JP3369677B2 - Temperature and humidity sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature and humidity sensor. 2. Description of the Related Art In recent years, an environment called ice temperature and high humidity is used.
Attention has been focused on food preservation technology at 0 ° C. and 80 to 100%. [0003] As a food preservation environment, since temperature and humidity play a large role, temperature and humidity are detected with high accuracy.
It is necessary to perform control according to the detected value. In general, humidity in an ice temperature storage at room temperature is detected by a humidity sensor which detects a change in electric resistance or capacitance caused by water molecules adsorbed on a moisture-sensitive film made of a polymer film or ceramic. Used. [0005] However, when such a sensor is used in an ice temperature environment, there is a problem in that dew condensation occurs when outside air is introduced at the time of opening and closing the door of the storage, and thereafter, it becomes impossible to measure humidity for tens of minutes. There has been a problem that the characteristics of the sensor are deteriorated due to the repetition of such a condensation cycle. As described above, the conventional humidity sensor cannot perform accurate humidity detection due to dew condensation when used in an ice temperature and high humidity environment, and when trying to perform accurate humidity detection, the outside air is opened and closed by opening and closing a door. You must wait until the condensation from the introduction has disappeared. Therefore, the present inventor aims to continuously perform humidity detection with high accuracy in an ice temperature and high humidity environment without being affected by dew condensation, and to locally heat only the periphery of the humidity detection means. A heating means for detecting the humidity of the environment to be measured while heating to a predetermined temperature or higher, and measuring the ambient temperature and the environmental temperature of the humidity detecting means and measuring the humidity from these values and the detected humidity. (Japanese Patent Laid-Open Publication No. Hei 4-118547) has proposed a humidity detecting device for detecting the humidity. As shown in FIGS. 9 and 10, for example, this humidity detecting device has a thickness of 1 mm, a height of 5 mm, and a high thermal insulating property.
A first sensor chip T1 having a humidity sensor, a heater and a first temperature sensor on a substrate 100 made of glass epoxy having a width of 15 mm, and a second sensor having a second temperature sensor for measuring an environmental temperature. The sensor chip T2 is mounted. Here, the sensor chip has a diameter of 25 on the substrate.
It is connected by a gold wire W of μm. First sensor chip T
1, a heater 102 made of a titanium nitride (TiN) thin film having a thickness of 0.1 μm is provided on a silicon substrate 101 via a silicon oxide film (not shown), and a silicon oxide (SiO ₂ ) 106 as an insulating film is provided. Through the first layer
Temperature sensor 103, a lower electrode 141 made of a platinum thin film, a moisture-sensitive film 142 made of a polyimide film, and an upper electrode 143 made of gold. 143
The humidity sensor 104 which is taken out from the apparatus is provided side by side. On the other hand, the second sensor chip T2 is provided on the sensor head substrate 100 at a distance from the first sensor chip T1.
The second temperature sensor 105 is provided via the. According to this configuration, since the humidity is detected in a state where only the periphery of the humidity detecting means is locally heated to a predetermined temperature or higher, even when outside air enters,
The humidity can be measured immediately without dew condensation, and since the humidity is measured without dew condensation, deterioration of the sensor itself can be prevented. [0010] However, in this sensor structure, when the first sensor chip is heated, a large amount of heat escapes through the sensor substrate, and the temperature of the second sensor chip also increases. As a result, there has been a problem that it is impossible to accurately measure the environmental temperature. Furthermore, the first
The heat required to heat the sensor chip also increases by the amount of the escape, and there is a problem that the sensor power consumption is large. Therefore, if the sensor chip is floated with a wire in order to reduce the escape of heat, the mechanical strength becomes insufficient,
Conversely, if the wire diameter is increased to about 160 μm in order to maintain the mechanical strength, there is a problem that heat escape through the wire increases. In addition, since the second sensor chip needs to avoid the thermal influence of the first sensor chip, it needs to be installed at a predetermined interval, which causes a problem that the device becomes large. Was. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a temperature and humidity sensor having high measurement accuracy and responsiveness and capable of being miniaturized. According to the present invention, there is provided, in the present invention, a humidity detecting means for detecting humidity; and a humidity detecting means disposed on the chip substrate surface in close proximity to the humidity detecting means. A first sensor chip including a first temperature detecting means for detecting a temperature around the means, a heating means for locally heating the vicinity of the humidity detecting means to a predetermined temperature or higher, and mounted on the sensor substrate And a second temperature detecting means for detecting the temperature of the environment in which the first sensor chip is installed.
