JPH08136490A - Ambient air detecting apparatus equipped with temperature compensating function - Google Patents

Abstract

PURPOSE: To use the output of a temperature sensor for temperature compensation as it is by installing an ambient air sensor and temperature sensors besides the former sensor all together in the same chip and making the temperature sensors generate high voltage while the temperature by heat radiation being kept low. CONSTITUTION: An ambient air detecting apparatus equipped with a temperature compensating function has a substrate 31 having a cavity 32, a plurality of bridges 331 , 332 , 333 laid over the cavity 32, an ambient air sensor 341 installed in one bridge among a plurality of the bridges, and temperature sensors 342a , 342b . 343a , 343b . Electric current high enough for the ambient air sensor to sense the ambient air in the surrounding is applied to the ambient air sensor and electric current low enough for the temperature sensor not to radiate heat is applied to the temperature sensor, so that the output voltage of temperature components of both sensors is made same and the difference of output voltage of both sensors is directly obtained to detect the ambient air in the surrounding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmosphere meter, and more particularly, it has at least two sensors (for measuring an ambient temperature and for measuring an ambient atmosphere) which are heated in a measuring atmosphere, and the resistance of these sensors. The present invention relates to a self-temperature-compensated atmosphere meter that detects the surrounding atmosphere based on the difference in values, such as a thermometer, hygrometer, gas concentration meter, infrared meter, partial pressure meter, flow meter, vacuum gauge, dew point meter, and heat wire. It can be used for various instruments such as a wind anemometer.

[0002]

2. Description of the Related Art There is known a method of thermally detecting a predetermined gas concentration contained in a mixed gas atmosphere based on a difference in thermal conductivity which changes according to the molecular weight of the predetermined gas. Among the atmosphere meters that utilize this principle, hygrometers have a particularly wide range of applications, such as electronic equipment parts such as semiconductors, optical precision equipment,
Since it is widely used as a detection end for quality control for humidity control in industrial processes such as textiles and foods, and for environmental control of hospitals, buildings, etc., the atmosphere meter according to the present invention will be referred to as a hygrometer hereinafter. The case of application is described as an example, but the present invention is not limited to a hygrometer, and relates to a general atmosphere meter having different mixed gas concentrations, specifically, the above-mentioned various instruments. Thus, for example, the principles of humidity detection of hygrometers are roughly classified into those that detect the amount of change that changes electrically and mechanically due to humidity, but both electrical and mechanical ones are based on various principles. There is something. However, there are many problems such as reliability and life, and in general, the response is poor.

Among these, a hygrometer utilizing the thermal conductivity of gas is known to have excellent responsiveness and high reliability. The amount of heat that flows through the upper and lower surfaces of a predetermined cross section in the isotropic body in the normal direction in a unit time is proportional to the temperature gradient in the normal direction and the cross-sectional area, and this proportional constant is the thermal conductivity. The thermal conductivity of a gas is a function of the constant pressure specific heat, and the constant pressure specific heat is a function of the gas molecular weight. Therefore, the thermal conductivity differs between the case where only air is used and the case where the air contains gas components or water having different molecular weights. A hygrometer utilizing the difference in thermal conductivity of gas obtains humidity from the amount of change in resistance value of a resistor caused by the difference in the amount of heat released from a heated resistor into the atmosphere.

FIG. 16 is a partial cross-sectional view showing the structure of a conventional hygrometer. The hygrometer 10 includes a temperature compensating element 1 and an atmosphere (humidity) detecting element on a heat equalizing plate 6 made of aluminum or the like having high heat conductivity. 2 and 2 are arranged close to each other. The temperature compensating element 1 and the atmosphere detecting element 2 both have a resistor 5 of the same size standard arranged in a microbridge shape on a cavity 4a provided in the detecting chip 4, and the chip 4 is fixed to a heat equalizing plate 6. It is fixed on the base 8 having high heat conductivity and bonded between the resistors 5 via the lead pins 9 insulated by a hermetic seal. The difference between the temperature compensating element 1 and the atmosphere detecting element 2 is that in the temperature compensating element 1, the resistor 3 is sealed in the dry air of a constant pressure by the sealing cap 3, whereas the atmosphere detecting element 2 is sealed. Stop cap 3
The upper surface of is covered with a breathable mesh 7.

In the hygrometer constructed as shown in the figure, both the temperature compensating element 1 and the resistor 5 of the atmosphere detecting element 2 are heated with a constant electric power via the lead pin 9. Temperature compensation element 1
Since the resistor 5 is covered with dry air having a constant pressure inside the sealing cap 3, the resistor 5 changes only by the ambient temperature without being affected by the humidity of the outside air and detects the outside air temperature.

On the other hand, since the upper surface of the sealing cap 3 is covered with the mesh 7, the resistance of the resistor 5 of the atmosphere detecting element 2 changes depending on the temperature and humidity of the atmosphere containing moisture. Therefore, the resistance change due to humidity is calculated by subtracting the resistance value of the resistor 5 of the temperature compensation element 1 from the resistance value of the resistor 5 of the atmosphere detection element 2. The change in resistance value is actually detected as a voltage value.

However, the temperature compensating element 1 sealed by the sealing cap 3 has a small thermal conductivity which slows the heat conduction between the resistor 5 and the sealing cap 3 when the ambient temperature changes rapidly. Sealing cap 3 due to the air buffer layer
The outside air temperature fluctuation around the outer circumference cannot be swiftly followed and the response of ambient temperature detection is delayed.

On the other hand, in the atmosphere detecting element 2 having the mesh 7, the atmosphere temperature is directly transmitted to the heated resistor 5, so that the response is fast. Therefore, when the atmosphere changes rapidly, an error occurs between the ambient temperature detected by the detection element 2 and the ambient temperature detected by the temperature compensation element 1.

FIGS. 17 (a), (b) and (c) are diagrams for explaining the occurrence of a detection error due to a response delay in the atmospheric temperature detection of the conventional hygrometer. As shown in FIG. 17 (a), the ambient temperature T was 20 ° C. from time t ₀ (0 second) to t ₁ (0.01 second), but suddenly after T ₂ (0.02 second) T = 4
When the temperature rises to 0 ° C. and is kept at the constant temperature T = 40 ° C. after the time t ₂ , at each time, FIG.
The temperature change component (indicated by voltage) of the detection element 2 of FIG.
FIG. 17B shows the temperature change component of the temperature compensation element 1.
The temperature compensating element 1 is detected as indicated by the hatched line in (c).
In, it is detected with a considerable time delay.

That is, when the ambient temperature is the time t ₁ (0.01
When the temperature T = 20 ° C. is started to rise uniformly for 2 seconds), ΔE ₁ b is immediately detected from the detecting element 2 as shown in FIG. However, in the temperature compensating element 1, the temperature in the state of T = 20 ° C. is detected. Time t _{1 to} t ₂ (0.01 to 0.02 seconds)
And the detecting element 2 at time t ₂ later, 17
As shown in (b), the temperature compensating element 1 responds quickly to the change in the ambient temperature T, and the temperature changes ΔE ₁ b and ΔE ₂ b are detected, whereas the temperature compensating element 1 is shown in FIG. 17 (c). like,
There is no temperature change until time t ₂ (0.02 seconds).
_The temperature variation ΔE ₃ c is detected after ₂ , that is, the temperature variation around the outer circumference of the cap cannot be followed and the response is delayed.
As a result, a humidity detection error corresponding to a detection delay of ΔE ₁ b, ΔE ₂ b and ΔE ₃ b−ΔE ₃ c occurs. Therefore,
When the intermittent driving method is used in which these elements are applied with electric power for a short time, the temperature detected by the temperature compensation element 1 is obviously different from the ambient temperature.

