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Workbench Wednesday 24: No-Contact Current Measurements

 

 

One of the safest ways to measure current is with a clamp. Clamps do not require you to break the circuit and they safely measure wires with thousands of amps. In this video, we measure DC current in the lab, AC current of a reflow oven controller, and the DC current in a car using a Tenma 72-722672-7226 True RMS Clamp Meter.

 

Bill of Material:

 

Product NameManufacturerQuantityBuy KitBuy Kit
72-722672-7226 - Clamp Meter, Auto, True RMS, 600 A AC, 600 V AC, 600 V DC, 28 mm Jaw Opening Max.Tenma1Buy NowBuy Now
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  • Great episode! Thank you.

     

    I'm more of a tech (hack) than an engineer so I need some help with a project.

    I need to build an over current alarm circuit for AC. The current in the circuit is typically between 70mA and 200mA. I'm going to have it alarm around 350mA.

    I've been looking at different current sensors and I'm not really sure what to use. Hall effect or Current transformer.

    Then there's the actual circuit to make the alarm. I'm assuming a differential opamp but I'm a little lost as to how to configure it.

    I've been researching it but I'm a bit confused. My plans is to drive a small piezo buzzer.

    I would rather not break the circuit and would like to use a split core CT for ease of installation. But I'm not sure if that will give me enough sensitivity/resolution.

     

    I'd really appreciate any advice or pointing me in the right direction.

    Thanks!!!

    Mitch

  • in reply to kb3gkc

    Hi Mitch,

     

    There are specially configured Op Amps called Comparators that might work well for your application. They will not only trigger at a tipping point like the 350 mA that you mentioned but they also have some hysteresis so that you get a definite On - Off from them. I have used the LM 339 quite a bit but here are others that you can look at as well.

     

    John

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