JPS62282254A - Tuning fork type quartz temperature/humidity sensor - Google Patents

Abstract

PURPOSE:To simultaneously measure temp. and humidity and to miniaturize the title sensor, by changing the frequency and equivalent series resistance of a tuning fork type quartz vibrator and detecting temp. from the change in frequency while detecting humidity from the change in equivalent series resistance. CONSTITUTION:A turning fork type quartz vibrator piece is used as an electrode and covered with a seal pipe having a hole to constitute a tuning type quartz vibrator 9. The quartz vibrator 9 is connected to an oscillation circuit 10 and subjected to sine oscillation at constant amplitude by an AGC circuit 12. The current flowing to the quartz vibrator 9 is passed through a buffer 13 and only a signal component having the same phase as the vibration voltage of the quartz vibrator 9 is taken out by a synchronous detection circuit 11. Thereafter, said signal component is rectified by a rectifier 14, amplified by an amplifier 15 and outputted from an output terminal 16. The change in equivalent series resistance is detected on the basis of the change in the current of the quartz vibrator 9 to measure humidity. Because the temp. characteristic of the quartz vibrator 9 changes on the basis of the change in frequency, temp. is detected from the frequency by a quartz vibrator 9 having a known temp. characteristic. Therefore, temp. and humidity can be simultaneously measured by one sensor and this sensor is effective for an air conditioner.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a tuning fork type crystal temperature/humidity mancer.

[Background of the invention]

Due to the strong demand for energy conservation and the development of microcomputers, new fields of application for various sensors are expanding, and there is a need for the development of higher performance sensors. In particular, there has been a strong demand for humidity sensors, whose development has been delayed compared to the conventional sensor field, and temperature sensors, which are used very often, and the development of compact and low-cost temperature and humidity sensors. is desired.

[Problems with conventional technology]

Conventional temperature sensors include, for example, thermocouples, which detect temperature by measuring thermoelectromotive force, and which are currently widely used, and thermistors, which utilize the fact that electrical resistance changes greatly depending on temperature. There are infrared temperature sensors and the like that detect the temperature of an object by measuring infrared rays emitted by the object. In addition, the humidity 7 degree sensor uses, for example, a swellable organic film such as hair or nylon film, and uses the fact that the evaporation rate of water differs depending on the humidity to reduce the temperature drop of the wet bulb due to evaporation. ! l! Wet and dry bulb type sensors that detect humidity by measuring I, infrared type sensors and microwave type sensors that utilize electromagnetic wave absorption, as well as electrolyte thread sensors, polymer sensors, which have been recently researched.
There are metal and metal oxide based sensors. However, both the temperature sensor and the humidity sensor described above are independent of the sensor and σ deviation.

Temperature and humidity are important in managing a variety of things, so sensors like the ones mentioned above are currently being used to measure them in a wide range of fields, but the sensors themselves have to be used alone.
To control temperature and humidity.

You can use two types of measuring instruments, or you can use one type of recently developed III meter with only two sensor parts, or you can use a single element with two measuring instruments, each with its own measurement frequency. I had to either change it and measure it. In other words, there is no prior art sensor that can simultaneously determine both temperature and humidity. In addition, among humidity sensors, polymer-based sensors, which have become particularly popular in recent years, use a polymer membrane that is a moisture-sensing agent, and recent ones have a longer lifespan in high-humidity environments. However, it has the disadvantage that it is susceptible to high humidity atmospheres and dew condensation because it swells due to adsorbed moisture, resulting in poor adhesion to the substrate and peeling. For this reason, even in applications that do not necessarily require measurement at high humidity, such as the control of air conditioning equipment, condensation may form on the element surface due to the effects of sudden changes in indoor temperature, which poses experimental problems. Ta. Moreover, the sensors of the prior art were often large and expensive.

[Purpose of the invention]

The present invention aims to solve the above-mentioned problems and provide a small, low-cost temperature/humidity sensor that can measure both temperature and humidity simultaneously, eliminating the drawbacks of the conventional technology. It is something.

