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Low R measurement on a DMM

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modoran:

--- Quote from: PushUp on April 06, 2023, 11:34:19 am ---

With this power cable it is impossible to pass any test and this does prove, that any sticker, which should guarantee safety is bullshit! The cable is marked 0.75mm², but this cannot be the case with 315mOhm:



--- End quote ---


So it is 0.75mm² or not ? Measuring resistance of the cable and calculating resistivity of copper, but what if it is aluminium or iron or other cheaper metal, but still 0.75mm² ?

PushUp:
As long as the measured values are within its limit, it is fine, which is obviously not the case in my example. Some pat tester such as my already sold "Benning ST 725", gives you even a hint, when you measure PE resistance of a cable (it is the same cable from my desoldering station, as I keep it as a bad example) and you are over 300mOhm (here: 320mOhm, by the way it is the same value as shown by the Fluke 1507): in this case "table" means, that there is something totally wrong...






...and you should check the list of values, as there are no exceptions allowed, when you want to be on the safe side, because 300mOhm is the limit and worst scenario, which means, that you always and forever have to be way under this value and should not pass 150mOhm in the extreme case:






When length and thickness would also give a good value and they are within its limit, the producer will obviously choose the cheapest possible material.

However, as far as my measurements are concerned, most chinese producer even don't pay attention to safety issues and when your house burns down due to overheating, it is your problem, as long as you or your family will survive the fire.

My example and measurements do prove, that this becomes totally normal, so that it is up to you, to check any cable and/or testgear before using it - the safeyt stickers are useless and that is why I wrote in my first post, that anybody should have or at least use a pat tester!


This cable, for instance, was from my first 15 Inch Eizo Monitor and I have never ever seen such a good value of 50mOhm anymore, which underlines my observation...







Cheers!  ;)

HighVoltage:
I have always been using a Gossen Metrawatt Secutest for my VDE 701/702 requirements.

Nice to see some other instruments here for the same purpose.
Thanks for the many pictures.

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