|
|
Is there any possibility that the TR Phasing test result would be wrong? Currently we encounter one wrong result every 3000 tests but the retest result is correct.
The attached is the test program and it only tests the inductor polarity.
Best Regards
Steven
|
| |
|
|
|
 | |
|
|
Dear Steven,
This isn't something I have seen happening before, but because it passes on a retry, I would conclude that something is wrong with the testing system or test parameters that causes this. First of all, do you have the latest AT3600 firmware installed? The latest version is V3.20 and is available on this website. I cannot find any reference to this ever being a problem that was fixed but at least we can then rule this out as an effect. Does the AT3600 pass self test? This is a good test to make sure that the phase will be measured accurately.
If you have the latest firmware and the AT self test passes then the only thing I can imagine happening is that there's a phase shift going on all of the time through the past at 20KHz (maybe set up by the leakage inductance and the test fixture capacitance). Perhaps this shift results in the polarity test being on the edge all of the time and sometimes it just crosses the test criterion. In this case perhaps testing at a slightly lower frequency is a possibility? The PHAS test can be used (if you have it installed on your AT) to measure the phase shift in degrees and see if this is a possibility.
If you continue to have problems then you are welcome to send me a sample part for me to test here. Just send it to applications support at our UK office address and I will work out what is going on. Let me know if you have any other observations or ideas about how this may happen, for example, do you have an unusual fixture system that uses trailing leads?
Best regards,
Tim.
|
| |
|
|
| |
|
|
Hi Tim,
Thanks for your prompt response.
The AT3600 passes self test. And we also find that the air-gap between energized winding and DUT may affect the test result. Do you know how to calculate the distance? Or I should keep them as close as possible. The inductance of energized winding is 1mH, test frequency is 20kHz and test voltage is 100mV.The specification of our DUT is below.
Inductance(μH): 0.56
DCR(mOhms): 3.00
SRF(MHz): 60
Isat(A): 30
Irms(A): 20
Regards
Steven
|
| |
|
|
| |
|
|
Dear Steven,
From your description it sounds as though you are inserting a winding onto a fixture that has a permanently fitted primary. Is that correct? It is difficult for me to advise much further without all of the details, but I can definitely say that if you have a variable in your testing (i.e. the distance can change with each part) then you will get problems. The distance between primary and secondary will effect the mutual inductance and leakage inductance so I think what I suggested previously is happening. The further away they are, the more phase shift you are getting, and hence it will eventually fail the polarity test.
I would suggest you modify the system to prevent the distance from varying very much and make it as close as possible. If you cannot always make it close then I would still recommend fixing the position but instead using the PHAS test rather than the TR polarity as you can then test for an absolute phase shift to within chosen limits. If you would like to give me more details about your DUT and fixture I may be able to help further.
Best regards,
Tim.
|
| |
|
|