JP2003156395A - Infrared temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared temperature sensor that can be reduced further in size, can be attached to the front end of a measuring probe, because the sensor can be used without attaching any sensor frame nor waveguide to the sensor, and can measure the body temperature of the user of the sensor with high accuracy, without being affected by the ambient temperature. SOLUTION: This infrared temperature sensor is constituted of an insulator- made base which serves as the base of the sensor, an insulator-made sealing cap laminated upon the base, so that internal spaces are formed between the base and cap, and an infrared sensor and a temperature-compensating member arranged respectively in the internal spaces formed between the base and cap. The base and cap are respectively formed of materials, having proper thermal conductivity. The cold junction of the thermopile of the infrared sensor and the temperature-compensating member are respectively provided to have proper thermal conductivity between the base and cap and a heat-generating member is provided between the base and the jointing surface of the cap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact thermometer, and more particularly to a thermometer of the type in which the tip of the probe is inserted into the ear canal to measure the temperature of the eardrum, or the thermometer tip is brought into contact with the human body. It relates to an infrared temperature sensor for use in a thermometer for measuring the surface temperature of a.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are views for explaining the structure of a conventional infrared temperature sensor (A), and FIG. 5 is a view for explaining a method of mounting the conventional infrared temperature sensor (A). As is well known, the infrared sensor B used for this type of temperature measurement has a cold junction due to the Seebeck effect, that is, a temperature difference occurs between the cold junction and the hot junction of the thermopile C composed of a plurality of thermocouples. It utilizes the phenomenon that a potential difference occurs between the hot junctions according to the temperature difference. In order to use such an infrared sensor as a temperature measuring sensor, a means D (generally a thermistor is used) for compensating for the cold junction temperature of the thermopile C is required as in the thermocouple. Become. This temperature compensation means D
Is applied in a form built in the infrared temperature sensor A together with the infrared sensor B or an external form provided separately from the infrared temperature sensor A (in the case of FIGS. 3 and 4, it is a built-in type).

The infrared absorber E of the infrared sensor B is an object to be measured that has passed through the infrared transmission filter F (not shown).
The temperature rises by absorbing the infrared rays from the, but the temperature rises also by absorbing the infrared rays radiated from the wall surface G of the package head of the infrared temperature sensor A. In normal usage, the wall surface G of the package head can theoretically be regarded as the same temperature as the infrared sensor B itself. However, in reality, when a sudden temperature change is given by an external factor, a temperature difference occurs between the package head and the infrared absorber E inside the sensor, and as a result, the infrared temperature sensor output is It becomes transiently unstable and outputs an undesired unnecessary voltage, which causes a measurement error. Also, when the environmental temperature is rising, the tip temperature rises faster than the infrared temperature sensor, which causes a positive error.On the other hand, when the environmental temperature is falling, the tip temperature rises faster than the infrared temperature sensor. As a result, the error becomes negative.

For this reason, as shown in FIG. 5, the temperature change of the infrared temperature sensor A is made uniform and gentle.
The infrared temperature sensor A itself is installed in a metal holder or a sensor frame H having good thermal conductivity, and is further surrounded by a probe I so that air or plastic as a heat insulating material is interposed between the infrared temperature sensor A and the sensor frame H. Has been formed. Further, a gold-plated metal tube or a waveguide J is provided in front of the infrared temperature sensor A so that the emissivity becomes as small as possible, and the influence of thermal radiation from the measurement object (human body) is reduced. However, providing a sensor frame and a heat insulating material around the infrared temperature sensor A and providing the waveguide J on the front surface leads to an increase in the size of the product as a measurement probe (thermometer), and the influence of the temperature change is substantial. Since there is a dimensional limit to making it practically zero, there was no choice but to allow some measurement error.

Further, as described above, a thermistor is generally used as the cold junction temperature compensating means D, but if the cold junction K of the thermopile C and the thermistor D are poor in thermal coupling, a temperature difference occurs between them. As a result, there will be an excess or deficiency in cold junction temperature compensation and accurate measurement will not be possible. For this reason,
In the recent infrared temperature sensor, by mounting the thermistor D in the same package as the infrared sensor B, the degree of thermal coupling between the cold junction K of the infrared sensor and the thermistor D is increased. However, since the cold junction K of the infrared sensor and the thermistor D are only arranged in the same package, the degree of thermal coupling between the two is still low, and the measurement error due to the temperature difference between the two cannot be eliminated. It was not there.