In the atmosphere detecting device having the temperature compensating element and the atmosphere detecting element as described above, unless the dry air is enclosed at a constant pressure, the thermal conductivity of the enclosed gas changes, and the temperature detecting characteristic of the temperature compensating element itself is changed. It can change and lose its compensation role.

Further, since the ambient humidity is detected by using the constant pressure of the air enclosed in the temperature compensating element as a compensation reference, the thermal conductivity also varies if the ambient humidity pressure (outside pressure) changes. Therefore, the effect of the standard becomes smaller. Therefore, it is necessary to precisely control the enclosure conditions for enclosing the humidity of dry air and dry air at a constant pressure, and these variations appear as characteristic variations during production, and at the same time, it is difficult to balance the combination of the detection element and the temperature compensation element. As a result, the yield rate becomes low.

Further, since the temperature of the temperature compensating element is constant, the pressure of the dry air is constant, so that the pressure of the gas to be detected, that is, the thermal conductivity, changes when the element is used in the surrounding meteorological conditions or high altitude areas. Temperature compensation is possible if the internal pressure changes in the same way as the external atmospheric pressure according to the operating conditions.
In particular, since the sealing cap does not have a flexible material and structure in which the sealing cap is deformed due to atmospheric pressure fluctuation and the internal pressure is also changed, an accurate detection value cannot be obtained.

Further, when the atmosphere to be detected is partially uneven, in the conventional example shown in FIG. 16, the distance between the detecting element and the temperature compensating element is relatively large, so the detected signal is It is meaningless because it is a comparison value in the state of each place, and it shows values at different detection positions, not values at one point (same position). Therefore, it is preferable that the detecting element and the temperature compensating element are as close as possible, and preferably, they may be combined on one substrate.

In view of the above situation, the applicant of the present invention is
First, when the detection element (sensor) is heated in an atmosphere in which a specific gas concentration is measured and the heating power is small,
The resistance value changes almost only with the ambient temperature without being affected by the specific gas concentration, and the resistance value becomes a function of the ambient temperature.When the heating power is large, the resistance value of the sensor is different from the ambient temperature and the specific gas concentration. By utilizing the fact that it becomes a function of, the sensor is arranged in a microbridge shape in a sealing cap having a mesh, and a small electric power not affected by a specific gas concentration and a large electric power affected by a specific gas concentration Atmosphere detection device that calculates the specific gas concentration at the same place by the same sensor by continuously heating the sensor and subtracting the resistance value when the sensor is driven at high power from the resistance value when it is driven at low power did.

FIG. 18 is a diagram for explaining the principle of a hygrometer as an example of the above-described atmosphere detecting apparatus proposed by the applicant of the present invention. For the sake of easy understanding, the humidity of a conventional hygrometer is shown. Description will be made in comparison with the measurement principle. In FIG.
White arrows (a ₁ ) → (b ₁ ) → (c ₁ ) → (d ₁ ) are humidity measurements by the applicant, (a ₁ ) → (b ₁ ), (a ₂ ) →
(B ₂ ) → (b ₃ ) shows a flow of conventional humidity measurement. FIG. 18 (a ₁ ) is a structural diagram of the humidity detecting element, FIG. 18 (a ₂ ).
18 is a temperature compensating element structure diagram, in which 3 is a sealing cap, 5 is a resistor (referred to as a sensor), 6 is a soaking plate (base), 7 is a mesh, 9 is a lead pin, and FIG.
In the humidity detecting element shown in (a ₁ ), the detecting element 5 is welded to the tips of parallel lead pins 9 penetrating through the base 3 made of a high thermal conductive material with a hermetic seal at a predetermined minute interval. The sealing cap 3 having the mesh 7 is fixed to the base 6. The detection element 5 has a positive temperature characteristic, for example, platinum, tungsten, nichrome, kathal, or a negative temperature coefficient, for example,
A fine wire or thin film of SiC (silicon carbide), TaN (tantalum nitride) or the like, or a micro temperature sensitive element such as a thermistor is connected.

The resistance value of the above-mentioned detection element 5 changes according to the ambient temperature and humidity when it is heated at a low temperature or a high temperature, and its heat capacity is extremely small.
For this reason, the detection element 5 uses a micro temperature sensitive element composed of a fine wire or a micro body in a micro bridge structure, reaches a predetermined thermal equilibrium temperature in a short time during heating, and immediately stops the surroundings when heating power is stopped. I try to return to the temperature.

The temperature compensating element 5 shown in FIG. 18 (a ₂ ) has the same standard as that of the humidity detecting element 5 shown in FIG. 18 (a ₁ ), and the detecting element 5 is sealed with a mesh-less sealing cap. It was done. Hereinafter, FIG. 18 having the above structure
FIG. 18 shows a conventional humidity detection principle using the humidity detecting element shown in (a ₁ ) and the temperature compensating element shown in FIG. 18 (a ₂ ).
The principle of humidity detection previously proposed by the applicant using only the humidity detecting element shown in (a ₁ ) will be described.

19 (a) and 19 (b) are voltage-current characteristic diagrams of the humidity detecting element, and FIG. 19 (a) is a diagram showing the humidity characteristic, in the humidity detecting element of FIG. 18 (a ₁ ). , Voltage-current characteristics A ₁ (dotted line) when the ambient temperature is constant at 30 ° C and humidity is 200 g / m ³ and voltage-current characteristics A when the humidity is 0 g / m ^3.
₂ (solid line) is a characteristic curve, and FIG. 19 (b) is a diagram showing temperature characteristics. The voltage-current characteristic B ₁ (dotted line) when the temperature is 20 ° C. and the voltage-current at 30 ° C. at a humidity of 0 g / m ³ are shown. Characteristic B ₂
(Solid line), a characteristic curve showing voltage-current characteristics B ₃ (dotted line) at 40 ° C., where the horizontal axis represents the detection element applied voltage and the vertical axis represents the detection element applied current.

In the voltage-current curve at 30 ° C. showing the humidity characteristic of FIG. 19A, the applied current to the humidity detecting element is 2
At a small heating current of mA or less, the A ₁ curve and the A ₂ curve are substantially overlapped and the corresponding voltage is about 0.8 V or less, and at this low current heating, the temperature characteristics not affected by humidity. For a large current of 8 mA applied to the detection element, the A ₁ curve shows about 3 V (volts) and the A ₂ curve shows about 4 V. With high current heating, the higher the humidity, the smaller the voltage generated in the detection element. , The voltage corresponding to the humidity can be obtained.

Humidity 0 g / indicating the temperature characteristic of FIG. 19 (b)
In the voltage-current curve at m ^3, since there is no humidity around the detection element, when a constant current, for example, 2 mA is applied to the detection element, the voltage generated across the detection element is the curve B ₁ ,
As shown in B ₂ and B _3, it is shown that the higher the ambient temperature, the higher the temperature, and the lower the ambient temperature, the lower the temperature.

