4-20ma

Dear all,

"when we want to test the ma we place ammeter in series with the meter. how about if i want to test the module with ammeter placed direct on the output terminals ''disconnect the meter'', will the module decrease the output voltage and show 12ma for half way reading?"

You are correct, the module automatically adjust the output voltage and your meter reading is still 12 ma.

"or that will be short circuit case as i connect the ammeter direct to the output terminals and the module will detect short circuit ???"

Even the output is short-circuted, your module will keep the output current 12 ma. The module will not detect the short-circuit, but will work properly. Many 4-20mA modules will work with 0 to 1 or 2kOhms output resistance. So, output can be shorted.

Regards

hi

thats exactly what i want to know, many thanks for your reply. and also thanks for every body who reply on this forum!

These are constant current devices for a wide output resistance range. Hence the amount of output resistance (provided it is within the range) will not affect the reading. BTW: if you directly put the ammeter at the output it is a virtual short circuit isn't it ?

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Regards,

Craig