JPS6215819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a thermometer that utilizes resonance absorption phenomena such as nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR).

FIG. 1 is a block diagram showing an example of a conventionally known thermometer of this type. In the figure, 1 is a temperature sensor, and the temperature-contacting part at its tip contains, for example, KClO ₃ ,
A cell is provided in which a material such as NaClO ₃ whose resonance absorption frequency is temperature-dependent and a high-frequency coil are enclosed. 2 is a variable frequency sensor oscillator, 3 is its control circuit, and these constitute means for detecting the resonance absorption frequency of the NQR material.
4 is a counter, and 5 is a clock pulse generator for operating the counter 4.

For example, a marginal oscillator is used as the sensor oscillator 2, and the variable range of its oscillation frequency is larger than the range of the nuclear quadruple nuclear resonance absorption frequency (hereinafter referred to as absorption frequency) of the NQR material corresponding to the temperature range to be measured. determined. The high-frequency coil L enclosed in the cell of the temperature detector 1 constitutes an oscillator tank circuit together with the capacitor C of the sensor oscillator 2, and emits electromagnetic waves generated as the sensor oscillator 2 oscillates to the NQR material. The control circuit 3 sweeps the frequency of the sensor oscillator 2 in a variable range. When the oscillation frequency matches the absorption frequency and the electromagnetic wave is absorbed by the NQR material and the output amplitude of the sensor oscillator 2 decreases, the control circuit 3 detects this decrease in the output amplitude and changes the output amplitude of the sensor oscillator 2. The oscillation frequency is fixed at this absorption frequency. For example, a lock-in amplifier is used as a control circuit that performs such an operation.

The frequency of the sensor oscillator 2, which is fixed at the absorption frequency, is measured by a counter 4. Here, since the absorption frequency has a correspondence relationship with the temperature to be measured, the temperature to be measured can be accurately known from the measured value of the counter 4. For example, when KClO ₃ is used as an NQR material, the absorption frequency changes from 29 to 27.5 MHz in the temperature measurement range of -200°C to +125°C.

By the way, in a device with such a configuration, if a general commercially available product is used for the counter 4, the absorption frequency signal is amplified inside the counter, and this signal performs the operation of switching a large current at the absorption frequency. Frequency signals are radiated into space as noise radio waves. Although the radiation of such noise radio waves can be reduced to some extent by shielding the entire counter 4, it cannot be completely eliminated. When a noise radio wave from the counter 4 is applied to the high-frequency coil L or the sensor oscillator 2, the frequency of this noise radio wave is the same as the oscillation frequency of the oscillator 2, so it affects the oscillation width and causes measurement errors. There was a risk that this would occur. Furthermore, if the counter 4 is operated with a clock signal of, for example, 1 MHz, its n harmonics will be mixed in, making it impossible to measure temperatures corresponding to 28 MHz and 29 MHz, for example, in a thermometer using KClO ₃ as the NQR material. There are drawbacks to this.

The present invention has been made to eliminate these drawbacks of conventional devices, and is intended to realize a thermometer of this type that operates reliably.

FIG. 2 is a block diagram showing an embodiment of the present invention. In the present invention, the absorption frequency signal ν _t obtained from the sensor oscillator 2 is applied to the frequency converter 6, where it is converted into a frequency signal of ν _t −ν _B , and then this is counted by the counter 4. This is what I did. 7 is a circuit for obtaining a reference frequency signal ν _B that is applied to the frequency converter 6 when a mixer is used. Here, a frequency doubler circuit that receives the signal from the clock pulse generator 5 as input is used There is. Here, the frequency of ν _B is
It is chosen such that the nth harmonic of ν _t −ν _B is not equal to the absorption frequency ν _t .

For example, when the absorption frequency ν _t changes from 27.5 to 29.0MHz, ν _t /2 = 13.75 to 14.5MHz, 2ν _t /3 = 18.3
Since each range of 3 to 19.33 MHz and 3v _t /4 = 20.63 to 21.75MHz corresponds to n harmonics of ν _t below 22 MHz, for example, 20 MHz outside these ranges is selected as ν _B. . If ν _B is selected to be 20 MHz, in this case, the counter 4 only needs to measure 7.5 to 9 MHz, and the number of digits of the counter may be one digit smaller than when directly measuring absorption frequencies of 27.5 to 29.0 MHz. Furthermore, if the clock pulse given from the clock pulse generator 5 to the counter 5 is 10 MHz, this n harmonic will not match the absorption frequency, and will be added to the frequency converter 6.
A frequency signal ν _B of 20 MHz can also be easily obtained using a frequency doubler circuit.

As explained above, according to the present invention, the absorption frequency obtained from the sensor oscillator is converted into a different frequency signal before being measured. The measurement frequency signal is not fed back to the sensor, making it possible to realize a thermometer that operates reliably and stably. Further, the converted signal can be transmitted to a remote location, for example, by a telemeter system. In this case, if ν _B or a reference clock pulse signal is also transmitted at the same time, it is sufficient to provide an accurate clock pulse generation source on either the receiving side or the transmitting side.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional resonance thermometer, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1...Temperature detector, 2...Sensor oscillator,
3...Control circuit, 4...Counter, 5...Clock pulse generator, 6...Frequency converter, 7...Reference frequency signal generation circuit.

Claims (1)

[Claims] 1. In a thermometer equipped with a resonant material whose resonant absorption frequency is temperature dependent and a detection means including a sensor oscillator that detects the resonant absorption frequency of this material, the resonant absorption frequency ν _t obtained from the detection means and another reference frequency signal ν _B to obtain a frequency signal of ν _t −ν _B , and the frequency ν _B of the reference frequency signal is changed to n harmonics of ν _t −ν _B. A thermometer utilizing a resonance absorption phenomenon, characterized in that the resonance absorption frequency ν _t is selected so as not to fall within a variation range, and a frequency signal of the ν _t −ν _B is measured.