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[Solved] Measuring Coil Resistance: Constant vs. Jumping Values with Picotest Multimeter & Manual Meter

faramir1 8859 15
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  • #1 16887770
    faramir1
    Level 4  
    Hello, I am tasked with measuring the coil resistance. By doing this manually with a meter, the resistance is constant and does not jump, while when I use the picotest multimeter, the resistance jumps terribly. I will add that I measured the resistors with a multimeter and it was ok, the resistance slightly changed. Anyone know what this problem may be?
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  • #2 16887781
    jarek_lnx
    Level 43  
    Different meters have different noise immunity and this may be the reason.

    What is this coil? is this coil shielded? or is it exposed to variable magnetic fields and is there any known source of such a field nearby?
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  • #3 16887837
    Adamcyn
    Level 38  
    Are all the numbers jumping?
    jarek_lnx wrote:
    or is it exposed to variable magnetic fields

    Following this lead, attach capacitors of different capacities to the coil and check if there is a difference.
    Also check the behavior of the Picotest on other coils.
  • #4 16887974
    Freddy
    Level 43  
    faramir1 wrote:
    Hello, I am tasked with measuring the coil resistance.
    Under what conditions? For DC or AC?
  • #5 16887994
    Adamcyn
    Level 38  
    Freddy wrote:
    For DC or AC?

    In the case of alternating current, the Author would use the term reactance.
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  • #6 16888012
    Freddy
    Level 43  
    Adamcyn wrote:
    In the case of alternating current, the Author would use the term reactance.
    If he knows what it is and if he is a teacher
    faramir1 wrote:
    I have a task
    he didn't do much myku :)
    Picotest - there is more than one. What settings in Picotest during measurements? This is also very important.
  • #7 16888048
    Adamcyn
    Level 38  
    It is possible that the Picotest measures by pulse, supplying energy to the magnetic field of the coil and when changing the direction of the pulse, this energy is returned from the coil to the meter, interfering with the correct measurement of resistance.
  • #8 16888145
    faramir1
    Level 4  
    He measures using a multi-point card from his own program, this is the pic35 test m3500a. I tried using the card reader program that is on the picotest page and shows the same jumping resistance. In this case, I could only rule out software errors. I don't remember at the moment what settings I will look at when I come to work.
  • #9 16888276
    Adamcyn
    Level 38  
    Freddy wrote:
    What settings in Picotest during measurements? This is also very important.

    If Autorange, then Picotest sends various current pulses to set the correct range, resulting in:
    Adamcyn wrote:
    supplying energy to the magnetic field of the coil and when changing the direction of the pulse, this energy is returned from the coil to the meter, interfering with the correct measurement of resistance.
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  • #10 16888381
    faramir1
    Level 4  
    I will check tomorrow with this setting autorange may help

    Added after 13 [hours] 10 [minutes]:

    I don't know a bit how to configure it in a multimeter, I can prompt you with what other commands, as long as someone knows.

    Added after 3 [hours] 19 [minutes]:

    However, this is not the range because I set it manually on the front panel, I closed the channels, the manual measurement is like from the card.
  • #12 16889901
    faramir1
    Level 4  
    The best part is that as much as this resistance from the front panel and not using a multi-point card, this resistance is correct and amounts to 40 ohm
  • #13 16890034
    Adamcyn
    Level 38  
    faramir1 wrote:
    as far as this resistance from the front panel and not using a multi-point card is this resistance is correct and is 40 ohm

    Maybe the oscilloscope will show the differences in measurement.
  • #14 16890398
    faramir1
    Level 4  
    The measurement using the card is 35 ohms 8 and 5 ohms for 1,2 and 3 channel. However, the measurement using the 40 ohm front panel was measured with a meter and also 40 ohms. Tomorrow I will look at it through the crossing power and signal cables to the monitor with my measurement.
  • #15 16947407
    faramir1
    Level 4  
    Hello, I have recently worked on improving results and obtained better results in setting integration time. Now the multimeter shows with accuracy to one. However, this is not enough in my case because I received the instruction to get accuracy to 0.1 ohma. Maybe you write what you set in your multimeters so that it affects the accuracy I manipulated range and resolution.
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Topic summary

The discussion revolves around measuring coil resistance using a Picotest multimeter compared to a manual meter. Users report that while the manual meter provides stable resistance readings, the Picotest multimeter shows fluctuating values. Possible causes for this discrepancy include differences in noise immunity between meters, the influence of external magnetic fields, and the measurement method employed by the Picotest, which may involve pulsing current. Suggestions include testing the Picotest on different coils, using capacitors to observe changes, and checking settings such as autorange. Users also mention the importance of integration time settings for achieving accurate measurements, with a goal of reaching precision to 0.1 ohm.
Summary generated by the language model.
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