Kei_3706A fails uA zero parameter

Hi,
During the re certification of my 3706A, the spec for this parameter is +/--3.000000E-10. My unit has failing this with a value of 4.400000E-10 or higher, how do i bring this value down. Recalibrating the unit according to the manual is not sufficient to do so.  The recalibrating procedure will pass with no issues. Does anyone have any suggestions please.

Rdgs Paul

During the re certification of my 3706A, the spec for the uA zero parameter is +/--3.000000E-10. My unit has failing this with a value of 4.400000E-10 or higher, how do i bring this value down. Recalibrating the unit according to the manual is not sufficient to do so.  The recalibrating procedure will pass with no issues. Does anyone have any suggestions please.

Double checking:  when you access the zero, are you open circuit/not connected to your current source standard?

Prior to the DC Amps adjustment, did you first do the DC Volts?
The DC volts procedure has both a zero and full scale procedure step, whereas DC Amps has only full scale.
Perhaps tweaking up the DCVolts offset will impact the DC Amps offset.

Internally, the amps function is measuring the volts across a resistive shunt, so DC Volts could be related.

If you have done both DCV and the Amps is still out of tolerance, I suggest you contact your local sales office/service center.

Yea, I have done the DCV first as per verification procedure. Yes, no cables connected, only a LAN cable. I have several times re calibrated ( Fluke 5730A ) the unit but this parameter stays just outside spec. on all of my 4 units. I was in spec the first year (2018)  i did this but after that it keeps failing. Currenly im checking the ppm spec's on the 3706A and the 5730A. How can you tweak the dcv offset?

 

There is a Verification procedure and a separate Adjustment procedure.
When I used "tweak" I was thinking to carry out the Adjustment procedure.

For just the DC Amps, you've indicated the zero is out of tolerance.
Is it only 10uA range, or is the 100uA range also affected?
What about the full scale 10uA level?  Is that in spec?  Have you adjusted it whether it seems to need it or not?

And I was just guessing that perhaps the adjusted DCV zero might have some impact on the DC Amps A/D converter readings too.

If it continues to be out of tolerance, it seems an RMA for service to understand root cause is needed.