David L. Jones writes:
A current adapter for multimeters?
“But don’t most multimeters already have current measurement ranges?” I hear you ask. Well, yes, they do of course. But most multimeters, be they a no-name $10 hardware store throwaway model, or a $1000 highly accurate brand name meter, all suffer from two rather annoying issues with their current measurement ranges – burden voltage and reduced accuracy.
The biggest problem with current measurement ranges is called “burden voltage”. This is the voltage that the internal current shunt resistor drops as you pass your circuit current through it. The burden voltage is typically specified in millivolts per Amps (mV/A). The value will change for different current ranges, so you might have 1mV/A, 1mV/mA, or 1mV/μA for example.
Normally you may not give burden voltage a second thought, as like many, you probably think it’s fairly insignificant in most applications. In fact, most people would be hard pressed to tell you what the burden voltage of their particular multimeter actually is. It’s usually buried away in the user manual, if it’s mentioned at all. Next time you borrow a colleague’s meter, ask them what the burden voltage is, and watch their reaction…
µCurrent – A Professional Precision Current Adapter for Multieters - [Link]