Analog_vs_Digital_Meters

Impedance is the biggest difference between analog

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Unformatted text preview: he voltmeter. Impedance is the biggest difference between analog and digital voltmeters. Since most digital voltmeters have 50 times more impedance than analog voltmeters, digital meters are more accurate when measuring voltage in high resistance circuits. For example, if you are using a low impedance (20,000 ohms per volt) analog meter on the 20 volt scale (the voltmeter represents 400,000 ohms resistance to the circuit) to measure voltage drop across a 1,000,000 ohm component in a circuit, two and a half times as much current is flowing through the meter than through the component. You are no longer measuring just that component, but the component plus your meter, giving you a false reading of the actual voltage drop across the component. This situation might lead you to believe the voltage at the component is low or that there is high resistance somewhere in the circuit or that the component is defective when it is just the meter you are using. If you use a digital meter with 10 million ohms of impedance to test the same component, only 1/10 of the current will flow through the meter, which means it has very little effect on the circuit bei...
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