In FIG. 18, in FIG. 18 (b ₁ ), (b ₂ ),
(b ₃ ), (c ₁ ), (d ₁ ) are the absolute humidity (g / m) on the horizontal axis.
³ ) is a graph showing the output voltage (V) on the vertical axis. FIG. 18 (b ₁ ) is a humidity detecting element 5 shown in FIG. 18 (a ₁ ).
Ambient temperature when applying a current of 8mA to 20 ℃, 3
0 ° C., a view showing a straight line B _11, B ₁₂ and B ₁₃ showing the relationship between the absolute humidity and the output voltage at 40 ° C., is in the negative proportional to the output voltage and the absolute humidity, ambient temperature Proportional to.

On the other hand, in the temperature compensating element shown in FIG. 18 (a ₂ ), the output voltage naturally changes irrespective of the absolute humidity as shown in FIG. 18 (b ₂ ) in proportion to only the ambient temperature. To do. Straight lines with ambient temperatures of 20 ° C., 30 ° C. and 40 ° C. are designated as B ₂₁ , B ₂₂ and B ₂₃ , respectively.

The output corresponding to the absolute humidity at the same ambient temperature is subtracted from FIGS. 18 (b ₁ ) and 18 (b ₂ ). When the straight lines B ₁₃ to B ₂₃ , B ₁₂ to B ₂₂ , and B ₁₁ to B ₂₁ are subtracted, as shown in FIG. 18 (b ₃ ), only the absolute humidity is negative regardless of the ambient temperature. A relational line B ₃₃ between the absolute humidity and the output voltage, which is in a proportional relationship, is obtained.

In the hygrometer shown in FIG. 18 (a ₁ ), when the detection element 5 is driven with a low current, for example, 1 mA, the absolute humidity is affected as shown in FIGS. 19 (a) and 19 (b). However, the output voltage proportional to only the ambient humidity of 20 ° C., 30 ° C. and 40 ° C. is obtained, and the parallel straight lines c ₁ , c ₂ , c ₃ shown in FIG. 18 (c ₁ ) are obtained. This shows the same relationship as FIG. 18 (b ₂ ), and FIG. 18 (c ₁ ) and FIG.
From the relationship of (b ₁ ), as shown in FIG. 18 (d ₁ ), an output straight line B ₀ having a negative proportional relationship only to the absolute humidity equal to the characteristic of FIG. 18 (b ₃ ) is obtained.

In the above description, the case where the humidity detecting element is driven by a constant current has been described. However, since the heat capacity of the detecting element 5 is extremely small and the response is excellent, it may be driven by a pulse current having a short time width. . Alternatively, constant voltage or constant voltage pulse driving may be used.

FIG. 20 is a diagram for explaining the driving method of the humidity detecting element shown in FIG. 18 (a ₁ ).
(A ₁₎ pulse current driving method, FIG. 20 (a ₂₎ shows a pulse voltage driving method. That is, this humidity detecting element is
As long as the driving is performed according to the humidity characteristic curve of 9 (a) and the temperature characteristic curve of FIG. 19 (b), the driving pulse may be constant current or constant voltage. In the case of the constant current pulse drive shown in FIG. 20 (a ₁ ), the constant current pulse power supply 11 and the detection element 5 are connected in series to detect the voltage Vout across the detection element 5. In the pulse voltage driving method of FIG. 20 (a ₂ ), the constant voltage pulse power supply 12 and the detection resistor R ₀ and the detection element 5 are connected in series to form a voltage Vou across the detection resistor R _0.
detect t. In any case, two kinds of constant current or constant voltage pulses having different temperature values during driving are applied to the detection element 5.

FIG. 20 (b) is a diagram showing an example of a current pulse train at the time of current pulse driving shown in FIG. 20 (a ₁ ). The peak value of the detection element 5 is changed from time t ₁ to time t _2. Two
A small pulse current of mA and pulse width of 50 ms (millisecond) is applied, and subsequently, the peak value is 8 m from time t ₂ to time t _3.
At A, a large pulse current with a pulse width of 50 ms is applied. After a rest time of 100 ms from time t ₃ to time t ₄ , it is driven again by a current pulse train of small current pulses of 2 mA and 8 mA and large current pulses of the same time width.

FIG. 20C shows a voltage (Vo) generated between the detection elements 5 by the current pulse driving shown in FIG.
ut) of the voltage pulse train, a voltage pulse with a time delay occurs at the rise of the current pulse. Therefore, it is necessary to detect the voltage within the time width of c ₁ and c ₂ where the voltage value is stable. Note that the drive current pulse train shown in FIG. 20B has a rest period of 8 m between times t _{3 and} t _4.
The time width in which the heat generation temperature of the detection element 5 is substantially the ambient temperature after the application of the pulse current A is selected.

In FIG. 20B, the small current pulse and the large current pulse are continuously applied to the detecting element 5, but the large current is applied after a predetermined stabilization time has elapsed after the small current was applied. However, since a time delay occurs for each drive current pulse, high response cannot be detected. On the other hand, according to the driving method shown in FIG.
As indicated by the dotted line d _{1 in} (d), the responsiveness of the output voltage when a large current pulse is applied is enhanced by preheating due to the small current drive.

FIGS. 21 (a) and 21 (b) show current pulse waveforms and voltage pulse output waveforms when a large current pulse drive is continuously driven by a small current pulse current. First, with a time width T ₁ . Large current pulse (8mA) for temperature and humidity detection
21 and then continuously driven by a small current pulse (2 mA) for temperature detection of the time width T ₂ , the output voltage is as shown in FIG.
As shown by B ₁ in (b), the time delay of the start-up at the time of driving the large current pulse becomes large, and similarly, the time delay at the time of the fall becomes large as shown by B ₂ , so that the small current pulse The output voltage stabilization time during driving becomes long and detection with excellent responsiveness cannot be performed.

22 (a), (b), (c) and (d) are
FIG. 22 (a) is a diagram for explaining the relationship between the environmental change and the output characteristic of the humidity detecting element shown in FIG. 18 (a ₁ ). FIG. 22 (a) shows the temperature change on the time axis and FIG. 22 (b) shows the time axis. 22C shows the applied current waveform, and FIG. 22D shows the detected output voltage waveform by the applied current corresponding to the temperature change and the humidity change.

The applied current is a continuous pulse current consisting of a large current pulse of 8 mA applied with a small current pulse of 2 mA with a predetermined rest time, and this pulse current is time t _0.
It is outputted once during ~ t ₁ , t ₁ ~ t ₂ and t ₂ ~ t ₃ . On the other hand, the temperature change is as shown in FIG.
20 ° C., 30 ° C., 4 during the period of time t ₁ to t ₂ from 0 ° C.
It is assumed that the temperature changes to 0 ° C. and is kept at 30 ° C. in other periods. Further, humidity change is to change the 10 g / m ³ or 30 g / m ³ in the period of constant humidity 20 g / m ³ from the time t ₂ ~t ₃ as shown in FIG. 22 (b).

[0034] Thus, in a period of time t ₀ ~t ₁ temperature, constant humidity both are changing only humidity for a period of time changes only the temperature t ₂ ~t ₃ during a period of time t ₁ ~t _2. As a result, the detected output voltage waveform becomes an output voltage corresponding to constant temperature and humidity during the period from time t ₀ to t ₁ as shown in FIG. 22D, and constant humidity during the period from time t _{1 to} t _2. Therefore, the output voltage is proportional to only the temperature, and the subtraction value obtained by subtracting the output voltage during the small current driving from the output voltage during the large current driving becomes constant. In this case, there is no humidity influence. On the contrary,
In the period from time t ₂ to time t ₃ when only the humidity changes, the output voltage during the small current driving is constant even in the case of the humidity ,, and changes due to the humidity only during the large current driving. The output voltage at this time is small when the humidity is high, and is large when the humidity is low. Next, a description will be given based on a drive circuit that performs such calculation.

