Fluke A40 Shunt Calibration

[danielw22]

Hello EEVblog members, if you could please help me with this question it would be much appreciated. I recently sent some A40 shunts to Fluke for ISO17025 Accredited cal. The shunts came back and the reports only have AC-DC difference in uA/A at various frequencies. Maybe I am not understanding properly, but I don't see how we can use this data. I would have expected a DC resistance value, and then we could calculate the AC value with the AC-DC differences they did provide.

When selecting which level of calibration in the online Fluke RMA, the options were:
-Calibration, Accredited   
-Full Frequency Calibration With 5790a
-Full Frequency Calibration With 792a
-Full Frequency Calibration

We went with the first option (Calibration, Accredited).
Any advice appreciated.

[mendip_discovery]

Can you share the results part of the certificate?

The maths should be fairly straightforward.

If you have questions then ask the lab as they should be able to inform you.

[danielw22]

Hi Mendip, thanks for the reply. Full report is attached here. I've also asked Fluke but they usually don't reply to any emails from our lab technicians and engineers.
*edit, I see page 2 didn't scan, but page 2 is just the list of equipment used for the calibration.*

[alm]

The Fluke A40/A40A series was designed for use with the Fluke 540B to measure AC currents by comparing them to a known DC current and adjusting the DC current until the RMS value of the DC current matches the RMS value of the AC current (by comparing the voltage across the shunt). The A40 are not specified for absolute resistance, only for the difference between DC resistance and AC impedance. Their resistance is such that with the 90 Ohm resistance of the 540B is parallel, the voltage is about 0.45 V at full load, but since you are just comparing currents, the absolute value doesn't matter. See also the discussion here. I attached a relevant snippet from the Fluke 1988 catalog.

So sounds to me like it was calibrated based on the intended usage and to factory specifications. If you want a different procedure, you should discuss that with the lab in advance.

The A40B series is different and is specified for absolute resistance.