JP4621363B2 - Infrared thermometer - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a thermometer that measures temperature in a non-contact manner, and mainly relates to an infrared thermometer that measures the temperature of the eardrum by inserting a probe tip into an ear hole.
[0002]
[Prior art]
As shown in FIGS. 9 and 10, the conventional infrared thermometer includes a thermopile A for measuring the relative temperature with the object to be measured and a thermistor B for measuring the temperature of the thermopile in the can C. An infrared sensor D is provided. Thermopile A is an infrared absorbing film G caused a temperature change by absorbing through infrared filter F provided the infrared of the object or found on top of the can C, are respectively joined to the cold junction to a heat sink H, the hot junction The thermopile A appears as a combination of the outputs from the plurality of thermocouples I.
[0003]
Such an infrared sensor D takes out the temperature change of the infrared absorption film G generated by absorbing the infrared ray of the object to be measured as an electric signal by the Seebeck effect of the thermocouple I, so that the heat sink H serving as a reference temperature and the object to be measured Detect temperature difference between objects . At the same time, the resistance value of the thermistor B is measured to detect the temperature of the infrared sensor D itself, and the control circuit performs processing to add the temperature measured by the thermopile A and the temperature measured by the thermistor B. The temperature of the object to be measured is obtained.
[0004]
The thermopile A thus configured not only absorbs infrared rays from the object to be measured, but also absorbs infrared rays radiated from the wall surface of the head of the can C. Normally, the wall surface of the head of Can C can theoretically be regarded as the same temperature as the infrared sensor itself, but in reality, when a sudden temperature change is given due to external factors, A temperature difference is generated between the absorption film G, and as a result, the output becomes transiently unstable and an unintended unnecessary voltage is output.
[0005]
For this reason, in the conventional infrared thermometer, as shown in FIG. 11, the infrared sensor D is installed in a metal holder J with good thermal conductivity so that the temperature change is uniformly and gently applied to the infrared absorption film G. Further, a metal waveguide M that is wrapped with heat insulating members K and L such as air and plastic and plated with gold so that the emissivity becomes as small as possible is provided on the front surface of the infrared sensor D, and the heat radiation from the object to be measured is provided. It was necessary to configure so as to reduce the influence. Further, the thermistor B used as a cold junction temperature compensation sensor produces a temperature difference if the thermal coupling between the thermocouple I and the cold junction is poor, and accurate measurement cannot be performed. It was installed in C and configured to increase the degree of thermal coupling between the cold junction and the thermistor.
[0006]
In such a conventional infrared thermometer, since the distance between the infrared sensor D and the measured object is equal to the length of the metal waveguide M while the environmental temperature is rising, the infrared sensor D and the metal waveguide are disposed. A temperature difference was generated between the M tip and the tip temperature was higher than the infrared sensor temperature, causing an error in the positive direction. On the other hand, while the environmental temperature is decreasing, the temperature at the tip of the metal waveguide M is lower than the temperature of the infrared sensor D, and a negative error occurs. In order to reduce such an error, it is conceivable to reduce the influence of the temperature change by wrapping the infrared sensor D with the metal holder J. However, the use of the metal holder J causes an increase in the size of the product. As a result, there was a product limit on the dimensions.
[0007]
On the other hand, each output from the thermopile A and the thermistor B is processed in a control circuit N as shown in FIG. Since the output from the thermopile A is extremely weak, particularly in the case of body temperature measurement, it was amplified to a level where signal processing is possible with an amplification factor that has been calibrated in advance in accordance with variations in the performance of the thermopile A used. Later (N1), linearization processing is performed to linearize the non-linear output (N2), and emissivity correction (N3) is performed to correct the deviation of the measurement reading due to the difference in emissivity of the object to be measured. Is called. Since the output from the thermistor B is also non-linear, linearization processing (N4) is performed. Each output from the thermopile A and a thermistor B which each process is performed, the outputs of the thermistors B thermopile A After the summing (N5), is temperature conversion (N6), to display the temperature By displaying (N7), the temperature is measured.
