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How do I use this Test Function on a DMM?
My DMM has a function for a 20mA loopback circuit. It rates 4mA at 5% and 20mA at 100%
So what would I use this test function for? Instead of using the Amps test function?
My DMM has a function for a 20mA loopback circuit. It rates 4mA at 5% and 20mA at 100%
So what would I use this test function for? Instead of using the Amps test function?
Comments
11 years ago
Its used for testing industrial control systems that use what is called a 4-20mA loop. The instrument modulates the current with whatever its reading, and the voltage developed across the instrument powers it.
It is a robust way of reading and driving remote instruments and is very popular.
http://en.wikipedia.org/wiki/Current_loop explains the principles.
Steve
Answer 11 years ago
steveastrouk,
Oh, so cool! Thank you so much! I am looking it up on the wikipedia. Thanks for the link.
11 years ago
. What steveastrouk said plus 4mA should be 0%, not 5%.
11 years ago
Leds use 20ma, maybe it's used for that?