Patent GB-853139-A (GB)
Title: Improvements in or relating to electric analog computing systems
IPC: G06G7/20
Filed: 1958-04-22
Abstract: 853,139. Electric analog calculating systems; potentiometric voltage measurement. INDUSTRIAL NUCLEONICS CORPORATION. April 22, 1958 [July 1, 1957]. No. 12778/58. Class 37 Theory. The statistical variance (#<SP>2</SP>) of a large number of individual measurements may be computed from the formula wherein # = standard deviation X = value of an individual measurement N = the number of individual measurements which is represented by wherein T=time analogous to N e = instantaneous values of electrical signals analogous to successive values of X Construction. Electric analogue apparatus for computing variance # comprises an input 10, 12 receiving successive individual signals, representing corresponding characteristics to be statistically analysed, derived e.g. from apparatus gauging successive articles in flow production for instantaneous deviations from a standard value, which are applied to a feedback operational amplifier 58 over normally open relay contact 54a, resistor 52, resistor 252 and contact 1 of switch 248, which is otherwise operative to earth and input over contact 2. The amplifier input may be biased from potentiometer 236 energized from a negative source, while a calibration voltage is connected to the junction of resistors 52, 252 from the slider of potentiometer 244 varied by knob 254 and excited from positive or negative sources selectable by switch 246, through variable resistor 242. The amplifier 58 output is connectible over normally open relay contacts 54d, potential divider 70, 72, and switch 74 in position 1 to an integrator 18 having amplifier 76 in shunt with capacitance 80, and normally open resetting relay contacts 88a in series with: resistor 86; the integrated output being connected over normally closed relay contacts 54e to the input of a phase sense converter 20; alternatively fed directly from amplifier 58 over normally open relay contacts 54c; wherein a positive going signal passes directly over halfwave rectifier 90 to output while a negative going signal is phase reversed by amplifier 94 to a positive going signal fed to output over halfwave rectifier 92. The combined output feeds a squaring circuit 22 wherein plural halfwave rectifiers 126, 127, 128, 130 are connected in series with corresponding resistors 118, 120, 122, 124 to the input of amplifier 108 and to the respective sliders of potentiometers 132, 134, 136, 138 series energized from a negative source over variable resistor 141; the amplifier input being directly connected to output 106 over resistance 116. The squared output may be connected over normally open relay contacts 54f to the input of integrator 24 comprising amplifier 50 with a shunting capacitance 150 and resistor 156 in series with normally open resetting relay contacts 88b feeding voltage divider 158, 160; the slider of the latter being connected over summation resistor 164 to line 166, or alternatively over normally closed relay contacts 54g to voltage divider 142, 144; the slider of the latter being also connected over summation resistor 162.to line 166, which is returned over normally closed relay contacts 54b to the input of amplifier 58 whose output also appears across resistance 64 and potentiometer 66; the junction of which is connected over normally , open contacts 190d to one input of a servosystem recorder 30 which is returned to earth over series normally closed relay contacts 196a, 190c; the slider of 66 being returned to the contact junction over normally open contacts 196b. The remaining servosystem input is derived from the slider of potentiometer 184 in series with resistors 186, 188, across a D.C. source also shunted by resistor 182 in series with potentiometers .178, 180; the slider of the former being earthed over normally open relay contacts 190a and that of the latter over normally closed contacts 190b. The combined control signal is cyclically interrupted by A.C. driven chopper 194 to excite biphase motor winding 202 whose reference winding 204 is excited from the A.C. feed to adjust potentiometer 184 to zeroise the input and deflect indicator 206 of recorder 170 laterally of its chart. Successive cycles are controlled by motor 210, A.C. energized over switch 218 to continuously drive cams 212, 214 cut to respectively open and close snap action switches 217, 216 in that order. Relays 196, 190 are respectively de-energized and energized to correspondingly de-energize relay 54 at normally closed contact 190e, and to de-energize relay 88 at normally closed contact 190f in series with normally closed contact 196c. which is opened when relay 196 is energized; relays 54, 88 being supplied from rectifier 222. Other contacts of relays 54, 88, 190, 196 are correspondingly operated. Operation. Initially, motor 210 is de-energized by switch 218 with cams 212, 214 in positions shown for energization of relay 196 and deenergization of 190. Relay 54 is energized and relay 88 is de-energised so that contacts 54a, 54c, 54d, 54f are closed and 54, e.g. are open. Switch 248 is in position 2 and the input to amplifier 58 is zeroised by dial 254 and potentiometer 244. Potentiometer 236 is adjusted to zeroise the output of amplifier 58. Potentiometer. 