Acoustic thermometers

Claim 2

An acoustic thermometer comprising an acoustic resonator which during operation is positioned at a location at which the temperature is to be determined, a source of pulses of ultrasound, an acoustic transmission line over which said pulses are transmitted from the source to the acoustic resonator and over which the resulting echo signals are returned, said transmission line being supported in at least one loose bearing having a low acoustic impedance relative to the line impedance, and electronic means automatically to vary the carrier frequency of the ultrasound supplied by the source to maintain the acoustic resonator in resonance as the temperature of the acoustic resonator varies.

Claim 3

A thermometer as set forth in claim 1 wherein said electronic means comprises means to derive said echo signals from said transmission line, the waveform of each said echo signal having a crossover at resonance, and means to derive an error signal from said echo signals and to supply said error signal to said source to control the carrier frequency of said ultrasound such that the phases of said echo signals prior to crossover are 180* different from the phases of said echo signals after crossover.

Claim 4

A thermometer as set forth in claim 1 wherein said electronic means comprises means to derive said echo signals from said transmission line, the waveform of each said echo signal having a crossover at resonance, means to derive a reference signal from said source, means to compare a few oscillations of each said echo signal before crossover with said reference signal, means to invert said reference signal, means to compare a few oscillations of each said echo signal after crossover with the inverted reference signal, whereby two voltages respectively proportional to the overlap of each echo signal and said reference signal, and the overlap of said echo signal and said inverted reference signal are derived, and means to derive the difference between said two voltages to produce an error signal which is supplied to said source to control the carrier frequency of said ultrasound such that the phases of said echo signals prior to crossover are 180* different from the phases of said echo signals after crossover.

Claim 5

A thermometer as set forth in claim 3 wherein said means to compare said oscillations with said reference and inverted reference signals are two AND gates.

Claim 6

A thermometer as set forth in claim 3 wherein said means to derive thE difference between said voltages to produce an error signal comprises an integrating amplifier.

Claim 7

A thermometer as set forth in claim 1 wherein said acoustic transmission line is acoustically coupled at one end to said acoustic resonator and at the other end to a magnetostrictive transducer forming said source and having a driving coil.

Claim 8

A thermometer as set forth in claim 6 wherein said magnetostrictive transducer has two ends, one end being acoustically coupled to said acoustic transmission line and the other end being acoustically coupled to an acoustically reflecting termination which is spaced at half a wavelength at the frequency of said ultrasound from said magnetostrictive transducer, so that the forward and reflected waves reinforce.

Claim 9

A thermometer as set forth in claim 1 further comprising means digitally to display the frequency of said ultrasound.

Claim 10

A thermometer as set forth in claim 1 further comprising a conversion circuit to which a signal of the frequency of said ultrasound is supplied by said source, said circuit supplying an output signal representing the temperature of said acoustic resonator corresponding to said frequency, and display means digitally to display the temperature corresponding to said output signal.

Claim 11

A thermometer as set forth in claim 1 wherein said acoustic resonator is acoustically coupled to said acoustic transmission line by way of a coupler.

Claim 12

A thermometer as set forth in claim 1 wherein said acoustic resonator is a single crystal.