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Data Aq. from a Keithley 2440 4-wire Source Meter

Posted: January 28th, 2014, 8:57 am
by GeoffRivers

I'm hoping to do some testing on a system that changes its sheet-resistance over time. I have a Keithley 2440 source meter for 4-wire tests, but I would love a way to automate the data acquisition. I have a Daq-card from another company (Measurement Computing, PCIM-DAS16JR/16), which uses a 37 pin interface (C37FF-x), but the manufacturer has told me that there's nothing they can do on their end to enable communication with the Keithley 2440.

Is there one of the following:

An interfacing system that would adapt the output of the 2440 and allow the already purchased Daq to record the results
A low-cost DAQ system, preferably with USB interface, that the 2440 would work with
A multi-channel source meter capable of 4-wire measurement with simple USB or other interface for easy data aquisition
Or, any other system that can help me in this application.

Thanks for any help you can provide.

Re: Data Aq. from a Keithley 2440 4-wire Source Meter

Posted: January 28th, 2014, 3:07 pm
by Andrea C
Hi Geoff,

Instruments such as the 2440 have both GPIB and RS-232 communication interfaces. With these interfaces, you can send commands to the 2440 so that it takes measurements and then sends the measured results back to the computer in ASCII strings.

The GPIB is easier to use, but you will need a GPIB interface on your computer. You could buy something like the KUSB-488B. This plugs into USB port on computer and then the other end can connect to the GPIB interface of the 2440.

Alternately use the RS-232 interface if your computer has COM ports.

What do you estimate is the resistance of your material that you want to monitor over time? Will it be Gig Ohms, 100 Meg Ohms, KOhms, etc?


Re: Data Aq. from a Keithley 2440 4-wire Source Meter

Posted: January 29th, 2014, 6:09 am
by GeoffRivers
The material should be starting on the order of magnitude of 100 Mega ohm*cm or slightly less, and dropping to something on the order of 0.001 to 0.0001 ohm*cm. It is this transition that I am hoping to study.

Re: Data Aq. from a Keithley 2440 4-wire Source Meter

Posted: January 29th, 2014, 10:21 am
by GeoffRivers
That USB connector may solve my initial study, where one sample is studied at a time. I'll certainly look into it.

However, my later testing, due to start this summer, requires 16 samples to be monitored concurrently.

Half of the samples are to have a constant low-level DC current applied (on the order of 10 mA, with good stability) for approximately 3 months (this may involve a switch running duty-cycles, so that a single current source can be used). Meanwhile, all samples need to be tested approximately once per day over the 3 months, by 4-point test using a square wave current application. The square wave is so that I get reverse-direction for comparison. The two applied currents would not be concurrent, as long as the application duration is well controlled. I have been considering that two current sources with appropriate switching could do the job, but it would require that both the switching and the sources be controllable by the same PC or program. I'm not sure what's necessary for all of that. Voltages would be read using a 16-channel extension that we have for our daq board, which unfortunately cannot act as our current source.

Any suggestions or solutions would be appreciated and certainly considered. And thanks for your time!