[0008]
For this reason, in the conventional infrared thermometer, thermopile A and thermistor B had to be individually calibrated. In particular, thermistor B is supplied by the manufacturer whose resistance-temperature characteristic variation is suppressed within a small error range, whereas the output voltage characteristic variation of thermopile A is very large and is used as a thermometer. For this purpose, a complicated temperature calibration operation has to be performed using a special apparatus such as a blackbody furnace.
[0009]
[Problems to be solved by the invention]
The object of the present invention is to substantially reduce the influence of environmental temperature change on the infrared sensor to zero (0), so that the infrared sensor is attached to the tip of the probe and is closer to the object to be measured. An object of the present invention is to provide an infrared thermometer capable of measuring temperature.
[0010]
Another object of the present invention is to provide an infrared thermometer that can substantially calibrate the thermistor B and can eliminate the need to calibrate the thermopile A.
[0011]
[Means for Solving the Problems]
The infrared thermometer according to the present invention was invented by paying attention to the characteristic that the output voltage of the thermopile is always zero when the temperature of the thermopile and the temperature of the object to be measured are the same. A thermopile for measuring the relative temperature between the thermopile and a thermistor for measuring the temperature of the thermopile, and controlling the temperature of the thermopile cold junction so that the output of the thermopile is zero (0) The above-described problem is solved by providing a temperature control means for the purpose.
[0012]
When the output of the thermopile becomes zero by the temperature control means, the temperature at the cold junction of the thermopile is the same as the temperature of the object to be measured. Therefore, the temperature of the object to be measured can be measured by detecting the temperature of the thermopile detected by the thermistor. This is because the thermopile is used only to determine whether the output is zero, regardless of its output voltage characteristics, and for the thermopile, a complicated temperature using a special device such as a blackbody furnace is used. This means that it is not necessary to perform calibration work, and temperature correction may be performed for a thermistor having performance guaranteed by the manufacturer.
[0013]
The infrared thermometer according to the present invention also controls the temperature of the cold junction with reference to the thermopile output, and measures the detected temperature of the thermistor when detecting that the thermopile output is zero. Can be configured. In the infrared thermometer according to the present invention, the temperature control means may include a thermistor that is thermally integrated with the cold junction of the thermopile and a control circuit for controlling the heat generation amount of the thermistor. a cold junction and a thermally integrated pressurized thermal element can also be composed of a control circuit for controlling the heating value of the heating element. Furthermore, the infrared thermometer according to the present invention can also have an infrared sensor attached to the tip of the probe.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
In the infrared thermometer according to the embodiment of the present invention, as shown in FIG. 1, the infrared sensor 1 is provided at the distal end portion of the probe 2 constituting the body of the thermometer. In the infrared sensor 1, as shown in FIGS. 2 and 3, a thermopile 10 and a thermistor 11 are supported by a support 14 made of a heat insulating material inside a can 13 having an infrared filter 12 at the top.
[0015]
The thermopile 10 includes a plate-shaped heat sink 15 having an opening therein, an infrared absorption film 16 provided at an opening position on the upper surface of the heat sink 15, a cold junction and an infrared absorption film thermally integrated with the heat sink 15. 16 and a plurality of thermocouples 17 each having a hot junction thermally integrated with 16. The thermistor 11 is formed in a plate shape or a thin film shape, and is laminated on the lower surface side of the heat sink 15 so as to be thermally integrated with the heat sink 15. An infrared reflection film 18 is disposed on the lower surface side of the infrared absorption film 16 so that heat from the heat sink 15 does not affect the infrared absorption film 16.
[0016]
The output of the thermopile 10, that is, the combined output of the outputs of the thermocouples 17, is taken out from the terminals 19a and 19a and input to the control circuit 20 shown in FIG. The thermistor 11 is connected to terminals 19b and 19b, and the terminals 19b and 19b are connected to the control circuit 20. The control circuit 20 converts a comparator 21 for determining the output of the thermopile 10, a microcontroller 22 for controlling energization to the thermistor 11 in accordance with the output from the comparator 21, and converts the resistance value of the thermistor 11 into temperature. The A / D converter 23 for displaying the temperature and the display 24 for displaying the temperature detected by the thermistor 11.
