PIEZOELECTRIC OR ELECTRET SENSING DEVICE

• US 20150301105A1
• Filed: 10/16/2013
• Published: 10/22/2015
• Est. Priority Date: 10/29/2012
• Status: Active Grant

• Current Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Original Assignee: IEE International Electronics & Engineering SA (Aerospace Hi-Tech Holding Group Company Limited)
• Inventors: Lamesch, Laurent
• Granted Patent: US 9,678,144 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60R 25/00 Fittings or systems for preventing or indicating unauthorised use or theft of vehicles locks for vehicles E05B77/00-E05B85/00
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01R 29/22 Measuring piezoelectric properties
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H10N 30/302 Sensors

Abstract

A piezoelectric and/or electret sensing device (10) comprises a piezoelectric and/or electret transducer (12) for producing a measurement current in response to mechanical stimulus, and a control and evaluation circuit connected to the transducer. The control and evaluation circuit (14, 24, 26, 28, 30) comprises a transimpedance amplifier (14) having a first and a second input, the transducer being operatively connected between the first input and a reference node, and an electrical waveform generator (22) for generating an electrical waveform, the electrical waveform generator being operatively connected between the second input and the reference node. The transimpedance amplifier controls the first input such that the difference in electric potential between the first input and the second input be cancelled and outputs an output voltage indicative of electrical current flowing across the transducer. The control and evaluation circuit identifies a first component of the output voltage indicative of the measurement current and a second component of the output voltage indicative of the current caused by the generation of the waveform and detects a short circuit and/or a broken wire based upon the second component.

Claims

1. A piezoelectric electret sensing device, comprising a piezoelectric electret transducer for producing a measurement current in response to mechanical stimulus,

and a control and evaluation circuit connected to said transducer;

said control and evaluation circuit comprising a transimpedance amplifier having a first input and a second input, said transducer being operatively connected between said first input and a reference node; and

an electrical waveform generator for generating an electrical waveform spectrally separated from said measurement current, said electrical waveform generator operatively connected between said second input and said reference node;

said transimpedance amplifier being configured to control said first input such that a difference in electric potential between said first input and said second input be cancelled and to output an output voltage, with respect to a potential at said reference node, indicative of electrical current flowing across said transducer;

wherein said control and evaluation circuit is configured to identify within said output voltage a first component of said output voltage indicative of said measurement current and a second component of said output voltage, said second component being spectrally separate from said first component and indicative of current caused by generation of said waveform;

and wherein said control and evaluation circuit is configured to detect at least one of a short circuit or a broken wire based upon said second component.

2. The sensing device as claimed in claim 1, wherein said control and evaluation circuit comprises a processing chain for identifying said first component, said processing chain for identifying said first component comprising a filter operatively connected to said transimpedance amplifier, said filter being configured so as to suppress said second component.

3. The sensing device as claimed in claim 1, wherein said control and evaluation circuit comprises a processing chain for identifying said second component, said processing chain for identifying said second component comprising a synchronous rectifier, synchronized on said waveform.

4. The sensing device as claimed in claim 1, wherein said control and evaluation circuit comprises a processing chain for identifying said second component, said processing chain for identifying said second component comprising a mixer, operatively connected with said transimpedance amplifier and said electrical waveform generator for multiplying said output voltage with said waveform, and a low-pass filter.

5. The sensing device as claimed in claim 1, wherein said control and evaluation circuit comprises a processing chain for identifying said second component, said processing chain for identifying said second component comprising an IQ demodulator for identifying said second component as a complex voltage comprising an in-phase part and a quadrature-phase part.

6. The sensing device as claimed in claim 1, wherein said electrical waveform generator comprises an AC signal source, such as, e.g. an oscillator.

7. The sensing device as claimed in claim 1, wherein said electrical waveform generator is configured to generate a pseudo-random noise waveform, e.g. a sine carrier wave modulated by a binary pseudo-random noise code.

8. The sensing device as claimed in claim 1, wherein said control and evaluation circuit is configured to detect said at least one of a short circuit or a broken wire by comparing said second component with a threshold.

9. The sensing device as claimed in claim 1, wherein said control and evaluation circuit comprises an analog-to-digital converter operatively connected with said transimpedance amplifier for converting said output voltage into a digital signal and a processor configured to identify said first component and said second component by analysing said digital signal.

10. The sensing device as claimed in claim 9, wherein said processor comprises at least one of an application-specific integrated circuit, a digital signal processor, a field-programmable gate array and a microcontroller.

11. The sensing device as claimed in claim 1, wherein said control and evaluation circuit is configured to detect said short circuit or broken wire by comparing the second component with a respective threshold.

12. The sensing device as claimed in claim 5, wherein said control and evaluation circuit is configured to detect said short circuit or broken wire by monitoring whether said complex voltage remains within a predefined area of the complex plane.