Piezo electric accelerometer pulse testing

Claim 3

A method according to claim 1, in which the response or non-response of the transducer is detected by comparing the strength of the transducer response signal to said predetermined magnitude, wherein said detecting steps comprise: generating at least one signal a if the strength of the transducer response signal exceeds the required signal strength, generating at least one further signal b if the number of signals a exceeds a first predetermined number, and generating said first signal if the number of signals b exceeds a second predetermined number, said first signal thereby being indicative of the operational status of the piezoelectric transducer.

Claim 4

A method according to claim 2 in which the transducer response signal is amplified before comparison is made with the predetermined magnitude.

Claim 5

A method according to claim 2 in which said first signal is used to operate indicator means, whereby the operational status of the transducer is indicated.

Claim 8

A method according to claim 5 in which said first and second switches are operatively linked to an oscillator in such a manner that the oscillator output controls said switches, said switches respectively being closed and opened once during each cycle of oscillation, said first switch thereby applying a repeating voltage pulse to the piezoelectric transducer.

Claim 9

A method according to claim 6, in which said oscillator is a voltage controlled oscillator, said oscillator having its output frequency controlled by means of a voltage ramp input to said oscillator, said voltage ramp input being repeated at regular intervals of time.

Claim 10

A method according to claim 6, in which the signal from the oscillator is passed to a pulse shaper before being transmitted to said first and second switches, said pulse shaper producing a pulse of constant width which is then passed direct to said switches to control their opening and closing.

Claim 11

A method according to claim 5, wherein signal detecting means performs the functions of: comparing the strength of signals from the piezoelectric transducer to a required signal strength corresponding to said predetermined level, generating at least one signal a if the strength of the signal from the transducer exceeds the required signal strength, generating at least one further signal b if the number of signals a exceeds a first predetermined number, and generating a one of said discrete signals if the number of further signals b exceeds a second predetermined number, said one discrete signal being indicative of the operational status of the piezoelectric transducer.

Claim 12

A method according to claim 9, in which the signal from the piezoelectric transducer is amplified before comparison is made with the required signal strength.

Claim 13

A method according to claim 9, in which generation of said further signal b is performed by a first counter circuit element and a bistable circuit element connected in series, said counter circuit element being adapted to produce an output signal only when said first predetermined number of signals a have been exceeded, said bistable circuit element being adapted to change from a first stable state to a second stable state on receipt of said output signal and to emit said further signal b when changing from said second stable state to said first stable state.

Claim 14

A method according to claim 11, in which both said circuit elements are reset to an initial ''''no signal received'''' condition by means controlling the operation of the first, second and third switches, said circuit elements being reset at the time when said second switch is caused to open.

Claim 15

A method according to claim 9, in which generation of said one discrete signal is performed by a second counter circuit element adapted to produce said one discrete signal only when said second predetermined number of further signals b have been exceeded.

Claim 16

A method according to claim 13, in which said second counter circuit element is reset to an initial ''''no signal received'''' condition at the end of every test of the transducer.

Claim 17

A method according to claim 13, in which said oscillator is a voltage controlled oscillator, said oscillator having its output frequency controlled by means of a voltage ramp input to said oscillator, said voltage ramp input being being repeated at regular intervals of time, and in Which said second counter circuit element is reset to an initial ''''no signal received'''' condition at the end of every voltage ramp input to the voltage controlled oscillator.

Claim 18

A piezoelectric transducer testing system for indicating whether the transducer is properly connected in circuit and in an operable state, said system comprising: a voltage source means connectable across the piezoelectric transducer for applying at least one voltage pulse across the piezoelectric transducer, signal detecting means connectable to said piezoelectric transducer for detecting a resulting response from the transducer and for producing a first signal output if said response is greater than a predetermined magnitude and a second signal output if said response is less than said predetermined magnitude, control means for effectively sequentially connecting said voltage source means and said signal detecting means to said piezoelectric transducer, and signal indicator means connected to said signal detecting means for indicating a first discrete condition in response to said first signal output and a second discrete condition in response to said second signal output, whereby the operational status of said transducer is indicated.

