I have several equipment diagrams showing that I need to provide "loop power" for a 4-20mA device. What is the typical voltage requirement for such systems? Is there any. Does anyone know a good primer on 4-20 systems?

 

Typical is 24vdc, but you really should check the installation and operating manuals for the instrumentation that is to e installed -- not everyone does it the same way! LUCK.

 

24VDC

Gil

 

Typically its 24 voltDC. This can vary dependant upon the system loading. As the load increases the need is for higher voltages to achieve 20mAmps. Check with the instrument supplier who generally provide a graph of voltage against load. Don't forget to shield the signal.

Wynton

 

If you go to:
"http://www.almegcontrols.com/4-20_converter.htm":http://www.almegcontrols.com/4-20_converter.htm

you will see a diagram in the lower left corner. Click on the dia. for a full size drawing on connecting a 4-20 device.

Thanks Bob Hogg
[email protected]

 

You don't need higher voltages, you need greater current capacity.

Jeff.

 

Loop power is used to in analogue transducers and is typically 24VDC. However if the circuit resistance is high, a slightly higher voltage is often applied. I experienced voltages upto 28VDC
provided by certain controllers. However small change in voltage does not affect measurement accuracy as the criteria for measurement is current not voltage.
Hope it helps