FIG. 23 is a block diagram showing an example of a drive circuit in the case of performing humidity measurement using the detecting element shown in FIG. 18 (a ₁ ). In the figure, reference numeral 15 denotes a constant current detecting element (sensor). ) 5 (a constant current circuit), 16 is a coefficient setting circuit, 17 is a hold circuit, 18 is a subtraction circuit, 19 is an output terminal, and the constant current circuit 15 has the detection element 5 and one end grounded. The series resistance with the reference resistance R is loaded, the voltage of the reference resistance R is fed back to the inverting input terminal of the constant current circuit 15, and the switch SW ₁ having a, b and c contacts is connected to the non-inverting input terminal. To be done. The a contact of the switch SW ₁ has a reference voltage V _REF 1, the b contact has V _REF 2, and the c contact is grounded, and the reference voltages V _REF 1 and V _REF 2 have V _REF 1 = 2R (mV) (1 ) V _REF 2 = 8R (mV) (2) is set.

Further, at the output end of the constant current circuit 15, a, b
A switch SW ₂ having a contact is connected, and the a contact has
A coefficient K is set for converting the temperature at low temperature heating into the ambient temperature when calculating the humidity. For example, a coefficient setting circuit 16 having an amplification degree variable according to K is connected, and a subtraction circuit is provided at the b contact. It is connected to one of the input ends of 18 and inputs the output voltage V ₃ when a large current flows at the time of high temperature heating.

A switch SW ₃ having an a-contact and a c-contact and a hold circuit 17 are connected between the coefficient setting circuit 16 and the subtraction circuit 18. The a contact of the switch SW ₃ is connected to the hold circuit 17.

The switches SW ₁ , SW ₂ and SW ₃ of the drive circuit configured as described above are interlocked with each other, and the a, b and c contacts of the switches SW ₁ , SW ₂ and SW ₃ are simultaneously switched by switching. To be When the contact is switched to the a-contact, a voltage equal to the reference voltage V _REF 1 is applied to the reference resistor R connected to the inverting input terminal of the constant current circuit 15, and the detection element 5 receives 2
A constant current of mA flows. Similarly, when switching to b contact,
A voltage equal to the reference voltage V _REF 2 is applied to the reference resistor R, and a constant current of 8 mA flows through the detection element 5.

FIG. 24 is a waveform diagram in each part of the drive circuit shown in FIG. 23. The operation of the drive circuit will be described below with reference to FIGS. 23 and 24. Switch SW ₁ (SW ₂ , S
W ₃ also driven synchronization) FIG. 24 (a), (switched by the drive voltage period of the pulse by a time t ₁ ~t ₂ and time t ₂ ~t ₃ of voltage waveform b), the detection element 5 according to the switching In Figure 2
Drive currents 2 mA and 8 mA indicated by is flow in 4 (c). a switch SW ₂ when it is switched to a contact
The voltage V ₁ shown in FIG. 24D, which is proportional to the ambient temperature, is output to the contact. The voltage V ₁ is input to the coefficient setting circuit 16 and multiplied by a preset coefficient K, and the voltage V ₂ (= KV ₁ ) shown in FIG. 24 (e) is output. Switch SW ₂ is a
When switched to the contact, the output voltage V ₁ is not a value that is correctly proportional to the ambient temperature, and therefore is a coefficient for correcting the voltage V ₁ so as to correspond to the ambient temperature. K = (V ₃ −humidity change Min) / V ₁ (3)

The hold circuit 17, as shown in FIG. 24 (f), and outputs a voltage V ₂ equal _{V '2 (= V 2)} .
The voltage V ₃ and V ′ ₂ (= V ₂ ) are input to the subtraction circuit 18, and the voltage V proportional to the absolute humidity shown in FIG. 24 (h) is output. That is, V = V ₃ −V ₂ (4) is obtained.

FIG. 25 is a configuration diagram for explaining an example of a conventional atmosphere detecting device suitable for use as described above. FIG. 25 (a) is a plan view and FIG. 25 (b) is a diagram. 25
The sectional view on the BB line of (a) is shown, 21 is S, for example in the figure.
The i substrate and 22 are cavities provided in the Si substrate 21.
A bridge 23a made of an insulating film 23 such as O ₂ or Ta ₂ O ₅
On the bridge 23a, for example, Pt, Ni
A resistor pattern 24 made of Cr or the like is provided, and further,
S is formed on the resistor pattern (micro heater) 24.
A protective film 25 made of iO ₁ , Ta ₂ O ₅ or the like is provided, and a current flows from the bonding wire 26 to the resistor pattern 24 through the resistor pattern 24a. The warm (heat) part A is heated.

For example, the case of measuring the humidity by using the detector as described above will be described as an example.
Since the resistance value of 4 depends on the ambient temperature and humidity, for example, first, a minute current such that the humidity sensitivity becomes 0 is measured to measure the resistance value related to the ambient temperature, and then a current having humidity sensitivity is applied. The resistance value related to the ambient temperature and humidity is measured, and then the measured value related to the temperature is subtracted from the measured value related to the temperature and humidity to measure the ambient humidity.

In the detection device as described above, by arranging the material of the sensor section and the arrangement thereof, for example, temperature, humidity, gas, infrared rays, pressure, vacuum degree, acceleration, flow rate, flow velocity, etc. can be measured. As a physical phenomenon, the following principles 1 to 7, namely, 1. As the resistance value change of the electric resistor, 2. It has a sensitive film for desorbing an atmosphere and the electric resistance value of the sensitive film changes. 3. It has a sensitive film that desorbs an atmosphere, and the capacitance of the sensitive film changes. 4. A sensitive film for desorbing an atmosphere is provided, and a change in weight of the sensitive film is used as a change in resonance frequency. 5. Having a sensitive film for desorbing the atmosphere, the reaction heat is generated by the chemical reaction of the sensitive film, and this heat is used as the resistance value change of another resistor. It is measured by using the temperature change as the output voltage change of the thermocouple membrane. Thus, the above 1 to 6
When measuring the physical quantity of the object to be measured using the measurement principle of, the measured value is affected by the temperature, so if the temperature of the object to be measured is not known accurately, a meaningless measurement result Become.

As described above, the present applicant has previously proposed that, as a method capable of accurately detecting the temperature under the condition that the ambient temperature fluctuates, the temperature detected value at the time of large applied power is temperature-compensated. Proposed to use the temperature detection value at small applied power,
As a signal processing method to realize this, at a small applied power,
The output voltage value V ₁ with respect to temperature is obtained, this is amplified based on a constant conversion value to obtain V _2, and the output voltage value V ₃ with respect to temperature and humidity at a large applied power is obtained, V ₃ −V _{By 2,} the humidity measurement value after temperature compensation is detected separately. By doing so, the microheater having a small heat capacity has a small thermal time constant and a high-speed response, and therefore this separation detection can be performed even when the large and small applied powers are switched in a short time. This allows
It becomes possible to detect the state of the atmosphere with one micro heater (humidity detection element), and the following merits are further produced. a. It became unnecessary to adjust the variation and output balance by combining with the temperature compensation element. b. The variation due to the combination with the temperature compensation element made it unnecessary to manage the characteristics over time. c. It can cope with ambient pressure fluctuations. d. The number of detecting elements has been reduced from two to one, and the size can be further reduced. e. Power consumption has been halved. f. Compensation and detection can be performed at the same position, which enables highly accurate detection. g. Compensation and detection temperature response can be made almost the same, and detection can be performed with high accuracy.

