Measurement apparatus

Claim 2

In an apparatus for making measurements which are functions of variations in a physical parameter, the combination comprising: a. means for producing an AC signal; b. a bridge circuit responsive to said AC signal and having a plurality of terminals including a terminal coupled to a reference impedance and a probe member coupled to a second terminal and an output terminal; c. said probe member having an impedance related to said reference reactance and adapted to vary as a function of the physical parameter; and d. an output circuit coupled to said bridge circuit and including an envelope detector adapted to produce an output signal which is a function of variations in the probe impedance parameter and representative of a physical measurement.

Claim 3

Non-contacting apparatus for making physical measurements which are functions of variations in an electrical parameter comprising: a. means for producing a stable modulated AC signal; b. a bridge circuit responsive to said AC signal and having a plurality of terminals and a plurality of impedances located in arms thereof; c. a reference impedance coupled to one of said bridge terminals and a coaxial cable coupled to at one end to another of said terminals and having a probe member coupled to the other end of said coaxial cable and adapted to vary the reactance of the coaxial cable as seen by such other terminal in accordance with variations in an electrical parameter and produce a voltage standing wave; and d. an envelope detector coupled to a terminal of said bridge circuit and adapted to produce an output signal which is a function of variations In said voltage standing wave and is representative of the physical measurement.

Claim 4

Non-contacting apparatus for making physical measurements which are functions of variations in an electrical parameter comprising: a. means for producing a stable modulated AC signal; b. a bridge circuit responsive to said AC signal and having a plurality of terminals and a plurality of impedances located in arms thereof; c. a reference impedance coupled to one of said bridge terminals and a coaxial cable coupled to at one end to another of said terminals and having a probe member coupled to the other end of said coaxial cable and adapted to vary the reactance of the coaxial cable as seen by such other terminal in accordance with variations in an electrical parameter and produce a voltage standing wave; and d. an envelope detector coupled to a terminal of said bridge circuit and adapted to produce an output signal which is a function of variations In said voltage standing wave and is representative of the physical measurement.

Claim 5

The invention as set forth in claim 2 wherein said modulation signal producing means includes first and second crystal oscillators coupled together.

Claim 6

The invention as set forth in claim 2 including recording means responsive to said output signal for recording data representative of the physical measurement.

Claim 7

The invention as set forth in claim 2 including means coupling said modulation signal producing means to said bridge circuit for presenting a predetermined impedance to said bridge circuit.

Claim 8

The invention as set forth in claim 5 wherein said predetermined impedance is substantially zero.

Claim 9

The invention as set forth in claim 5 wherein said probe is coupled to a semi-balanced circuit having a plurality of reactance elements and said probe includes two electrodes.

Claim 10

The invention as set forth in claim 5 wherein said probe is coupled to a balanced circuit having a plurality of reactance elements and said probe includes two electrodes.

Claim 11

The invention as set forth in claim 5 wherein said probe is coupled to an un-balanced circuit having a plurality of reactance elements.