Proximity switch with continuously operable test circuit responsive to bipolar double pulses
First Claim
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1. A self-testing proximity switch comprising an oscillator for generating an oscillating signal wherein the proximity of an object causes a damping of the amplitude of said oscillating signal;
- a demodulator coupled to said oscillator and responsive to said oscillating signal for providing a demodulated signal having a value indicating the amplitude of said oscillating signal;
a trigger stage coupled to said demodulator and providing a trigger output of the proximity switch and assumming one of two switching states in response to the value of said demodulated signal exceeding a higher threshold and assuming the other of said switching states in response to the value of said demodulated signal falling below a lower threshold;
a clocked test pulse source which feeds test pulses to said oscillator, said test pulses having positive and negative amplitudes sufficient to cause said trigger stage to toggle temporarily from either one of said switching states to the other of said states for the duration of a respective polarity of said test pulses and then return to the previous state; and
a test circuit coupled to said trigger stage and responsive to the toggling of said trigger stage caused by said test pulses and providing a test output signal for indicating any absence of said toggling to thereby signal a malfunction of said proximity switch;
wherein said oscillator operates in an analog manner with an oscillation amplitude that is continuously variable in response to said dampening, andsaid test pulses are bipolar double pulses which are combined with the supply voltage and/or supply current fed to said oscillator to modulate said amplitude of oscillation in response to said bipolar double pulses, said test pulses having no substantial affect on the internal operating parameters of said oscillator.
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20 Claims
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1. A self-testing proximity switch comprising an oscillator for generating an oscillating signal wherein the proximity of an object causes a damping of the amplitude of said oscillating signal;
- a demodulator coupled to said oscillator and responsive to said oscillating signal for providing a demodulated signal having a value indicating the amplitude of said oscillating signal;
a trigger stage coupled to said demodulator and providing a trigger output of the proximity switch and assumming one of two switching states in response to the value of said demodulated signal exceeding a higher threshold and assuming the other of said switching states in response to the value of said demodulated signal falling below a lower threshold;
a clocked test pulse source which feeds test pulses to said oscillator, said test pulses having positive and negative amplitudes sufficient to cause said trigger stage to toggle temporarily from either one of said switching states to the other of said states for the duration of a respective polarity of said test pulses and then return to the previous state; and
a test circuit coupled to said trigger stage and responsive to the toggling of said trigger stage caused by said test pulses and providing a test output signal for indicating any absence of said toggling to thereby signal a malfunction of said proximity switch;wherein said oscillator operates in an analog manner with an oscillation amplitude that is continuously variable in response to said dampening, and said test pulses are bipolar double pulses which are combined with the supply voltage and/or supply current fed to said oscillator to modulate said amplitude of oscillation in response to said bipolar double pulses, said test pulses having no substantial affect on the internal operating parameters of said oscillator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- a demodulator coupled to said oscillator and responsive to said oscillating signal for providing a demodulated signal having a value indicating the amplitude of said oscillating signal;
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16. A self-testing proximity switch comprising an oscillator for generating an oscillating signal wherein the proximity of an object causes a damping of the amplitude of said oscillating signal;
- and demodulator coupled to said oscillator and responsive to said oscillating signal for providing a demodulated signal having a value indicating the amplitude of said oscillating signal;
a trigger stage coupled to said demodulator and providing a trigger output of the proximity switch and assumming one of two switching states in response to the value of said demodulated signal exceeding a higher threshold and assuming the other of said switching states in response to the value of said demodulated signal falling below a lower threshold;
a clocked test pulse source which feeds test pulses to said oscillator, said test pulses having positive and negative amplitudes sufficient to cause said trigger stage to toggle temporarily from either one of said switching states to the other of said states for the duration of a respective polarity of said test pulses and then return to the initial state; and
a test circuit coupled to said trigger stage and responsive to the toggling of said trigger stage caused by said test pulses and providing a test output signal for indicating any absence of said toggling to thereby signal a malfunction of said proximity switch;wherein said oscillator operates in an analog manner with an oscillation amplitude that is continuously variable in response to said damping, said test pulses are in the form of bipolar double pulses, said oscillator has an input terminal for combining the test pulses with the supply voltage and/or current fed to said oscillator for modulating the amplitude of oscillation in an analog manner such that the amplitude of oscillation is also continuously variable in response to a signal at said input terminal, and said bipolar double pulses are fed to said input terminal so that said amplitude of oscillation is modulated in an analog manner by said test pulses, said test pulses having no substantial affect on the internal operating parameters of said oscillator. - View Dependent Claims (17, 18, 19, 20)
- and demodulator coupled to said oscillator and responsive to said oscillating signal for providing a demodulated signal having a value indicating the amplitude of said oscillating signal;
Specification