Abstract: A weighing device uses frequency measurement to determine weight. One body (3; 23; 68) is of known mass and another body (8; 28; 66) also of known mass is spring (9; 29; 83) connected to it. This body carries the load whose mass is to be determined. Both bodies can oscillate in one mode in an effectively isolated system, being carried by springs (2, 13; 22, 33; 65, 67) from a support (1; 21; 60, 62). The oscillations are electromagnetically generated, but when a certain amplitude is attained the drive is cut off and the system resonates freely. The frequency varies with the mass of the bodies, and so a load on one can be weighed by reference to the frequency, which can be detected through the electromagnetic means (12, 32, 76) which provided the initial drive pulses.