electrodes 24 and 25 the symbol d 1 is the thickness of the glass plate the symbol d o being the initial distance of the gap between the weight 5 and the glass plate 22 23 the symbol x being the displacement in the distance of the gap due to applying an acceleration the symbol u03b5 o being the dielectric constant of vacuum the symbol u03b5 1 being the dielectric constant of the glass using these values the electrostatic capacitance c 1 between the equivalent external electrode 24 and the weight 5 is expressed as follows the symbol s is the effective area of the electrostatic capacitance in the weight portion serving as the movable electrode against the electrode 24 it can be understood from the above equation that when a displacement in gap x takes place due to applying an acceleration the electrostatic capacitance c 1 varies and the acceleration therefore can be obtained by measuring the magnitude of c 1 on the lower electrode a similar phenomenon occurs the gap displacement is opposite and the capacitance c 2 can be expressed as follows fig5 shows a second embodiment according to the present invention in this case additional electric conductive portions 26.