A process transmitter output ( 4-20mA , 2 wire ) is required to be connected to two different Instruments viz, PID controller & Multipoint Recorder . The measurement & control loop function is extremely critical & therefore it is desirable that a fault in one instrument should not affect the operation of the other instrument . Moreover the Recorder being used for multiple points , should be connected in a way that if there is a fault in one channel , the other channels should not be affected. A bulk power supply of +24V DC is available for sourcing power.

The PID controller being used for a critical application , there is a need for protecting the input & output sections from high voltage surges which may get induced on the input / output signal lines due to various electrical disturbances . So the Process transmitter signal output should be isolated from the PID controller input , and the PID controller output be isolated from the field output device. Likewise each input section of the Multichannel Recorder is also required to be protected from field disturbances by use of an Isolator.

The above two requirements can be fulfilled by using a Signal isolator at the input side & the output side. However the 4-20mA output of a single Signal isolator connected to both the instruments in series , does not guarantee measurement loop integrity of individual instruments. Therefore the input signal is required to be conditioned , isolated & split into two independent signals for connecting separately to the PID controller & Recorder.

Since +24VDC power is available, a solution with SIM-Micro series modules can be realized. All the requirements of the application can be fulfilled by using

The SIM-Micro series DC current Signal splitter isolates the Process transmitter output from inputs of the Controller & the Recorder . The two output sections of the Signal splitter are isolated from each other & also the power supply by means of in-built DC/DC converters .This ensures complete measurement loop integrity as irrespective of the fault in one loop the other loop shall continue to operate without loss of its functionality.

At the output side of the Controller , 1 no. SIM-Micro series DC Current Signal Isolator ( with 2 port input side isolation ) isolates the Controller output from the field device.