How to eliminate multiplexers resistance during measuring?

[glenjoy]

microOhm Meter

I need to measure many resistance banks, I will be using a two wire voltmeter and a couple 16to1 multiplexers, 16 because there are 16 resistances/resistors and the output to the testers cable.

Problem is, how to eliminate the multiplexers' resistance, I really need an advise or circuit, not a link for the theory of four wire/kelvin measurment because I know that already.

 

[tjalps]

Re: microOhm Meter

Hello!

Maybe you can tray with small signal reed relays? Only sugestion.

Regards!

 

[glenjoy]

Re: microOhm Meter

No reed relays please, that is why I will be using multiplxers to avoid the cost and maintenance of the relays.

 

[glenjoy]

Re: microOhm Meter

Hi,

Can please put other inputs, btw, does an Ohm meter supplies the load undertest a constant current then read the voltage drop?

I will post later the schematic I have in mind.

 

[tjalps]

Re: microOhm Meter

Hello!

But with multipklexers you can have problems with chnage of resistance
because of temperature change. What do you think? I now that test equipment manufacturers use usualy reed relays. And life time of this reeed relays are quite long. Which MUX do you have in mind?

Regards!

 

[glenjoy]

Re: microOhm Meter

I am planning to use the MUX's of Maxim/Dallas Semiconductor. They are analog MUxs. Yes I know Test Equioments uses reed relays, but the problem is the cost and maintenance, I used to work as a Test engineer in Maxim semiconductor, and have background and exposure in test equipments, this project I am doing now is also for them, somewhat a donation.

 

[artem]

The best way is to measure voltage (connected through musltiplexer ) on resistor connected to current source (also connected through multiplexer)
As internal voltmeter resistance is much high than any miltiplexer connection , accuracy will be quite good .
Let say 10MOhm/100 Ohm =10e5. It is much more than resolution of your multimeter (if it is not professional one ).

Or :
Put one shortcircuit on each multiplexor , and measure multiplexor resistance before making other measures . Then sub got value from resistors
measure . (Take care of current/ resistance dependance in miltiplexors ).