Multimeter readings for wiring


Active Member
I am testing my wiring and sensors and have a question about the multimeter readings. The one I am using is a digital model and when I test the circuit with it set to 2k the number bounces around close to and sometimes exactly at 000. When the circuit is open it displays a 1. I understand that it measures the resistance in the circuit, but is it ok if it does not stay on one number?

Thanks for the info...

When you use a multimeter to measure continuity (i.e. if the circuit is making a connection) you want to set the meter on the lowest resistance scale if it is not autoranging.

Usually you wind up testing a wire "pair" because the meter can only have access to one end of a cable run at one time. You can just use a jumper clip to short out the pair at the other end.

When you use your meter to test the two wires make sure your fingers are not making contact with the lead's ends. The reading should be something like one to five ohms or so depending on the wire type and length.

Then you should make sure that the wires are not "shorted out" to each other. You do this by making sure the wires in a cable bundle are spread out so they can not make electrical contact with each other (on both ends), then set the meter on the highest scale for resistance (if it is not autoranging) and you should get an "infinity" reading as you measure between the wires with your lead tips. Here again, make sure your fingers are not touching the ends of the leads or your body resistance will influence the readings.

My meter shows "OL" for infinity. I believe others may show "1".

To see what your meter "reads" for infinite resistance, turn your meter on and touch the leads together and look at the reading. It should be zero (might bounce around slightly). Then separate the leads and look at the reading. That will be your "infinity" reference reading.

Did this make sense?
BSR, thanks for the reply. Most of everything I have learned I got from your How-To on security wiring.

The multimeter I have does not autorange, it has the different selections such as the 2k, with 20 being the lowest. I had misread your how-to in that regard, I have been using 2k instead of 20.

The ones that are bouncing around a bit is a 22/2 wire with five window sensors wired in series.

Tommorow I will try on the lower setting and see what the number does.


ctwilliams said:
The ones that are bouncing around a bit is a 22/2 wire with five window sensors wired in series.
BTW, are you using any EOL's in that circuit? That would influence a resistance reading also.

The reading can bounce around a little (say inbetween an ohms reading) but if it goes beyond that I would suspect a loose connection.