Meter Dmm
how does a digital multi-meter (DMM) measure resistance?
how does a digital multi-meter (DMM) measure resistance?
It uses an opamp to generate a constant current, which varies with range. Typically, for the 2000 ohm range, it would be a 1 mA current, so the voltage across the resistor is proportional to the resistance value, 2.000 volts for 2000 ohms, 1.000 volts for 1000 ohms, etc.
That voltage is fed into the voltmeter circuits that are part of the meter. And that’s it, you get a reading of 0000 to 2000 ohms.
Other typical ranges are 200.0 ohms for a 10 mA source, 20k for a 100µA source, 200k for a 10µA source, 2000k for a 1µA source. In each case, the full scale voltage is 2.000 volts.
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