EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: rfbroadband on March 06, 2017, 03:47:54 am
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I used the 2460 in constant current mode (CC) a while back and was surprised about the lower than expected output impedance. To my surprise the output impedance of the 2460 in CC mode is not specified in the datasheet. In short, I characterized the output impedance in CC mode. The measurements results for the different current ranges are attached below. It is not surprising that the output impedance will decrease for higher current ranges, as the internal capacitance of the larger output devices will dominate ZOut. Just to be accurate, be aware that my measurement setup is only valid for impedances of up to 20kOhm.
I discussed this with Keithley and the applications engineer agreed that the output impedance should definitely have been specified in data sheet and he will get the info for me shortly. Long story short, Keithley will not specify (or at a minimum release a few basic guidelines) on the output impedance of the 2460 in CC mode. The attached graph was sent to R&D and R&D simply refuses to clarify : ZOut for current range x should be y.
I would like to point out that I am not arguing that the impedance should be a certain value for a given current range, I simply wanted to know what I should expect.
This is supposed to be the state of the art SMU on the market that costs 7k$ and the manufacturer is refusing to release a basic DC output impedance spec of the SMU in cc mode.
Maybe some of you will find attached results interesting.
The 2450 and 2460 are in general very nice units but it is disappointing that Keithley will not release basic impedance specs.
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There should be some impedance specs - at least typical values.
The curves look about as expected: the CC mode looks like an an capacitance. Something like 2-3 µF for the 1 A range is not that bad.