Patent GB-1011874-A (GB)
Title: Improvements in or relating to devices for the measurement of transistory values
Inventor: MOULIN JEAN
IPC: G01G3/142
Filed: 1962-06-19
Abstract: 1,011,874. Voltage measurement; measuring weight electrically. MATISA MATERIEL INDUSTRIEL S.A. June 19, 1962, No. 23601/62. Headings G1N and G1U. Apparatus measuring a main transitory variable value on which is superposed oscillations of mean frequency within a known range, comprising transducers adapted to transform the disturbed value into two initial and identical analog signals; means for passing such analog signals separately into identical first and second low pass filters; means for passing the attenuated signals from the first and second low pass filters to a single integrator adapted to integrate the combined attenuated signals for a period equal to the lowest period of oscillation of the said superimposed oscillation; signal delay means whereby the entry of the first analogue signal to the first low pass filter is delayed with respect to the entry of the second analogue signal to the second low pass filter by an interval equal to approximately 1/3 of the integration period, and indicating means measuring the emergent signal from the integrator. In Fig. 2, a platform 14 having parallel rails 15 is carried by supports 10 to 13 mounted with strain gauges 6a, 6b to 9a, 9b connected in corresponding Wheatstone bridges 16a, 16b to 19a, 19b Fig. 3 in series groups of four to develop signals 2, 3 at junction box 20. Fig. 4 shows an operational cycle for the apparatus in which to represents the start of first signal 2; t<SP>1</SP> 0  the start of the second signal 3; t 1 , t 2  the start and end of the integration of the first signal; t 1 <SP>1</SP>, t 2 <SP>1</SP> the start and end of the integration of the second signal; t 3  the end of the reading operation. Then t<SP>1</SP> - t<SP>1</SP> 0  = t<SP>1</SP> 1  -t 1  = t<SP>1</SP> 2  - t 2  = T the time lag between signals 2, 3 emergent from the signal delay means. Two signal delay means are arranged Fig. 6 as four parallel paths 21 to 24 in which path 21 comprises a flip flop circuit 25 followed by bistable multivibrator operating relay 27 with contacts 27a, 27b. Path 22 comprises a flip-flop circuit! 28 and a succeeding flip flop circuit 29 of which one side energizes voltmeter 54 (not shown) and the other operates relay 31 with contacts 31a, 31b. Path 23 comprises first flip-flop circuit 32 second flip-flop circuit 33, and bi-stable multiplier 34 operating relay 35 having contacts 35a. Path 24 comprises first flip-flop circuit 36, and second flip-flop circuit 37 of which one side is connected to oscillator 45 and the other bi-stable multivibrator 35 operating relay 39 having contacts 39a, 39b, 39c. Signals 2, 3 from Fig. 3 traverse normally open contacts 27a, 31a to low pass filters 40, 41; the outputs 43 passing over normally open contacts 35a to form output 42 and pass over normally open contact 39a to output 44, which is normally shunted to earth over series contacts 27b, 31b. In an integrator Fig. 7) output 44 is modulated at 46 operated by oscillator 45 to a signal supplied over amplifier 48 and transformer 49 coupling to a limiter 50 and double diode accumulator 51 controlled by normally closed contact 39b followed by null balancer 52 supplying a signal over normally earthed changeover contacts 39c to voltmeter 54, counter 55, and printer 56. As the wheels and axle of a truck roll over rails 15, a shock is applied to the strain gauges, comprising the axle weight and oscillations of the truck on its springs at a frequency between f 1  and f 2 ; e.g. 5 and 10 c.p.s. so that the identical signals 2, 3 comprise a main signal representing axle weight and an oscillatory signal lying in the known range. An initial pulse 57 emitted as the wheels enter the platform determines the initial instant to which synchronises paths 21 to 