Quartz thermometer
First Claim
1. A quartz crystal thermometer comprising a single quartz element having at least a first and a second pair of electrodes and vibrating simultaneously in two different modes which are not mechanically coupled with each other and which correspond to two different frequencies of vibration, each of said first and second pairs of electrodes being arranged for providing high piezoelectric coupling with one corresponding mode of the said two modes of vibration and for providing no piezoelectric coupling with the other mode, one of the said two frequencies of vibration being a standard frequency and the other being dependent on the temperature of the quartz crystal, the thermometer further comprising a first and a second oscillator circuit respectively connected to the said first and second pairs of electrodes, and a frequency comparison device for comparing the oscillation frequencies of the first and second oscillator circuits and providing an output which is a measure of the detected temperature.
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Abstract
A quartz crystal thermometer in which a standard frequency is generated by a first oscillator circuit incorporating a quartz crystal element and in which a frequency which varies with temperature is generated by a second circuit incorporating the same quartz crystal element. Two electrode pairs are provided on the single quartz crystal element in order to excite two different modes of vibration of the quartz crystal element, with the metallization being on only one or on both of the major faces of the quartz crystal element. In accordance with preferred embodiments, an AT- or a BT-cut quartz crystal plate is utilized. The ratio of the said two frequencies provides an accurate measure of the temperature.
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Citations
8 Claims
- 1. A quartz crystal thermometer comprising a single quartz element having at least a first and a second pair of electrodes and vibrating simultaneously in two different modes which are not mechanically coupled with each other and which correspond to two different frequencies of vibration, each of said first and second pairs of electrodes being arranged for providing high piezoelectric coupling with one corresponding mode of the said two modes of vibration and for providing no piezoelectric coupling with the other mode, one of the said two frequencies of vibration being a standard frequency and the other being dependent on the temperature of the quartz crystal, the thermometer further comprising a first and a second oscillator circuit respectively connected to the said first and second pairs of electrodes, and a frequency comparison device for comparing the oscillation frequencies of the first and second oscillator circuits and providing an output which is a measure of the detected temperature.
Specification