Claim 19

A piezoelectric transducer testing system for indicating whether the transducer is properly connected in circuit and in an operable state, said system comprising: a voltage source means connectable across the piezoelectric transducer for applying at least one voltage pulse across the piezoelectric transducer, signal detecting means connectable to said piezoelectric transducer for detecting a resulting response from the transducer and for producing a first signal output if said response is greater than a predetermined magnitude and a second signal output if said response is less than said predetermined magnitude, control means for effectively sequentially connecting said voltage source means and said signal detecting means to said piezoelectric transducer, and signal indicator means connected to said signal detecting means for indicating a first discrete condition in response to said first signal output and a second discrete condition in response to said second signal output, whereby the operational status of said transducer is indicated.

Claim 20

A system according to claim 16, in which said voltage source means is connectable to the transducer by means of a first switch and said signal detecting means is connectable to the transducer by means of a second switch, said first switch being open when said second switch is closed and vice-versa.

Claim 21

A system according to claim 17, in which said first and second switches are opened and closed once per oscillation of an oscillator.

Claim 22

A system according to claim 17, in which the transducer may be short-circuited by means of a third switch connected across said transducer, said third switch being adapted to close for a short time after the first switch has opened and before the second switch is closed.

Claim 23

A system according to claim 19, in which said first, second and third switches are operable in response to signals from an oscillator, said switches being closed and opened once during each cycle of oscillation.

Claim 24

A system according to claim 16, in which said signal detecting means comprise amplifying means, signal strength comparator means, and noise inhibition means.

Claim 25

A system according to claim 21, in which comparator means compares the strength of amplified transducer signals with a required strength and produces an output signal only when said transducer signals exceed said required strength.

Claim 28

A method according to claim 23, in which a repeating voltage is applied at one or more frequencies of application, at least one of said frequencies being substantially a sub-harmonic of the resonance frequency of the piezoelectric transducer.

Claim 29

A method according to claim 24, in which the voltage pulses are applied at a frequency which varies with reSpect to time.

Claim 30

A method according to claim 23 in which a second further signal is generated only when more than a first predetermined minimum number of first further signals are generated, said indicator signal being generated only when more than a second predetermined minimum number of said second further signals are generated.

Claim 31

A method according to claim 23 in which a. first switch means is closed to apply the voltage pulse, and b. said first switch means is then opened and second switch means is closed to connect the transducer to signal detecting and noise inhibiting means which receive transducer response signals and generate the indicator signal for operation of the indicator means.

Claim 32

A method according to claim 27 in which the transducer is selectively shorted circuited by means of a third switch, said third switch being adapted to close for a short time after the first switch is opened and before the second switch is closed.

Claim 33

A method according to claim 27, in which a repeating voltage pulse is applied by the first switch means.

Claim 34

A method according to claim 29, in which the repeating voltage pulse is applied at one or more frequencies, at least one of said frequencies being substantially a subharmonic of the resonance frequency of the piezoelectric transducer.

Claim 35

A method according to claim 30, in which said repeating voltage pulse is applied at a frequency which varies with respect to time.

Claim 36

A method according to claim 31 in which both first and second switch means are controlled by the output of a voltage-controlled oscillator such that said switch means are closed and opened once during each oscillation, said oscillator having its output frequency controlled by a periodic voltage ramp input to said oscillator.

Claim 37

A method according to claim 32, in which the piezoelectric transducer is selectively short circuited by third switch means, said third switch means being adapted to close for a short time after the first switch means is opened but before the second switch means is closed, said third switch means also being controlled by the oscillator output.

Claim 38

A system according to claim 32, in which the first switch is adapted to open and close at a frequency which is substantially a sub-harmonic of the resonant frequency of the transducer.

Claim 39

A system according to claim 34, in which the first switch is adapted to open and close at a frequency which varies with respect to time, such that at least one of the frequencies so produced is substantially a sub-harmonic of the resonant frequency of the transducer.

Claim 40

A system according to claim 35, in which the first switch is opened and closed once per oscillation of a voltage controlled oscillator, the input to said oscillator being operatively connected to a voltage ramp generator, whereby the output frequency of the oscillator is varied with respect to time.

