Transmitter issue

[Steve & Lizzie]

Dear All

An instrumentation issue -

A machine is utilising three 4 to 20ma pressure transmitters for control
purposes. They are all on different circuits which have their own supplies.

For certain reasons it has become desirble to have just one transmitter
perform the function of all three (same pressure being measured) - how can
this be acheived? A spliter has been tried and whilst this did indeed
generate three signals from one instrument (the original and two additional
outputs) it could not be connected into the existing installation - for each
circuit a loop was required and it's own voltage was present, whereas the
splitter generated its own power etc.

Is there a method or device that can do this?

Any advice is greatly apprecited.

Thanks in advance

Steve

 

[Spehro Pefhany]

Dear All

An instrumentation issue -

A machine is utilising three 4 to 20ma pressure transmitters for control
purposes. They are all on different circuits which have their own supplies.

For certain reasons it has become desirble to have just one transmitter
perform the function of all three (same pressure being measured) - how can
this be acheived? A spliter has been tried and whilst this did indeed
generate three signals from one instrument (the original and two additional
outputs) it could not be connected into the existing installation - for each
circuit a loop was required and it's own voltage was present, whereas the
splitter generated its own power etc.

Is there a method or device that can do this?

Any advice is greatly apprecited.

Thanks in advance

Steve

As John says, isolators will work, but make sure you don't try to use
the loop-powered type as they will probably have too much voltage
drop. You would series the inputs of the two isolators with one load.

In some cases, you can series all three loads and use a single supply,
but you'd have to watch the voltage drop, voltage limit, compliance
and grounding issues.



Best regards,
Spehro Pefhany

 

[[email protected]]

It sounds easy in principal, and damned useful.  I expect there is, but

To the principal's office with you!

 

[Howard Kowall]

or you could buy a small shoe box plc with 1 4-20ma in and 3 out