JPH09257588A - Radiation temperature meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation temperature meter having a correcting function for compensating a change with lapse of time of a bolometer without providing a dedicated thermostatic equipment. SOLUTION: A characteristic that R25 as a parameter of the thermistor characteristic of a bolometer 102 and R25 among the constant B can be controlled on a point of change with lapse of time is utilized. An attachment 104 for shading and heat insulation is installed in a sensor case 101 of a drum temperature meter so as to form a measuring system at a high temperature stability, and while a compact thermistor 103 is thermally connected to a bolometer 102 so as to monitor the bolometer temperature. At the time when temperature change of the compact thermistor 103 is stabilized in a constant range, a resistance value of the thermistor inside of the bolometer 102 is obtained so as to obtain the R25 , and a result is stored in a RAM.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation thermometer which detects infrared rays emitted from a measurement object such as an eardrum by an infrared sensor using a thermistor and measures the temperature of the measurement object in a non-contact manner.

[0002]

2. Description of the Related Art In recent years, a radiation thermometer has been used in various fields in which an infrared sensor is provided in a temperature sensing part to measure the temperature in a non-contact manner. Infrared sensors include thermopiles and bolometers that utilize the temperature rise when infrared rays are absorbed. A thermopile is an element that outputs a voltage (thermoelectromotive force) corresponding to radiant energy, and a bolometer is an element that outputs a resistance value corresponding to radiant energy. Generally, a bolometer is composed of a thermistor whose electric resistance changes with temperature (thermistor bolometer).

A non-contact radiation thermometer using these sensors is a tympanic temperature thermometer (hereinafter, referred to as a "drum temperature" representative of the deep temperature of the human body).
It is called an eardrum thermometer. ) Is also used as. The eardrum thermometer is configured, for example, by providing a minute thermistor bolometer in the sensor section (temperature sensitive section).

[0004]

However, if the eardrum thermometer is required to have a resolution (0.01 ° C. or less) and an accuracy higher than those of the conventional female thermometer, the change over time of the sensor becomes a problem. In other words, when the resolution is coarse, aging of the sensor does not cause much problem, but since the thermistor generally has aging, in order to maintain the resolution and accuracy at a high level, it is necessary to calibrate at regular intervals. It is actually used in that way.

For example, a thermistor bolometer (hereinafter,
Simply called a bolometer. In the case of an eardrum thermometer using
If the two parameters (R ₂₅ and B constant, which will be described later) that represent the thermistor characteristics of the bolometer change over time, the change in resistance for the same radiant energy will be different from that at the time of product shipment, so the initial accuracy can be maintained. Disappear. Therefore, when a high resolution and high accuracy are required for the eardrum thermometer, it is required to have a calibration function for compensating for the change over time of the sensor (comprising a thermistor).

The present invention has been made by paying attention to the above-mentioned problems in a radiation thermometer using a thermistor such as an eardrum thermometer, and a radiation thermometer having a calibration function for compensating for the aging of the thermistor is provided. The purpose is to provide.

[0007]

In order to achieve the above object, the present invention provides a radiation thermometer which senses infrared rays radiated from a measuring object by an infrared sensor using a thermistor and measures the temperature of the measuring object. In the state where the sensor temperature detecting means for detecting the temperature of the infrared sensor, the detachable infrared blocking means used in the calibration mode for blocking the infrared sensor from external infrared rays, and the infrared blocking means are used. Calculating means for calculating the value of the predetermined characteristic parameter of the thermistor based on the output value of the sensor temperature detecting means in the case of falling within a predetermined temperature range and the output value of the infrared sensor. Storage means for storing the result of the means.

According to the structure of the radiation thermometer of the present invention, when the thermistor of the infrared sensor is calibrated in order to compensate for the aging, first, the infrared sensor is switched from the external infrared rays by using the infrared cutoff means. Cut off. As a result, the infrared sensor is shielded from light and sufficiently insulated from the surrounding atmosphere, so that a measurement system with good temperature stability is created. The sensor temperature detecting means is thermally coupled to the infrared sensor and detects the temperature of the infrared sensor itself. That is, the temperature of the infrared sensor is monitored by the sensor temperature detecting means. The calculating means is an output value (temperature of the infrared sensor) of the sensor temperature detecting means when the output change of the sensor temperature detecting means is within a predetermined temperature range and an output value of the infrared sensor (thermistor The resistance value) is used to calculate the value of a predetermined characteristic parameter of the thermistor. This result is stored in the storage means and used for subsequent measurements. In this way, the change with time of the infrared sensor (thermistor) is compensated. The characteristic parameters of the thermistor to be calibrated are set to be dominant in terms of aging.

The operation will be described in more detail as follows. Here, a bolometer is taken as an example of the infrared sensor. Generally, a bolometer contains a plurality of thermistors. The thermistor characteristic has two parameters (R ₂₅ , B constant) as shown in the following formula 1. R = R ₂₅ exp {B (T ⁻¹ −T ₂₅ ⁻¹ )} Equation 1 Here, R: resistance value of the thermistor R ₂₅ : resistance value of the thermistor at 25 ° C. B: B constant T: absolute temperature T ₂₅ : Absolute temperature of 25 ° C. (298.15 [K]) In this equation, variables are R and T.

