Rel, relative circuit

[M0BSW]

Hello ,
One of my meters has the REL button which is really handy for precise measurement, the others do not and can have as much as 3 ohms, my question is it possible to make a stand alone REL circuit, to go between leads and meter, I guess the leads would have to be short between the meter and a rel circuit.
I've try to search for a circuit to do this but no luck so far, it would be a good experiment if possible.
thank you
Paul

[alm]

You would need a circuit with a resistance of -3 ohm. Some circuits exhibit a negative resistance over a limited range, but I don't think any of them would work in this application. You could of course build your own resistance meter that outputs a DC voltage and uses the DMM as a display.

[M0BSW]

You would need a circuit with a resistance of -3 ohm. Some circuits exhibit a negative resistance over a limited range, but I don't think any of them would work in this application. You could of course build your own resistance meter that outputs a DC voltage and uses the DMM as a display.

So am I right in thinking you would have to put in ohms to match the ohms of the leads to null or cancel it out.

[SeanB]

No, you need to manually subtract the lead value off of the reading. You do not easily get a negative value resistor ( otherwise known as a battery) that is both adjustable and which will work in all multimeter circuits on all ranges.

Basically just short the leads before using the lowest resistance range, then record that value at the time and subtract it from the reading. You will notice that this reading does vary as you remove and replace the test leads and will vary slightly with temperature. It really will only affect the lowest resistance ranges, and if it is 3 ohms you might want to try applying contact cleaner to the leads and the meter sockets ( a small amount using an ear bud to wipe the sleeve clean, it will come out dirty) and try again.

[M0BSW]

Ok Sean, I made a resistor box when I connect to the none rel meter I have a  reading of 0.3 ohms, with every thing at zero,when I dialed in 10 ohms it read 10.03/4, so taking the 0.3 off made it right now. that's that solved cheers.

[SeanB]

Nice to hear that. Simple enough, and with a meter with relative reading the same applies about having clean connections.