Patent GB-907840-A (GB)
Title: Improvements in or relating to the recording of variable quantities
Inventor: GILBERT REGINALD LESLIE GLEABE
IPC: H03M7/12
Filed: 1959-04-08
Abstract: 907,840. Electric selective signalling systems. BRITISH TELECOMMUNICATIONS RESEARCH Ltd., and MARCONI INSTRUMENTS Ltd. July 4, 1960 [April 8, 1959], No. 11886/59. Class 40 (1). In a data recording and monitoring arrangement for recording at suitable intervals variable values of data derived from a plurality of stations and comparing them with predetermined values and checking that the rate of change of the values of the data does not exceed a predetermined value, readings of the data concerned are recorded at predetermined intervals for all the stations in turn on a register of the magnetic drum type, the position on the drum on which recording is to take place being determined by a marking in a separate control track which is automatically moved to a different position after each recording has been completed so as to determine the position of the succeeding recording. In the embodiment described 600 thermo-couples are successive sampled at a rate of five every second and each reading is stored on a magnetic drum from where it is read by an arithmetic unit and compared with a prestored upper value for that thermo-couple. Each reading is also subtracted from the corresponding previous reading for that thermo-couple and compared with prestored upper and lower values for the rate of change of that thermo-couple. If any of these three limits is exceeded an alarm is given. The drum store has sufficient capacity for 10 readings of each of the two thermo-couples and the contents of the drum are continuously being read out to a printer. A further printer, an " on demand " printer is also provided to which data can be directed from any selected position on the drum. The 600 thermo-couples (Fig. 2, not shown), are scanned by a rotary switch and each produces an amplitude significant voltage. This amplitude is converted into a corresponding pure binary eleven bit number and recorded on the drum. In further revolutions of the drum this number, together with the previous reading obtained from the thermo-couple first sensed and the reference values referred to above, are read from the drum and passed to an arithmetic unit where the necessary comparisons are made, the recording on and reading from the drum being controlled by a pulse from a marker track on the drum, this pulse being precessed one position each time the scanning switch advances. The data transmitted to the arithmetic unit is also recoded to a binarvcoded-decimal form and passed to a store for printing. Analogue-to-digital converter.-An unknown voltage from a thermo-couple via contacts RR1, RR2, Fig. 9, is repeatedly compared, across a resistance R, with a voltage produced by binary weighted resistors R1, R2 ... R11. Transistor switches TR1, TR2 . . . TR11 are successive turned-on and each one step on unless the voltage so produced is larger than the unknown voltage when it is immediately turned off again. Non-linearity of the thermo-couple characteristic is compensated for by a transistor TRO which saturates when the thermo-couple voltage corresponds to about 330‹ C., which causes the response curve of the digitiser to be as shown in Fig. 10. Binary to binary-coded-decimal converter.- The result of the analogue-to-digital conversion is stored, in pure binary form, in a register of flip-flops. This is converted to a binary-codeddecimal form by counting the register down to zero and simultaneously counting up a binarycoded-decimal counter. Magnetic drum.-Each single scan of the 600 thermo-couples is stored in a set of three tracks, Fig. 1, each track storing 200 readings. The drum contains 10 such sets of three tracks and since each complete scan of the 600 thermocouples takes 2 minutes the drum holds data relating to the previous 20 minutes. The drum also holds, on further sets of tracks, the prestored maximum values.