141 is adjusted for an arbitrary voltage to appear across potentiometers 132 to 138 and by adjustment of potentiometer 244 known voltages are applicable to the squaring circuit whereby potentiometers 132 to 138 are adjustable in turn to obtain accurately squared outputs at point 112. Potentiometers 178, 180 are then set to define zero positions for recording the input error signal and the required variance thereof, and an input error signal is applied to terminal 10 representing a known percentage deviation of the measured characteristic from a predetermined level. Switch 248 is placed in position 1, potentiometer 244 is zeroised and the amplified signal appears across resistance 64 and potentiometer 66, the slider of the latter being connected to the recording servosystem 30 over closed contacts 196b and 190c, whereby the potentiometer is adjustable for a given range of recorded deviation signals, which is calibrated by reference to potentiometer 244 and a valve voltmeter at point 50 with switch 248 in position 2. In calibration for variance, the switch 74 is then opened to disable the integrator so that the second RHS term of equation (2) above is zeroised, and a known signal is set in from potentiometer 244. The timing motor is started and switch 217 closes to energize relay 190; relay 196 remaining energized so that relays 54, 88 are de-energized. Switch 216 opens and de-energizes relay 196, while shortly after, relay 190 is de-energized. Relays 54, 98 are energized, and the recorder input is earthed together with the arm of potentiometer 180 over contacts 190b, 190c, 196a. The servomotor drives arm of potentiometer 184, to its centre, and integrators 18, 24 are reset by closure of contacts 88a,. 88b. Cam 212 closes switch 216 energizing relay 196 and the recorder input is released and connected to the slider of potentiometer 66, while relay 88 is de-energized. Relay 190 is next de-energized so that the slider of potentiometer 180 is connected to ground. The deviation signal is amplified at 58 and recorded in instrument 170 while the amplified. signal is squared and integrated at 22, 24, integrator 18 being disabled by open switch 74. At the end of the integration cycle, cam 214 closes switch 217 to energize relay 190, and ground is transferred from slider of potentiometer 180 to that of 178. The input of the recorder is transferred to the resistance 64 while relay 54 is de-energized and relay 88 is held de-energized. Contacts 54a are now open, removing input signals from amplifier 58 now connected to line 166, while the amplifier output is disconnected from the input of converter 20 which is connected to output of integrator 18 (disabled by switch 74), The input is disconnected from integrator 24 while the output of the squaring circuit is connected across potential divider 142, 144, across which there is no voltage output, so that the second term of equation - (2) above is zero. A voltage from integrator 24 across potential divider 158, 160 is proportional to the square of the deviation voltage during the integrating cycle, and the constant 1 is adjusted T by the slider of 160 so that line 166 acquires a, voltage representing the first term of equation (2), fed back to amplifier 58 to produce the appropriate recorded indication. On a successive integrating cycle, switch 74 is closed, and integrater 18 operates, so that the voltage across potentiometer 144 is proportional to the second term of equation (2) above, and the slider of potentiometer 144 is adjusted to represent 1/T for equality with the third term of give zero variance induction. After calibration, potentiometer 244 is zeroised, switch 248 is in position 1 and an input signal is applied to terminal 10, 12 from a measuring device. Motor 210 is energized, over switch 218, at a point of the cycle at which relays 190, 196 are de-energized and 54, 88 are energized. The input signal is thus amplified but not recorded since the servosystem input 192 is grounded together with the slider of potentiometer 180. A moving pen records. straight line 264 at instrument 170 and contacts 88a, 88b reset integrators 18, 24. Cam 212 closes switch 216 energizing relay 196 whose contacts 196c de-energize relay 88, releasing the integrators. Contacts 196a, 196b release the recorder input 192 and connect it to the slider of potentiometer 66, so that a voltage e representing the value of the input characteristic is recorded at instrument 170, and voltages representing fedt, e2 and fe<SP>2</SP>dt are developed at points 82, 112 and 262. Cam 214 closes switch 217 to energize relay 190 to release the slider of potentiometer 180 and ground the slider of potentiometer 178. The recorder input is transferred from the