Patent GB-1482406-A (GB)
Title: Digital calculating apparatus
IPC: G06F7/552
Filed: 1973-07-31
Abstract: 1482406 Digital calculator SOLARTON ELECTRONIC GROUP Ltd 29 July 1974 [31 July 1973] 36325/73 Heading G4A The system described is similar to that of Specification 1,321,067 except that only one register and recirculation loop are provided, the simultaneous adding (or subtracting )cycles of the earlier Specification being performed sequentially in the single register and circulation loop. The register may be a shift register, serial by BCD digit, parallel by bit or a suitable random access store and as described the system is used to linearize the (digital) output from a non-linear transducer (e.g. a thermocouple) by evaluating polynomial equations. To reduce the degree of the polynomials used the (temperature) range is split into two and the coefficients of respective third order polynomials and the range break point are stored in two sections of an R.O.M. 50. In operation the digital output x of the thermocouple is loaded in register 24 and the range break point S (from R.O.M. 50) is subtracted to determine the range (using a sign bit in stage 24h). S is then added to the contents of register 24 to reinstate x. The value x is then normalized so as to lie between 0À1 tand 1À0 and the contents of register 24 are recirculated to generate by exponential progression a value of "1". In this operation x is circulated via inputs 30a and 36 and added to itself until it is greater than one, the number of addition cycles being counted at 77 n 0  and stored in stage 74a. Further circulations via input 30b are then performed to subtract one tenth of the contents of register 24 from itself until the result is below "one", the number of subtractions n 1  being stored in stage 74b. The process is repeated until all stages 74a-74e contain counts n 0 -n 4  and the contents of register 24 are #1. The contents of register 24 (initially #1) are then added and subtracted in a manner similar to that described above using the count values n 0 -n 4  which are read from store 74 (non-destructively) into counter 77 which is decremented as the additions (or subtractions) are performed. As a result register 24 contains l/x = Y. The number Y is then changed to 1 by exponential progression as above generating counts n 0 '-n 4 ' which overwrite the values n 0 -n 4  in register 74. The polynomial for temperature in terms of x is of the general form which may be rewritten This latter equation is then evaluated by clearing register 24 and reading a 3  from R.O.M. 50 into the cleared register. The stored value is then added to 1/10i of itself under the control of counts n i  (i = 0, 1, 2, 3, 4) to generate a 3 /Y. The value a 2  is then added in and the contents added to 1/ 10 i of themselves under the control of the counts n i  to generate (a 3 /Y + a 2 ).1/Y. The procedure is repeated until a 0  is added when the contents of register 24 represent T. As described above each addition (or subtration) represented by a unit count n i  and n i ' (i = 0, 1, 2, 3,4) is a single addition (or subtraction). However in general terms the number of additions (or subtractions) performed is given by n i .N and n i .M where N=1, 2, 3 ... and M#N. For example if N = 2 and M = 1 square rooting may be performed as described in Specification No. 1,321,067. The R.O.M. 50 can also contain values such as log 10 2; log 10 0À9; log 10 1À01 to enable the circulation loop to perform linear progressions (Specification 1,321,067 and the R.O.M. 50 may be replaced by other means such as a paper tape reader or manual switches. The whole system is controlled by a programmed R.O.M. 90 addressed by an advancing counter 92. Although special purpose hardware is described it is stated that the arrangement could be embodied in a suitably programmed computer.