hi Instrument experts,

I am a beginner in this field. Please help me to solve this.

is it possible to connect a transmitter output to another transmitter? I mean if we connect the 4-20 mA output of one transmitter parallel to other transmitters slot of PLC, what will happen?

will we get the same output for both transmitter?

Is there any voltage/Milli amps drop, noise issue, PLC defect any thing?

Please advice me. this is for bypassing one transmitter. We don't have spare transmitter right now.

 

> is it possible to connect a transmitter output to another transmitter?

No.

> if we connect the 4-20 mA output of one transmitter parallel to other transmitters slot of PLC, what will happen?

I'm assuming that a 'transmitters slot of PLC' is a PLC analog input connected to a transmitter.

If a single transmitter's 4-20mA output is connected, in parallel, to two analog inputs (on the same PLC/DCS/controller/recorder/I/O module) then each input will receive (approximately) half of the loop current (any difference in input resistance will determine the difference in current). An analog input that gets half the loop current will indicate half its (linear) scaled value. This assumes nothing else is connected to the analog inputs.

> this is for bypassing one transmitter. We don't have spare transmitter right now.

When a transmitter fails, manual, or hand mode is sometimes used to control the loop in the absence of an input signal. Depends on the loop.

Substituting a signal other than the original input signal in a control loop requires very careful and cautious consideration. Most plants do not have duplicate process signals that can be freely substituted for other signals. Controlling to a PV that's not in the loop is not control, it's wishful thinking.

Lack of an input to a control loop is a control issue, more so than an instrument issue. As a beginner, you really need some on-site experienced control expertise to deal with whatever the situation is there.