A dwell meter measures the dwell angle of the contact points in the distributor. A dwell meter is much more accurate than setting the points gap with a feeler gauge.

The dwell angle of the points is the angle of point closure; the smaller the dwell angle, the smaller the dwell angle, the wider the points gap, and vice-versa. Workshop manuals will give the specification for the dwell angle in the tuning data section.

A dwell meter is particularly useful in the case of used points where metal transfer between the points makes accurate checking difficult using feeler gauges. To carrying out the dwell angle measurement, the dwell meter is connected in accordance with the manufacturer's instructions. The engine is started and run at idle, and the dwell angle read off the meter. If the reading is outside the prescribed limits, the distributor cap and rotor arm must be removed and the contact breaker points adjusted to the correct setting, while the engine is cranked over on the starter. When the dwell angle has been adjusted, the ignition timing must be reset.