Measure Voltage in Parallel
First, decide whether you want to measure AC or DC voltage (all voltages and currents in this lab will be DC), and configure your multimeter appropriately. Then connect the voltmeter in parallel across the circuit element.
Notes
- Notice that some of the current flowing in the circuit actually flows through the voltmeter. This current must be very small in relation to the total circuit current I. Thus, the internal resistance of a voltmeter is very high.
- You must be VERY careful to make sure that your multimeter is configured correctly before placing it in parallel across a circuit element. Ammeters have very LOW internal resistance, and can be damaged when placed in parallel across circuit elements. See the Caution! page for more details.
- A voltmeter measures a voltage change, which may be positive or negative. All voltmeters are designed to give a positive reading whenever the red probe is placed on the side of the circuit element that is closest to the positive pole of the battery. Red to positive.
- Because the voltmeter is placed in parallel with the circuit element, you do not need to physically alter your circuit in order to measure voltage.
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