A multimeter is a measuring instrument used to check for AC or DC voltages in electrical components and PCB prototype boards. It also checks for resistance and continuity. The multimeter is a standard tool used by all electronic hobbyists and professionals. They are available in both digital and analog models from most hardware and specialty electronic stores and Web sites.
Buying a multimeter and learning how to use it is necessary for those of us who are repairing or building our own PCB prototypes or electrical devices.
Parts of a Multimeter
Most multimeters will have the following parts and components:
- A display with level indication (analog needle or digital depiction)
- A switch for amps, ohms, and volts
- Switches or knobs for selecting a range
- A knob for adjusting ohms
- An indicator for continuity
- Positive connector and Negative connector
- Positive probe and negative probe
Using a Multimeter
While basic analog multimeters allow you to measure current, resistance and voltage, advanced multimeters allow you to also monitor capacitance and transistor gain. While analog multimeters show the necessary data, new digital multimeters have easy to read displays and also have built in safety measures that are supposed to withstand improper connections.
Depending on the type of meter used and the function you want to measure, you must do different things with your multimeter to get your measurement. At its simplest, however, a multimeter works by connecting the two probes in series or parallel to the circuit you are measuring. Some measurements include:
Measuring Resistance - After turning on your multimeter, set it to resistance mode (Greek symbol for Omega). Take the positive and negative probes and touch the two together. You should get a reading of 0. Now take the device or component being measured and touch the red and black probes at opposing ends. After you have attached to the ends, your meter should still show zero. In the case where it doesn't show a zero, you can try to lower the measurement scale. The meter is probably defective and needs to be replaced if lowering the measurement scale doesn't get you a 0.
Measuring Voltage - Now set your meter to measure DC voltage. This will let you test voltage in circuit boards, batteries, or other components. Now take both the positive and negative probes, and touch them to their respective sides of what is being measured. If you get a negative number you need to switch the probes.
Current or Amp Measurements - To measure current your meter must be placed in series with the circuit you are measuring. If it's not placed in series you will damage the meter. If you are measuring DC set the function to A=, when measuring AC set the function to A-. Find the positive side of the circuit and touch the red probe to it. You may need to cut the wire or disconnect the wire. After you have found the black or negative terminal, attach the black probe. Now turn on your meter and write down your measurement.
Finally, working with electricity is always dangerous. For the safety of you and your meter, be sure to read any manufacturer's documentation before you test something.
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