JPS61245030A - Piezo-electric oscillator type temperature sensor - Google Patents

Abstract

PURPOSE:To improve resolving power and to decrease the influence of noise by providing a signal transmission part consisting of an oscillating circuit provided with a piezo-electric oscillation type device having high temp. dependency and a frequency dividing circuit and a signal reception part having a PLL circuit. CONSTITUTION:The signal transmission part 3 consisting of the oscillating circuit 11 provided with the piezo-electric oscillation device 12 consisting of a quartz crystal, LiNbO3, etc. and the frequency dividing circuit 31 and the signal receiving part 5 provided with the PLL circuit 4 consisting of a phase comparator circuit 41, a low-pass filter 42 and a voltage control oscillating circuit 43 are connected by a transmission path 6. The temp. to frequency characteristic of the piezo-electric oscillation device 12 has excellent linearity and detects the temp. by converting the same to the frequency and therefore said device contributes to an improvement in the resolving power. Since the output frequency of the oscillating circuit 11 is divided down by the frequency dividing circuit 31, the optional selection of the frequency which is the center of the output frequency is made possible and the output of a high grade which is less effected by noise is obtainable by the circuit 4.

Description

[Detailed Description of the Invention] [Summary] In a temperature sensor configured using a piezoelectric vibrating device such as a crystal resonator or a lithium niobate (LiNbO3) resonator, the output signal of the temperature detection section can be transmitted wirelessly or by wire. This allows the detected temperature to be accurately read without being affected by noise during the transmission process by transmitting it to a remote location.

[Industrial application field]

The present invention relates to a temperature sensor that detects temperature by converting it into a frequency, and particularly relates to a piezoelectric vibrator type temperature sensor that has a function of transmitting an output signal of a temperature detection section to a remote location wirelessly or by wire.

For example, thermistors and the like have been used as temperature sensors for consumer appliances such as home air conditioners and refrigerators, which can be inexpensive because high resolution is not required.

However, temperature detection errors of 0.1°C are becoming a problem in increasingly sophisticated automobile electronic control systems and air conditioners that digitally display room temperature.

To deal with this problem, crystal and Li are used as temperature sensors that have high resolution and operate stably over long periods of time.
Temperature sensors equipped with piezoelectric vibrating devices such as NbO3 and capable of detecting temperature by replacing it with frequency have been in the spotlight.

[Conventional technology]

FIG. 3 is a block diagram showing the main parts of a conventional thermometer equipped with a piezoelectric vibrating device.

In the figure, the conventional thermometer consists of a temperature detection section 1 and a display section 2, and the display section 2 is, for example, a frequency counter.

The main part of the temperature detection section 1 is an oscillation circuit 11 such as a Colpitts oscillation circuit, which is made of crystal or L
It is equipped with a piezoelectric vibration device 12 such as iNbO3,
A signal with a frequency corresponding to the detected temperature is output from the output terminal 13. The temperature detection section 1 has an extremely high resolution because it detects temperature by replacing it with a frequency, and has the advantage of operating stably over a long period of time.

The frequency counter also includes a gate circuit 21, a counting circuit 22 that counts the output frequency of the oscillation circuit 11 while the gate circuit 21 is open, and a display circuit 23 that displays the count value of the counting circuit 22. Opening and closing of the circuit 21 is performed by a gate control circuit 24 and a reference time generator 25. This frequency counter 2 may display the output frequency of the oscillation circuit 11 as it is on the display circuit 23;
An appropriate frequency dividing circuit is inserted before the counting circuit 22 to create the oscillation circuit 1.
In some cases, the output frequency of 1 is converted into temperature and displayed on the display circuit 23.

[Problem that the invention seeks to solve]

For example, if air conditioning equipment is controlled based on temperature measurements obtained from one location indoors, problems may occur such as temperatures in other areas becoming too high or temperatures in other areas becoming too low. . To eliminate such problems, temperature sensors are usually installed at various locations in the building, and air conditioning equipment and the like are controlled so that the temperature at each location falls within a predetermined temperature range. However, a thermometer consisting of a temperature detection section and a frequency counter equipped with a piezoelectric vibrating device such as crystal or LiNbO3 is extremely expensive, and it is economically difficult to install such expensive temperature needles at various locations in the building. . Therefore, a method is generally used in which only temperature detection units are installed at various locations in the building and the temperature at each location is measured using a frequency counter installed in the center.

However, even if the temperature detection section and the frequency counter are connected by wire or wirelessly, there is a problem in that as the distance between them increases, the influence of noise increases, making it difficult to measure the frequency.

[Means for solving problems]

FIG. 1 is a block diagram showing an embodiment of a piezoelectric vibrator type temperature sensor according to the present invention, and the same objects are represented by the same symbols throughout the plan.

The above problem lies in the transmitting section shown in FIG. 1, which is composed of an oscillation circuit 11 equipped with a piezoelectric vibrating device 12 such as crystal or LiNbO3, and a frequency division circuit 31 that divides and outputs the output frequency of the oscillation circuit 11. 3. Receiver equipped with a phase-lon loop (PLL) circuit 4 that is composed of a phase comparator circuit 41, a low-pass filter 42, and a voltage-controlled oscillation circuit 43, and oscillates in synchronization with the frequency divided by the frequency divider circuit 31. This problem is solved by the piezoelectric vibrator type temperature sensor of the present invention, which has a transmission line 6 that connects the frequency dividing circuit 31 and the PLL circuit 4 wirelessly or by wire.

[Effect]

In FIG. 1, the output frequency of the oscillation circuit 11 is determined by the frequency dividing circuit 3.
Since the frequency is accurately divided by 1 and the frequency increases or decreases according to temperature changes around the divided frequency, the central frequency can be arbitrarily selected by changing the division ratio of the frequency dividing circuit 31. The transmitter 3 can be configured in accordance with the characteristics of the transmission path 6.

