Detector apparatus

Claim 2

In apparatus for detecting changes of a sensed quantity, of the type comprising a sensitive element responding to changes in said quantity by varying an electrical potential and an amplifier fed at an input thereof with said potential and providing an output signal representative of said charges, the improvement which comprises: a resistance/capacitance signal transfer circuit determining a time constant; a high input impedance active element having an input and an output; means including said signal transfer circuit coupling said amplifier output signal to the input of said active element; and negative feedback path means including a resistor coupling the output of the active element to the amplifier input whereby changes in said potential are transferred by way of said signal transfer circuit to said negative feedback path with a delay determined by said time-constant.

Claim 3

The improvement cliamed in claim 1 wherein the amplifier provides a signal denotive of changes in the sensed quantity and the high input impedance element provides a signal which is a function of the value of the sensed quantity, whereby the apparatus enables the detection of both change of quantity and rate-of-change of quantity.

Claim 4

The improvement claimed in claim 1 wherein the amplifier is a transistor and the high-impedance element is a field-effect transistor.

Claim 5

The improvement claimed in claim 1 wherein the amplifier includes a field-effect transistor and the sensitive element is connected to the base of a transistor connected in series with said negative-feedback resistor, the potential at the junction of said transistor and resistor being applied to the grid of the field-effect transistor.

Claim 6

The improvement claimed in claim 4 wherein the output potential of the amplifier is applied to the resistance/capacitance circuit by way of a Zener diode connected in series with a resistor.

Claim 7

In apparatus for detecting changes in the magnitude of a quantity of the kind including a sensitive element determining an electrical potential representative of the quantity and an amplifier formed by a field-effect transistor having an input and an output, and means applying the potential to the transistor input to yield at the transistor output a signal representative of said potential, the improvements which comprises: a resistance/capacitance signal transfer circuit defining a time-constant; a high-input impedance active element; means including said signal transfer circuit coupling said signal to said active element input; negative feedback path means including a transistor coupling said active element output to said amplifier input whereby the changes in said potential are transferred by way of the active element to the negative feedback path with a delay determined by said time-coNstant, means coupling said sensitive element to the base of said transistor in said feedback path; and means coupling the potential at the junction point of said transistor and said feedback path to the gate of the field effect transistor, whereby variations in either sense of said quantity may be detected.

Claim 8

In apparatus for detecting changes in the magnitude of a quantity of the kind including a sensitive element determining an electrical potential representative of the quantity and an amplifier formed by a field-effect transistor having an input and an output, and means applying the potential to the transistor input to yield at the transistor output a signal representative of said potential, the improvements which comprises: a resistance/capacitance signal transfer circuit defining a time-constant; a high-input impedance active element; means including said signal transfer circuit coupling said signal to said active element input; negative feedback path means including a transistor coupling said active element output to said amplifier input whereby the changes in said potential are transferred by way of the active element to the negative feedback path with a delay determined by said time-coNstant, means coupling said sensitive element to the base of said transistor in said feedback path; and means coupling the potential at the junction point of said transistor and said feedback path to the gate of the field effect transistor, whereby variations in either sense of said quantity may be detected.