Wherein the first sensor chip comprises a first thermally and electrically insulating wire for mechanical connection and a second wire for electrical connection on the sensor substrate. Are connected by That is, the present invention detects the humidity while heating it to a predetermined temperature or higher, and performs conversion based on the environmental temperature, thereby performing highly accurate humidity measurement while preventing the influence of dew condensation. A humidity detecting means for detecting, and a first temperature detecting means for detecting a peripheral temperature of the humidity detecting means are provided, and a heating means for locally heating the vicinity of the humidity detecting means to a predetermined temperature or more is provided. The apparatus is arranged to locally heat the periphery of the humidity detecting means and the first temperature detecting means to a predetermined temperature or higher, and detects the output of the humidity detecting means, the output of the first temperature detecting means and the environmental temperature. The conversion is performed based on the output of the second temperature detecting means, and the humidity is detected. According to the above construction, since the mechanical connection and the electrical connection are achieved by independent members, a material having a low thermal conductivity is used for the mechanical connection. By increasing the diameter of the wire to such an extent that the escape of heat does not pose a problem, and by making the electrical connection thin, the heat loss due to the heat conduction of the wire can be minimized. Further, a second temperature detecting device equipped with a second temperature detecting means is provided.
Even if the sensor chip is placed in close proximity, the second temperature detecting means is not heated by the heat of the first sensor chip due to the heat conduction from the wire and does not cause a temperature rise. The humidity can be detected with high accuracy. As in the conventional temperature and humidity sensors shown in FIGS. 9 and 10, the humidity is detected while only the periphery of the humidity detecting means is locally heated to a predetermined temperature or higher. Even when outside air enters, the humidity can be measured immediately without dew condensation. Further, since humidity is measured without dew condensation, deterioration of the sensor itself can be prevented. Further, the measurement of humidity can always be performed continuously. The heating temperature of the heating means is desirably set to a temperature at which dew condensation does not occur even when the heating means is exposed to outside air or the like. For example, in the case of a food storage, as an example, heating is performed at 7.5 ° C. during normal operation, and at 35 ° C. only during dew condensation. Embodiments of the present invention will be described below in detail with reference to the drawings. FIGS. 1 and 2 show a temperature and humidity sensor according to a first embodiment of the present invention. This temperature / humidity sensor is installed for detecting temperature / humidity in an ice temperature storage, and a heater and a first heater are provided on a sensor head substrate 100 made of a glass epoxy substrate having high thermal insulation. A first sensor chip T1 having a temperature sensor and a humidity sensor of the type described above and a second sensor chip T2 having a second temperature sensor for measuring environmental temperature are connected in a state of being spatially floated by wires. Have been. The first sensor chip T1 is electrically connected to the drive circuit on the sensor head substrate 100 by six gold wires W1 having a diameter of 25 .mu.m.
The second sensor chip T2 is supported by four glass epoxy wires W2 so as to achieve a mechanical connection.
In this example, electrical connection to the drive circuit on the sensor head substrate 100 is achieved by two gold wires W1 having a diameter of 25 .mu.m and four glass epoxy wires W2 of 0.8 mm.times.0.2 mm.
, So that a mechanical connection is achieved. The humidity sensor 4 is formed of a platinum thin film via a silicon oxide film S on a heater 2 made of a titanium nitride film formed on a silicon substrate 1 via a silicon oxide film (not shown). The lower electrode 141, a moisture-sensitive film 142 made of a polyimide film, and an upper electrode 143 made of a gold thin film are sequentially laminated, and the capacitance change of the moisture-sensitive film 142 due to humidity is measured by the lower electrode 141. It is taken out from the upper electrode 143. The first temperature sensor 3 is composed of a meander-like resistance pattern made of a platinum (Pt) pattern disposed on the heater 2 via the silicon oxide film S, in addition to the humidity sensor. The temperature is detected from the change in the resistance value based on the change. Further, the second temperature sensor 5 is provided with a first
Like the temperature sensor 3, a meander-like resistance pattern composed of a platinum (Pt) pattern formed on the silicon substrate 1 with the silicon oxide film S interposed therebetween is used to detect the temperature from a change in resistance based on a change in temperature. And constitute a second sensor chip. Next, measurement of temperature using the temperature and humidity sensor will be described. The outputs of the humidity sensor 4, the first temperature sensor 3 and the second temperature sensor 5 are measured respectively. Each of these measured values is represented by a (% R.
