| 摘要 |
978,214. Photo-electrically controlled force measuring apparatus. L. CAHN. March 17, 1961 [March 18, 1960], No. 9907/61. Heading G1A. In an electric dynamometer of the type in which a reaction member is deflected from a null position by the force to be measured so actuating a transducer supplying a feed-back signal to an electric motor which applies a restoring force to oppose the deflection of the reaction member, there is provided a circuit for adding to, or subtracting from, the feedback signal a constant quantity so as to give rise to a difference signal registered by output means as a measure of changes in the applied force. In the embodiment described, a shaft 10 rotatable about its longitudinal discs has mounted on it a rotor winding W of a torque motor 24 and affixed to it a balance beam 16 extending transversely to the shaft. Suspended from the beam is a weighing container 18 and a rectangular shutter 30 is secured to the end of the beam remote from its counterbalance, the shutter being mounted in the path of light from a source 32 through a rectangular aperture in a mask 38 to a photo-cell 34, which may be photo-emissive. The output of the photo-cell is supplied to a feedback circuit 40 which supplies via a temperature sensitive resistive network 43 (applying correction for variations in ambient temperature) a signal to the motor so as to oppose motion of the shaft and beam and so maintain constant the illumination of the photo-cell. An output from the feedback circuit is also fed via an instrument control system or range shifter 44 to a voltmeter or recorder 48 calibrated in terms of force. The range shifter comprises means to add to or subtract from the feedback signal fed to the instrument 48 a standard voltage so that deviations of the measured force from a standard may be observed.
|
