A microbarograph

The sensing elements of the temperature-compensated microbarograph described are flexible bellows driving the plates of a capacitance micrometer. Various design factors are discussed, including protection against mechanical distortion, thermal expansion, vibration and level change, and the adjustment of frequency response. Mechanical and electrical details are given of instruments capable of dynamic sensitivities of 0.05 μb, with low and high frequency response cut-offs adjustable over the range 0.0001 to 1 c/s. Long-term stability is good; temporary zero shifts of the order of a few microbars may occur for an ambient temperature change at a rate of 1 degc per hour. When used with a transistorized recorder the complete instrument is readily portable and has self-contained power supplies.