H. ), B (° C.) and c (° C.). First, as shown in FIG. 3, a saturated water vapor curve at each temperature is determined. Here, the vertical axis is the amount of saturated steam (g / m ³ ), and the horizontal axis is the temperature (° C.). Assuming that the amounts of saturated steam at the temperatures b and c are B and C, respectively, the amount of steam x (g / m ³ ) on the heater 2 where the first temperature sensor and the humidity sensor are placed is expressed by the following equation (1). ). X (g / m ³ ) = a × B / 100 (1) Thereafter, the humidity y is obtained by calculating the ratio of the internal temperature, that is, the saturated water vapor amount C at the output c of the second temperature sensor.
(% RH) can be determined. Y (% RH) = x / C × 100 = a × B / C (2) In this manner, the humidity under the ice temperature can be obtained extremely easily and with high accuracy. . According to such a configuration, in the case of the conventional example, the heat dissipation coefficient was 13.34 mW / ° C., but according to the structure of the present invention, the heat dissipation coefficient was 3.57 mW / ° C. For heating, the power can be reduced to about 27% and the thermal effect on the second sensor chip can be greatly reduced. Further, since the first sensor chip has a small thermal effect, the first sensor chip and the second sensor chip can be disposed closer to each other, and the device can be downsized. it can. In the above embodiment, not only the first sensor chip but also the second sensor chip achieve the electrical connection and the mechanical connection with different wires. Such a configuration may be adopted. In the above-described embodiment, the humidity y is calculated ignoring the change in the gas volume due to the temperature change. However, in order to obtain a more accurate humidity value, the calculation is performed using the concept of the saturated steam pressure. May be. This example will be described below. Fig. 4 (a)
And (b) are explanatory diagrams. First, the amount of water vapor x in the environment is represented by x (g / m ³ ) = (y / 100) × C (3), and the amount of water vapor x ′ on the heater is such that the air itself expands in proportion to the absolute temperature. Therefore, it is expressed by the following equation. X ′ (g / m ³ ) = x × (c + 273) / (b + 273) = (y · C / 100) · (c + 273) / (b + 273) (4) Further, x ′ is a relative humidity a on the heater. When (% RH) is used, it can be expressed as the following equation. X ′ (g / m ³ ) = (a / 100) × B (5) From equations (4) and (5), the environmental humidity can be expressed as equation (6). Y (% RH) = a · (B / C) · (b + 273) / (c + 273) (6) From the definition of absolute humidity, the weight, mole number, molecular weight, and volume of water are defined as m _w , n _w , and M, respectively. _w, when the _{V, D = m w / V} = n w · M w / V (7) the state equation of gas is (6). (E: water vapor pressure,
(R: gas constant, T: absolute temperature) eV = n _w RT (8) Equation (9) can be derived from equations (7) and (8). _{D = M w e / (RT} ) (9) (9) from equation saturated vapor amount ^{B (g / m 3),} C (g / m 3) is (10)
It can be expressed as an equation. [0046] _{B = M w e s (b} ) / {R · (b + 273)} (g / m 3) C = M w e s (c) / {R · (c + 273)} (g / m 3) ( 10) where e _s (b) and e _s (c) are b (° C.) and c
It is the saturated steam pressure at (° C). Eventually, substituting equation (10) into equation (6) yields equation (11). Y (% RH) = a · _es (b) / _es (c) (11) In this manner, extremely accurate humidity can be calculated. Next, a second embodiment of the present invention will be described. In this example, the second temperature detecting means, that is, the second sensor chip is omitted, and the relationship between the temperature of the first sensor chip and the applied power is measured at least at two points.
It is characterized in that the environmental temperature is calculated from this relationship curve. As shown in FIG. 5, this device has a sensor chip 1 having a heater, a temperature detecting means and a humidity detecting means formed in the same manner as the first sensor chip used in the first embodiment.
1, power measuring means 12 having an ammeter and a voltmeter for measuring the power applied to the heater, power feeding means 13,
And a drive control means 14. The drive control means 14 controls the power supply to the heater as shown in the flowchart of FIG.
mW, 105mW, 500mW of electric power to the heater,
An environment temperature is calculated from the relationship between the applied power of mW and 105 mW and the heater temperature, and the humidity is detected. That is, first, 105 mW of electric power is supplied to the heater power (step 600), and the bias temperature is set to 7.
