6517A Electrometer Trouble

[cobychuck]

    We've been having issues with our 6517A and so far the manual has not been a lot of help.  We are attempting to adjust the unit as it was found to be out of tolerance.  So far we've received nothing but offset and gain errors through Voltage and through the two ranges of current we've attempted.  We're even getting an error message during the offset adjustment before the range adjustments even start. 
    The calibration adjustment is all through the front panel controls and the manual does not describe what is happening during the adjustment steps.  I do not know why we're getting the errors.

[cobychuck]

    We were able to get the Voltage cal to pass without the gain errors but the current does not want to pass.  I've tried a couple different setups but nothing seems to make a difference regarding the gain errors.

[Hawaii596]

Not doing that model, but we've been doing numerous electrometers lately.  I can say in our case, we found that the units were very particular about where you connect which cables, etc.  I knitpicked specifically how the cabling was connected in one case, and it made the difference between OOT and In Tolerance.  I also ended up trying multiple procedures.  One time the GIDEP (T.O. type) produced one result, and going back to the original Keithley manual  made a difference.  The other thing we experimented with was varying the resistance to volts ratio.  Where they said 100 Megohm and 1.9V (for example), we tried 10 Megohm and 190 mV (I think - too early for Ohm's Law math).

Not sure if this helps, but that was what gave us difficulties.

[jwilley127]

Connections are always critical...what type of external standards are you using?  Using the service manual procedure?  Just an "FYI", but the 5156's are becoming quite scarce and my company has built a direct replacement. (5156DR)  I've shipped four units with two more on order.  Should have an NSN soon as a contract was just recently awarded. (http://www.jswilley.com/Resistance.html)  Drop me an email if you have any further questions.

[calibr8tor]

Jeff is always trying to sell us something 

[jwilley127]

Can't blame a guy for trying....but I think the Navy & Air Force should have at least one 5156DR in their inventory too.  It's a really cool new product!