[0045]

However, the detection device previously proposed by the applicant of the present invention is the output voltage value V ₁ at a small applied power.
However, the temperature compensation is not always sufficient because the influence of noise and linearity of the amplifier circuit and the like appears inevitably when this is amplified. In order to improve the accuracy of temperature compensation, it is desired to set the value of V ₁ which is not affected by noise during amplification, but for that purpose, V ₁ should be set to a large value. However, in order to detect only the temperature, the heater must have a low exothermic temperature.

The present invention has been made in view of the above-mentioned circumstances, and a new micro-heater for V ₁ and a heater for detecting temperature and humidity are separately provided in one chip. _{The 1st} pattern is designed to generate a high voltage even at a low heat generation temperature. However, it is considered that the voltage can be quadrupled if the film thickness of the resistor is set to 1/4 or the line width is set to 1/4, but since the heat capacity is almost the same, heat is generated by the increase in power consumption. The temperature rises (the voltage also becomes four times or more), and this cannot be realized simply by increasing the operating resistance value of the V ₁ pattern.

[0047]

In order to solve the above problems, the present invention provides (1) a substrate having a cavity, a plurality of bridges bridged over the cavity, and among the plurality of bridges. An atmosphere sensor disposed on one bridge and a temperature sensor disposed on another bridge of the plurality of bridges, wherein the atmosphere sensor has a high sensitivity to the ambient atmosphere. The temperature is set to a heat generation temperature, the temperature sensor is set to a low heat generation temperature at which the temperature sensor can detect only the ambient temperature, and the ambient atmosphere is detected by obtaining the difference between the output voltages of the both sensors. ) The atmosphere sensor and the temperature sensor respectively constitute adjacent sides of the Wheatstone bridge circuit, and the currents flowing through the two sensors are made different, and further, (3) the temperature sensor is duplicated on a single bridge. That are pieces formed, and further,
(4) Having a plurality of bridges for temperature sensors, and having one or a plurality of temperature sensors on each bridge.
(5) The temperature sensors arranged on the bridge for the temperature sensor are connected in series, and further,
(6) The sensors arranged on the temperature detecting bridge are arranged so that they can be connected in parallel, and
(7) The resistance value of the temperature detecting sensor is larger than the resistance value of the atmosphere detecting sensor, and (8) the dimensions of the temperature detecting sensor and the atmosphere detecting sensor are made uniform. And increasing the heat capacity of the temperature detecting sensor so that the current flowing through the temperature detecting sensor is the same as the current flowing through the atmosphere detecting sensor, and (9) the penetration of the cavity through the substrate. A cavity having bridges on the upper and lower surfaces of the through cavity, one bridge having a temperature detecting sensor and the other bridge having an atmosphere detecting sensor, and (10) trimming on the substrate. The resistance pattern is trimmed, and the current flowing through the temperature detection sensor is adjusted by trimming the resistance pattern, and (11) the temperature detection sensor,
A small current is constantly applied to heat the atmosphere detecting sensor so as to prevent water and the like from adhering to the atmosphere detecting sensor, and (12) the atmosphere sensor has a negative temperature coefficient of heat generation. It is characterized by being a material.

[0048]

The present invention has a substrate having a cavity, a bridge disposed above the cavity, and an atmosphere sensor disposed above the bridge, and a current is passed through the atmosphere sensor to cause resistance of the atmosphere sensor. In a thermal-dependent detection device that measures the measured object that depends on the temperature of the ambient atmosphere rather than its resistance value, a further bridge is provided on the cavity, and an ambient temperature is detected on the bridge. A resistor is provided, and the detection value of the object to be measured detected by the atmosphere sensor is corrected by the resistance value of the resistor.

[0049]

【Example】

[Embodiment 1] FIG. 1 is a plan view for explaining an embodiment of a detection apparatus according to the present invention, in which 31 is, for example, S
Substrates i, 32 and 32 'are cavities formed in the substrate 31, and the cavities 32 may be through cavities penetrating the substrate 31 or non-penetrating cavities having a bottom portion as shown in FIG. . As shown in FIG. 25, an insulating film of, for example, SiO ₂ , Ta ₂ O ₅ or the like is applied to the upper portion of the substrate 31, and a plurality of (three in the illustrated example) bridges made of this insulating film are bridged. 33 ₁ , 33 ₂ , 33 ₃ are formed in the upper part of the cavity 32. In the case of the illustrated example, humidity is assumed as the measured object, and therefore, these bridges 33 ₁ , 33 ₂ ,
On 33 ₃ , for example, a temperature / humidity detection resistor pattern 34 ₁ (atmosphere sensor) made of Pt, NtCr, etc. and temperature detection resistor patterns 34 _2a , 34 _2b , 34 _3a ,
34 _3b (temperature sensor) and conductor patterns 35 ₁ , 35 ₂ , 35 ₃ for supplying power to these resistor patterns or detecting the resistance value of these resistor patterns
Is provided. A protective film made of SiO ₂ , Ta ₂ O ₅ or the like is formed on these patterns, for example, as shown in FIG.

Thus, the exothermic temperature of the exothermic part is kept low,
Moreover, in order to obtain a large output V ₁ , the same micro patterns may be connected in series by the number corresponding to the amplification factor. In FIG. 1, 34 _2a , 34 _2b , 34 _3a , 34
_3b is a resistor for temperature detection, which is connected in series on a bridge arranged on the cavity 32, and 34 ₁ is a resistor for temperature and humidity detection.

FIG. 2 is a diagram showing an example of use of the detection device shown in FIG. 1. FIG. 2 (a) is a block diagram, FIG. 2 (b) is an electric circuit diagram, and FIG. As shown in a), a small current of 2 mA is applied to the four resistors 34 _2a , 34 _2b , 34 _3a , and 34 _3b connected in series, and a large current (8 mA) is applied to the resistor 34 ₁ at the same time. This is designed to obtain the potential difference between the resistors. By doing so, the humidity can be detected by one operation. That is, the resistors 34 _2a , 34 _2b , 3
Since only 4 mA flows to 4 _3a and 34 _3b , the heat generation amount of each of these resistors is the same as in the conventional case, but in the present invention, four of them (the number corresponding to the amplification factor) are connected in series. Therefore, it is possible to obtain an output voltage equivalent to that directly amplified without using an amplifier.

3A and 3B are views for explaining the driving method of the detection device shown in FIG. 1. FIG. 3A shows the case of constant current drive, and FIG. 3B shows the case of constant voltage drive. In the case of constant current driving, temperature detecting resistors (temperature sensor) 34 _2a , 3
4 _2b , 34 _3b and 34 _3a are set to a low current (for example, 2 mA) such that these resistors hardly generate heat, and the current flowing to the temperature / humidity detecting resistor (atmosphere sensor) 34 ₁ is changed to the atmosphere. large current sensor 34 ₁ is required to increase to a temperature that is sensitive to the atmosphere to be measured (e.g., 8m
In the case of the constant voltage drive, the voltage applied to the temperature sensor and the voltage applied to the atmosphere sensor are made equal, and as a result, the current flowing through the temperature sensor is reduced (for example, 2).
mA), increase the current flowing through the atmosphere sensor (for example,
8 mA).