[0017]
As shown in FIG. 5, when the measured object temperature is higher than the cold junction temperature of the thermopile 10, the output of the thermopile 10 shows a positive value, and the output of the comparator 21 takes a "0" state. At this time, the microcontroller 22 sends a cold junction heating signal to the FET 25 (only shown in FIG. 4) to turn it on, and energizes the thermistor 11 to generate heat. The heat generated from the thermistor 11 is transmitted to the cold junction of the thermopile 10 via the heat sink 15, and the cold junction temperature starts to rise and finally reaches the temperature of the object to be measured. The output of the thermopile 10 when the cold junction temperature is to be measured temperature is zero, this time, the output of the comparator 21 becomes "1", the microcontroller 22 immediately stops by Unihiya contact heating signal FET25 is ing and OFF To do. Even if the cold junction heating signal is stopped, the temperature of the cold junction continues to rise, so the output of the thermopile 10 becomes negative after passing through the zero point. However, as the heat sink 15 cools, the cold junction temperature starts to fall and is again covered. By returning to the measured object temperature, the output of the thermopile 10 also returns to zero, and the output of the comparator 21 also returns to “0”. When the output of the comparator 21 returns to “0”, the resistance value of the thermistor 11 is detected by the A / D converter 23, and the information is converted into temperature by the microcontroller 22 and displayed on the display 24.
[0018]
Here, the thermistor 11 is used as a heating means for the cold junction until the cold junction temperature reaches the temperature of the object to be measured. For this reason, when the cold junction temperature returns to the temperature of the object to be measured again, the thermistor 11 is detected. Note that the temperature is measured.
Further, as described above, when the output of the thermopile 10 is zero, the temperature of the thermopile 10 and the measured object temperature are the same, and the thermistor 11 measures the cold junction temperature of the thermopile 10, It will be readily understood that the detected temperature of the thermistor 11 is the same as the temperature of the object to be measured.
[0019]
[Example 2]
FIGS. 6 and 7 are diagrams showing an infrared sensor used in an infrared thermometer according to another embodiment of the present invention, except that the heating element 26 is laminated on the lower surface of the thermistor 11 as described above. It is structured in the same way as the example. The heating element 26 is connected to a control circuit 20A to be described later via terminals 19c and 19c.
[0020]
The heating element 26, which is a feature of the present embodiment, increases the cold junction temperature in a shorter time by separately performing the heating operation of the cold junction of the thermopile 10, which was performed by the thermistor 11 in the above embodiment. And the load on the thermistor 11 for measurement is reduced. For this reason, any member can be used as the heating element 26 as long as it can generate heat when energized. However, the heating element 26 generates heat efficiently with a small amount of electric power, while exhibiting good heat dissipation characteristics when switched to a non-energized state. It is preferable to apply the member having. As shown in the figure, the heating element 26 may be disposed in a stacked state with the thermistor 11 and the heat sink 15, but may be disposed so as to directly contact the heat sink 15. In this case, care should be taken not to cause a difference between the cold junction temperature of the thermopile 10 and the measured temperature of the thermistor 11 so that the heat of the heating element 26 does not directly affect the infrared absorption film 16 or the like. It is.
[0021]
As shown in FIG. 8, in the control circuit 20A in this embodiment, the thermistor 11 is caused to generate heat by the microcontroller 22 turning on the FET 25 in the above-described embodiment. The control circuit 20 is configured in the same manner as the control circuit 20 of the above-described embodiment except that a cold junction heating signal is directly sent to the device to generate heat.
[0022]
In the present embodiment, the temperature of the object to be measured is also measured by sending a cold junction heating signal from the microcontroller 22 to the heating element 26 to heat the cold junction temperature of the thermopile 10 to the object temperature to be measured. The heating is stopped when the output of 10 becomes zero, and the temperature of the object to be measured is measured by measuring the resistance value of the thermistor 11 when the output of the thermopile 10 once becomes zero again. The In the case of the present embodiment, since the heating of the cold junction and the measurement of the cold junction temperature are performed by the heating element 26 and the thermistor 11, respectively, the cold junction temperature is heated to the temperature of the object to be measured and the thermopile 10 is heated. It is also possible to measure when the output of becomes zero. However, in order to avoid that the heat from the heating element 26 directly or indirectly thermally affects the components of the infrared sensor and thereby causes measurement errors, the heating is stopped and the thermopile 10 is stopped. It is preferable to measure when the output of is zero again.
