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  1. Diver233
    Offline

    Diver233 Fire alarms

    Location:
    UK
    i am hoping you may be able to help. I’ll try to explain my problem, any help gratefully received.

    Part of what I do is train fire alarm engineers and as part of the practical is battery calculations, which we need to measure the stand by and full alarm load off the battery leads.
    So the process is swap leads to mA position and switch to mA reading, connect leads in series to the battery disconnect main power so now mA is displayed for stand by the press sounder button on fire panel and you have alarm load.

    Despite every time explaining not to do anything different & not to do it until I say etc etc nearly every course some one will either not change the leads or something stupid and bang as a minimum fuse blown.

    What I am asking, is there a multimeter that does not need leads switching or as some sort of non fuse blowing feature that will allow non listening people to not blow meters?.
     
  2. spinlondon
    Online

    spinlondon Forum Mentor

    Location:
    Harlow Essex
    Was about to say yes, then realised the multimeters are connected in series.
    I doubt very much that you’ll find a multimeter that can withstand being connected in series.
    You may be able to obtain an ammeter that can, but the size and cost will be large.
    Would it not be better to use an Amp Clamp?
     
    • Agree Agree x 1
  3. Diver233
    Offline

    Diver233 Fire alarms

    Location:
    UK
    Do the amp clamps go as low as 95mA?
     
  4. Rob
    Online

    Rob Control System Engineer Respected Member

    Location:
    USA/UK
    You can get low range current clamp meters, however because you're measuring DC current they will not be as widely available as the AC versions.
    Something like this would do:

    https://www.amazon.com/General-Technologies-Corp-CM100-Current/dp/B001TCWL1E

    Maybe worth contacting the site sponsor test-meter.co.uk and see if they can recommend something for you. You also get a discount for being a member.
     
    • Agree Agree x 2
  5. dmxtothemax
    Offline

    dmxtothemax Regular EF Member

    Location:
    Australia
    Business Name:
    David Haddock Electronic Repairs
    The last time I say a multi meter that could with stand that sort of abuse with out blowing was 30 odd years ago and the meter was an "AVO - 8 " with built in resetable circuit breaker. You may be able to find a few old one's floating around, but they are collectors items now days.
     
  6. telectrix
    Online

    telectrix Scouser and Proud of It Respected Member

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    i've still got 2 of them. one is actually in calibration. there's always a few on ebay.
     
    • Agree Agree x 1
  7. davesparks
    Offline

    davesparks Forum Mentor

    Location:
    guildford
    Don't allow them to energise the circuit until the test connections have been checked by yourself
     
    • Like Like x 1
    • Agree Agree x 1
  8. SparkyChick
    Offline

    SparkyChick Making a banana smoothy for my fave gorilla Staff Member Moderator

    Location:
    South Wales
    Business Name:
    SparkyChick
    Do you supply the multimeters? If so, I would stop providing them and make a course pre-requisite that they have their own, people take more care when they've had to shell out for the gear.

    And maybe take an old meter and blow it up with a small stage pyrotechnics device, film this and play it to them to demonstrate what could happen if they get it wrong. Bit OTT perhaps but will lighten the mood. Could even maybe make it really good and include a ballistics gel hand, overpower the explosion so it damaged fingers :D
     
    • Agree Agree x 2
    • Like Like x 1
    • Funny Funny x 1
  9. bill01803
    Offline

    bill01803 Regular EF Member

    Location:
    Devon
    Di-Log do one
     
  10. snowhead
    Online

    snowhead Respected Member

    Location:
    Mildlands
    Fused leads, if available for the meters you use, with a fuse rated lower than the internal one.
     
    • Like Like x 1
  11. TonyMitchell
    Offline

    TonyMitchell Electrician's Arms

    Location:
    Berkshire, UK
    ... not forgetting to ensure your organ is on full display in the background throughout... :)
     
    • Funny Funny x 2
  12. Rob
    Online

    Rob Control System Engineer Respected Member

    Location:
    USA/UK
    Good idea, but they must follow a strict proving routine if they use the multimeter for dead testing. This is the main reason multimeters are not recommended for this purpose.

    If they manage to pop the fuse in the test lead, they will never read voltage.
     
    • Agree Agree x 1
  13. Vortigern
    Offline

    Vortigern Regular EF Member

    Location:
    England
    Business Name:
    F.H. Electrical
    Just an idea, but how about you dispense with that method altogether. Instead just assay the load each point demands from the manufacturer (say 80ma) and so 10 call points 800ma and just test the battery disconnected out of the box on the table separately?
     
  14. Diver233
    Offline

    Diver233 Fire alarms

    Location:
    UK
    That’s what I have had to resort to, however sometimes they decide they know better and alter the leads.
     
  15. static zap
    Offline

    static zap Regular EF Member

    Location:
    west midlands
    [QUOTE="dmxtothemax, post: 1515525, member: 88482".....]
    May be able to find a few old one's floating around, but they are collectors items now days. [/QUOTE]
    -------
    A) Being a bit heavier they don't enjoy mechanical shock ..
    (1.2 Metres onto concrete )..as well
    -Less bounce-
    B) ---Using a cheap replaceable external shunt ---
    .... could try measuring voltage across a 10 Ohm 2W resistor...
    ..but that's not the real test 0.95V
    ( -ten times bigger in mV-)
    and may burn fingers if put across 12V !
    C) A virtual environment "meter" ..may be the only fix for this "pretend listening" behavior (testing the tester)
     
    • Agree Agree x 1
    Last edited: Mar 11, 2019
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