Multi function tester

Discussion in 'Electricians' Talk' started by SORASSPY, Nov 14, 2021.


    SORASSPY New Member

    I'm looking to get a new multi function tester, one that can read Zs values, I had a Megger 1720 which couldn't read Zs values, but passed calibration. I don't feel confident using it, so looking for recommendations on one that can. thanks
  2. The Happy Builder

    The Happy Builder Screwfix Select

    You need to explain further, why does your tester not measure Zs?

    SORASSPY New Member

    it's does read Zs, but its not accurate, Ze is 0.25 ohms, Zs at a socket next to the board is 0.80ohms, this is way to high in my opinion. I'm looking to get a new tester but don't want to end up in the same situations. I've heard fluke are better for Zs reading?
  4. The Happy Builder

    The Happy Builder Screwfix Select

    Presumably there an RCD protecting the socket, which is adding a significant uplift to the test result?

    Are you measuring the Ze using the high current test and the Zs using the no trip setting getting a difference in test results due to different methods of measurement?

    Do you think spending hundreds of pounds on a new meter will mean you will get different test results with the new meter?

    Loop tests aren’t repeatable in so much as if you do the same test three times you will get three different test results, so don’t expect absolutely precise repeatable test results.

    Save your money and keep your tester until you are more familiar with it and testing in general.
  5. Bazza-spark

    Bazza-spark Screwfix Select

    Surely, if it passed calibration it must be telling something like the truth, but as Happy says 3 tests will give different reading.
  6. sparko69

    sparko69 Screwfix Select

    If you aren't happy with the 0.80 reading then just get the r1+r2 and add it to the Ze. As others have pointed out the no trip loop test will always give different readings

    SORASSPY New Member

    I bought a second hand Kewtech kt63 it's well used, but I got it calibrated and reading were really good, the same socket Zs is 0.35 ohms. I'm just curious to which testers are better for reading Zs if I were to buy a new one. i was looking to get a kt65dl.
  8. sparko69

    sparko69 Screwfix Select

    Megger multifunction testers were the first to be able to do 2 lead no trip Zs tests and that was a big advantage for testing at light switches etc. Different brands have different pros and cons
  9. Tony Goddard

    Tony Goddard Screwfix Select

    If the tester passed its calibration, it will be accurate, and another makers tester won't be any better - I have two Meggers, an MFT1553 multifunction and a stand alone loop tester - more than happy with both of them, they are pretty much the top end of the test gear market.

    As the others have said Zs readings are not repeatable, so if the number is within the maximum permitted value, pop it on the certificate and move on!

    If the Megger results are always higher than the kewtech it could be that eith you havn't nulled the Megger or the croc clips / leads are damaged / worn and putting extra resistance in - mine started tripping on no trip last year, it wasn't the meter, but the lead set that was defective.

    SORASSPY New Member

    the Megger gave a reading of 1 ohm one time I did the Zs test, so it would just pass as it under 1.1 ohms but if were to install and more sockets I would have to fit a 25a or 20a amp breaker.
  11. sparko69

    sparko69 Screwfix Select

    If you were to install extra sockets you would presumably do the necessary dead tests before you energised the circuit and so you would have the r1+r2 reading for the circuit so you wouldn't need to worry about a live Zs test result
  12. The Happy Builder

    The Happy Builder Screwfix Select

    Honestly, don’t even consider buying a new tester until you have more experience.

    I have a Megger 1741 with the “confidence” display, sometimes I have to stop the test and start again because it seems like it’s never going to make it mind up and finish the test, it just goes on, and on, and on, and on, and on forever.
    Last edited: Nov 14, 2021

    SORASSPY New Member

    what experience do I need, I plugged one tester in the socket pressed the button I got a reading of between 0.8 ohm and 1 ohm. I put another tester in the socket press the button I get a reading of 0.35 ohms which is more realistic reading of a socket next to the board. I've read endless online that Megger can't read Zs readings on non trip settings, so was curious to which other testers are accurate when doing Zs values
  14. Teki

    Teki Screwfix Select

    Did you zero (null) the leads on both testers before doing the tests?

    SORASSPY New Member

  16. The Happy Builder

    The Happy Builder Screwfix Select

    You need the experience to interpret the test results.

    Learn to test, test to learn.

    Anyone can plug a loop tester into a socket and do a loop test, however interpreting the test results and analysing them is a completely different matter.

    British Gas engineers in amongst others were given simple plug in socket testers that give a “Traffic light” test results of green, amber or red visual indicators, many of them went into meltdown when they got a amber or red light in a TT earthed installation and condemned it.

    SORASSPY New Member

    I tried everything, the Megger cost me alot of money so a bit ****** off.
  18. The Happy Builder

    The Happy Builder Screwfix Select

    I am pretty sure that you didn’t, as the nulling value is preset in the set up menu and generally you will never need to alter it, you can by measuring the resistance of the leads and altering the preset by going into the setup menu, but it’s better to leave it alone.
  19. The Happy Builder

    The Happy Builder Screwfix Select

    I really doubt there is anything wrong with the meter.

    SORASSPY New Member

    there is one socket in this house, it's next to the board the Ze is 0.25 ohms. R1 + R2 is something like 0.1 or 0.01

    Megger Zs between 0.80 and 1 ohm

    Kewtech Zs 0.35 ohms.

    what does your experience tell you?

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