In the circuit example shown in FIG. 2B, the atmosphere sensor (34 ₁ ) and the temperature sensors (34 _2a , 34 _2b ,
34 _3b and 34 _3a ) respectively form the adjacent sides of the Wheatstone bridge, the current flowing through the atmosphere sensor is set to, for example, 8 mA by adjusting the resistances R ₁ and R ₂ . The current flowing through the temperature detecting sensor can be set to, for example, 2 mA, whereby the output of the atmosphere sensor (ambient temperature + atmosphere of the measured object can be set in a single operation without switching the currents flowing through the sensors). ) And the output of the temperature sensor (ambient temperature) can be obtained, and from this, the ambient atmosphere that is the object to be measured can be obtained.

However, the present invention is not limited to the above embodiment, and the method shown in FIGS. 3 (c) and 3 (d), for example, a minute current is first passed through the temperature sensor to measure the ambient temperature. Then, a current that is sensitive to the ambient atmosphere in which the sensor is to be measured is applied to the atmosphere sensor to measure the ambient temperature and the ambient atmosphere, and then the ambient atmosphere is measured by calculating the difference between them. In this case, since the temperature-compensated output voltage is at substantially the same level as the temperature-humidity output voltage, the signal processing circuit can be made simpler and the accuracy is high. be able to. Furthermore, since the temperature sensor and the atmosphere sensor are separately configured, it is possible to configure the Wheatstone bridge without using the pulse current having the two-stage waveform as shown in FIG. 3C. Even if not, as shown in FIG. 2 (e), the temperature sensor and the atmosphere sensor are separately supplied with the corresponding currents, for example, 2 mA and 8 mA at the same time.
By flowing, temperature compensation can be performed simultaneously with the atmosphere measurement, as in the case of the Wheatstone bridge.

FIG. 4 is a plan view for explaining another embodiment of the present invention. In the figure, 31 is a substrate, 32 is a cavity formed in the substrate 31, and above the cavity 32, The atmosphere sensor 34 ₁ and the temperature sensors 34 ₂ and 34 ₃ are bridged. Thus, in this embodiment, the temperature sensors 34 ₂ and 34 ₃ are independently provided (in the embodiment shown in FIG. 1, they are provided in series on the substrate 31 in advance), and the external circuit side so,
It is designed to be connected in series and in parallel and has an expanded usability. Furthermore, the temperature sensor and the atmosphere sensor have the same structure, which reduces variations, stability over time, and chip area. It is intended to be useful for etc.

FIG. 5 is a diagram showing an example of use of the detection device shown in FIG. 4. FIG. 5 (a) shows a state at the time of temperature detection, and FIG. 5 (b) shows a state at the time of temperature / humidity detection. As shown in FIG. 5 (a), three sensors 34 ₁ , 34 ₂ , 34 ₃ are connected in series by a switch SW, and a current of, for example, 3 mA is applied from the constant current source 11 to them, In order to obtain 3.5V at the output terminal OUT, the temperature and humidity are detected as shown in Fig. 5 (b).
As shown in, when only the temperature / humidity sensor 34 ₁ is connected and 9 mA is supplied from the constant current source 11 to this, an output voltage of 3.5 V is obtained at the output terminal OUT. In addition,
In this case, since the temperature sensor and the temperature / humidity sensor have the same configuration as described above, either of them may be used for temperature / humidity detection.
4 using a _first sensor, during the second temperature and humidity measurements, 34 ₂
As shown in the figure, when the sensors used for temperature and humidity measurement are sequentially scanned and changed, such as using the sensor
The life can be tripled.

FIG. 6 is a plan view for explaining another embodiment of the present invention. In the figure, 31 is a substrate, 32 and 32 'are cavities, 34 ₁ is a temperature / humidity sensor (high temperature drive), 34 ₄ Is a temperature sensor (low temperature drive), 35 ₁ and 35 ₂ are lead patterns, 3
6 is a bonding wire, 37 is a lead frame, 38
Is a frame base, and 39 is a package base. In this embodiment, as the temperature sensor 34 ₄ , a material having a larger static resistance value than the temperature / humidity sensor 34 ₁ , for example, a long pattern length or a large specific resistance is used. A single temperature sensor is used to function as a plurality of temperature sensors shown in FIG. 1 or 4. In this case, the temperature sensor 34 _4, frame-based, so that susceptible to base potential heat of the package base or the like, disposed on the side closer to the base.

7A and 7B are views for explaining another embodiment of the present invention. FIG. 7A is a plan view and FIG. 7B is FIG.
In the cross-sectional view taken along the line BB of (a), in the figure, 34 ₁ is an atmosphere sensor and 34 ₅ is a temperature sensor. In this embodiment, the same size as the atmosphere sensor 34 ₁ is used as the temperature sensor 34 _5. However, the heat capacity is larger than that of the atmosphere sensor. Specifically, as shown in FIG. 7B, an electric insulating layer 40 is further provided on the electric insulating layer above the resistor (heater) of the temperature sensor 34 ₁ (in other words, the temperature sensor 34 ₅
The thickness of the insulating layer on the heater of ( ₁ ) is made thicker than the thickness of the insulating layer on the heater of the temperature / humidity sensor 34 ₁ ), thereby increasing the heat capacity of the temperature sensor 34 ₅ and thereby also the sensor of the temperature. A large current can be applied, for example, a current of the same magnitude as the current applied to the temperature / humidity sensor can be applied, the drive power supply is shared with the atmosphere sensor, and the drive power supply circuit is simplified. According to this embodiment, the atmosphere sensor and the temperature sensor can be formed in the same size pattern, so that the variation between the two patterns can be controlled by the appearance and the electric resistance value of the pattern is the same. Therefore, the electric resistance test can be easily performed. Moreover, the control of the thickness of the electrical insulating layer 40 can be accurately realized in an additional step even after the detection element is completed.

8A and 8B are views for explaining another embodiment of the present invention. FIG. 8A is a front view, FIG. 8B is a back view,
8C is a sectional view taken along the line CC of FIG. 8A. In this embodiment, the cavity 32 is a through hole penetrating the substrate 31, and the above-mentioned temperature sensors are formed on the upper and lower surfaces of the through hole 32, respectively. 34 ₅
And the atmosphere sensor 34 ₁ are provided, and the thickness of the protective insulating layer 40 on the temperature sensor 34 ₅ side is made thicker than the protective insulating layer 40 ₁ on the atmosphere sensor 34 ₁ side. Therefore, as in the embodiment shown in FIG. The heat capacity on the sensor 34 ₅ side is increased. In the embodiment shown in FIGS. 7 and 8, the heat capacity increasing layer 40 can be made of an insulating material such as SiO ₂ or Si ₃ N ₄ , or a metal material.
A high specific resistance material (= high output voltage) such as Ir, Rh, or NiCr is used for the temperature detection pattern, and P is used for the temperature and humidity detection pattern.
It is advisable to select a low specific resistance material (= low output voltage) such as t or Au.

