Figure 4-5.Measuring the voltage drop of a resistor.
When measuring a dc voltage drop across a component in a circuit, you must connect the voltmeter
in parallel with the component. As you can see in figure 4-5, the positive (red) lead is connected to the
positive side of the resistor, and the negative (black) lead is connected to the negative side. A voltage
reading is obtained on the meter when current flows through the resistor.
Some voltmeter readings will require the use of a ground as a reference point. Under these
conditions, one voltmeter lead is connected to the equipment ground, and the other lead is connected to
the test point where voltage is to be measured. Be sure to observe polarity.
Measuring ac Voltages
To measure ac voltages, you must set the function switch to the AC position. The same procedure
used to measure dc voltages applies, except that in reading the voltage, you use the AC volts scale (the
polarity of the test leads is not important). When measuring very low or high frequencies of ac voltages,
you should be aware that the multimeter has a tendency to be inaccurate. View A of figure 4-6 is a