Modbus Serial Output Transmitter for AC Phase Angle & Power Factor

• Internal conversion of input to six-digit reading:
  • Digital span adjust from 0 to ±999,999
  • Digital zero adjust from -999,999 to +999,999
• Inputs from NPN or PNP proximity switches, contact closures, digital logic, magnetic pickups down to 12 mV, or AC inputs up to 250 Vac.
• Triggers on positive or negative pulse edges
• DIN rail mount housing only 22.5 mm wide
• Universal AC power, 85-264 Vac
• Priced at only $275 (basic phase angle transmitter)

• Low voltage power, 10-48 Vdc or 12-32 Vac

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.

The Laureate 4-20 mA phase angle transmitter 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.

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 langle..

The Laureate 4-20 mA 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 meter 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°.

Power Factor Measurement
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.

Standard features include:

• Serial communications, isolated. User selectable RS232 or RS485, half or full duplex, Modbus or Laurel ASCII protocol.
• Analog transmitter output, 16-bit, user scalable and isolated. User selectable 4-20 mA, 0-20 mA or 0-10V levels.
• Dual solid state relays for control or alarm, isolated. Rated 120 mA at 130 Vac or 170 Vdc.
• Transducer excitation output, isolated. User selectable 5V@100 mA, 10V@120 mA or 24V@50 mA.
• Universal AC power supply for 85-264 Vac.