Equation 1 shows that the natural logarithm lnR of R is a linear function of T ^-1 . That is, the slope is B
The points through which the constant and the function pass are (T ₂₅ , R ₂₅ ), and these two are parameters.

By the way, from the results of the acceleration test such as the high temperature test in which the bolometer is left in a high temperature atmosphere to examine the change of the thermistor characteristics, the above two parameters (R ₂₅ , B
It has been found that the (constant) does not change at the same rate, but that the change with time of R ₂₅ is dominant. Therefore, it can be considered that the B constant is constant and only R ₂₅ changes.

Usually, in order to obtain the thermistor characteristics, there are two parameters, so it is necessary to obtain the resistance value of the thermistor at two different temperatures (note that the resistance value is measured at three or more temperatures, It is more desirable to obtain the R ₂₅ and B constants by the least squares method). In this case, the measurement system is required to have small temperature changes temporally and spatially at two different temperatures.

Since such a measuring system becomes a dedicated constant temperature equipment, it is difficult to always have it in a clinical site in terms of space, cost and maintenance. However, as described above, if it can be considered that one of the two parameters of R ₂₅ and the B constant does not change (actually, the B constant does not change), the resistance value at a certain temperature is The thermistor characteristics can be obtained only by measuring. If there is only one point, it is relatively easy to prepare a measurement system that has a small temperature change temporally and spatially.

That is, as in the present invention, the bolometer (infrared sensor) is shielded from the external infrared rays by using an infrared ray blocking means (for example, an attachment described later) which can be freely attached and detached, so that the bolometer is shielded from light and the surrounding atmosphere. Insulate sufficiently to create a measurement system with good temperature stability. In this system, it suffices that the temperature change is small, and the absolute value of the temperature does not require precision. Therefore, a measurement system satisfying the above conditions can be relatively easily obtained without providing a dedicated constant temperature equipment.

On the other hand, a sensor temperature detecting means (for example, a small thermistor described later) for monitoring the temperature of the bolometer itself is thermally coupled to the bolometer (infrared sensor), and this sensor temperature detecting means (small thermistor). ) Temperature change within a certain range (for example, ± 0.0
When the temperature falls within the range of (05 ° C), the resistance value of the thermistor in the bolometer is calculated. When the sensor temperature detecting means is composed of a small thermistor, it takes a certain amount of time to measure the bolometer temperature because the thermal constant is large unlike the bolometer. Further, it is required that the change with time is smaller than that of the bolometer.

After that, calibration means (for example, C described later) is used.
(PU, etc.), the obtained resistance value and temperature are calculated by the above equation 1
By substituting calculates the R _25, for example by changing the R ₂₅ that was set when shipping goods to compensate for aging of the bolometer.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a main part of the radiation thermometer according to the present invention, showing a structure of the main part and a use state in a calibration mode.

This radiation thermometer is, for example, an eardrum thermometer using a bolometer 102 as an infrared sensor.
The bolometer 102 is housed in the exterior 101 of the sensor unit (temperature sensing unit) of the eardrum thermometer. Bolometer 1
A small thermistor 103 for monitoring the temperature of the bolometer itself is attached to 02 as a sensor temperature detecting means so as to be thermally coupled to the bolometer 102. The size of the small thermistor 103 for monitor is, for example, 1 × 1 × 2 [mm]. In the mode for calibrating the eardrum thermometer, the attachment 104 as an infrared ray blocking means is attached to the sensor unit exterior 101 of the eardrum thermometer. The attachment 104 shields light and insulates. By using this attachment 104, the bolometer 102 of the eardrum thermometer is shielded from light and sufficiently insulated from the surrounding atmosphere to form a measurement system with good temperature stability.

FIG. 2 is a block diagram showing a circuit configuration of the eardrum thermometer shown in FIG. The bolometer 102 contains two minute thermistors 201a and 201b. One thermistor 201a is a thermistor capable of receiving infrared rays from the outside through an aperture (opening or entrance window) not shown, and the other thermistor 201b has the same thermistor characteristics as the thermistor 201a, but since it has no aperture, it does not emit infrared rays. It is a thermistor that is not affected by. In this way, the thermistor 2 that can receive infrared rays
By providing two thermistors 01a and 201b which are not affected by infrared rays, the resistance value R of both
By detecting the difference between s and Rr, electrical noise and thermal disturbance can be removed to obtain a net amount of infrared rays, and highly accurate temperature measurement can be performed. Moreover, the small thermistor 103 for monitoring is composed of only one thermistor 202.

Two thermistors 2 in the bolometer 102
The resistance values Rs and Rr of 01a and 201b and the resistance value R of the thermistor 202 in the small thermistor 103 for bolometer temperature monitoring that is thermally coupled to the bolometer 102.
t is the resistance / voltage conversion circuit 203a, 203b, 20
By 3c, the voltage Vs, V corresponding to each resistance value
r, Vt.

