An acceleration sensor comprises a tube formed of an electrically-conductive non-magnetic material; a stop defining an end of the tube which moves longitudinally thereof in response to temperature; a magnetically-permeable element, such as a iron washer, proximate with the end of the tube; and a sensing mass in the tube comprising a pair of permanent magnets secured to the opposite sides of an iron spacer so as to place a pair of like magnetic poles thereof in opposition. In operation, the sensing mass interacts with the iron washer so as to be magnetically biased against the stop, while the stop moves longitudinally of the tube to maintain a nearly constant threshold magnetic bias on the sensing mass irrespective of variations in sensor temperature. The sensing mass is displaced in response to acceleration of the housing from its first position against the stop towards a second position in the tube when such acceleration overcomes the magnetic bias, while the tube itself interacts with the sensing mass to provide magnetic damping therefor. Upon reaching the second position in the tube, the sensing mass bridges a pair of electrical contacts with an electrically-conductive surface thereof to indicate that a threshold level of acceleration has been achieved. An electrical coil is secured proximate with the iron washer which, when energized, reversibly magnetizes the latter, whereby the sensing mass is either repelled to the second position in the tube or more strongly biased against the stop.