As an uncertified amateur part-time mechanic and all-around handy person, I love using the correct tool to make the job easier. I bought my first multimeter after I painted my parents’ house, so my dad would buy me my first car (72 Ford Bronco). I loved my Bronco, but it came with a wide range of issues, rust being #1 (I lived in Massachusetts at the time), and it did not come with a radio. Yes, you heard me correctly, no radio. After I picked up the Bronco and parked it in my parents’ yard, it was time to get to work. So back in the dark ages before Google and the internet, you had to learn by the simple philosophy of trial and error to repair issues and hope not to dont make things worse. I self-taught myself to install radios, amps, and speakers in my beloved Bronco using my trusty Multimeter to test power, ground, and speaker connections. While my multimeter was quite helpful for auto work, I started looking at all of the other options on the dial, and I was like, what do I use that setting for. Well, not that we are the light ages with Google and the internet, here is what I found out for the other settings, for auto and your home wiring.
Voltage
Multimeters can measure direct current (DC) voltage and alternating current (AC) voltage, so they need to display more than one voltage symbol. On some older models, the designation for AC voltage is VAC. These days, it’s more common for manufacturers to place a wavy line over the V to signify AC voltage.
To indicate DC voltage, place a dotted line above a solid line over the V. To get voltage readings in millivolts (one-thousandth of a volt), set the dial to mV.
Current
Like voltage, current can be AC or DC. Because the unit for current is ampères, or amps, the symbol for it is A.
AC voltage
“V” with a wavy line over it.
AC Current
“A” with a wavy line over it.
DC voltage
“V” with one dotted and one solid over it.
DC Current
“A” with two lines, one dotted and one solid, over it.
AC or DC millivolts
“mV” with one wavy line or a pair of lines, one dotted and one solid, over it.
Milliamps
mA.
Microamps (millionths of an amp)
µA (µ is the Greek letter mu).
Resistance
A multimeter measures resistance by sending a small electric current through the circuit. The symbol for the unit of resistance, the ohm, is the Greek letter omega (Ω). Meters don’t distinguish between AC and DC resistance, so there are no lines above this symbol.
On meters with range selection options, you can select the kilohm (1,000 ohms) and megaohm (one million ohms) scales, which are kΩ and MΩ, respectively.
- Ω = Ohms.
- kΩ = Kilohms.
- MΩ = Mega ohms.
Continuity
Use a multimeter to test for a break in an electrical circuit. The meter measures resistance, and there are only two outcomes. Either the circuit is broken (open), in which case the meter reads infinite resistance, or the circuit is intact (closed), in which case the meter reads 0 (or close to it).
Because there are only two possibilities, some meters beep when they detect continuity. This function is denoted on the dial settings by a series of left-facing brackets of increasing size, like a sideways version of the wireless reception symbol on a laptop.
Diode and Capacitance Tests
Electronics technicians are more likely to use the diode and capacitance tests than electricians or homeowners. But if you have a meter with these functions, it helps to know what the symbols mean.
The diode test function looks like an arrow pointing toward the center of a plus sign. When this function is selected, the meter will indicate whether a diode (a standard electronic component that converts AC current to DC current) is working.
The capacitance function resembles a right-facing bracket to the right of a vertical line. A horizontal line crosses both. Capacitors are electronic devices that store charge, and the meter can measure the charge.
The temperature function measures the temperature of the circuit wires. A thermometer denotes it.
Jacks and Buttons
Two leads are supplied with every multimeter, one black and one red. Some meters have three jacks and some four. The jacks you plug the leads into depend on what you’re testing.
- COM is the standard jack, and it’s the only black one. You always plug the black lead into this jack.
- A is the jack where the red lead goes if you’re measuring high current up to 10 amps.
- mAVΩ is the jack for every other measurement, including sensitive current measurements, voltage, resistance, and temperature, if the meter has only three jacks.
- mAµA is the jack for sensitive current measurements (less than one amp) if the meter has four jacks.
- VΩ is the jack for all other measurements except current.
At the top of the meter display, above the dial, you usually find two buttons, one to the left and one to the right.
- Shift. To save space, manufacturers may assign two functions to some dial positions. You access the function marked in yellow by pressing the shift button, which is usually also yellow and may or may not be marked.
- Hold. Pressing this button freezes the current reading for later reference.
Manual vs. Auto Range
An older analog multimeter with a needle requires multiple range settings. If the meter had only an extensive range, it couldn’t be used for sensitive measurements because the needle would hardly deflect. On the other hand, if the meter had only a small range, any measurement exceeding that range, no matter what it was, would deflect the needle to its maximum.
Digital multimeters with LED displays were introduced in the 1970s, and today most multimeters are digital. Some still have range settings that you select with a dial. But increasingly, the meter automatically determines the range.
Because these multimeters don’t have range settings (which can occupy up to 18 dial positions), auto-range multimeters can have more functionality than those with manual range settings.
As I am someone who likes to collect tools for various projects, I have one place to gather my multimeter’s owner’s manual and all the other tool manuals for easy reference. This way, I can always refer back in the future to answer my questions.