4-20 mA & Serial Data Transmitter for AC RMS Voltage or Current

The Laureate 4-20 mA and RS232/RS485 output, AC RMS input transmitter provides six voltage input ranges and four current input ranges, all factory calibrated and jumper selectable. A special 5.000A range utilizes a built-in 0.01 ohm shunt resistor to accept the output of 5A current transformers, with no need for a stepdown transformer. The current readings can be scaled digitally as needed. High common mode rejection allows stable readings with current shunts located on the high side of the line. Digital filtering is selectable for noisy signals.

True RMS precision circuitry is used to determine the root-mean-square of complex waveforms from DC to 5 kHz. Spikes up to 3.0 times the maximum of each range are accurately measured.

Accuracy is 0.03% of full scale for the transmitters with 1 Megohm input resistance, signals from DC to 5 kHz, and signal amplitude down to 0. The crest factor (Vp / Vrms) is 3.0 at full scale, increasing to 300 for a signal amplitude of 1% of full scale. A version with 10 Megohm input resistance is available as a factory special, but decreases the maximum frequency from 5 kHz to 1 kHz for three of the voltage ranges.

True RMS readings in as little as one 50/60 Hz AC line cycle are unmatched in the industry. Such a high read rate allows anomalies to be detected and alarmed before they become expensive problems. On/off control and alarm can be achieved dual solid state relays, which are standard. Transmitter can also capture peak and valley for times as short as one 50/60 Hz AC power line cycle.

Standard features of Laureate LT transmitters include:

• 4-20 mA, 0-10V or -10V to +10V analog transmitter output, isolated, jumper-selectable and user scalable. All selections provide 16-bit (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.
• Serial communications output, 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.
• Dual solid state relays, isolated, for alarm or control. Rated 120 mA at 130 Vac or 180 Vdc.
• Universal 85-264 Vac power. Low-voltage 10-48 Vdc or 12-32 Vac power is optional.
• AC or DC coupling is jumper selectable. AC coupling is suitable for applications such as measuring the ripple on a DC power supply. Multiple integral cycles are averaged for signals above 50/60 Hz. A single cycle is captured for signals from 3 Hz to 50/60 Hz. Below 3 Hz and at DC, the capture rate is every 333 ms.

Easy Transmitter programming is via Laurel's Instrument Setup Software, which runs on a PC under MS Windows. This software can be downloaded from this website at no charge. The required transmitter-to-PC interface cable is available from Laurel (P/N CBL04).