Mass measuring system

Abstract

An apparatus for measuring the precise sample mass and corresponding sample weight, being tolerant of and relatively insensitive to unwanted background environmental forces, while functioning independently of the force of gravity, uses a vibratory method and a feedback means to monitor and to sustain the sample mass in oscillation at the mechanical resonant frequency of the system in which the sample mass is introduced. The sample mass is forced to oscillate continuously by electromagnetic action, whereby the resultant motion is transmitted by springs and a transmission structure to supporting piezoelectric transducers. These transducers generate an output voltage signal representative of the sample pan's motion, that is amplified and returned to an electromagnetic drive coil in order to sustain oscillation and maintain the closed-loop nature of this system. These oscillations are monitored and the associated frequency measurements used in calculating the sample mass. A microprocessor is employed to solve a series of complex equations for calibration parameters which dynamically describe not only system mass but also system damping and spring constant while monitoring environmental variables such as temperature to correct the calculations for their effects. The result is a digital display of sample mass in corresponding weight units.