Sourcing and Sinking Headache

Hi,

Are panel meters "generally" source or sink specific?

I.e. is it just how you wire the sensor into the panel meter which determines the configuration? I know sensors are sink/source specific.

The reason I ask is we have a setup where we are using a 4-20mA instrumentation amplifier (3 wire) which is sourcing. But we are unsure what the previous sensor was, it was most likely sinking.

The panel meter has terminals +V, 0V and Iin on the back. I would assume that seeing as the +V is being supplied by the panel, as long as the current source device is wired in correctly as a current source device then it would be fine.

We would setup the amp as +V = 12V, 0V = 0V and Output = 4-20mA referenced to 0V. From my experience sink amps are referenced to +V. But seeing as there is no reference as such in this circuit it wouldn't matter.

Thanks,

Generally source or sink have to do with the type of Digital I/O not analog I/O.
Analog I/O's are passive or active .

A Panel meter is neither.

For voltage input meters, they should present a high impedance to the source.

For milliamp meters, they are simply inserted into the current loop, and have a minimal burden resistance. Some mA meters might provide loop power, but that isn't required.

nonuke said:

Generally source or sink have to do with the type of Digital I/O not analog I/O.
Analog I/O's are passive or active .

Click to expand...

Unfortunately the terms do get interchanged.See link..

http://api-usa.com/appnotes/api_sink-source.pdf

Panel meters are usually passive. (sinking) As rdast said.

Maybe this will help. IDNR where it came from but useful.

RussB said:

Maybe this will help. IDNR where it came from but useful.

Click to expand...

Common AB analog input Installation Instructions diagram. I use this more than I'd like to admit, particularly for the wiring of polarity.