Rheonics SME has self-powered 4-20mA analog outputs. This means that any connection to a controller device must be considered as a 4-wire transmitter. A 4-wire transmitter consists of two power wires and two signal wires. The two power wires supply the power to the transmitter, while the two signal wires transmit the signal back to the controller device. 

1. Wiring diagram for SME electronics

Figure 1. Wiring diagram for Rheonics SME.

2. Electrical Parameters

Load impedance: 0 to 720 Ohms

Output range: 4-20mA, (3.5mA error)

Galvanic isolation: none


Wiring Option (A)

  • Connect positive terminal of current input module to desired channel terminal of SME device
  • Connective negative terminal of current input module to negative power supply terminal used for SME device


Wiring Option (B)

  • Connect positive terminal of current input module to desired channel terminal of SME device
  • Connect negative terminal of current input module to V- terminal of SME device

3. Is the Rheonics SME a passive or active device?

Rheonics SME is considered 4-wire transmitter, in other words, it is an active sensor transmitter. Passive sensor devices are in general 2-wire transmitters require to be powered by external power supplies, instead, active sensor devices will use the same power supply from the transmitter to create a controlled analog output.

Figure 2. 4-wire transmitter, a block diagram of the Rheonics SME.

An active analog output incorporates circuitry to actively drive and control the output signal.

It has the following characteristics:

1. If a test is done by measuring the analog output with the device powered on, we are going to receive a voltage output or a current output different from zero.

2. The output from the Rheonics sensor must be connected to a sinking input from a PLC.



  • The 4/20mA outputs are not galvanically isolated. It is not recommended to route the 4/20mA to off-site locations if the corresponding 4/20mA input does not provide galvanic isolation.
  • Only for Ex Sensors. Power Input:  240V Maximum AC Single Phase, this is exclusive for Ex sensor configuration and would be the best to protect the zener barriers used in the configuration, only single phase power supplies should be used.