| 摘要 |
1506737 Proximity detectors DUCELLIER & CIE 26 March 1975 [3 April 1974] 12628/75 Heading G1N [Also in Division F1] A proximity detector includes a resonant circuit made up of an inductor 10 in parallel with a capacitor 11 which circuit is connected with transistor 3 to provide an oscillator, oscillations of which are halted by the passage of a conductor element 18 in front of the inductor 10. An amplifier constituted by a transistor 13 delivers an output signal, which varies between two levels as a function of the passage of the conductor, to a terminal 17 through a current limiting resistor 14. The supply for the detector is provided by a Zener diode 1, current to which is limited by a resistance 2 in series with it. Bias for the transistor 3 is supplied via resistor 7 and diodes 8, 9 through a tapping on the inductor 10. In an alternative embodiment Fig. 2 (not shown) the collector of the amplifier transistor 13A is returned to the cathode of the Zener diode through a current limiting resistance 14A. This arrangement requires only two terminals since the current limiting resistance 2 is external to the detector. A further development Fig. 3 (not shown) uses an additional transistor (19) and resistances (20, 21) to limit the base current drawn from the amplifier transistor (13B) and to provide a low output impedance. The detector may be used in an I.C. engine ignition timing circuit (see Division F1). |
