How is measuring miliamper with multimeter,and is there miliamper
measuring prosedure,please draw
Thank you so much
The meter must go in *series* with the load whose current you
want to measure. (If you put it across the load like you do for
measuring voltage, it acts like a short circuit and pops an
internal fuse.)
With a portable (battery operated) DMM you can typically
just put it in series with the hot or ground power lead to the
circuit under test. I usually use the positive lead, and connect
the positive DMM lead to the positive power supply, and the
negative DMM lead to the positive input on the load. But if
you reverse the meter leads, you just get negative readings...
no problem.
If you have an AC-operated meter you may want to insert it
in the ground lead instead, so that the ground of the meter and
the ground of the power supply are connected, and the positive
meter lead goes to the ground of the circuit under test. This
does mean that if you are also probing the circuit for voltage
with a scope or another meter, that the ground reference may be
"off" by the drop of the current measuring shunt in the meter.
This may or may not be a problem.
Note that the above assumes you want to measure DC current.
Cheap DMMs don't have AC current ranges, or low AC voltage
ranges. If you are trying to measure low AC currents (why?),
then you should probably be looking for someplace in the circuit
where the current passes through a resistor, and just measure
the AC voltage drop across the resistor with a scope and use
Ohm's Law to get current.
Best regards,
Bob Masta
dqatechATdaqartaDOTcom
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