FIG. 9 is a diagram for explaining a driving method of the detection device shown in FIGS. 7 and 8. As described above, FIG.
In the embodiment shown in FIG. 8, since the heat capacity of the temperature sensor is large, even if a large current is passed through the temperature sensor, the temperature of the temperature sensor hardly generates heat, and a low heat generation temperature can be realized. Therefore, as shown in FIG. 9A, the same amount of current (for example, 8 mA) can be applied during temperature detection and temperature / humidity detection, so that the drive circuit can be shared. Therefore, the driving circuit becomes simpler. Note that FIG. 9B shows the output voltage waveform at that time. Further, in the embodiment shown in FIGS. 7 and 8, since the temperature sensor and the atmosphere sensor are separately provided, as shown in FIGS. 9C and 9D, the same current (for example, , 8 mA).

By combining the characteristics of the temperature sensor and the temperature / humidity sensor, higher precision measurement can be expected. Since the patterns are placed as close as possible on the same board, the characteristics are relatively uniform, but in order to further improve accuracy and to improve the combined yield, the resistance value of the resistor part is checked and trimmed. And good.
However, since the microsensor has a structure supported on the cavity, it does not have the strength to withstand the local probing of the pattern (probe measurement for measuring the resistance value) and the laser trimmer. Therefore, we will install the resistance check electrode and the trimming pattern on the substrate other than the cavity, and in that case, consider which sensor this adjustment pattern is connected to is more effective. A. It is disadvantageous to S / N if an adjustment pattern having no humidity detection function is added to the temperature / humidity detection sensor due to the high temperature operation. b. If an adjustment pattern is added to the sensor that detects the temperature by low-temperature operation, the resistance value (output voltage) of the adjustment section depends on the temperature of the substrate, that is, the temperature of the surrounding atmosphere.
It has an advantageous effect on the detected temperature value. The resistor of the adjustment pattern may be made of a material having a very small temperature coefficient of resistance. Therefore, it is preferable to attach it to the temperature detection sensor. Since it is preferable to inspect each of the sensor pattern and the trimming pattern during manufacturing, a resistance check electrode is provided at an intermediate position. In particular, even if the overall resistance value is within the standard (there is a large resistance due to a missing sensor)
This is because there is a possibility of + (small resistance due to shorting of the trimming pattern) = within the standard.

FIG. 10 is a plan view for explaining another embodiment of the present invention made based on the above viewpoints.
The resistor pattern between b and b'in the figure is a trimming resistor pattern added by the present invention, and the resistor pattern in this portion is trimmed at the time of manufacturing to make the characteristics uniform and highly accurate. It should be noted that this trimming resistance pattern does not have a cavity below the pattern. If this pattern is above the cavity, the pattern will be deformed by heat collection by the laser during trimming, or
There is a risk that local heat will be generated due to thinning due to the deletion of the pattern, leading to disconnection.

FIG. 11 is a process chart for explaining an example of a method for manufacturing the detection device shown in FIG.
It is a line sectional view. First, the substrate 31 is prepared (see FIG. 11).
(A)), then a lower insulating layer 41 such as SiO ₂ is formed on the substrate 31 (FIG. 11 (b)), and a resistor layer 34 (35) is formed on the entire surface thereof (FIG. 11 (b)). c)). Then, on the resistor layer, patterns 34 ₁ , 34 _2a , 34 _2b ,
35 ₁ and 35 ₂ etc. are formed (FIG. 11D), and then a resistance value inspection, laser trimming, and a resistance value inspection are repeated to obtain a desired resistance value.

FIG. 12 is a diagram for explaining an example of the above-mentioned resistance value inspection, in which the terminal a has temperature sensors 34 _2a and 34 _2b.
And a trimming resistance value (trimming resistor pattern 35 ₂ ′) inspecting terminal, and a terminal b is a resistance value adjusting inspection of the trimming resistor 35 ₂ ′ and a bridge circuit connecting terminal between terminals ab, And the resistance value between ac are measured, and the resistance value between the terminals cb is adjusted according to the desired resistance value b
The resistance value between b '(the resistance value of the trimming pattern 35 ₂ ') is adjusted.

After the resistance value inspection, laser trimming, and resistance value inspection are performed as described above, the upper insulating layer 40 is formed (FIG. 11E), and finally, the atmosphere detecting resistor 3 is formed.
4 _1, to form a cavity 32 in the substrate 31 at the bottom of such a temperature detecting resistor 34 _2a, 34 _2b (FIG. 11 (f)). As described above, the trimming is performed before the upper insulating layer 40 is covered, but by this, the distortion of the resistor layer in the trimmed portion is alleviated by the covering, and the reliability is improved. The resistor layer of the trimming resistor may be made of another electric resistance material.

Further, since the microsensor has a high-speed heat rising characteristic, when it is used for detecting the concentration and flow rate of the atmosphere such as humidity and gas, the measurement interval is set to the second level, so that there is no problem in practical use. Intermittent driving with heat generation is sufficient. The merit in this pulse heating is as follows: a. The power consumption is reduced to almost the pulse duty ratio. b. The life of the resistance heating element is extended by the rest time. As a disadvantage, a. If gas or condensation that is difficult to separate occurs during the downtime, it will be difficult to return to the original state. In particular, since the heat capacity of the heating element is small, it is more serious than the conventional large capacity heater. As a method of improving this demerit, (1) always generate heat without pulse heat generation. When the exothermic temperature is around 300 ° C. during operation, it is preferable to perform stepwise driving so as to maintain around 100 ° C. during the standby so as to prevent water condensation. (2) With the method of (1), in order to further extend the life,
Desorption of another gas and water near the microsensor at all times 10
Provide a dedicated heater to maintain around 0 ° C. In this way, the expected life of the microsensor can be extended. In addition, it is necessary to install it in the vicinity (periphery) of the microsensor so that the desorbed material thermally decomposed at 100 ° C. does not redeposit and cause trouble.

FIG. 13 is a plan view for explaining one embodiment of the present invention, which is made based on the above viewpoint.
₁ is an atmosphere (ambient humidity and temperature) sensor (microsensor), and 34 ₂ and 34 ₃ are ambient temperature sensors and adsorbed gas (adsorbate) desorption heaters (microheaters). In the present invention, the vicinity of the microsensor 34 ₁ is used. the micro heater 34 ₂ as moisture or gas does not adhere to the microsensor 34 _1,
34 ₃ is provided, as shown in FIG.
These micro heaters 34 ₂ and 34 ₃ are, for example, 100
The micro sensor 34 is heated by being heated to ℃.
_In order to prevent gas and moisture from adhering to ₁ , the micro heaters 34 ₂ and 34 ₃ are heated to, for example, 150 ° C. to detect the ambient temperature, and the micro sensor 34 ₁ is
For example, it is heated to 400 ° C. and the atmosphere (for example, ambient temperature and humidity) is detected.

In the above description, it is assumed that the temperature sensor and the atmosphere sensor are made of a heat generating material having a positive temperature coefficient such as Pt as shown in FIG. 15 (a). ), If a material having a negative temperature characteristic is used, a large output voltage V ₁ can be obtained even with a small current I ₁ , and the same effect as that of each of the above-described embodiments can be achieved. You can That is, if there is a current value dependency and a large current is applied with a large V ₁ and a large current is applied with a small V ₃ , a single conventional microsensor and its circuit can easily perform processing. However, V ₃ and V ₁ are close to each other, I ₁ V ₁ << I ₃ V ₃ , temperature-humidity dependency is the same as before, and a heat-generating material such as impurity-diffused Si and SiC is used. I will. In this case, a large output voltage can be obtained with a small applied power (at the time of temperature detection), so that it is possible to perform temperature compensation with sufficiently high accuracy by two-stage application by one conventional microsensor. Materials such as Si and SiC for temperature detection and Pt, NiCr, Ir for temperature and humidity detection are used.
It is also possible to combine two heaters.

