PURPOSE: To measure the absolute value of mass by supporting the movable part of the balance on a housing through two diaphragm, and constituting a dynamic type electro-acoustic transducer at one terminal of the movable part and an electrostatic type electro-acoustic transducer at the other terminal.

CONSTITUTION: The movable part A is supported on the housing 6 through two diaphragms 7. The circular plane D of a movable part body 3 and the circular plane F of a fixed electrode 11 constitute a capacitor and the DC voltage of a battery B is applied to constitute the electrostatic type electr-optic transducer H. When a mechanical or electric shock is applied to the movable part A or electric circuit, the electric output of the transducer H is amplified 15. The circuit oscillates when the phase difference between the input and output of the amplifier 15 is selected properly. The mass (m) of a body 1 to be measured is calculated from m=M(f02/fm2-1), where f0 is the resonance frequency of this oscillation system, fm is the oscillation frequency when the body 1 to be meas- ured is placed on a measuring pan 2, and M is the substantial mass of the movable part A. For the purpose, the mass M and frequency f0 are measured previously, and then the mass (m) is calculated by measuring the frequency fm.