# How to Detect A Short

1. Mar 6, 2012

### Blah937

This is a theoretical question. Say we are imagining a way to detect whether a pair of circuits might be shorted together. There’s already hardware and firmware that sends pulses out on both of the circuits, and measures the response on the outputs. So, would we want to recommend additional hardware and/or software to apply test loads (R and/or C), or different signals, to any of those circuits?

In any case if the above doesn't make sense...how can we generally detect if there is a short in our circuit? I'm not looking for just apply a DMM and see if it beeps. lol. Thanks though! Any input would be greatly appreciated.

2. Mar 6, 2012

3. Mar 6, 2012

### Staff: Mentor

You pretty much use a technique analogous to what the DVM beeping tells you. Apply a voltage through a moderate source impedance and measure the voltage on the far side of the source impedance. Alternately you could measure the current through the source impedance, but just do whatever is easiest in your circuit.

4. Mar 6, 2012

### davenn

well the other option is .... the short cct is likely to be where the greatest amount of circuit damage is done and from whence the smoke has issued :tongue:

Dave

5. Mar 6, 2012

### skeptic2

Once when troubleshooting a board I had access to an ohmmeter that could measure milliohms. I could actually measure the resistance of the traces and by following the path of least resistance I was able to find the short fairly rapidly.

When I used to program board testers, we programmed the testers using a known good board. With that board we generated a table of known shorts and known opens. When an unknown board was tested, running through the shorts and opens was very fast and very effective. Only after passing shorts and opens would the tester check the impedances between nodes.

6. Mar 6, 2012

### Averagesupernova

Also known as ATE.