An automatic control and recording system for the null‐type vacuum microbalance of Czanderna and Honig [Anal. Chem29, 1206 (1957)] has been assembled from commercial components. A variable permeance transducer is employed to detect beam movement and to control a force to restore the beam to the null position. This force is recorded in a selection of ranges extending from 0–20 000 &mgr;g to 0–5 &mgr;g with accuracies ranging from 0.1% to 2% of full scale. On the most sensitive settings the balance can detect weight changes as small as 0.01 &mgr;g in loads up to 1 g. Stabilities of 0.1 &mgr;g have been observed for periods of many hours on the most sensitive ranges. The balance is undamped, and no corrections are made to the restoring force if beam oscillation is centered about the null point.