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Problem using 2182a for low voltage measurement using 6221

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sgaba2
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Joined: January 19th, 2015, 1:49 pm
Country: United States

Problem using 2182a for low voltage measurement using 6221

Post by sgaba2 » January 19th, 2015, 1:57 pm

I am using 6221 as my generator. Trying to measure low DC voltage using 2182A. As I lower the current, under 1 microamps, it starts giving erroneous values. Above 1 microamps, it is working fine. What could be a possible reason for this?
Thanks

Dale C
Keithley Applications
Keithley Applications
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Re: Problem using 2182a for low voltage measurement using 62

Post by Dale C » January 20th, 2015, 6:14 am

What level of voltage is to be measured?
If you source 1uA into 1 ohm then it is 1uV, the Model 2182A should be able to measure this to about 40nV accuracy.

sgaba2
Posts: 2
Joined: January 19th, 2015, 1:49 pm
Country: United States

Re: Problem using 2182a for low voltage measurement using 62

Post by sgaba2 » January 20th, 2015, 8:50 am

I am using a 500 ohm resistor and when I reduce current below 1 microamps and use the voltage given by nano-voltmeter to verify resistance, I get erroneous and inconsistent values. Above 1 microamp, values are consistent.

Dale C
Keithley Applications
Keithley Applications
Posts: 2846
Joined: June 10th, 2010, 6:22 am
Country: United States
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Re: Problem using 2182a for low voltage measurement using 62

Post by Dale C » January 20th, 2015, 11:24 am

Ok, 1uA through 500 ohms is 500uV. The Model 2182A is certainly able to measure that level.
Can you tell me more about the setup?
Are you using delta mode?
What is the NPLC setting.
What voltage range is set on the 2182A?
Can you connect the output of the 6221 to a --ammeter to see if it is outputting the proper value?
Etc...

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