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Analog Vs Digital Ohm Meters

Discussion in 'The Tool Shed' started by Mark T., Aug 29, 2021.

  1. Aug 29, 2021
    Mark T.

    Mark T. Member 2022 Sponsor 2020 Sponsor

    Gilbert, AZ
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    Is anyone aware of any advantages of using an analog ohm meter over a digital ohm meter or vice versa?
     
  2. Aug 29, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    My unprofessional experience?

    Analog needle not as super-precise, but is nice to see variations and trends. The meters are delicate.

    Digital, the opposite. Much less fragile, very precise, but no good for watching changing values.

    I'm sure there are exceptions
     
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  3. Aug 29, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    IMHO -

    Today, you can't build an analog meter for the price of a digital multimeter. These modern digital meters are a single semi-proprietary chip with a plastic case - quite standardized. If you need to visually track time-varying voltage or current, the analog meter is great. An AC analog voltmeter is the best for things like aligning the tuner and IF in radios, where you are looking to peak-up an AC output.

    I expect the main issue with a digital meter is the conversion speed. Any digital reading requires an ADC (analog to digital convertor) and the faster the ADC, the more expensive. Feed an inexpensive digital meter a time-varying signal and it will freak out, and never convert to a single number. You can see this - look at a music signal or something like that with a cheap multlimeter and the display will be flashing between digits constantly with no sensible reading. They will read constant AC like line voltage just fine though.

    Use an analog meter, and it will time-average the signal while the needle wobbles around the average. Useful, where the digital meter is not.

    With a digital multimeter, however, you get a lot of features. They'll all have AC and DC volts, amps (typically two ranges, say 0-100mA and 0-10A), ohms and a diode test (audible continuity). If you do any electronics work, having a capacitance setting is very useful. Inductance is harder, but sometimes they have it. Maybe they have frequency counter? Many have a setting to read a thermocouple, giving you temperature.

    You pay extra for the front-end circuitry that time-averages accurately and gives you a true RMS (root-mean-square) reading, but I don't know what you'd use this for in automotive. You pay extra for high-voltage safety, though the High-Pot rating of many of these meters seems unlikely. More digits costs more money. Your better-quality meters will have more internal protection against a mitt-fisted operator. (Don't test capacitance unless you discharge the cap first).
     
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  4. Aug 29, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    :rofl: Working on my electric fence charger today - got a good spark when I pulled the capacitor out!
     
  5. Aug 29, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    One of my colleagues at the lab loves old equipment, and he had a bunch of huge oil-filled capacitors stored under the sink in one of the labs. Not huge capacitance (10uF? 20uF?) but big voltage rating, like 5000 or 10000 volts. They all had solid wire wrapped around and between both posts. No possibility of them having any residual charge.

    These were probably paper in oil (PCBs) and I recall these can regain some charge after they were nominally discharged. Apparently some electrons could slowly migrate out of the paper and put a charge on the plates. Can't happen if the plates are wired together.

    I have not been in that room in years - they are probably gone now.
     
    Last edited: Aug 29, 2021
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  6. Aug 30, 2021
    Mark T.

    Mark T. Member 2022 Sponsor 2020 Sponsor

    Gilbert, AZ
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    Nov 9, 2015
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    Thanks for the thoughtful responses. I don't anticipate needing to use one often but I think I will keep both around. Most seem inexpensive enough to at least keep the kids and grand kids puzzled.
     
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