polarity indicator circuit

Polarity Indicator Circuit

Is is easy to test the polarity of a circuit’s point whether it is positive or negative by using the tester circuit featured here. The tester circuit has a high input impedance (around 1 megaohms) to avoid loading the point being tested. In testing sensitive points however, (inputs of opamps), the input impedance must be taken into consideration.

The opamp 741 is the core of the polarity indicator circuit. Its non-inverting input is used to test the points for polarity. It has a gain of around 150 which enables it to test low voltage levels. The test result is displayed through the two LED’s D1 and D2. D1 lights up by positive polarity and D2 lights up by negative polarity. Take note that the pin profile on the diagram is based on the TO-5 package profile.

Polarity indicator circuit diagram

polarity indicator circuit


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  • Chandana

    How we can check the polarity? The non inverting terminal should be connected where? Can we use wires instead of probes?if we use probes which terminal should be connected to ground and which terminal should be connected to the device

  • Chandana

    Want to know how this circuit works or what is the theory behind the circuit.can this circuit be used to check the polarity of ordinary battery(1.5v)

  • Mandeep

    i have circuit which produce either +15 or -15 Volt. i have made LED indication circuit which have 2 LED for indication, but problem is that 1 LED is ON when output is +15 volts and 2 led ON when output is zero (ground- low).

    so i Required one circuit which have both positive and negative indication on +/-15 Volts.
    Is this circuit working for that?

  • asf

    I can’t get this circuit to work . Am using 9V batteries and have connected positive and negative of each battery together to ground. Is that the right way to do it?

  • Ganta.Dileepkumar

    The circuit was nice, sir I want to know that this circuit can be used for testing 230v ac supply.

    • mtrisonvincentyahoo-com

      where should i put the -12v and how will the lEdS would work??”PLease reply asap i just need it

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