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

Responds in 1 power line cycle response with 0.1% accuracy. DIN Rail mounted, digitally programmable.
Navigation:  Home > LT transmitters
AC RMS transmitter
Standard Features
  • 4-20 mA, 0-20 mA, 0-10V or -10V to +10V transmitter output, 16 bits, isolated
  • RS232 or RS485 serial data output, Modbus or Laurel ASCII protocol, isolated
  • Dual 120 mA solid state relays for alarm or control, isolated
  • True AC RMS measurement in one 50/60 Hz AC line cycle
  • 0.2, 2, 20, 200, 300V and 600V AC voltage ranges
  • 2, 20, 200 mA and 5A AC current ranges
  • All input ranges user-selectable and factory calibrated
  • AC or DC coupling for signals from DC to 10 kHz
  • Measurements from 0% to 100% of full scale
  • 0.1% accuracy of full scale at crest factor to 3.0
  • Universal 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac power

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 10 kHz. Spikes up to 3.0 times the maximum of each range are accurately measured.

Accuracy is an exceptional 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 are provided by dual solid state relays, which are standard. The 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.

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.

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).

Specifications Back to top
Laureate 4-20 mA and RS232/RS485 Transmitter for AC RMS Voltage or Current Input

Analog Input Range Resolution Input Ohms Error at 25°C
Voltage Ranges
0-100% of FS, 10 Hz to 10 kHz (AC coupling) or DC to 10 kHz (DC coupling)
200.00 mV
2.0000 V
20.000 V
200.00 V
600.0 V*
300.0 V
10 µV
100 µV
1 mV
10 mV
100 mV
100 mV
22 MΩ
1 MΩ
1 MΩ
1 MΩ
1 MΩ
1 MΩ
0.1% FS ± 2 cts
0.1% FS ± 2 cts
0.1% FS ± 2 cts
0.1% FS ± 2 cts
± 0.8 V
± 0.8 V
Current Ranges
0-100% of FS, 10 Hz to 10 kHz (AC coupling) or DC to 10 kHz (DC coupling)
2.0000 mA
20.000 mA
200.00 mA
5.000 A
0.1 µA
1 µA
10 µA
1 mA
100 Ω
10 Ω
1 Ω
0.01 Ω
0.1% FS ± 2cts
0.1% FS ± 2cts
0.1% FS ± 2cts
± 20 mA

* Range ETL certified to 300.0 V

Analog Output (standard)
Output Levels
Compliance at 20 mA
Compliance at 10V
Output Resolution
Output Accuracy
Output Isolation
4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10Vdc (user selectable)
10V (0-500Ω load)
2 mA (5 kΩ load)
16 bits (65,536 steps)
0.02% of output span plus conversion accuracy
250V rms working, 2.3 kV rms per 1 minute test
Serial Data Output (standard)
Signal Types
Data Rates
Output Isolation
Serial Protocols
Modbus Compliance
Ethernet Connector
RS232/RS485 Connector
Digital Addresses
RS232 or RS485 (half or full duplex), jumper selectable
300, 600, 1200, 2400, 4800, 9600, 19200 baud
250V rms working, 2.3 kV rms per 1 min test
Modbus RTU, Modbus ASCII, Laurel ASCII
Modbus over Serial Line Specification V1.0 (2002)
RJ45 jack for 10/100Base-T Ethernet cable
Screw terminals for easy daisy chaining
247 for Modbus, 31 for Laurel ASCII
Dual Relay Output (standard)
Relay Type
Load Rating
Two solid state relays, SPST, normally open, Form A
120 mA at 140 Vac or 180 Vdc
Power Input
Standard Power
Low Power Option
Power Frequency
Power Isolation
Power Consumption
85-264 Vac or 90-300 Vdc (DC operation not ETL certified)
10-48 Vdc or 12-32 Vac
DC or 47-63 Hz
250V rms working, 2.3 kV rms per 1 min test
Electrical Connections
129 x 104 x 22.5 mm case
35 mm rail per DIN EN 50022
Plug-in screw-clamp connectors
Operating Temperature
Storage Temperature
Relative Humidity
Cooling Required
0°C to 55°C
-40°C to 85°C
95% at 40°C, non-condensing
Mount transmitters with ventilation holes at top and bottom.
Leave 6 mm (1/4") between transmitters, or force air with a fan.

* For purposes of accuracy calculation, the full scale range for the 200V and 600V scales is 2000V (20,000 counts), and the full scale range for the 5A scale is 20A (20,000 counts).


Laureate LT transmitter pinout

Ordering Guide Back to top
Laureate 4-20 mA & RS232/RS485 Data Transmitter for AC RMS Voltage or Current Input
Click on the radio buttons to build a model number with pricing (shown below the Ordering Guide). Prices are in US dollars and do not include shipping or duty charges (export sales).
Please see our explanations and limitations applicable to pricing and online orders Prices shown are in US Dollars and are Laurel's manufacturer's suggested retail price (MSRP) in the USA. Orders are processed manually, not directly by our shopping cart system. You don't have to supply credit card information when placing an online order.

North American Orders. Laurel does not sell factory-direct in the USA or Canada. Online sales orders are filled through distribution. During the ordering process, you will have the chance to select an authorized Laurel distributor, or you can ask Laurel to refer you to a distributor. The distributor will then contact you to quote shipping, tax and duty (where applicable), and arrange for payment.

International Orders. If your ship-to address indicates that you are outside of the USA or Canada and Laurel has a distributor in your country, we will forward your order to that distributor for follow-up. If Laurel does not have a distributor in your country, we will email you an order acknowledgment and a pro forma invoice which states the product price, shipping charges, and wire transfer information, which includes a $25 bank wire transfer fee.

Questions about your order? Please email your distributor or sales@laurels.com

Configured model number LT20RMV1
Configured price per model $275
Quantity 1
Extended price $275
LT  4-20 mA & RS232/RS485 output transmitter
LTE  4-20 mA & Ethernet output transmitter
Main Board
2  Standard Main Board
4  Extended Main Board
Note: Extended allows custom curve linearization and rate from successive readings.
0  85-264 Vac or 90-300 Vdc
1  12-32 Vac or 10-48 Vdc
2  Power over Ethernet (for LTE only)
Signal Input
True AC RMS Volts
RMV1  200.00 mV
RMV2  2.0000 V
RMV3  20.000 V
RMV4  200.00 V
RMV5  600.0 V (range ETL certified to 300V)
True AC RMS Amps
RMA1  2.0000 mA
RMA2  20.000 mA
RMA3  200.00 mA
RMA4  5.000 A
Note: The same AC RMS signal conditioner can be user configured for AC Volts or AC Amps, and is precalibrated in EEPROM for all AC Volt and AC Amp ranges listed.  
CBL04  RS232 cable, 7ft. Connects RS232 screw terminals of LT
transmitter to DB9 port of PC.
CBL02  USB to RS232 adapter cable. Combination of CBL02 and CBL04
connects transmitter RS232 terminals to PC USB port.
Back to Top