In the mode in which the eardrum thermometer measures the eardrum temperature, the voltages Vs and Vr based on the bolometer 102 are set.
Only the multiplexer 204 and the A / D converter 205
It is input to the CPU 206 through the. The CPU 206 is
Based on the input data Vs and Vr, the ROM 208 in which the measurement program is written, the non-packup RAM 209 for temporarily storing the data, and the backlap RAM 210 in which the previous calibration data is stored are used for the eardrum temperature. Is calculated and the result is displayed on LCD (Liquid Crystal Display)
It is displayed on 207.

When the eardrum thermometer is in the calibration mode (calibration mode), the CPU 206 functions as a calculation means. Therefore, the CPU 206 is connected to the backup RAM 210 as a storage unit for storing the calibration data.

FIG. 3 is a flow chart showing the operation in the calibration mode. When the eardrum thermometer is in the calibration mode, as shown in FIG. 1, the attachment 10 that shields and shields the sensor unit exterior 101 of the eardrum thermometer in advance.
Wear 4. Here, the thermistor 20 shields the light.
This is to prevent 1a from receiving infrared rays from the outside (to be precise, infrared rays should not enter the viewing angle of the thermistor 201a).

When the calibration is started, the voltage data Vs, Vr
, Vt is the multiplexer 204 and the A / D converter 2
It is input to the CPU 206 through 05 (step S
1). The CPU 206 calculates the temperature Tt of the thermistor 202 from the input data Vt (step S2). Then, it is determined whether the change in the temperature Tt is within the temperature range (for example, ± 0.005 ° C.) set in the calibration program written in the ROM 208 (step S3). If NO as a result of this determination, the process returns to step S1, but if YES, that is, the change of the temperature Tt is within the predetermined temperature range (± 0.
005 ° C.), the CPU 206 considers that the temperature of the bolometer 102 has become constant, that is, the thermistor 202 is thermally coupled to the thermistors 201a and 201b in the bolometer 102, so these thermistors are not. Temperatures Ts and Tr of 201a and 201b
Is the same as the detected temperature Tt (Ts = Tr = Tt), the thermistor 201
The parameter R ₂₅ of each of a and 201b is calculated (step S4), and the result is backed up in RAM2.
Write in 10 and use for subsequent measurements (step S
5). It should be noted that the reason why only the parameter R ₂₅ is obtained is that the parameter of this R ₂₅ is dominant in terms of temporal change, as described above.

When the CPU 206 is reset,
The measurement is performed using R ₂₅ at the time of shipping of each of the thermistors 201a and 201b.

In the above example, it is assumed that the calibration is performed in the air in consideration of simplicity, but the invention is not limited to this. In order to further increase the temperature stability,
It is also possible to calibrate by immersing the bolometer in the liquid. As a liquid (infrared ray blocking means) used at this time, a fluorinate or the like having electrical insulation is a candidate.

Further, in the above example, only R ₂₅ is calibrated by utilizing the fact that R ₂₅ of the parameters of the thermistor is dominant in terms of change over time, but it is not limited to this. Absent. Even if the B constant becomes more dominant in terms of change over time due to a change in the material of the bolometer, and even if only the B constant needs to be calibrated, it can be handled in the same manner as in the case of R ₂₅ .

Further, although the eardrum thermometer has been described as the radiation thermometer in the above example, it is needless to say that it is not limited to this. The present invention can be applied to any kind of radiation thermometer using a thermistor.

[0029]

As is apparent from the above description, according to the present invention, the radiation thermometer is provided with a calibration function for compensating for the aging of the thermistor of the infrared sensor without a dedicated thermostatic equipment. Highly accurate temperature measurement is possible with an inexpensive structure.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a radiation thermometer according to the present invention, showing a structure of the main part and a usage state in a calibration mode.

FIG. 2 is a block diagram showing a circuit configuration of the eardrum thermometer shown in FIG.

FIG. 3 is a flowchart showing an operation in a calibration mode.

[Explanation of symbols]

101 ... Exterior of sensor unit of eardrum thermometer 102 ... Bolometer (infrared sensor) 103 ... Small thermistor for monitor (sensor temperature detecting means) 104 ... Attachment (infrared blocking means) 201a, 201b, 202 ... Thermistor 203a, 203b, 203c ... Resistance / Voltage conversion circuit 204 ... Multiplexer 205 ... A / D conversion unit 206 ... CPU (arithmetic means) 207 ... LCD 208 ... ROM 209 ... Non-backup RAM 210 ... Backup RAM (storage means)

Claims (1)

[Claims] 1. An infrared sensor using a thermistor,
In a radiation thermometer that senses infrared rays radiated from a measurement target and measures the temperature of the measurement target, a sensor temperature detection unit that detects the temperature of the infrared sensor, and is used in a calibration mode, and the infrared sensor is an external sensor. Detachable infrared ray blocking means for blocking infrared rays, and its output value when the output change of the sensor temperature detecting means in a state where the infrared ray blocking means is in use falls within a predetermined temperature range and the infrared sensor A radiation thermometer comprising: a calculating unit that calculates a value of a predetermined characteristic parameter of the thermistor based on an output value; and a storage unit that stores a result of the calculating unit.