METRON QA-ST Electrical Safety Analyzer Help - Page 1
Forum section: electronics / beginners

author: daisizhou
author_rank: Super Contributor
timestamp: October 03, 2025, 01:26:37 am
content: Hallo everyoneI have had this METRON QA-ST for a while, but I am still confused about how to use it.If anyone knows the above functions, please tell me, thank youquestion:1、In the "Prot.Earth" section, the measurement results of DC resistance and AC resistance are different. Why is this?Please see picture "22" is DC resistance, picture "33" is AC resistance，I used the 1 ohm resistor and 100ua test point that came with the host.2、How is Leakage Current-VDE used?(I read the user manual and it didn't explain it in detail)*manual->https://archive.org/details/manual_Metron_QA-ST_User_and_Service_Manual*

author: jwet
author_rank: Frequent Contributor
timestamp: October 03, 2025, 03:07:09 pm
content: That PDF manual is kind of a mess for some reason. Here is some help with your questions1. The AC/DC ground measurements measure ground resistance at DC vs. Ground resistance at line frequency. The idea is that you that you should have a low resistance and low reactance path from case to ground. These would differ if the internal ground lead is long or not well bonded.2, Leakage Current VDE. VDE is the european standards , close related to IEC, the U.S. uses UL but most quality equipment is designed against global specs. The leakage specs (pass/fail) are a bit tighter in the european spec and differ for medical equipment especially. They are something like .5 mA for UL and .25 mA for europe if I remember correctly. You're best to look them up (IEC 60335). This is partially due to most european equipment running on 220V vs. 120V.This is a bit older model and the standard may have changed over the years. Its important to do the tests but the pass/fail limits and some test conditions may have changed over the years. I contact factory to see what if anything is different. Of course, they will be motivated to sell you their newest model but its unlikely that things changed much.

author: daisizhou
author_rank: Super Contributor
timestamp: October 03, 2025, 10:53:37 pm
content: Quote from: jwet on October 03, 2025, 03:07:09 pmThanks.1.I am using the host test point 1 ohm，In "Port.Earth" mode, the measured AC value is 2.07 and the DC value is 1.01. This does not seem to be in line with expectations. The AC value is always greater than the DC value. I don't know why.Quote from: jwet on October 03, 2025, 03:07:09 pmDo you mean that "Leakage current-VDE" and "Leakage current" + "Patient Leakage current" are the same, the only difference is that "Leakage current-VDE" complies with European standards?By the way, Metron has been acquired by Fluke and no longer has after-sales support.

author: jwet
author_rank: Frequent Contributor
timestamp: October 04, 2025, 05:10:39 am
content: I think the AC values will always be more than the DC values because they represent the sum of the DC resistance and AC reactance. These should be summed as vectors so the AC reading would square root (DC^2 + AC^2).I think Leakage Current VDE and Leakage current are closely related but there is a difference in how UL and VDE specifically want you to run the test. You'd have to read the standards in detail or find a better expert than I.It will take some study to sort this out. Good luck.