[0006]

The present invention allows the infrared temperature sensor to be made even smaller in size and can be used without the addition of a sensor frame or waveguide so that it can be attached to the tip of a measurement probe. Therefore, it is an object of the present invention to provide an infrared temperature sensor that enables highly accurate body temperature measurement that is not affected by environmental temperature.

[0007]

An infrared temperature sensor according to the present invention is laminated so as to form an internal space between an insulating base serving as a base and the insulating base, and
It is composed of an insulator sealing lid having an opening at its central portion, an infrared sensor and a temperature compensating member which are respectively arranged in the internal space between the insulator base and the insulator sealing lid. The cold junction and the temperature compensating member of the thermopile of the infrared sensor are respectively provided with good thermal conductivity between them and the insulator base. The insulator base and the insulator sealing lid are each made of a material having good thermal conductivity, and the heat generating member is provided between the joint surfaces of the insulator base and the insulator sealing lid.

In order to measure the temperature, the cold junction of the thermopile of the infrared sensor and the temperature compensating member are heated to a required temperature by heating the insulating base and the insulating sealing lid by heating the heating member. . When the infrared sensor is sensitive to infrared rays from the measurement object, a relative temperature output is generated according to the difference between the temperature of the infrared sensor and the temperature of the measurement object. At the same time as detecting this relative temperature output, a temperature compensating output corresponding to the cold junction temperature of the thermopile at that time is detected from the temperature compensating member. The temperature of the measurement object is measured by electrically processing these two outputs and performing temperature correction. When the measurement is completed, the heating of the insulator base and the insulator sealing lid is stopped and the temperature of the insulator base and the insulator sealing lid is returned to room temperature to prepare for the next measurement.

As described above, since the present infrared temperature sensor heats the entire infrared temperature sensor uniformly, the infrared temperature sensor is hardly affected by changes in the ambient temperature and can be directly provided at the tip of the measuring probe. Further, the infrared sensor and the temperature compensation member are provided in a form sealed in a package composed of an insulator base and an insulator sealing lid, and the temperature of the cold junction is directly heated by heating the package by a heating means. Can be changed,
The amount of heat generated by the heat generating member required to change the temperature of the cold junction can be minimized, and the heating time required to change the temperature of the cold junction can also be minimized. As a result, the time required for temperature measurement can be shortened,
It is possible to minimize the possibility that an external factor, which may be a factor of measurement error, may adversely affect the temperature, and thus to perform more accurate temperature measurement.

In a more preferable application form of the present invention, ceramic is used as a material having good thermal conductivity used for an insulator base and an insulator sealing lid, and
The insulator base and the insulator sealing lid each have a thickness necessary for conducting heat from the heating means to the whole well, but can also be molded in a smaller volume so as to have a smaller heat capacity. . Thereby, the heating of the insulating base and the insulating sealing lid and the return to normal temperature can be performed in a shorter time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In an infrared temperature sensor according to an embodiment of the present invention, as shown in FIGS. 1 and 2, an internal space 2 is formed between an insulator base 1 serving as a base and an insulator base 1. Between the insulating sealing lid 3, the infrared sensor 4 and the temperature compensating member 5 provided on the insulating base 1 in the internal space 2, and the joint surface between the insulating base 1 and the insulating sealing lid 3. And a heat generating member 6 provided in the.

The insulator base 1 and the insulator sealing lid 3 are
It is made of a material having electrical insulation and good thermal conductivity. Each of them has a thickness necessary for good conduction of heat from the heat-generating member 6 while being molded in a smaller volume so as to have a smaller heat capacity. Ceramic is suitable as a material that can satisfy all of these. The insulator sealing lid 3 is provided with an opening 8 provided with an infrared transmission filter 7 for allowing only infrared rays to reach the infrared sensor 4 from the outside.