[0069]

As is apparent from the above description, according to the present invention, the following effects can be achieved. In a sensor that heats the sensor to measure an object to be measured in the ambient atmosphere, the larger the sensor size, the larger the heat capacity,
Although the response speed will be slow, if the heat capacity is increased in order to increase the output voltage of the temperature-compensation detection sensor, this delay may be a concern, but the heat generation temperature is low, so the time to reach that temperature is short. I knew that it was good, and there was no problem. A temperature detection sensor may be placed on the board, but since the heat capacity of the board is too large and it takes time to adapt to the temperature of the surrounding atmosphere, it is better to place it on the cavity to detect temperature and humidity. The detection characteristics of the sensor will be more accurately temperature compensated. The humidity compensation sensor and the temperature / humidity detection sensor will be used in combination, but since they are manufactured in the immediate vicinity on the same substrate, the combination accuracy is high even in view of the variation in microfabrication technology. Since both the temperature detection part and the temperature / humidity detection part are exposed under the same conditions, it is possible to cope with atmospheric pressure fluctuations as compared with the method of packaging the temperature detection part in a package. Temperature compensation and temperature detection can be performed simultaneously.

[Brief description of drawings]

FIG. 1 is a plan view for explaining an embodiment of an atmosphere detecting device with temperature compensation according to the present invention.

FIG. 2 is an electric circuit diagram showing a usage example of the detection device shown in FIG.

FIG. 3 is a current and voltage waveform diagram for explaining a driving method of the detection device shown in FIG.

FIG. 4 is a plan view for explaining another embodiment of the present invention.

5 is an electric circuit diagram showing an example of use of the detection device shown in FIG.

FIG. 6 is a plan view for explaining another embodiment of the present invention.

FIG. 7 is a plan view and a cross-sectional view for explaining another embodiment of the present invention.

FIG. 8 is a front view, a rear view, and a sectional view for explaining another embodiment of the present invention.

9 is a voltage and current waveform diagram for explaining a driving method of the detection device shown in FIGS. 7 and 8. FIG.

FIG. 10 is a plan view for explaining another embodiment of the present invention.

11 is a process chart for explaining an example of the method for manufacturing the detection device shown in FIG.

12 is an electric circuit diagram for explaining an example of a resistance value inspection of the detection device shown in FIG.

FIG. 13 is a plan view for explaining another embodiment of the present invention.

FIG. 14 is an electric circuit diagram for explaining an example of use of the detection device shown in FIG.

FIG. 15 is a diagram for comparison with a sensor having a negative temperature coefficient (conventional) and a sensor having a negative temperature coefficient (present invention).

FIG. 16 is a partial cross-sectional view showing the structure of a conventional hygrometer.

FIG. 17 is a diagram for explaining the occurrence of a detection error due to a response delay in detecting an ambient temperature of a conventional hygrometer.

FIG. 18 is a diagram for explaining the principle of a hygrometer as an example of an atmosphere detection device previously proposed by the applicant.

FIG. 19 is a voltage-current characteristic diagram of the humidity detecting element.

FIG. 20 is a diagram for explaining a driving method of the humidity detecting element shown in FIG. 18 (a ₁ ).

FIG. 21 is a diagram showing a current pulse waveform and a voltage pulse output waveform for driving the humidity detecting element previously proposed by the applicant.

FIG. 22 is a diagram for explaining the relationship between environmental changes and output characteristics of the humidity detecting element shown in FIG. 18 (a ₁ ).

23 is a block diagram showing an example of a drive circuit in the case of performing humidity measurement using the detection element shown in FIG. 18 (a ₁ ).

FIG. 24 is a waveform chart in each part of the drive circuit shown in FIG. 23.

FIG. 25 is a configuration diagram for explaining an example of a conventional atmosphere detection device.

[Explanation of symbols]

31 ... Si substrate, 32, 32 '... Cavity, 33 ₁ , 3
3 ₂ , 33 ₃ ... Bridge, 34 ₁ ... Atmosphere sensor, 34 ₂ ,
34 ₃ , 34 ₄ ... Temperature sensor, 35 ₁ , 35 ₂ ... Lead pattern, 36 ... Bonding wire, 37 ... Lead frame, 38 ... Frame base, 39 ... Package base,
40 ... Electrical insulating layer, 41 ... Lower insulating layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01N 25/64 Z G01R 17/12 A

Claims (12)

[Claims] 1. A substrate having a cavity, a plurality of bridges bridged over the cavity, and one of the plurality of bridges.
An atmosphere sensor arranged on one bridge and a temperature sensor arranged on another bridge of the plurality of bridges, and the atmosphere sensor has high heat generation in which the atmosphere sensor is sensitive to the surrounding atmosphere. Temperature compensation, the temperature sensor is set to a low heat generation temperature at which the temperature sensor can detect only the ambient temperature, and the ambient atmosphere is detected by obtaining the difference between the output voltages of the both sensors. Atmosphere detector. 2. The atmosphere sensor and the temperature sensor respectively form adjacent sides of a Wheatstone bridge circuit,
The temperature-compensated atmosphere detection device according to claim 1, wherein the currents passed through the both sensors are made different. 3. The temperature sensor according to claim 1, wherein a plurality of the temperature sensors are formed on a single bridge.
Atmosphere sensor with temperature compensation according to. 4. A plurality of temperature sensor bridges are provided,
4. The temperature-compensated atmosphere detection device according to claim 1, wherein one or more temperature sensors are provided on each bridge. 5. The temperature-compensated atmosphere detecting device according to claim 4, wherein the temperature sensors arranged on the bridge for the temperature sensor are connected in series. 6. The temperature-compensated atmosphere detecting apparatus according to claim 4, wherein the sensors arranged on the temperature detecting bridge are arranged in parallel. 7. The temperature-compensated atmosphere detection device according to claim 1, wherein a resistance value of the temperature detection sensor is larger than a resistance value of the atmosphere detection sensor. 8. The size of the temperature detecting sensor and the atmosphere detecting sensor are made uniform, the heat capacity of the temperature detecting sensor is increased, and a current flowing through the temperature detecting sensor is applied to the atmosphere detecting sensor. 8. The atmosphere detecting device with temperature compensation according to claim 1, wherein the current is the same as the current flowing through the device. 9. The cavity is a through cavity penetrating the substrate, and bridges are provided on the upper and lower surfaces of the through cavity, one bridge has a temperature detecting sensor, and the other bridge has an atmosphere detecting sensor. The temperature-compensated atmosphere detection device according to claim 1, wherein 10. A resistance pattern for trimming is provided on the substrate, and the resistance pattern is trimmed to adjust a current flowing through the temperature detecting sensor. The atmosphere detection device with temperature compensation according to any one of the above. 11. The temperature detecting sensor is kept from adhering moisture or the like to the atmosphere detecting sensor at all times.
11. The temperature-compensated atmosphere detection device according to claim 1, wherein a small current is applied to heat the atmosphere detection sensor. 12. The atmosphere sensor is an exothermic material having a negative temperature coefficient, and the atmosphere sensor is an exothermic material.
An atmosphere detection device with temperature compensation according to any one of 1.