24. Flip-flop 25 operates for period (t 2  - t 0 ) during which multivibrator 26 energizes relay 27 to close contacts 27a applying signal 2 to filter 40 and to open contacts 27b removing the earth shunt on signal 44. Flipflop 28 determines the idle period (t<SP>1</SP> 0  - t 0 ) and at instant t<SP>1</SP> 0  flip-flop 29 operates for period (t<SP>1</SP> 2 -t<SP>1</SP> 0 ) during which multivibrator 30 energizes relay 31 to close contacts 31a applying signal 3 to filter 41 and to open contacts 31b so as to maintain removal of the earth shunt from signal 44 after instant t 2  at which relay 27 is released to close contacts 27b. At instant t<SP>1</SP> 2  flip-flop 29 positively impulses voltmeter 54 to initiate a recording time base, and flip-flop 32 operates at instant to and lags for period (t<SP>1</SP> 1  - t 0 ) before triggering flip-flop 33 determining an interval (t<SP>1</SP> 2  - t<SP>1</SP> 1 ) during which multivibrator 34 holds relay 35 operated closing contacts 35a during integration period (t<SP>1</SP> 2 -t<SP>1</SP> 1 ). Flip-flop 36 lags for period (t 1 -t o ) and at instant t 1  triggers flip-flop 37, when multivibrator 38 operates relay 39 for period (t 3  - t 1 ) to close contacts 39a, so that signal 44 is transmitted for period (t<SP>1</SP> 2  -t 1 ). Contacts 39b, 39c correspondingly open and signal 53 is applied to voltmeter 54 for period (t 3  - t 1 ) while multivibrator 37 permits oscillator 45 to operate. Contacts 27a, 31a allow signals 2, 3 to pass to initially damped low pass filters 40, 41. Signal 42 from filter 40 is applied to the integrator Fig. 7 during period (t 2  - t 1 ) determined by contacts 39a, 27a and signal 43 from filter 41 is applied thereto during period (t<SP>1</SP> 2  - t<SP>1</SP> 1 ) determined by contacts 35a, so that the combined signal 44 is applied to the integrator during period t 1  to t<SP>1</SP> 2 .  From instant t 1  to instant t 3  oscillator 45 is operative to amplitude modulate signal 44, and the positive excursions thereof from transformer 49 are limited at 50 by a diode polarized to voltage 50, and applied to double diode accumulator 51 capacitance summing the successive excursions and applying the sum voltage at low impedance to stage 52 utilizing a stabilized voltage to compensate for the standing zero level; the resultant direct voltage 53 representing the weight of the truck axle. At instant t<SP>1</SP> 2  the input of interruptor 46 is short circuited, and the summation charge on accumulator 51 ceases to increase until instant t 3 , when contacts 39b close to discharge the accumulator capacitance. At intent t<SP>1</SP> 2  a positive pulse derived from inversion of flip-flop 29 triggers the voltmeter 54 to indicate the stored voltage during interval (t 3  - t<SP>1</SP> 2 ). Photo-cell 58 obturated during the passage of each truck and illuminated thereafter triggers storage counter 55 to add the weights of successive axles and record the total truck weight on printer 56. At instant t<SP>1</SP> 2  contacts 31b close in series with contacts 27b already closed since instant t 2 , to earth the integrator input, which receives a signal 44 from instant t 1  to instant t<SP>1</SP> 2  comprising signal 42 from t 1  to t<SP>1</SP> 1 ; signals 42 and 43 from t<SP>1</SP> 1  to t 2 ; and signal 43 from t 2  to t<SP>1</SP> 2 ; the duration of the integration periods (t 2  - t 1 ) and (t<SP>1</SP> 2  - t<SP>1</SP> 1 ) being selected to approximate to the minimum frequency of the interference oscillation, while the interval between application of signals 42 and 43 is selected to be 1/ 3  (t 2  -t 1 ) (Fig. 5 not shown). The apparatus may be applied to measure pressure, temperature, fluid flow by use of appropriate transducers, or electric voltage or current; while mechanical or pneumatic delay means, lowpass filters, relays, and integrators are stated to be capable of replacing the electrical devices described.