Modbus & Serial Output Transmitter for AC RMS Voltage or Current Input

• Easy setup with PC-based Instrument Setup Software
• DIN rail mount housing only 22.5 mm wide
• Detachable screw-clamp connectors
• Dual solid state relays for alarm or control, isolated
• RS232 or RS485 serial communications, isolated
• Universal AC power, 85-264 Vac
• Priced at only $270 (basic AC transmitter)

• Extended main board for custom curve linearization & rate from successive readings
• Low voltage power, 10-48 Vdc or 12-32 Vac

The Laureate Modbus & serial 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 to accept the output of 5A current transformers, with no need for a stepdown transformer. The current readings can easily be scaled digitally as needed.

True RMS precision circuitry is used to determine the root-mean-square of complex waveforms from DC to 10 kHz. Spikes up to 3.0 times the maximum of each range are accurately measured.

Accuracy is 0.1% of full scale* for signals from DC to 10 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.

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.

AC or DC coupling is jumper selectable. AC coupling accommodates signals from 10 Hz to 10 kHz and is suitable for applications such as measuring the ripple on a DC power supply. DC coupling accommodates signals from 0 Hz to 10 kHz. 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.

Use with current Transformers. High common mode rejection allows stable readings with current shunts located on the high side of the line. Five amp input capability allows the output of 5A current transformers to be applied directly to the transmitter, with no need for a stepdown transformer. The transmitter output can easily be scaled for the type of current transformer. Digital filtering is selectable for noisy signals.

LTM Series serial output transmitters send data via an isolated serial port, which is user configurable for RS232 or RS485 and full or half duplex operation. 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 allows up to 31 Laureate devices to be addressed on the same RS485 data line. It is simpler than the Modbus protocol and is recommended when all devices are Laureates. It also allows use of Laurel Datalogging Software.

Standard features of Laureate transmitters include:

• Serial data output, isolated. User selectable RS232 or RS485, half or full duplex, Modbus or Laurel ASCII protocol.
• 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.
• Analog transmitter output, 16-bit, user scalable and isolated. User selectable 4-20 mA, 0-20 mA or 0-10V levels.
• Universal AC power supply for 85-264 Vac.

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).

* For purposes of accuracy calculation, the full scale range for the 300V and 600V scales is 2000V (20,000 counts), and the full scale range for the 5A scale is 20A (20,000 counts).