GB749525A - Improvements in means for measuring velocity changes - Google Patents

Abstract

749,525. Measuring speed. T. M. M. (RESEARCH), Ltd. Aug. 18, 1954 [July 16, 1953], No. 19742/53. Class 40(1) A magnetic recording tape is driven by a moving member, whose linear or angular speed variations are to be measured, past a recording head fed with constant frequency electric pulses; subsequently the tape is driven at constant speed past a pick off, the output signals of which vary in frequency according to the speed of the member and are preferably translated to corresponding potential variations to operate a C.R.T. indicator. Recording, Fig. 5. A bar 20 carrying adjustable blocks 22 which may be rested on a part 24 of a machine, is then rocked via the handle 21 to press the magnetic tape 2 between a shaft 1 whose speed is to be investigated and a pinch roller 3, whereby the tape is driven over guides 26 past the recording head 4, fed from a standard frequency oscillator at a speed proportional to that of shaft 1 Reproduction, Figs. 3, 4. The pick-off signals obtained when the record tape is driven at constant speed are amplified, squared, and applied at A to a differentiating network B, the resultant positive pulses firing a thyratron V1 normally biased to cut off. Positive pulses thus derived from V1 at point C are fed directly to an amplitude sampling triode V3 and through a delay line 14 to fire momentarily a triode V2. A condenser Ce normally charged over a resistor R is rapidly discharged as V2 fires. The saw-tooth voltage developed across Ce thus rises from a constant minimum to a peak value substantially proportional to the time between the positive pulses at C (curve E). Slightly before the peak values are reached, the triode V3 is momentarily fired, by the direct positive pulses from point C, and conducts in series with V4 which functions as a cathode follower loaded by V3 so that the cathode voltage F is brought approximately to E, that of the grid of V4 substantially at the time of occurence of the peak values. A condenser CS follows these peaks (curve F, Fig. 4) and is connected across the Y plates of a C.R.T. 16. The X plates may be fed from a time base to display the speed of shaft 14 against time or the time base may be omitted and the Y trace photographed on a moving film