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Models 2601A, 2602A, 2611A, 2612A, 2635A, 2636A
Models 2601B, 2602B, 2604B, 2611B, 2612B, 2614B, 2634B, 2635B, 2636B
we use the connection to the chassis ground in the Phoenix connector. when I remove that connection. we do not get any measurements.
In the box between the Keithlay and the object we have put a 5 M ohm resistor. Without that we get very poor measurements on low values (pA). I think that resistor is causing problems. before we got the 2635B we used a Keithley 263 and that worked very well without that resistor and the connection to the chassis.
I do not know much about this so I hope I can get some help.
- Connection to the object under test.pdf
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- Keithley Applications
- Posts: 1565
- Joined: October 15th, 2010, 10:35 am
- Country: United States
For your object under test, what do you mean by guard?
In the case of the 263 calibrator, you were connecting an isolated and floating signal source to your object under test. In the triax, that product made use of center pin and inner shield for HI and LO.
To have the equivalent from the 2635B, you'd remove the jumper on the green Phoenix to float the SMU and then have your converter box would have two triax: for for HI and one for LO. Inside the box, route them to your object under test.
For the resistor part, I'm not sure. If you are forcing I with voltage limit, make sure the I*R drop on the series R is accounted for in the voltage limit. For low pA, the 2636B is likely to be much faster responding product vs. the 263. Turning on some digital filtering and increasing the NPLC might allow you to have more similar outcomes.
I still need to use the resistor. we started using it because the object measured a noisy signal. and for the low signals the noise went below zero, making the objects measurements to be below the true value.
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