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Null detector polarity tester circuit diagram

It’s very easy to test the polarity of a signal at a point from circuit ( if the voltage from test point is positive or negative ) by using a digital multimeter or using an null detector electronic circuit like in this diagram .  This null detector polarity tester circuit diagram is based on a common 741 operational amplifier that require few additional components to do the null detection .  The test result of the polarity indicator is displayed through the two LED’s  LED1 and LED2 .

This detector circuit diagram need to be powered by a 12-15 volts DC power source .
For a easy identification of the null you can use two different color LED’s .

Null detector circuit diagram

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