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Video Keithley 2460 Source Measure Unit (SMU) Review, Teardown and Experiments

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HKJ:

--- Quote from: Hugoneus on April 23, 2015, 03:33:50 am ---
--- Quote from: HKJ on April 22, 2015, 09:21:58 pm ---I.e. select source 1A, measure Auto or 1A and you risk getting overflow. The measure function cannot handle even 0.1% over range and the calibration of the unit is not that good:

--- End quote ---
The unit is supposed to do that. It has a hard limit on the "limit" you set. That is what it is supposed to do.
--- End quote ---

As usual a limit has some tolerance and in some cases a 1A limit can deliver slightly above 1A, but it is silly that the meter goes into overflow because of that, a included 1% over range in the measurement circuits would have avoided any problems like that.
As it is now the auto range function does always work.




--- Quote from: Hugoneus on April 23, 2015, 03:33:50 am ---
--- Quote from: HKJ on April 22, 2015, 09:21:58 pm ---Not really, I paid a bit above $8000 for it and hope to get some usage out of it, but the precision will be rather bad for the price.
With a limit of 100mA and measuring range of 1A (Next higher range) I get 100.2mA (With a specific setup), i.e. 0.2% error.

--- End quote ---

I am very surprised about that. I did a test on my unit. As you can see in the picture the error (compared to a new 7.5 digit meter) is less than 0.0174%. I suspect something might be wrong with your setup. I hope you can resolve the issue.

--- End quote ---

It is probably the measurement function that is a bit out, it is only using 10% of its range, this means offset errors are more significant.

es:

--- Quote from: HKJ on April 23, 2015, 06:04:52 am ---As usual a limit has some tolerance and in some cases a 1A limit can deliver slightly above 1A, but it is silly that the meter goes into overflow because of that, a included 1% over range in the measurement circuits would have avoided any problems like that.

--- End quote ---

In the brochure, they specify "OVERRANGE: 105% of range, source and measure."

HKJ:

--- Quote from: es on April 23, 2015, 02:24:30 pm ---In the brochure, they specify "OVERRANGE: 105% of range, source and measure."
--- End quote ---

This is not present in my 2460.
Limit 0.9999 measures 0.9999
Limit 0.99997 measures 0.99995
Limit 0.99998 measures overflow
Limit 0.99999 measures overflow

This is with the source=4 volt, another source value will give different results.
I am running software version 1.1.0c

HKJ:
The new firmware version for the 2460 fixes this problem.

HighVoltage:

--- Quote from: HKJ on July 02, 2015, 06:03:43 am ---The new firmware version for the 2460 fixes this problem.

--- End quote ---
Thanks for letting us know about the new FW
Downloading it now.

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