Patent GB-1069698-A (GB)
Title: An electrical calculating device
Inventor: TAIT DAVID ADAMS GILMOUR
IPC: G06G7/18
Filed: 1964-09-04
Abstract: 1,069,698. Electric analogue calculating. SOLARTRON ELECTRONIC GROUP Ltd. Aug. 23, 1965 [Sept. 4, 1964], No. 36364/64. Heading G4G. In apparatus for calculating the mean value of a function represented by a series of discrete analogue currents, the mean values of the derivatives of the function, and the standard mean deviations of these variables, a patchboard 10 comprises ten conductors 12 energized from A.C. transformer 16 with E.M.F.'s representing digital values 1 to 10, which are traversed by 25 groups 1 to 25, each of three conductors 18, 19, 20 corresponding to tenths, units and tens of respective analogue point values, and connectible as required to conductors 12. Conductors 18, 19, 20 of each group are connected over weight resistors 22, 23, 24 of values 100R, 10R, R to a summation junction 26 which receives a current representing the analogue value set upon each group. Alternatively, a switch matrix or digital to analogue converter may be used. The 25 junctions 26 are connectible over switches S1 to S25 (operative to disconnect redundant junctions and earth corresponding contacts) to contacts 28 of a 25 position commutator 30 whose wiper is connected to phase sensitive mean value meter 34 incorporating a synchronous rectifier in its input which is switchable out for mean modulus and RMS measurement. A multiturn inductive potentiometer 38 excited from the input of transformer 38 supplies an adjustable current to the meter through resistor Ao and conversion amplifier 36, and it is shown (Fig. 2, not shown) that if each commutator current flows for the full duration of its commutation cycle and the meter response time is of the same order of magnitude as the commutation period, and if potentiometer 38 is adjusted for minimum meter reading, the latter reads the mean deviation of the function represented by successive analogue currents. A second inductive potentiometer 40 energized in parallel with 38 has its wiper connected through a series of resistors B1 to B25 graduated in arithmetical progression, to the respective summing junctions 26, and through a resistor Bo to amplifier 36. If the meter is switched to read R.M.S. and potentiometer 40 is adjusted to-minimize the meter reading, the mean value of the first derivative of the function represented by successive analogue currents is indicated by the current in resistor Bo. A third inductive potentiometer 42 energized in parallel with 40 has its wiper connected through a series of resistors C1 to C25 graduated so that their first differences are in arithmetical progression to the respective summary junctions 26, and through a resistor Co to amplifier 36. The current Im to summary junction m is made equal to k(m-¢p)<SP>2</SP>, where p is the total number of junctions, and potentiometer 42 is adjusted to minimize the meter R.M.S. reading, and the current in Co denotes the mean second derivative of the function represented by the successive analogue currents. If potentiometer 38 is adjusted for minimum mean current and meter 34 is switched to read mean modulus or R.M.S., its reading represents mean deviation or standard deviation of the function. If then potentiometer 40 is adjusted for minimum meter reading, the latter represents the mean derivative, while if potentiometer 42 is adjusted for minimum meter reading, the latter represents the mean deviation or standard deviation of the second derivative. In a modification (Fig. 3, not shown) switches S1 to S25 are replaced by three position switches whose additional contacts are taken to a second commutator whose wiper is also connected to the amplifier input, whereby negative point values of the function may be set in. The potentiometers 38, 40, 42 are replaced by phase balanced transformers with tapped secondaries connected as before to resistors Ao, Bo, Co while the commutators comprise rings of reed relays energized sequentially by a magnet rotatable by a synchronous motor. Switches in the commutator outputs operated from supply frequency control the effective time of connection to each contact. The potentiometers may be automatically adjustable in a programmed sequence in response to servosystems responsive to the meter readings, so as to minimize the latter. Resistive potentiometers may replace inductive potentiometers, and the apparatus may operate on direct current or a random noise signal.