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select module for resistance measurment

Hi,

 

I I would like to measure a componant that have a 3-5 Ohm resistance.

Change in the resistance value during my experiment is 0.003 Ohm.

 

Using DMM is not prefered becouase it has only 1 channel and i don't want to use switching card in addition to the DMM.

 

So I m looking for the correct modules selection that will allow me to measure the resistance change using 4 probe methood.

That means a current source and analog input modules.(can be one if possible)

 

For this I need a stable current source and hi resolution Volt analog input modules.

 

the requirments are:

1) not more then 10mA current (avoid heating of the componant)

2) 8 channels (more is good).

3) sampling rate max 100 Hz can be less down to 10 Hz f it help to reduce cost.

4) Effective resolution (after accuracy,stability,offset temperature drift and noise(in the bandwith in 3) of  0.05 to 0.1  mOhm.

5) enviromental temperature where the equipment will be used is 25+- 5 degree.

 

I hope there a modules that can fit this requirments, if not i would be happy to know what is the nearest that possible.

I understand that PXI is the best platform for this but other platform is also possible.

 

Thanks.

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10mA with 0.1mOhm resolution results in ONE µV !! 

Additional thermoelectric EMV on the contacts etc....  

 

Some ideas

 

-use a AC bridge configuration with a preamp .... Ups ...resistors with a tempco less than 10ppm/K !! 

 

-ask Keithley 😉   , sorry NI

 

- a XXmA two pole current 'diode'  (maybe in an appnote from Jim Williams 🙂 ) in a 4 diode bridge sourced by a +- squarewave supply  , building an alternating current source, and a differential preamp ...  the pream is per channel , the rest might be done with muxer

 

did I mention 4 wire measurements?? 😄

 

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Hi.
I know that dmm 7.5 digit can do it but i is only 1 channel.
4 wire measurments is what im looking for and for this i need a current source and analog input. This is why i asked for the modules. So im still looking for a recommendation for the correct modules that can do the job and if not will be close to it.
Barak.
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Well maybe you measured changes in the 0.1mOhm region, and I don't know your setup, but you can't beat physics 😉

Make a shortcut as good as you can at your DMM and measure the the voltage .... what do you read?

 

Greetings from Germany
Henrik

LV since v3.1

“ground” is a convenient fantasy

'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'


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Hi.
I dont have the pxi dmm but i saw in the specification that it possible.
I was abble to measure tha above requirments using scxi 1521b module but with a slow drift of the reading.
I still hope some one from NI can say what are the modules of the pxi that can be sed to performe a 4 wite meadurments abd get as close as posdible to my requirments.
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