Analog Multimeters

The analog multimeter  or volt-ohm-milliameter(VOM).
The measurements made with a deflection-type VOM are read from the instrument by noting how far the pointer moves over a scale. Since a VOM has a number of scales, the correct one must be chosen based on the type of measurement you will be doing. The meters with a function dial (pointer) on the front must be set to the proper quantity being measured (voltage, current, or resistance) and to the appropriate size range.

On meters with no function dial, the leads must be plugged into the proper input terminals so the dial does not go off scale. Some meters may contain numerous input terminals on the front of the VOM. The choice of input terminal is determined by the type of measurement (voltage, current, or resistance). It is also determined by the amount (value) of the measurement.
VOMs are sensitive to polarity of direct current (DC) and voltage. In order to maintain proper polarity, the leads are red and black. The red lead is plugged into the positive (+) terminal on the meter. The black lead is the negative lead; it is plugged into the - or COM or negative terminal (depending on the labeling used on your meter).


The instruction booklet that comes with the meter is the best place to look for a description of your multimeter and examples on how to use it.

Follow these SAFETY PRECAUTIONS when using a VOM:
•    Disconnect or remove the power source before connecting in-line ammeters in circuits.
•    Connect the VOM in series with components in the circuit to measure current flow; in
parallel to measure voltage.
•    Always observe the correct polarity. Hook a positive lead (red) to the positive side of the circuit; hook a negative lead (black) to the negative side of the circuit.
•    When measuring resistance, first disconnect the resistor being measured from the circuit.
•    Set the meter to the highest range setting if you are not sure how large the voltage, resistance or current you are measuring is. Multi-meters do not offer resistance to current flow. If an ammeter is hooked up directly to a power supply, or if the current flowing through it is too large for the given setting, its fuse will burn out. If the current is too large, its fuse may not be able to protect it and the multi-meter may be damaged permanently.
•    Handle multi-meters carefully and do not drop them. They are delicate instruments.

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