detect whether current is ac or dc

Thread Starter

johnboyman

Joined Jun 1, 2019
32
Hello I have some circuit board that I am trying to repair for one of my appliances but I can't figure out if some parts are ac current or DC and don't want to break my multimeter. Are their ways to tap a circuit and find out weather it has ac or dc current running through it. Thanks.
 

dl324

Joined Mar 30, 2015
9,576
Are their ways to tap a circuit and find out weather it has ac or dc current running through it.
You can determine that from the schematic.

How can you break your meter? DVM's should be able to measure positive or negative DC current. With alternating current on the DC current scale, you should measure 0.
 

Glenn Holland

Joined Dec 26, 2014
695
Hello I have some circuit board that I am trying to repair for one of my appliances but I can't figure out if some parts are ac current or DC and don't want to break my multimeter. Are their ways to tap a circuit and find out weather it has ac or dc current running through it. Thanks.
If you're trying to find out "weather" it's AC or DC, current, you need to use an outside thermometer the measures the current temperature.:)
 

rsjsouza

Joined Apr 21, 2014
214
@johnboyman, are you trying to measure current or voltage?

At any rate, the safest way to find out if a specific point in your circuit has AC or DC or a combination of the two is to use the Volts ranges of your multimeter. Differently than the Amps (current) ranges, the Volts ranges has a very high impedance and therefore much harder to make mistakes.

In addition to the suggestions above, even if you measure a point as AC or DC, keep in mind it may not be "pure" but maybe a sum of the two. To be absolutely sure, make two independent measurements at each point (DC and then AC). Always take @dl324 suggestion as well: start with the highest range.
 

AnalogKid

Joined Aug 1, 2013
8,251
Start with the meter on an AC range, and see if there is a significant reading. If not (after the initial transient), then move to a DC range.

ak
 
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