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6430 100Mohm Measurement Issues

KUSB and KPCI DAQ Data Acquisition Products
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runderwo
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Joined: January 26th, 2015, 1:00 pm
Country: United States

6430 100Mohm Measurement Issues

Post by runderwo » January 26th, 2015, 1:13 pm

Hello,
We have a piece of new equipment that has a 6430 installed using 4 point probe to measure sheet resistance of various materials on glass panels. When measuring P+ silicon on glass, we cannot get consistent or correct results. We expect to measure around 50Mohms, but our readings are in the 100M's ranges. When checking the meter during measurement, we observe it is set to the correct current range of 100nA. Our measurements are not only incorrect but seem noisy.

When checking the voltage read, and then calculating the input current using what we believe is the "known" resistance, it suggests that the current source is not outputting the correct current. How can we verify the output current of the source is correct? This is a brand new piece of equipment and Keithley meter, and our results suggest a problem with the meter. Can you offer any help?

Also, we are measuring ITO on glass. We expect this to measure around 75ohms, and we can very noisy and inconsistent measurements.

Thank you.

Dale C
Keithley Applications
Keithley Applications
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Re: 6430 100Mohm Measurement Issues

Post by Dale C » January 26th, 2015, 1:23 pm

The connections on the Model 6430 are a little different than on a standard meter.
The inner conductor of the IN/OUT HIGH Connector on the remote preamp is the HI terminal.
The outer shield of the IN/OUT HICH connector on the remote preamp is the LO terminal.
So if you have a Model 237-ALG-2 triax to alligator clip cable the connections would be from RED to GREEN.
Not RED to BLACK.
Maybe this is the trouble?

runderwo
Posts: 4
Joined: January 26th, 2015, 1:00 pm
Country: United States

Re: 6430 100Mohm Measurement Issues

Post by runderwo » January 26th, 2015, 1:29 pm

Hi Dale,
Thank you for your response. I am here with our field engineer, Mr. Kim from KMAC Korea. We are not sure what is "Model 237-ALG-2 triax to alligator clip cable".

Mr. Kim says we are configured as shown in the manual under "Connections" on page 2-7 (Page 71), figure 2-3. Basically, we have a 4 point probe plugged into the remote preamp, with a banana plug going to the rear of the meter nto 4wire sense.

Dale C
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Re: 6430 100Mohm Measurement Issues

Post by Dale C » January 26th, 2015, 1:50 pm

If that is how it is connected then that is correct.
Just be sure the LO is the outside shield of the triax cable. Not the inner shield of the triax cable.
Can you post a photo of this and maybe a block diagram?

runderwo
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Joined: January 26th, 2015, 1:00 pm
Country: United States

Re: 6430 100Mohm Measurement Issues

Post by runderwo » January 26th, 2015, 2:10 pm

Hi Dale,
The meter connections are hard wired to the probe. Attached -.
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runderwo
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Joined: January 26th, 2015, 1:00 pm
Country: United States

Re: 6430 100Mohm Measurement Issues

Post by runderwo » January 26th, 2015, 2:24 pm

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Andrea C
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Re: 6430 100Mohm Measurement Issues

Post by Andrea C » January 26th, 2015, 4:59 pm

In contrast to other SourceMeter models such as the model 2400, the model 6430 has auto-sense resistors between the HI and Sense HI and also between the LO and Sense LO. When used with a four point probe, the auto-sense resistors will be in parallel with your device resistance.

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