Abstract: An apparatus for measuring a force or load comprising a vibratory beam which vibrates back and forth at a resonant frequency. The beam has first and second end nodal points and first and second ends adjacent to the first and second nodal points. The first end of the vibratory beam is coupled to the load for applying a stress to the vibratory beam that determines the resonant frequency at which the beam vibrates. In addition, masses are coupled to the beam intermediate of the first and second ends. The masses are arranged symmetrically on opposite sides of the beam and reciprocate at the resonant frequency. The reciprocatory masses are located at a position along the beam at which the greatest back and forth vibration of the beam at the resonant frequency occurs. Alternatively, a pair of vibratory beams are provided. The beams are coupled together at opposite ends to form a tuning fork, each beam having a portion which vibrates back and forth at a resonant frequency.

Abstract: The invention relates to a weight measuring apparatus utilizing a vibration type force sensor having a greatly increased Q and being inexpensive and easy to manufacture. The force sensor includes a single vibratory beam or a pair of vibratory beams, which oscillate at a particular measurement frequency related to the stress applied to the sensor by a weight. A rotational mass is coupled to a nodal point of the vibratory beam at the measurement frequency, and greatly influence the frequency at which the beam will vibrate. As a result, the tolerances for manufacture of the force sensor are greatly relaxed, and the pendulum-like movement of the rotational masses for a double-ended tuning fork type sensor tends to override any mismatch between the two parallel vibratory beams.