Patent ID: 9103709
Filing Date: 2015-08-11
Classification: G01F

Abstract:
1. Apparatus for precisely determining the position of a piston supported on a shaft within a prover during translation of the piston and shaft within the cylinder, said apparatus comprising: (a) a switch bar rigidly mounted with respect to the prover, said bar including a plurality of precisely located slots; (b) a channel having a pair of walls and being permanently attached to said switch bar for accommodating passage of a flag, mounted on said shaft, between said walls; (c) a light emitter/detector module detachably mounted within at least some of said plurality of slots and straddling said channel; (d) each said module including a light emitter disposed on one side of said channel for emitting a light beam and a light detector disposed on the other side of said channel for detecting the presence and absence of the light beam; and (e) said channel being disposed in the light path between said light emitter and said light detector, said channel including a first aperture disposed in one wall for sizing the cross-section of the light beam emitted by said light emitter and a second aperture disposed in the other wall for reducing the cross-sectional size of the light beam impinging upon said light detector to accurately correlate the position of the shaft and piston with the precise moment said flag interrupts the light beam.