[Structure of the invention]

Utilizing frequency changes and equal series resistance changes of a tuning fork type crystal oscillator, it is characterized by being able to simultaneously detect both temperature by frequency changes and humidity by equal series resistance changes.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on the drawings. 1st
The figures are views showing one embodiment of the present invention, in which figure (a) is an external perspective view, and figure (b) is an internal perspective view. Electrode (1
) is formed with a tuning fork-shaped crystal resonator piece (2) (hereinafter simply referred to as a crystal piece), a thread-colored edged glass (3) and a ring (4
) and a lead (5) of the hermetic terminal.
) with conductive adhesive (6) and covered by a sealing tube (8) with a hole (7) in the head. Here, an experiment conducted using the tuning fork type crystal resonator (hereinafter simply referred to as a crystal resonator) will be explained. The experiment was conducted using the most commonly used crystal unit for watches.

FIG. 2 is a block diagram of the humidity sensor circuit used in the experiment. The humidity sensor circuit in which the crystal oscillator (9) is set can be roughly divided into an oscillation circuit (10) and a synchronous detection circuit (11).
This is a crystal oscillation circuit with a C (automatic gain control) circuit (12), which oscillates sinusoidally with a constant amplitude. Then, the current flowing through the crystal oscillator is extracted through a buffer (13), and synchronous detection is performed to extract only the signal component that is in phase with the excitation voltage applied to the crystal oscillator. After that, rectification (14
)L, is amplified (15) and becomes the sensor output (16). Here, instead of directly detecting changes in one equivalent series resistance, changes in the current flowing through the crystal resonator are detected.

FIG. 3 is a calibration output diagram of the humidity sensor circuit. This is data obtained by measuring the output voltage when crystal oscillators with various equal series resistances are connected to a humidity sensor circuit. As you can see from the figure.

It can be seen that as the equal series resistance increases, the current flowing through the crystal oscillator decreases, which is correlated.

FIG. 4 is a diagram showing equal series resistance changes when relative humidity and temperature are changed using the humidity sensor circuit described above. As can be seen from the figure, there is a correlation between relative humidity and equal series resistance change for each temperature.

FIG. 5 is a diagram showing frequency changes with respect to temperature. The temperature characteristic of the crystal resonator is a negative quadratic curve, and the frequency changes with respect to temperature as shown in the figure.

In the experiment, a watch crystal oscillator was used, so the ZTC (zero temperature coefficient) was 25°C, but you can change the ZTC depending on the purpose.
By changing the TC, you can obtain the required curve. Furthermore, by changing the cut angle, it is possible to change the temperature characteristic curve itself, so it is possible to obtain even more frequency changes with respect to temperature. (For example, JP-A-58
-206935, JP-A-58-206936, JP-A-58
8-57812 etc. ) If the temperature characteristic curve is known,
Temperature can be easily measured from the output frequency.

〔Effect of the invention〕

As described above, according to the tuning fork type temperature/humidity sensor of the present invention, temperature and humidity can be measured simultaneously with one sensor, and
Since the moisture sensitive agent itself is not required, it is very advantageous in terms of cost, and is very convenient as a sensor for air conditioners, etc., for example. In addition, the tuning fork type crystal resonator, which is commonly used, is highly suitable for mass production and is extremely compact, which is why it was targeted. It has become possible to provide a small and low-cost sensor.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG.
) is an external perspective view, Figure (b) is an internal perspective view, Figure 2 is a block diagram of the temperature sensor circuit used in the experiment, Figure 3 is a calibration output diagram of the humidity sensor circuit, and Figure 4 is the humidity sensor. FIG. 5 is a diagram showing the change in equal series resistance when the circuit is used and the relative humidity and temperature are changed, and FIG. 5 is a diagram showing the frequency change with respect to temperature. 1, electrode 2, tuning fork crystal resonator piece 3, insulating glass 4, ring 5, lead 6, conductive adhesive 7, hole 8, sealing tube 9, crystal resonator 10, oscillation circuit 11, synchronous detection circuit 12 , AGc circuit 13, buffer 14, rectification 15, amplification 16, output Fig. 1 (0)

Claims (1)

[Claims] A tuning fork type crystal temperature/humidity sensor that utilizes frequency changes and equivalent series resistance changes of a tuning fork type crystal resonator, and is capable of simultaneously detecting both temperature by frequency changes and humidity by equivalent series resistance changes. .