Abstract: An accelerometer comprises a chamber and a proof mass supported by an elastic element within the chamber. The elastic element is formed of fused silica. A sensor senses displacement of the proof mass. Means to inhibit interaction of water vapour with the elastic element is provided.

Abstract: This invention relates to electromagnetic mapping wherein magnetic fields of two or three different and normally audio frequencies may be transmitted or received efficiently using induction coils with the same orientation and essentially the same spatial location. Flat, air cored coils are used and are overlapped so as to have essentially zero mutual inductance between pairs.

Abstract: An electric heating device is positioned in close proximity with a thermostat. An electrical energizing device energizes the heating device. The energizing device includes a switch for selectively actuating and deactivating the energizing of the heating device. A timer is coupled to the switch. The timer closes the switch thereby energizing the heating device and raising the temperature in the area of the thermostat above room temperature by .DELTA.T determined by the amount of heat generated by the heater and the distance between the heater and the thermostat. The timer opens the switch after a preselected period of time thereby deenergizing the heating device and lowering the temperature in the area of the thermostat to the room temperature whereby the thermostat controls the room temperature in accordance with the setting thereon.