Patent GB-755689-A (GB)
Title: Classification circuit
IPC: H03M1/00
Filed: 1954-06-15
Abstract: 755,689. Weigh-indicating apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. June 15, 1954 [June 19, 1953], No 17532/54. Class 40(1) [Also in Group XXXVI] A circuit for measuring electrical potential existing across a circuit element comprises first and second diodes, a coupling network common to the cathode circuits of both diodes (e.g. a resistor), a source of variable reference potential means for connecting said source in series with said element to apply the difference of their potentials to the first diode, and further means responsive to current flow through the first diode both to indicate and/or record the value of said reference potential and to influence said coupling network through said second diode so that the current flow through the said first diode is interrupted. The embodiments described measure the voltage across a capacitor in terms of a selected potentiometer tapping voltage and utilize a thyratron which fires when the selected potentiometer tapping voltage exceeds the capacitor voltage and the first diode is rendered conductive. In Fig. 1 with closure of switch S2A and S2B the difference voltage between + capacitor 10 and - capacitor C1 is impressed across diode 1A, 1C via common cathode resistor 12; also relays R1-R6 successively operate and change over in sequence synchronized stepping switches 30 and 31 i.e. relay contacts R1A-R6A and R1B-R6B. The stepping switch 30 is connected to tap-. pings on potentiometer 32 and successively decreases the negative potential on C1 until diode 1A, 1C is rendered conductive and when this occurs resistor 12 feeds through RC coupled amplifier 40 and fires thyraton 3 whereupon the later delivers a voltage into stepping switch 31 so that relay RR operates to stop the stepping switches 30, 31 and the appropriate lamp L2-L7 lights up and the corresponding print magnet actuates a printing mechanism to make a record peculiar to the selected potentiometer tapping. It is also arranged that when the thyraton fires the voltage drop across resistor 12 increases via the now conductive second diode 1B, 1D and cuts off the first diode 1A, 1C; also when RR operates the switch S2A, S2B opens automatically. Before further use of the circuit swith S3 is momentarily opened to extinguish thyraton 3 and de-energize the previously selected lamp and print magnet. In a second embodiment, Fig. 2, a D.C. source N is inserted between double diode 1A-1D cathode load comprising resistor 1H in parallel with crystal diode D and resistor 1L in series. In Fig. 2 the second diode 1B, 1D is normally conductive and when S2A, B is closed increments of positive potential from potentiometer 32A are delivered by stepping switch 30 to diode 1A, 1C and when this diode conducts a positive pulse from cathode load junction 52A amplified at 40 fires thyraton 3 so that via crystal diode D the potential at junction 52A rises and cuts-off diode 1A, 1C. The voltage across capacitor 10 may be related to the weight of a motor vehicle or the axles thereof so that the circuits shown may be used for classifying motor vehicles or axles thereof into various weight groups.