GB1280907A - Digital control calibration system - Google Patents

Abstract

1280907 Digital measurement of length GENERAL ELECTRIC CO 11 June 1970 [8 July 1969] 28405/70 Heading G4H Lengths of steel strip joined end to end are passed through a pickling bath with several lengths in the bath at a time and the difference in pulses emitted by two tachometers attached respectively to entry and exit pinch rollers indicates the total length of strip in the bath, but because of slip on the exit rollers the indication is inaccurate. The invention provides a calibration circuit which resets the indication on each strip leaving the bath. In Fig. 2 the difference in the two tachometer pulse trains drives via logic circuit 41 a counter 43 indicating the length of strip in the bath, although inaccurately. For calibration a counter 49 counts pulses from the entry tachometer and upon each fresh strip entering the bath &c. reading is shifted to register 55, and preceding stored counter shifted down by one register. A fresh strip is detected by detecting the joint between strips, at which a marker-hole is then punched and an electric signal simultaneously emitted to effect the above shifting. A photoelectric hole detector detects each strip leaving the bath and causes the successive transfer of the counter and shift register readings to a working counter 61. After each transfer, counter 61 is clocked to zero and counter 43, previously zeroed, simultaneously clocked up so it finally contains an indication of the sum of the length of strip in the tank. Counter 43 is then controlled by the tachometers until the next calibration. If the reading of counter 43 goes below a preset minimum more steel is added and less if counter 49 and shift register stages 55-57 become full as detected by AND gate 71.