GB646244A - Improvements in apparatus for counting impulses or determining the rate of occurrence of impulses - Google Patents

Abstract

646,244. Frequency measurement. MINISTER OF SUPPLY. June 28, 1948, No. 17264. [Class 37] [Also in Group XIX] In apparatus for determining the rate of occurrence of impulses, such as electrical impulses from a G.M. counter, by measuring the time taken for the occurrence of a predetermined number of impulses, additional impulses of a known frequency are added to those under measurement in order to reduce the counting period with low impulse rates such as occur when making background counts for radioactive measurements. The apparatus may comprise a scaling circuit adapted to reset the stylus of a timing printer to zero at the end of each count. The impulses under measurement are applied to the scaling circuit together with impulses derived from a constant frequency source which also drives the stylus across a recording surface to record the times of successive counts. In the apparatus shown, how ever, a differential gear 5 adds the impulses. A division (e.g. by 10 or 100) of the impulses from a G.M. counter 1 is made by a scaling unit 2 and the resultant pulses are applied to a magnetic clutch 3 to produce corresponding incremental rotations of a shaft 4. A second shaft 6 is similarly given incremental rotations of constant frequency by a clutch 7 controlled by a timer 8. The rotations of the two shafts are added by the differential 5 and fed to a counter 10 which generates a stop signal at the conclusion of each count. The stylus of a recording printer 9 is also driven by the timecontrolled shaft 6 and is re-set to zero by the stop signal at the conclusion of each count, the lengths of successive traces indicating the times taken. The clutch 7 may be omitted and the shaft 6 driven continuously by a constant-speed motor.