Furthermore, the PLL circuit 4 is configured to oscillate in synchronization with the frequency divided by the frequency dividing circuit 31, and even if the quality of the signal input to the phase comparator circuit 41 is degraded due to the influence of noise, It is possible to output high-quality signals with little influence from

Therefore, in a temperature sensor in which a frequency dividing circuit 31 and a PLL circuit 4 are inserted before and after the transmission line 6, the transmitting part that detects the temperature and the receiving part that counts the output frequency are connected by wire or wirelessly, and the interval between them is Even if the frequency spreads, the output frequency of the oscillation circuit 11 can be accurately counted without being affected by noise.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIG.

In the figure, the temperature sensor according to the present invention includes a transmitting section 3, a receiving section 5, and a transmission line 6 connecting the transmitting section 3 and the receiving section 5.

The transmitting section 3 is composed of an oscillation circuit 11 such as a Colpitts oscillation circuit and a frequency dividing circuit 31.
An oscillation circuit 11 including an O3 piezoelectric vibrator as a piezoelectric vibratory device 12 outputs a signal with a frequency corresponding to the temperature at the time. The output frequency of this oscillation circuit 11 is divided by the frequency dividing circuit 31 in the next stage, and the LiNbO3 piezoelectric vibrator sent from the output terminal 32 to the receiving section 5 via the transmission line 6 has a temperature versus frequency as shown in FIG. As shown in the characteristic diagram, the frequency changes linearly with temperature changes, and the "dispersion" is within ±1°C, which is excellent linearity, and the rate of change in frequency, or temperature coefficient, with respect to a 1°C temperature change It is about -90 ppm/'C.

For example, if the reference frequency of the vibrator is set to 12. Assuming OOOMHz, the frequency changes by 1080 Hz each time the temperature changes by 1°C.

A temperature sensor that utilizes the temperature dependence of a piezoelectric vibrating device in this way has an extremely high resolution because it detects temperature by converting it into a frequency, and has the advantage of operating stably over a long period of time. Furthermore, by dividing the output frequency of the oscillation circuit 11 by the frequency dividing circuit 31, it is possible to arbitrarily select the center frequency of the output frequency that changes with temperature, and the transmitter 3 is configured to match the characteristics of the transmission line 6. be able to.

For example, the output frequency 12 of the oscillation circuit 11. OOOMH
If z is divided into 1/1024 by the frequency dividing circuit 13,
The center frequency is 11.7 KHz, and each time the temperature changes by 1° C., the output frequency of the frequency divider circuit 13 changes by about I Hz. Also, the output frequency of the oscillation circuit 11 is set to 10.240.
If the frequency is divided into 1/4096 by the frequency dividing circuit 13, the center frequency becomes 2.50 KHz, and it becomes possible to transmit it to a distant place through a telephone line.

Further, the receiving section 5 has a PLL circuit 4 immediately after the signal input terminal 51.
The PLL circuit 4 is configured to oscillate in synchronization with the frequency divided by the frequency dividing circuit 31, and even if the quality of the input signal is degraded due to the influence of noise, the PLL circuit 4 is configured to oscillate in synchronization with the frequency divided by the frequency dividing circuit 31. Outputs fewer high-quality signals. Therefore, transmission line 6
A temperature sensor with a frequency dividing circuit 31 and a PLL circuit 4 inserted before and after the transmitter that detects the temperature and the receiver that counts the output frequency is connected by wire or wirelessly, and even if the distance between them increases, noise will not be generated. It is possible to accurately count the output frequency of the oscillation circuit 11 without being affected by this.

〔Effect of the invention〕

As described above, according to the present invention, an oscillation circuit for detecting temperature;
Piezoelectric vibration that can be connected to the circuit that counts and displays the output frequency of the oscillator circuit by wire or wirelessly to accurately detect temperature from a distance, has high resolution, and operates stably over long periods of time. A child-shaped temperature sensor can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a temperature versus frequency characteristic diagram of a LiNbO3 piezoelectric vibrator, and FIG. 3 is a block diagram showing a conventional thermometer. In the figure, 3 is a transmitter, 4 is a PLL circuit, 5 is a receiver,
6 is a transmission line, 11 is an oscillation circuit, 12 is a piezoelectric vibration device, 3
1 represents a frequency dividing circuit, 32 represents an output terminal, 41 represents a phase comparison circuit, 42 represents a low-pass filter, 43 represents a voltage controlled oscillation circuit, and 51 represents a signal input terminal. R (Earth month 6 days Guo tunli 1 host program) 20 brooms 1 Mouth retrieval seat (・C) Humidity, solidity, decline of bees, country land 2 days Conventional e warm atn main sound ph indicating ph”O Figure 21

Claims (1)

[Claims] 1) An oscillation circuit (11) comprising a piezoelectric vibrating device (12) such as crystal or lithium niobate (LiNbO_3).
), a frequency divider circuit (31) that divides and outputs the output frequency of the oscillation circuit (11), a phase comparator circuit (41), a low-pass filter (42), and a voltage a receiving section (5) comprising a controlled oscillation circuit (43) and a phase-locked loop circuit (4) that oscillates in synchronization with the frequency divided by the frequency dividing circuit (31); 31) and the phase-locked loop circuit (4), the piezoelectric vibrator type temperature sensor is characterized by having a wireless or wired signal transmission path (6). 2) The frequency dividing circuit (31) divides the output frequency of the oscillation circuit (11) to at least a frequency that can be transmitted over a telephone line, and the telephone line is used as the signal transmission path (6). The piezoelectric vibrator type temperature sensor according to item 1.