and 3) Reading Coordinates of Two Points method. The last method uses actual high and low signals, and the computer will prompt you.
Frequency Meter Calibration Screen
Calibration of the quartz crystal of the Laureate frequency meter requires the input of a known frequency from a calibrator. Apply the frequency, then enter the frequency in Hertz. Calibration will be automatic, with storage of the calibration factor stored in non-volatile memory.
Dimensions
Dimensioned CAD assembly drawings in EPRT, STEP, x_t, .dwg, pdf file formats: Laureate-transmitter-case.zip (zipping prevents browser from opening CAD files as text files).
| Using Laureate Meters, Counters or Transmitters to Synchronize Motor Generators |
|---|
 Synchronization of two motor generators requires that the two frequencies be identical, that the lines be in phase, and that the line voltages be close to each other. In this illustration, a single Laureate dual channel counter (or frequency transmitter) measures both frequencies to six-figure accuracy in a few line cycles. Another Laureate dual channel counter (or phase transmitter) measures phase angle to 0.1° resolution. Two Laureate AC RMS Voltmeters, which offer ranges of 200.00 V and 600.0 V, are used to display the two RMS voltage to 0.1% accuracy. |
CAL-Digital
Certificate of Calibration
$65.00
CBL02
USB-to-RS232 Adapter Cable
$47.00
CBL04
RS232 Cable for LT Transmitters
$47.00CBL12
12-foot Power Cable
$47.00CBL6
6-foot Power Cable
$41.00What Is the LT DIN Rail Digital Transmitter for AC Phase Angle and Power Factor Applications?
Where most transmitters measure a single signal, this LT DIN Rail Transmitter measures the relationship between two — specifically, the timing difference between two AC waveforms of the same period, typically the voltage and current applied to a load. That relationship is transmitted as either phase angle in degrees or power factor, alongside an isolated 4-20 mA analog output and digital serial data.
Industries That Use This Transmitter
- Power Generation — synchronizing motor generators before paralleling them onto a common bus, using phase angle, frequency, and voltage together to confirm safe connection.
- Utilities and Power Distribution — monitoring power factor on distribution feeders and substations to identify inefficiencies and support power factor correction planning.
- Industrial Automation — tracking power factor on large motor loads to flag correction capacitor bank issues or load imbalance before they affect billing or equipment life.
- Renewable Energy — monitoring phase relationships between inverter output and grid voltage during grid-tie synchronization for solar and wind installations.
- Test and Measurement — precision phase angle comparison between two arbitrary periodic signals in lab or calibration settings, independent of any power application.
How Phase Angle Is Measured
Phase angle in degrees indicates the lead or lag between two periodic signals of the same period, determined from their zero crossings — expressed as 360 × P1/P, where P1 is the time offset between the two signals' zero crossings and P is the full period. The two signals are applied to the Channel A and B inputs of the dual-channel pulse input signal conditioner. Resolution is selectable at 1°, 0.1°, or 0.01°, with accuracy that varies by frequency: 0.01° up to 100 Hz, 0.1° at 1 kHz, and 1° at 10 kHz — reflecting the practical tradeoff of measuring finer angular resolution at higher signal frequencies.
How Power Factor Is Derived
For sinusoidal signals, power factor is mathematically the cosine of phase angle — the ratio of real power (watts) to apparent power (volt-amperes) in an AC system. The transmitter computes power factor this way directly from the measured phase angle, reporting a value from 1.000 to 0.000 with 0.1% accuracy at power line frequencies. Since power factor itself is always positive by definition, the transmitter uses a negative sign as a convention to indicate a negative phase angle rather than an actual negative power factor, and it reports power factor as 0 for any phase angle greater than 90°.
Timing and Update Rate
Both phase angle and power factor are determined by timing crystal clock pulses over a selectable gate time (10 ms to 199.99 seconds). At the minimum 10 ms gate time, update rate can reach 20 readings per second at 50/60 Hz line frequency; longer gate times average more cycles together for improved accuracy at the cost of update speed.
Named Application: Synchronizing Motor Generators
Synchronizing two motor generators before connecting them requires that their frequencies match, their lines be in phase, and their voltages be close to each other. A documented setup for this uses three Laureate instruments together: one dual-channel counter measures both generators' frequencies to six-figure accuracy within a few line cycles, this phase transmitter measures the phase angle between the two lines to 0.1° resolution, and two AC RMS voltmeters (200.00V and 600.0V ranges) display each line's voltage to 0.1% accuracy — giving an operator or control system everything needed to confirm safe synchronization before closing the tie breaker.
Conclusion
The LT DIN Rail Digital Transmitter for AC phase angle and power factor gives a panel builder a precise way to measure the relationship between two AC signals — not just their individual values — and convert that relationship into a standard 4-20 mA output and serial data. Its frequency-dependent accuracy specification, direct power factor derivation from phase angle, and documented use in generator synchronization make it a purpose-built fit wherever the timing relationship between two AC waveforms, rather than either waveform alone, is what actually needs to be measured and controlled.
