False reading

Discussion in 'Electricians' Talk' started by Grant1969, Jun 12, 2024.

  1. Grant1969

    Grant1969 New Member

    Checking why I thought was a dead cable before cutting it I am getting strange readings.

    my fluke t6 is showing 0 voltage directly on the wires but 80-155 volts on the field sense.
    I understand this could give false readings but my cheap voltage tester stick is also picking up voltage.

    just to be clear I have tested the cables on the fluke on a working 240v power source and they seem to check out perfectly.

    Any ideas why this would be happening?
     
  2. Could be an induced voltage.
     
  3. What is field sense? Like a non contact indicator? What are you testing between? This might also be why an approved voltage indicator or test lamp only are used.
     
  4. Grant1969

    Grant1969 New Member

    Field sense is fluke’s non contact voltage indicator. It’s not perfect by any means but it’s odd that I would pickup a reading in this as well as a cheap voltage stick while wired meter reads 0
     
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  5. adgjl

    adgjl Screwfix Select

    You are using the testers for things they are not designed for. In general a tester that senses the electric field round a conductor is for proving live, not proving dead. These are two very separate requirements.
     
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  6. Grant1969

    Grant1969 New Member

    this is my point. I have a generic voltage stick tester and the fluke are showing a current. The test leads are showing 0.

    my question was why the discrepancy
     
  7. Because basically you don't understand what your meters are telling you, so are therefore misusing them.

    Sorry if that sounds harsh, but that really is the sum of it.
     
  8. Grant1969

    Grant1969 New Member

    I know exactly what my meters are showing. I don’t understand the discrepancy
     
  9. You don't understand th discrepancey because you don't understand what they are telling you.

    The correct test with the probes is telling you there is nothing present.

    The non-contact readings are detecting an induced voltage. Short out the end of the cable (with power off) then retest and your non-contact voltage will also be zero because you have discharged the cable.
     
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  10. WH55

    WH55 Screwfix Select

    A lot of good sense on this thread, OP. Also, not trying to be awkward, but why cut the cable rather than trace it back to source and disconnect correctly ?
     
  11. Grant1969

    Grant1969 New Member

    It is disconnected correctly from the source correctly. The cable is routed through inaccessible areas so I have have unclipped to that point and have several meters of cable tied up. Before cutting I went to double check and came across the issue.
     
    WH55 likes this.
  12. adgjl

    adgjl Screwfix Select

    You are reading the indication, but you do not understand what it is telling you. You cannot use a non-contact device to prove a conductor or cable dead. It follows that you cannot safely use it to determine whether you can cut a cable. You have three options:
    - follow the cable from a point where you can access the conductors, and follow the cable back to where you wish to cut it.
    - use live jointing techniques to access the cores at the point where you wish to cut it (I suspect you do not have the training to do this safely).
    - turn off all the power and hope for the best (not recommended).
     
  13. The Happy Builder

    The Happy Builder Screwfix Select

    What type of cable and how many conductors do you have inside the fork on the tester?
     

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