Digital Ammeters - help!

Discussion in 'Supporting Physics' started by SNewton, Jun 13, 2019 at 3:46 PM.

  1. Hi all,

    We've purchased a set of new digital ammeters and have gotten some unusual results when testing them. When using a 1.5A power supply (SATZ, grey), all of the ammeters have given readings of approximately 3.5A. There is also a buzzing noise and the LED on the power supply flickers. Any ideas why this might be happening?

    TIA!
     
  2. Nick Mitchener

    Nick Mitchener COMMITTEE

    Are you using a circuit to test them, what is in it?
     
    Andrew Goloskof likes this.
  3. Exactly what Nick says!
     
  4. If you haven't used additional components in the circuit, you are effectively shorting the power supply, which could damage the power supply or the ammeter.
     
    Andrew Goloskof likes this.
  5. Apologies for the late reply, it was a busy couple of days!

    I tested them in a series circuit - powerpack, bulb, ammeter and also in parallel with two bulbs.
     
  6. PhysicsSimon

    PhysicsSimon COMMITTEE

    What voltage did you have your power pack set to?
     
  7. Tested at 6V with MES bulbs. Also tried at 12V with a raybox, but still got the same readings.
     
  8. PhysicsSimon

    PhysicsSimon COMMITTEE

    Nope, don't understand that one at all - our 6V mes bulbs have a rated current of 0.06A (other variants are available).....the only way you could get to that sort of current would be if you'd fitted the ammeter across the component (as a voltmeter should be fitted) rather than in line
     
  9. Just tried again - I think Thursday-afternoon-me put the ammeter in the wrong place, doh! Thank you for the help.
     
  10. PhysicsSimon

    PhysicsSimon COMMITTEE

    No worries - we all do it (or similar) from time to time - not so long ago I did this the other way round (in line voltmeter) - just stood there wondering why the bulb didn't light - took ages (and a lot of lead swapping etc etc) to realise....Doh indeed!