Patent GB-1272796-A (GB)
Title: Apparatus for measuring a parameter of electric periodic signals
Inventor: GORSKY JURY MIKHAILOVICH
IPC: G01R25/00
Filed: 1969-10-23
Abstract: 1,272,796. Frequency and phase detectors. GOSUDARSTVENNY VSESOJUZNY ORDENA TRUDOVOGO KRASNOGO ZNAMENI NAUCHNO-ISSLEDOVATELSKY TEKHNOLOGICHESKY INSTITUT REMONTA I EXPLUATATSII MASHINO-TRAKTORNOGO PARKA AND SIBIRSKY ENERGETICHESKY INSTITUT SO AN SSSR. 23 Oct., 1969, No. 52041/69. Heading H3A. [Also in Divisions G1 and G4-G6] In a measuring system a cyclically recurring waveform is amplified 2, Fig. 1 and made available either directly or via an inverter 16, to a circuit 4 where a fixed reference voltage is subtracted and then passed via a differentiating circuit 8 and a gate 9 to a monostable device 10. The circuit described in Fig. 1 can measure either the repetition frequency of a cyclically occurring waveform, one cycle of which U I  is shown at (a) in Fig. 6, or the phase with respect to reference pulses U VI , Fig. 6 (e), the first point on each cycle at which the waveform crosses a preset level U i  with a positive slope. As described the cyclically occurring waveform U I  from a source 1, Fig. 1 is amplified 2, and by means of circuits 4 and 8, pulses U III , Fig. 6 (c) are produced at the points where the waveform U I  crosses, with positive slope, a level U i  set by a potentiometer 5. These pulses U III  pass via a normally open gate 9 to trigger a monostable device 10 which produces pulses U IV , Fig. 6 (d), of fixed amplitude and duration, which are averaged by a meter 7, a switch 6 being set in its position "B". Thus with the "B" setting of the switch 6, the meter 7 indicates the average frequency of the waveform U I . The pulses U IV , Fig. 6 (d) are also applied to a circuit 11 to produce pulses U V  Fig. 6 (e) (these correspond to pulses U III ) which are used to reset a bi-stable circuit 12, the bi-stable 12 being set regularly by reference pulses U VI , Fig. 6 (e), from a source 13. Thus will switch 6 in its "C" position the meter 7 receives a succession of pulses U VII , Fig. 6 (f), whose durations correspond to the phase of that point on the waveform U I  where the waveform crosses with positive slop the level U i . By means of an additional circuit 17, 18, 19, 20 the normally open gate 9 can be closed for selected periods so that when each cycle of the waveform U I  contains a multiplicity of peaks, as in Fig. 9 (a), and therefore a multiplicity of positive going cross-overs of the level U i , the phase of a selected one of the cross-overs can be determined. With switch 18 in its position "B" circuits 17 and 19 produce a pulse Fig. 9(d) starting at the positive going zero cross-over of the waveform U I  and having a duration set by a potentiometer 20. This pulse, Fig. 9(d) is applied to the gate 9 which is closed for its duration. Thus as shown, the first two pulses Fig. 9(d) produced by circuits 4 and 8, which as described above occur at positive going cross-overs of the level U;, are inhibited, and the first pulse to pass through to set the monostable circuit 10 is the third. In this way the phase of the third positive crossover of the level U; can be determined. In a modification (Fig. 2, not shown) particularly suitable when the reference generator 13 is a rotating part of an engine, the monostable device 10 is replaced by one (22) having an adjustable (23) pulse duration and a stoboscopic lamp (21) is energized by the trailing edge of the adjustable pulse U IV . The trailing edge is then adjusted until a mark of the rotating engine part appears at a reference position and the delay necessary to achieve this is measured in order to provide a measure of the required phase. In order to refer the resulting delay to a cycle of 360 degrees, (rather than measuring it as absolute time), a speed compensating network (24, 25) is provided. Instead of measuring the delay, the rotating engine part may have a calibrated scale associated with it.