How To Use A Digital Multimeter – Measuring DC Voltage
This article will teach you how to operate a typical digital multimeter. Names for meters can vary depending on manufacturer and can include digital multi-meter (DMM), digital volt-ohm meter (DVOM), multi-tester, voltmeter and others. We’ll take you through basic operation of the Craftsman Digital Mini Multimeter 34-82344 that we’ll be using. While we’ll guide you through specific steps for using this DMM, operation and use of other multi-meters will be similar. When purchased new, all meters come with instructions as to how their specific features work and what settings to select to read various electrical properties.
Reading DC (Direct Current) Voltage
1. CONNECT LEADS TO THE CORRECT PORTS OF THE DMM: The red lead should be plugged into the lower, right socket marked “V, Ohms, HZ…,” most tests will require that your red lead be plugged into this socket. The socket at the left marked 10A is for measuring amperage, also known as Current. The black meter lead should be plugged into the center socket marked “COM.”
2. SET DMM DIAL TO READ VOLTAGE: Turn the meter’s rotary dial to select voltage (marked with the symbol V).
3. PRESS “SELECT” BUTTON TO CHOOSE DC VOLTAGE: The volts symbol has a straight line and a wave line above the letter “V.” The straight line represents DC, or direct current voltage and the wave line represents AC, or alternating current voltage. To choose DC or AC functions press the red “Select” button at the top left of the meter. The display (upper left corner of the digital display) changes from DC to AC, or AC to DC depending on how many times the Select button is pressed. Press the Select button until “DC” is displayed.
4. CONNECT DMM LEADS TO BATTERY AND READ VOLTAGE: Connect the multimeter leads to a motorcycle or automotive battery to read volts. The red lead goes to the positive battery terminal. Look for the “+” symbol or in some cases a red colored battery cable to identify the positive battery terminal. The black meter lead is connected to the negative battery terminal —look for the “ – ” symbol. Battery voltage will be displayed on the meter. The voltage reading should be in the range of 12 to 13 volts DC.
The Craftsman meter has a feature called “auto-ranging” that automatically sets the voltage scale, or range, to read correctly when the leads are connected to a power source. The decimal point will be automatically placed to show correct voltage. A reading of 12.34 is 12 volts and 34 hundredths of a volt, or 12.34 volts. A reading of .132 volts is a tenth of a volt, plus 32 thousandths.
NOTE: When measuring components with higher output, the meter will adjust accordingly, displaying a “K” or “M” next to the number, signifying that output is in the range of thousands (K) or millions (M). These symbols usually are used when reading resistance, also known as Ohms.
While watching the meter, turn the ignition switch on. The voltage should decrease when this electrical load is placed on the battery caused by the ignition switch being in the on position. Turn the ignition off and the voltage should increase.
NOTE: Remove the meter leads from the battery and connect them in reverse. Black lead connected to the positive battery terminal and red to the negative battery terminal. The meter will still read the same voltage but there will be a “ – ” (minus) sign before the voltage number. This indicates that the meter is reading a negative voltage number, or reading in reverse. While it is fairly obvious when the meter is connected “backwards” to a battery, it’s not so easy to tell when connecting the meter leads to wires in a wiring harness on your motorcycle. Connecting the DVOM backwards will not harm the meter or your machine.
1. Connect meter leads in the correct ports.
2. Set meter dial to read Voltage.
3. Press Select button to choose DC voltage.
4. Connect DMM leads to battery and read voltage.
NOTE: Connecting meter leads backwards will result in a negative voltage reading, showing a “ – ” symbol before the number.
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