The temperature and the humidity are measured after a lapse of a predetermined time so that the temperature becomes 5 ° C. (step 601). Here, the environmental temperature is -3.
If it is 9 ° C., the temperature at this time is about 3.6 ° C. At this time, it is determined whether or not there is condensation (step 602). If the output of the humidity sensor exceeds 80% RH, it is determined that there is condensation. If there is dew condensation, flushing is performed (step 603), and the process returns to step 600 after a predetermined time. Here, the flushing means that the power applied to the heater is increased (500 mW is applied), the bias temperature is set to 35 ° C., and the dew condensation state is eliminated. On the other hand, when it is determined that there is no dew condensation, the power supply to the heater is reduced to 60 mW (step 604), the bias temperature is set to 4.2 ° C., and after a predetermined time, the temperature (the environmental temperature is set to − If it is 3.9 ° C., the temperature is about 0.3 ° C.), and the humidity is measured (step 605). At this time as well, it is determined whether or not there is dew condensation. When it is determined that there is no dew condensation, the environmental temperature is calculated from the heater temperature at the applied power of 60 mW and 105 mW, and the output of the humidity sensor is converted based on the output value of the humidity sensor at the applied power of 60 mW. To obtain the environmental humidity (step 606). The result is shown in FIG. The environmental temperature obtained from this figure was -3.9 ° C. As a result of measuring the actual temperature, it was the same. This also indicates that the environmental temperature can be detected with high accuracy only by the first sensor chip. In the above embodiment, the detection of the environmental temperature at the ice temperature has been described. However, even when the environmental temperature is near room temperature, the detection can be performed with high accuracy. FIG. 8 shows the measurement result at this time. As a result, while the actual environmental temperature was 24.3 ° C., the value obtained from the measurement result was 24.5 ° C.
Met. From this result, it can be seen that highly accurate detection is possible. Further, according to the above configuration, since all can be formed by the thin film technology, it is possible to greatly reduce the size. Although the capacitance change type sensor is used as the temperature / humidity sensor, a resistance change type sensor may be used, and when it is used in a high temperature region, Al ₂ O ₃ ceramics may be used. Good. Further, the material of the moisture-sensitive resistance film or the material of the insulating thin film can be appropriately changed. Further, the shape of the heater is not limited to the embodiment but can be appropriately modified. As described above, according to the present invention, the size and cost of the apparatus can be reduced.
Moreover, highly accurate humidity detection can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a temperature and humidity sensor according to a first embodiment of the present invention; FIG. 2 is a diagram showing the same temperature and humidity sensor; FIG. FIG. 4 is a diagram showing a saturated water vapor amount curve used in the measurement. FIG. 4 is an explanatory diagram for calculating humidity. FIG. 5 is a diagram showing a temperature / humidity sensor according to a second embodiment of the present invention. FIG. FIG. 7 is a flowchart illustrating a method of driving the temperature and humidity sensor according to the embodiment. FIG. 7 is a diagram illustrating measurement results of the temperature and humidity sensor. FIG. 8 is a diagram illustrating measurement results of the temperature and humidity sensor. FIG. 10 shows a sensor. FIG. 10 shows a conventional temperature and humidity sensor. [Description of References] 1 Substrate 2 Heater 3 First temperature sensor 4 Humidity sensor 5 Second temperature sensor 141 Lower electrode 142 Upper part of moisture sensitive film 143 Electrode 101 substrate 102 heater 103 first temperature sensor 104 humidity sensor 05 second temperature sensor 106 insulating film T1 first sensor chip T2 second sensor chip

Claims (1)

(57) [Claim 1] A sensor substrate provided with a wiring pattern, humidity detecting means formed on the surface of the chip substrate and detecting humidity, and the chip substrate in proximity to the humidity detecting means A first temperature detecting means disposed on a surface for detecting a peripheral temperature of the humidity detecting means; and a heating means for locally heating the vicinity of the humidity detecting means to a predetermined temperature or higher.
A first sensor chip mounted on the sensor substrate, and a second sensor chip including second temperature detection means for detecting a temperature of an environment in which the first sensor chip is installed; The sensor chip is connected on the sensor substrate by a first wire that is thermally and electrically insulated for performing a mechanical connection and a second wire that is electrically connected to the wiring pattern. The output of the humidity detecting means is converted based on the output of the first temperature detecting means and the output of the second temperature detecting means, and the humidity of the environment to be measured is measured. Characteristic temperature and humidity sensor.