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.

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 TDM 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 15 kHz
  • Measurements from 0% to 100% of full scale
  • 0.03% 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 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.

LT transmitter AC

True RMS precision circuitry is used to determine the root-mean-square of complex waveforms from DC to 15 kHz. Spikes up to 3.0 times the maximum of each range are accurately measured.

Accuracy is an exceptional 0.03% of full scale for signals from DC to 15 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 15 kHz and is suitable for applications such as measuring the ripple on a DC power supply. DC coupling accommodates signals from 0 Hz to 15 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 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 TDM ASCII. Modbus operation is fully compliant with Modbus Over Serial Line Specification V1.0 (2002). The TDM ASCII protocol is simpler than the Modbus protocol and is recommended when all devices are s.
  • 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 TDM'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 TDM (P/N CBL04).

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 15 kHz
(AC coupling) or DC to 15 kHz
(DC coupling)
200.00 mV 10 µV 22 MΩ 0.03% FS ± 2 cts
2.0000 V 100 µV 1 MΩ 0.03% FS ± 2 cts
20.000 V 1 mV 1 MΩ 0.03% FS ± 2 cts
200.00 V 10 mV 1 MΩ 0.03% FS ± 2 cts
600.0 V* 100 mV 1 MΩ ± 0.8 V
300.0 V 100 mV 1 MΩ ± 0.8 V
Current Ranges
0-100% of FS,
10 Hz to 15 kHz (AC coupling)
or DC to 15 kHz (DC coupling)
2.0000 mA 0.1 µA 100 Ω 0.03% FS ± 2cts
20.000 mA 1 µA 10 Ω 0.03% FS ± 2cts
200.00 mA 10 µA 1 Ω 0.03% FS ± 2cts
5.000 A 1 mA 0.01 Ω ± 20 mA
* Range ETL certified to 300.0 V
Analog Output (standard)
Output Levels 4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10 Vdc (user selectable)
Compliance, 20 mA 10V (0-500Ω load)
Compliance, 0-10V 2 mA (5 kΩ 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)
Type 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, TDM ASCII
Modbus Compliance Modbus over Serial Line Specification V1.0 (2002)
Ethernet Connector RJ45 jack for 10/100 Base-T Ethernet cable
RS232/RS485 Connector Screw terminals for easy daisy chaining
Digital Addresses 247 for Modbus, 31 for TDM 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
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 2 Watts
Dimensions 129 x 104 x 22.5 mm case
Mounting 35 mm rail per DIN EN 50022
Electrical Connections Plug-in screw-clamp connectors
Operating Temperature 0°C to 55°C
Storage Temperature -40°C to 85°C
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.
* For purposes of accuracy calculation, the full scale range for the 600V scale is 2000V (20,000 counts), and the full scale range for the 5A scale is 20A (20,000 counts).
 LT transmitter pinout

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