AC Current Calibration Question - Page 1
Forum section: electronics / general

author: danielw22
author_rank: Newbie
timestamp: December 12, 2024, 02:20:10 pm
content: Hello, I have some questions about AC current calibration and hoping to get some of your collective wisdom. When calibrating a Fluke 5700A/5720A for AC current, the A40 shunts are listed as required equipment. The A40 series has an uncertainty of 0.02% across all frequencies, so I don't understand how they can be used to calibrate a 5720A that has uncertainties as low as ~150ppm for some ranges. Does that 0.02% from A40 not need to be included in our uncertainty budget?Right now in the uncertainty budget we have:1) 5790A uncertainty from its cal cert2) 5790A manufacturer/datasheet uncertainty for the specific range(1 year stability)3) repeatability4) A40 AC-DC difference uncertainty from its cal cert5) the 0.02% A40 manufacturer/datasheet uncertainty (1 year stability)6) Resolution (number of digits)I can't see how we can get a low enough MU to calibrate the 5720A current output with that 0.02% A40 best 1 year spec. It is the most significant contributor to our budget by an order of magnitude. Should we be removing this line item from the uncertainty budget?

author: Overspeed
author_rank: Frequent Contributor
timestamp: December 12, 2024, 08:18:07 pm
content: HelloI remember to have seen a similar subject on this forum ?I link an interesting document on shunt AC et DC calibration and displayed valuesRegardsOS

author: mzzj
author_rank: Super Contributor
timestamp: December 12, 2024, 09:25:43 pm
content: A40 is first measured with the 5790 DC current range and measurement results are compared with the AC results. That way you need to only worry about the short-term stability and AC/Dc differences of the A40.

author: cscaccetti
author_rank: Newbie
timestamp: December 12, 2024, 09:43:22 pm
content: The "1-year absolute accuracy specification stated at k=2, approximately 95% confidence for the calibrated value. The specifications include 1-year stability, temperature effects overTCal ± 1 °C, and the measurement uncertainty of the calibrated value" listed on the data sheet at worse case is 176ppm on the 100A shunt, which is 176ppm. The average seems to be about 45ppm and a median of 29ppm (not including dc in either stat). So a magnitude better than 0.02%

author: scl1992
author_rank: Newbie
timestamp: December 15, 2024, 02:14:59 pm
content: The current shunts should be calibrated by such labs as NATIONAL PHYSICAL LABORATORY.Calibration Certificate examples of 100 mA, 1 A and 20 A shunts could be found inPrimary AC/DC Shunts - Transmille Calibration - DOCUMENTATIONhttps://transmillecalibration.com/primary-ac-dc-shunts/Drifts of the shunts should be much better than the specifications if the shunts have previous calibration histories.

author: mendip_discovery
author_rank: Super Contributor
timestamp: December 15, 2024, 08:51:36 pm
content: Quote from: danielw22 on December 12, 2024, 02:20:10 pmI think you have the right things in the budget but I think you need to read the attached PDF which is from the Fluke Website where it talks about the A40 shunts. If you have any previous calibration data on the shunt you might find it worth putting that into a spreadsheet and looking at the data and seeing if it would support changing the 0.02% spec you are using.