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Multimeter Question

The Fed

Old Guys Rule
I don't know if a circuit I'm testing for voltage is AC or DC. If I set my selector switch to AC and it turns out to DC, or vice versa, can I do any damage tot he circuit circuit? I'm not concerned about hurting the meter. The max voltage is 110.
 

mkv_martinez

Go Kart Champion
Are you talking about in your car or in general? In the car the only AC Circuit should be the Alternator AFAIK

If you are testing an outlet from a wall or something, that would be AC - if you are testing an electronic device (after its PSU and such) you are almost certainly looking at DC unless its a unique application

As for will you damage the meter, good question. Maybe someone more experienced can chime in, i'd say it depends on the quality. I have used cheapo ones that exploded for nearly no reason at all, and good ones that I guess have mini circuit breakers built in or something.
 

The Fed

Old Guys Rule
Refrigerator freezer compartment LED light. I'd rather test to see if there is power at the terminals of the light assembly then first replace the door switch, since I suspect it's not the switch and don't feel like pulling it out if I don't need to. I don't care if it ruins the meter, it's a $20 one.
 

gijoewoz

Go Kart Champion
LED are almost always DC, there may be some exceptions, but by nature since an LED is a diode, it only allows current through in one direction. Using AC would mean that half of the current would be blocked because the diode works as a one-way valve, only allowing current through half the time.
 

GolNat

Autocross Champion
Most meters have built in protection. There should be a schematic somewhere but if it’s an LED it should be DC like stated above. AC current is not ideal for Light Emitting Diodes!
 

mkv_martinez

Go Kart Champion
Refrigerator freezer compartment LED light. I'd rather test to see if there is power at the terminals of the light assembly then first replace the door switch, since I suspect it's not the switch and don't feel like pulling it out if I don't need to. I don't care if it ruins the meter, it's a $20 one.

Ah yeah sounds like you are on the right track. Check for voltage in DC and you'll see if its being triggered or not to know if its the light or the switch.
 
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