The infrared sensor 4 has a conventional structure and includes a plurality of thermocouples 9 forming a thermopile and an infrared absorption film 10 which generates heat by infrared rays transmitted through the infrared transmission filter 7. Formed as a wafer. The heat from the infrared absorption film 10 is the hot junction 9a of the thermocouple 9.
Be transmitted to. The hot junction 9a of the thermocouple 9 is the insulator base 1
Further, the cold junction 9b of the thermocouple 9 is thermally separated from the insulator sealing lid 3 and is thermally connected to the insulator base 1. As the temperature compensating member 5, a thermistor is generally used, and the temperature compensating member 5 is thermally connected to the insulator base 1 so that the temperature of the cold junction 9b of the thermocouple 9 is always the same.

The potential difference generated by the thermocouple 9 is due to the pair of terminals 11
a and 11a, and the compensation output of the temperature compensating member 5 is taken out from the pair of terminals 11b and 11b. on the other hand,
The heat generating member 6 generates heat by energizing the pair of terminals 11c, 11c, and heats the insulator base 1 and the insulator sealing lid 3. In the case shown, one terminal 1 of the temperature compensation member 5
1b is shown to extend below the infrared sensor 4 because the heat sink 12 provided on the infrared sensor 4 provided as a single wafer causes the measured potential of the thermopile to become unstable. It has a function as a common ground provided to avoid However, if an infrared sensor having a structure without the heat sink 12 is available, the common ground terminal 11b of the temperature compensating member 5 is provided as a terminal shape only for the temperature compensating member 5, and the shape of the insulator base 1 is the heat sink. Cold junction 9 of thermocouple 9 formed into a shape including 12
It will be readily appreciated that b can be formed to bond directly to the insulator base 1, thereby more efficiently maintaining the thermal relationship.

The infrared temperature sensor of the present invention constructed as described above measures the temperature of the measuring object as follows. First, the heat generating member 6 is caused to generate heat by energizing the terminals 11c, 11c of the heat generating member to heat the insulator base 1 and the insulator sealing lid 3, and the cold contact 9b of the thermopile and the temperature compensating member 5 are heated to a desired temperature. Heat to. The temperature raised by this heating is determined by various conditions such as the environmental temperature, the amount of heat generated by the heat generating member 6, the heat capacity of the infrared temperature sensor, etc., and as a result, the temperature is maintained at a constant temperature determined by these conditions. To be done. The opening 8 of the insulator sealing lid 3 with the infrared temperature sensor kept at a constant temperature
When is brought close to the object to be measured, infrared rays from the object to be measured (external ear canal when placed in the ear canal) are absorbed by the infrared absorbing film 10 through the infrared transmitting filter 7, and thereby the infrared absorbing film 10 generates heat. The potential difference generated according to the difference between the temperature of the hot junction 9a of the thermopile changed by this heat generation and the temperature of the cold junction 9b held at a constant temperature is detected via the terminals 11a and 11a. At the same time, the value (resistance value in the case of a thermistor) of the temperature compensating member 5 at the same temperature as the cold junction 9b is detected via the terminals 11b and 11b. The relative temperature between the infrared temperature sensor and the object to be measured is calculated by converting the value of the potential difference generated in the thermopile into the temperature, while the temperature of the cold junction 9b is calculated by converting the value of the temperature compensation member 5 into the temperature. Calculate the temperature of the object to be measured by combining the calculated values of both.

Considering the variation in the performance of the temperature compensation member, which is one of the factors of the measurement error, as an example, 5
When measuring in a non-heated state with a thermometer used at an ambient temperature of ℃ to 36 ℃, in the conventional case, the temperature compensation range of the temperature compensation member is 36 ℃ -5 ℃ = 31 ℃. Temperature compensation member 5
When a thermistor is used for the thermistor, the thermistor has variations in the B constant (the slope of the temperature-resistance curve), and it is difficult to maintain high accuracy in a wide temperature range. However, in the case of the present invention, assuming that the infrared temperature sensor (microscopically, the cold junction 9b) is heated to 32 ° C., the temperature compensation range of the thermistor is 36 ° C.-32 ° C. = 4 ° C., The error due to the variation of the temperature compensation member 5 can be almost ignored. In other words, the temperature compensation range of the temperature compensating member 5 can be narrowed by heating the insulator base 1 and the insulator sealing lid 3 to bring the temperature of the measuring object close to the temperature of the infrared temperature sensor. The temperature compensation accuracy with respect to can be improved. Therefore, the insulator base 1 and the insulator sealing lid 3 have good thermal conductivity so as to uniformly heat the entire body, and have a thickness that is not affected by a sudden temperature change due to an external factor. You need to have On the other hand, the insulator base 1 and the insulator sealing lid 3 have a smaller heat capacity so that the heating for the measurement and the return to the normal temperature for the next measurement can be performed in a shorter time. It is desirable to form a smaller volume.

