Elec rical circuit for the transferring and amplification of a piezoelectric transducer signal

Claim 2

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing in which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; an amplifier circuit Which is electrically insulated from ground potential and has two input terminals and two output terminals, the signal lead being connected to the input terminals of the amplifier circuit; a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential; means interconnecting the housing to ground potential; and means connecting the housing and signal lead screen whereby said housing and said screen are connected to ground potential at a single point adjacent said sensor.

Claim 3

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing in which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; an amplifier circuit which is electrically insulated from ground potential and has two input terminals and two output terminals, the signal lead being connected to the input terminals of the amplifier circuit; a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential; and a voltage stabilizer from which the amplifier circuit is energized and which has a reference potential lead connected to the electrical screen of the signal lead, the screen being connected to ground potential adjacent to the sensor only.

Claim 4

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing in which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; an amplifier circuit which is electrically insulated from ground potential and has two input terminals and two output terminals, the signal lead being connected to the input terminals of the amplifier circuit; a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential; and a voltage stabilizer from which the amplifier circuit is energized and which has a reference potential lead connected to the electrical screen of the signal lead, the screen being connected to ground potential adjacent to the sensor only.

Claim 5

An electrical circuit as claimed in claim 2, which comprises a resistor which is connected between the screen and ground potential adjacent to the amplifier circuit and which serves to complete the path for the supply current of the amplifier circuit.

Claim 6

An electrical circuit as claimed in claim 2, which comprises a supply terminal and a resistor, the resistor being connected between the screen and the supply terminal to which there is applied a potential which has the opposite sense relative to ground potential to the supply potential of the amplifier circuit, the resistor serving to complete the path for the supply current of the amplifier circuit.

Claim 7

An electrical circuit as claimed in claim 2, which comprises a supply terminal for the amplifier circuit and a switch element having a high internal resistance, the switch element being connected between the voltage stabilizer and the supply terminal.

Claim 8

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing in which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; a symmetrical signal amplifier circuit which is electrically insulated from ground potential and having two input terminals and two output terminals and two capacitors, the signal lead being connected to the input terminals of the amplifier circuit and each output terminal being connected through an individual capacitor to an individual input terminal; and a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential.

Claim 9

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing in which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; a symmetrical signal amplifier circuit which is electrically insulated from ground potential and having two input terminals and two output terminals and two capacitors, the signal lead being connected to the input terminals of the amplifier circuit and each output terminal being connected through an individual capacitor to an individual input terminal; and a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential.

Claim 10

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing iN which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; an amplifier circuit including two asymmetrical signal amplifiers each having an input terminal and an output terminal and each being provided with a capacitor connected between its input and output terminals, the reference potential of the amplifiers being that of the screen of the signal lead, and the input terminal of each amplifier being connected with an individual conductor of the signal lead, whereby, in use, the amplifiers convert the output signal of the sensor into two voltages symmetrical to the potential of the screen; and a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential.

Claim 11

An electrical circuit comprising: a bipolar piezoelectric sensor; a housing iN which the sensor is disposed, which screens the sensor; an insulated bipolar signal lead which extends through the housing and which is screened by an electrical screen; an amplifier circuit including two asymmetrical signal amplifiers each having an input terminal and an output terminal and each being provided with a capacitor connected between its input and output terminals, the reference potential of the amplifiers being that of the screen of the signal lead, and the input terminal of each amplifier being connected with an individual conductor of the signal lead, whereby, in use, the amplifiers convert the output signal of the sensor into two voltages symmetrical to the potential of the screen; and a differential amplifier having two input terminals, which are connected to the output terminals of the amplifier circuit, and an output terminal, the difference between the signals at the output terminals of the amplifier circuit being converted, in use, into an asymmetrical voltage signal between the output terminal of the differential amplifier and ground potential which acts as a reference potential.