Claim 41

Apparatus for testing the integrity of a piezoelectric transducer, comprising: a voltage source connectable across the transducer by first switch means, transducer response detecting means and electrical noise inhibition means connectable across said transducer by second switch means said first switch means, and indicator means responsive to an indicator signal generated by said detecting and inhibition means, said detecting and inhibition means comprising: a. signal strength comparator means in which the strength of the transducer response signals are compared to a minimum required signal strength and a further signal is generated only when the strength of said response signal exceeds said minimum strength, and b. signal counting means adapted to generate said indicator signal only when more than a predetermined minimum number of said further signals are generated, said indicator signal being indicative of the integrity of said transducer.

Claim 42

Apparatus for testing the integrity of a piezoelectric transducer, comprising: a voltage source connectable across the transducer by first switch means, transducer response detecting means and electrical noise inhibition means connectable across said transducer by second switch means said first switch means, and indicator means responsive to an indicator signal generated by said detecting and inhibition means, said detecting and inhibition means comprising: a. signal strength comparator means in which the strength of the transducer response signals are compared to a minimum required signal strength and a further signal is generated only when the strength of said response signal exceeds said minimum strength, and b. signal counting means adapted to generate said indicator signal only when more than a predetermined minimum number of said further signals are generated, said indicator signal being indicative of the integrity of said transducer.

Claim 43

A system according to claim 37, in which said comparator means comprises a zero crossing detector.

Claim 44

ApparatuS according to claim 37 in which a second further signal is generated only when more than a first predetermined minimum number of first further signals are generated, said indicator signal being generated only when more than a second predetermined minimum number of said second further signals are generated.

Claim 45

A system according to claim 39, in which said signal counting means comprises: a first counter circuit element adapted to receive signals from said comparator means and to emit an output signal only if a predetermined number of signals are received from said comparator means, a bistable circuit element adapted to receive signals from said first counter and to retain a first state if no signal is received, but to assume a second state if such a signal is received, said bistable circuit element being adapted to emit a signal when changing from said second state to said first state, and a second counter circuit element adapted to receive signals from said bistable circuit element and to emit an output signal only if a predetermined number of signals are received from said bistable circuit element.

Claim 46

A system according to claim 40, in which said first and second counter circuit elements and said bistable circuit element are periodically reset to their initial ''''no signal received'''' condition, said first counter circuit element and said bistable circuit element being reset at every oscillation of an oscillator, said oscillator also controlling the first and second switch means such that both said respective switch means open and close in turn once per oscillation of the oscillator, said circuit elements being reset when said second switch is opened.

Claim 47

A system according to claim 41, in which said oscillator is a voltage controlled oscillator having a voltage ramp input, repeated at regular intervals, said second counter circuit being reset at the end of each voltage ramp.

Claim 48

A system according to claim 40 in which said circuit elements can be manually reset to their initial ''''no signal received'''' condition.

Claim 49

A system according to claim 37, in which said indicator means is a three-way indicator whereby the opertional status of the transducer is indicated, said three-way indicator having: a ''''no-signal'''' position indicating that the transducer has failed or is not in circuit, a ''''signal'''' position indicating that the transducer is operating satisfactorily, and a ''''neutral'''' position indicating that the indicator itself is working.

Claim 50

A system according to claim 44, in which said three-way indicator is a meter for indicating an electrical quantity.

Claim 51

Apparatus according to claim 37 in which said first and second switches are operatively linked to an oscillator such that the oscillator output controls said switches, said switches respectively being closed and opened once during each cycle of oscillation, said first switch being open when said second switch is closed and vice-versa.

Claim 52

A system according to claim 46, including a pulse shaper and in which the output from the oscillator is first passed to the pulse-shaper which produces pulses of constant width which are then passed direct to said switches to control their opening and closing.

Claim 53

Apparatus according to claim 46 in which the oscillator is a voltage controlled oscillator, said oscillator having its output frequency controlled by means of a periodic voltage ramp input.

Claim 54

Apparatus according to claim 46 in which a third switch is adapted to short-circuit the transducer by closing for a short time after the first switch has opened and before the second switch is closed, said third switch also being operatively linked to the oscillator.