Further, by heating the insulator base 1 and the insulator sealing lid 3 to bring the temperature of the measuring object close to the temperature of the infrared temperature sensor, the relative temperature received by the infrared temperature sensor can be reduced. This means that the range of linearization at the time of temperature conversion can be narrowed by reducing the relative temperature at the time of measurement, so that the error due to non-linearization can be suppressed. As an example, when a body temperature of 37 ° C. is measured at an ambient temperature of 5 ° C., the relative temperature between the body temperature and the infrared temperature sensor is 32 ° C. Since the output of the infrared temperature sensor is non-linear with respect to the relative temperature, the sensor output is linearized to obtain the measured temperature. Assuming that the sensor is heated to 32 ° C. in this example, the relative temperature between the body temperature and the sensor is 5 ° C., and the range of linearization can be narrowed.

In the method of directly heating and controlling the infrared temperature sensor itself of the present invention, the temperature balance disorder in the ear canal at the time of inserting the probe, which the infrared temperature sensor having no conventional heating means has, is disturbed (the probe absorbs heat from the ear canal). It can be said that the measurement error is reduced as a result. Therefore, as a specific method, when turning on the power of the thermometer, the temperature close to the body temperature in advance,
For example, it is possible to heat the sensor up to around 32 ° C. and keep the temperature to reduce the measurement error during temperature measurement.

[0019]

According to the present invention, since the temperature to be measured and the temperature of the sensor can be brought close to each other by heating the insulating package, it is possible to measure the body temperature with high accuracy. Further, since the conventional infrared temperature sensor is a thin metal package, a rapid temperature change causes a change in temperature distribution, which causes a measurement error. By using the insulating package including the insulating cover and the insulating cover, heat can be evenly transmitted to the entire package, and thus is not affected by a sudden change in environmental temperature. Therefore, unlike the conventional case, the infrared temperature sensor does not need to be housed in the metal holder (sensor frame) and can be attached to the tip of the measurement probe to protect the waveguide or the waveguide as in the conventional case. It is not necessary to use the waveguide cover of.

[Brief description of drawings]

FIG. 1 is a partially fragmented perspective view showing an infrared temperature sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an infrared temperature sensor according to an embodiment of the present invention.

FIG. 3 is a partially fragmented perspective view showing the structure of a conventional infrared temperature sensor.

FIG. 4 is a sectional view showing the structure of a conventional infrared temperature sensor.

FIG. 5 is a partial cross-sectional view for explaining a method of mounting a conventional infrared temperature sensor.

[Explanation of symbols]

1 Insulator Base 2 Internal Space 3 Insulator Sealing Lid 4 Infrared Sensor 5 Temperature Compensating Member 6 Heating Member 7 Infrared Transmission Filter 8 Opening 9 Thermocouple 9a Hot Junction 9b Cold Junction 10 Infrared Absorption Film 11a, 11b, 11c Terminal

Claims (2)

[Claims] 1. An insulator base serving as a base, an insulator sealing lid which is laminated so as to form an internal space between the insulator base and has an opening at a central portion thereof, and the insulator base. And an infrared sensor and a temperature compensating member which are respectively disposed in an internal space between the insulating base and the insulating sealing lid, and the insulating base and the insulating sealing lid are respectively formed of a material having good thermal conductivity. The thermopile cold junction and the temperature compensating member of the infrared sensor are respectively provided with good thermal conductivity between the insulator base and the joint surface between the insulator base and the insulator sealing lid. An infrared temperature sensor provided with a heat generating member. 2. The material having good thermal conductivity is ceramics, and the insulator base and the insulator sealing lid each have a thickness necessary for good conduction of heat from the heat generating member. The infrared temperature sensor according to claim 1, wherein each of the infrared temperature sensors has a smaller heat capacity while having a smaller heat capacity.