AC Phase Angle and Power Factor Transmitter Frequently Asked Questions
Why does phase angle accuracy get worse at higher frequencies (1° at 10 kHz vs. 0.01° up to 100 Hz)?
Phase angle is derived from timing the offset between zero crossings using a fixed clock resolution; at higher signal frequencies, each cycle takes less absolute time, so the same clock resolution represents a larger angular uncertainty relative to the shorter period — this is a timing-resolution tradeoff inherent to the measurement method, not a limitation specific to this transmitter.
Why does the transmitter report power factor as 0 for phase angles greater than 90°?
Power factor is defined as the cosine of phase angle, and cosine becomes negative for angles beyond 90°; since power factor is conventionally treated as a positive quantity that doesn't extend meaningfully past that point in typical AC power applications, the transmitter reports 0 rather than a negative cosine value in that range.
What does the negative sign on a power factor reading actually indicate?
It's a documented convention indicating the underlying phase angle is negative (current leading rather than lagging voltage, or vice versa depending on wiring convention), not a claim that power factor itself is a negative quantity — power factor is fundamentally a magnitude between 0 and 1.
Can this transmitter measure phase angle between two signals of different frequencies?
No — phase angle is only meaningful and measurable between two periodic signals of the same period; if the two input signals have different frequencies, the phase relationship between them isn't fixed and phase angle in the traditional sense doesn't apply.
Why does a longer gate time improve accuracy for phase angle and power factor measurement?
A longer gate time allows the transmitter to average across multiple signal cycles rather than basing the reading on a single cycle, which reduces the relative impact of any single-cycle noise or timing jitter on the final reported value, at the cost of a slower update rate.
Does this transmitter measure real power (watts) directly?
No — it measures phase angle and derives power factor from it; actual real power in watts also depends on the RMS voltage and current magnitudes, which this transmitter doesn't measure itself (as shown in the generator synchronization example, separate AC RMS voltmeters are used alongside this transmitter for that purpose).
What signal types does this transmitter accept for phase angle and power factor measurement?
It accepts sinusoidal AC and square wave signals from 10 mV to 250 Vac, across a frequency range of 0.005 Hz to 10 kHz, applied to its two input channels.
Can this transmitter be used to measure phase angle between something other than voltage and current?
Yes — while voltage and current on a load is the typical application, the transmitter measures phase angle between any two periodic signals of the same period and frequency range that it accepts, regardless of what physical quantities those signals represent.
Can multiple phase angle/power factor transmitters be networked together?
Yes — up to 30 LT Transmitters and/or Digital Panel Meters can be daisy-chained on RS485 for LAN integration, or a high-speed Ethernet or WiFi communication board can be used instead for network connectivity.
AC Phase Angle and Power Factor Transmitter Questions From the Field
My phase angle reading seems to jump around even though the load appears stable — what should I check?
Instability in the phase angle reading is often linked to a gate time that's too short relative to the noise level on the input signals; increasing the gate time to average across more cycles is the standard first step before suspecting a wiring or load issue.
My power factor reading shows 0 even though I expect a small nonzero value — why?
If the actual phase angle between the two signals exceeds 90°, the transmitter is documented to report power factor as 0 rather than a negative cosine value; verifying the actual phase angle reading (not just the power factor) is the way to confirm whether this is expected behavior or a genuine problem with the load.
My two generators won't synchronize even though the phase transmitter shows a small angle — what else should I check?
Successful synchronization requires matching frequency, phase angle close to zero, and close voltage magnitudes together — a small phase angle alone doesn't guarantee synchronization if the frequencies aren't also closely matched or the line voltages differ significantly; checking all three parameters together (as the documented three-instrument setup does) is the standard approach.
My phase angle reading seems to have a consistent offset from what I calculate manually — what's the likely cause?
A consistent fixed offset often points to a wiring or reference-point mismatch between the two channels — such as the two signals being referenced to different points in the circuit — rather than a measurement fault; verifying both channels are referenced consistently is the standard first check.
Can electrical noise on one channel throw off my phase angle reading even if the other channel looks clean?
Yes — since phase angle depends on precisely timing zero crossings on both channels, noise affecting the zero-crossing timing on either single channel can distort the calculated angle; checking cable shielding, grounding, and signal quality independently on each channel helps isolate which one is actually the source of an unstable reading.
My power factor reading looks accurate at power line frequency but degrades at higher test frequencies — is that expected?
Yes — this follows directly from the documented frequency-dependent accuracy of the underlying phase angle measurement, since power factor is derived from phase angle; the specification explicitly notes accuracy is tightest near 50/60 Hz and looser at higher frequencies like 1 kHz or 10 kHz.
My reading updates too slowly for the fast response I need — what should I check?
Reducing the configured gate time toward its minimum (10 ms) increases update rate at some cost to averaging-based accuracy; balancing gate time against how much update speed the application genuinely requires is the standard tradeoff to review.
