resistance

  1. H

    how would i calculate resistance using Vcc, input impedance and logic-high threshold?

  2. KeenPensioner

    Insulation Resistance zero Ohms

    Hi all. As I've said before, I'm not an electrician but an adult learner. I have a second hand Fluke 1653B MFT which is out of calibration but I use a CalCard to see how far out it is and it's not too bad. I've watched a thousand videos on EICRs etc and just want to increase my knowledge - if...
  3. timhoward

    Insulation resistance difference both ends of ring final cct

    Initial fault was RCD tripping, narrowed down to a ring final cct. IR tests on that cct with all loads removed were showing almost zero between neutral and cpc. So I broke the ring apart and eventually found the nail through a cable, and got that all sorted. Now its testing ok in as much as...
  4. J

    Insulation Resistance query

    When doing domestic testing, I spend quite a bit of time removing loads & vulnerable equipment prior to carrying out IR tests- allowing me to test between L - N without risk to vulnerable equipment or getting inaccurate readings. I’ve spoken to a number of sparks who go straight to testing L&N...
  5. cliffed

    Short circuit protection on high resistance on live conductors

    Thoughts on this scenario,obviously a short circuit fault situation
  6. K

    Low Insulation resistance test on smoke detectors

    Hi Everyone Just a question bothering me as you cannot do Insulation resistance test on smoke detectors as they can become damaged so obviously smoke detectors are sensitive but they are also installed on lighting circuit so if perform low insulation resistance test 250V between Live and...
  7. D

    Insulation Resistance - Low Reading on Ring

    Newbie Testing Question: I am getting a very low IR reading between L&N on a kitchen ring (0.01M). The ring was working fine with no tripping before testing. Can anyone shed any light on what may be causing this low reading? Thanks
  8. J

    Insulation resistance on new installation

    I have recently completed a rewire as part of a complete back to brick renovation in a pretty standard domestic property. Upon carrying out initial verification I uncovered a few strange IR readings. Multiple circuits with low(ish) readings of around 150-200Mohm. However they all tended to rise...
  9. D

    Is it ok to do insulation resistance test on RCBO at 500v?

    I know you are not supposed to do a insulation test on circuits that are protected by an RCD at 500v because it may damage the electronic components inside the RCD so that's why you switch the RCD off before you test the individual circuits, however, what if the circuits are all protected by...
  10. Q

    Insulation resistance query old style hager rcbos

    When carrying out insulation resistance testing on old style rcbos (hager) I understand you are supposed to disconnect both line and neutral aswell as both the neutral and functional earth fly leads.....however does this in theory mean you need to disconnect the above for all rcbos at the same...
  11. P

    The subatomic concept of amper, after hitting a resistance.

    I have a fundamental question about the current My question is: why after hitting the protons of a resistor and thus reducing the voltage and the speed of electrons; (voltage is the distance between the electrons which the distance is smaller than the balance between two electrons which do not...
  12. S

    Please help me with this Capacitor, SCR, low resistance coil problem!!

    I want to discharge capacitor in micro seconds, In order to to that I used very low resistance coil but When capacitor is discharged, SCR kinda blow up, meaning the positive & negative got connected together because of low resistance. What can we place in negative terminal to make sure that...
  13. S

    Low insulation resistance and tripping circuit breaker

    I've just done an insulation resistance test between line and earth and got 0.0 Mohms for most circuits. Obviously this is an F1, but what I don't understand is why the CB doesn't trip. Is the answer that the resolution on my tester isn't high enough? So I could for example have 0.049Mohms and...
  14. J

    Insulation resistance on modern installations

    On initial verification of new installations I have been having a hard time with insulation resistance. With RCBOs, fixed LED luminaires, intelligent dimmer controls and other sensitive equipment now the norm on almost all installations how do we overcome this and still carry out effective and...
  15. D

    UK Low Insulation Resistance Test

    Hi guys, Hoping someone can clarify some things here. I had a socket replaced in my kitchen recently and as part of this, the electricians did an Insulation Resistance test and told me the reading was very low at just over 1 mega ohms. They advised me to basically rewire the ring (at...
  16. P

    Low resistance fault replicated on a made up rig

    Possibly a daft one this lads but any insight welcome. Have set a dummy rig up at home and am trying to replicate a low resistance fault on a ring main. No prob getting off scale high and zero readings but anyone think of a way of creating a low but not zero reading.
  17. h.abrar94

    How to calculate the resistance of steel armour under fault conditions 70 oC for CSA 95mm2

    Hi All, hope your all well. I was hoping if I can please get some advice in regards to SWA. In Particular using SWA as CPC. Cable size 95mm2 I have a table for SWA which shows various information, in the last two columns it shows the "resistance of steel armour under fault conditions at 70...
  18. A

    Max water bond resistance

    Hi all so I have a situation where a client is moving and they want the db changed for selling. Db change is easy enough as is running a bond to gas which is currently missing. The only issue is that the last eicr said that the water wasn't bonded. It would involve major works (tiled floors and...
  19. mak

    Insulation resistance test on a ring final circuit

    Might be trivial question. My understanding is that we test on either leg of the ring since both legs make up a radial, but some say they test both legs at once, i.e. LL to NN, it would make sense if the other leg is not insulated since this is a live test, but I don't see why not if the other...
  20. N

    Which is the best earthing scheme suitable for worst/large value of soil resistivity in order to get earth resistance value below 5 ohm?

    i don't the exact value of the soil resistivity as no survey of soil sample is carried out at the site .However Copper earthing electrode 50mm diameter of 2.5 m is driven where its circumference were filled with chemical compound power to the height of rod and earth resistance was found to be...

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