| 摘要 |
1286262 Measuring temperature electrically A E ELECTRONICS Ltd 29 Aug 1969 [30 Aug 1968] 41569/68 Heading G1N [Also in Division G4] Capacitors 39, 40, Fig.1, discharged to produce an output pulse to counter 55A by a unijunction transistor 43 each time the charge reaches a predetermined level are charged at a rate dependent on the temperature of a material in which a probe 26 is in contact. If the material is concrete or plastics the count represents its maturity. The detector 26 is preferably a thermistor and is positioned in a bridge circuit 26, 27, 28, 29, 30, 31, the resistor 31 being used to balance the bridge. The bridge output is applied to an operational amplifier circuit 38 so that the capacitors 39, 40 in the base circuit of the unijunction transistor 43 of a relaxation oscillator are charged and discharged. The switching point for transistor 43 is selected by variable resistor 44. The discharge pulse train is fed via a two-stage amplifier to the counter 55A. |
