Meter Voltmeter
What is the load of a multi-meter when used as a voltmeter.?
Also, how does the load of a multi-meter (voltmeter) affect the resultant voltage across two resistors in series in a simple circuit. What would be the affect of a load resistance on the voltage divider ( the two resistors in series) performance.
You need to know the internal impedance of the voltmeter, and that will depend on the voltage scale you are using. The meter should have a specification of “ohms per volt”. Multiply this by the full-scale voltage setting of the meter to get it’s internal resistance. Then apply parallel resistance formula to find the restance with the meter connected. For example, if you have a series resistance circuit with two resistors R1 and R2, and you want to measure the voltage across R2, you connect the meter across R2. If the meter has a specificaton of 1000 ohm per volt, and you are using the 10-volt scale, the internal impedance is 10,000 ohms. The value of R2 will be changed to (R2*10,000)/(R2+10,000).
This applies to passive multimeters; electronic meters (used to be called VTVM, but now most are digital) have such a high internal impedance that it can be ignored.
Tagged as:
autometer voltmeter,
meter voltmeter