[0023]
【The invention's effect】
According to the present invention, by laminating the thermistor on the thermopile via the heat sink, the thermal coupling between the cold junction of the thermopile and the thermistor can be increased, and the infrared sensor can be miniaturized. . In addition, since the thermopile cold junction is heated to the temperature of the object to be measured and the temperature of the object to be measured is measured, the infrared sensor is not affected by the external temperature, so that the infrared sensor is attached to the tip of the probe. Therefore, temperature measurement can be performed at a position closer to the object to be measured. In addition, a thermopile with a relatively large variation is used only as a means for determining whether or not the cold junction temperature and the measured object temperature are the same, and the measured object depends on a thermistor having a relatively small variation. Therefore, the temperature calibration work can be minimized.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an outline of an infrared thermometer according to an embodiment of the present invention.
FIG. 2 is a partial perspective view showing an infrared sensor used in an infrared thermometer according to an embodiment of the present invention.
3 is a cross-sectional view of the infrared sensor shown in FIG.
4 is a block diagram of a control circuit used with the infrared sensor shown in FIG.
FIG. 5 is a diagram for explaining the relationship between temperature and output during measurement in the control circuit shown in FIG. 4;
6 is a partial perspective view similar to FIG. 2 showing an infrared sensor used in an infrared thermometer according to another embodiment of the present invention.
7 is a cross-sectional view similar to FIG. 3 of the infrared sensor shown in FIG.
8 is a block diagram of a control circuit used with the infrared sensor shown in FIG.
FIG. 9 is a partial perspective view showing an infrared sensor used in a conventional infrared thermometer.
10 is a cross-sectional view of the infrared sensor shown in FIG.
FIG. 11 is a diagram for explaining an outline of a conventional infrared thermometer.
FIG. 12 is a block diagram of a control circuit used in a conventional infrared thermometer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Infrared sensor 2 Probe 10 Thermopile 11 Thermistor 12 Infrared filter 13 Can 14 Support body 15 Heat sink 16 Infrared absorption film 17 Thermocouple 18 Infrared reflective film 19a, 19b, 19c Terminal 20, 20A Control circuit 21 Comparator 22 Microcontroller 23 A / D Converter 24 Display 25 FET
26 Heating element

Claims (2)

A cold junction thermally integrated with a heat sink provided for thermopile attachment and a hot junction thermally integrated with an infrared absorption film provided to absorb infrared rays from the object to be measured. A thermopile for measuring a relative temperature between the measured object and the combined output from a plurality of thermocouples;
It is attached so as to be thermally integrated with the heat sink, and the temperature of the cold junction reaches the temperature of the hot junction where the temperature of the cold junction is equivalent to the temperature of the object to be measured, and the output of the thermopile becomes zero. A thermistor having a function of measuring the temperature of the cold junction and a function of applying a calorific value to the cold junction,
Temperature measurement control means for controlling transmission of the amount of heat generated from the thermistor to the cold junction via the heat sink so that the output of the thermopile becomes zero;
Equipped with a,
The temperature measurement control means transmits the amount of heat generated from the thermistor to the cold junction via the heat sink when the temperature of the cold junction is lower than the temperature of the hot junction, and the output of the thermopile is stop the heating by the thermistor when it is zero, when the output of subsequent to the thermopile detects that becomes zero again, it characterized that you measure display the detected temperature of the thermistor infrared Thermometer. A cold junction thermally integrated with a heat sink provided for thermopile attachment and a hot junction thermally integrated with an infrared absorption film provided to absorb infrared rays from the object to be measured. A thermopile for measuring a relative temperature between the measured object and the combined output from a plurality of thermocouples;
It is attached so as to be thermally integrated with the heat sink, and the temperature of the cold junction reaches the temperature of the hot junction where the temperature of the cold junction is equivalent to the temperature of the object to be measured, and the output of the thermopile becomes zero. A thermistor for measuring the temperature of the cold junction when
Laminated to the thermistor, and a heating element for applying a calorific value to the cold junction;
Temperature measurement control means for controlling transmission of the amount of heat generated from the heating element to the cold junction via the thermistor and the heat sink so that the output of the thermopile becomes zero,
The temperature measurement control means transmits the amount of heat generated from the heating element to the cold junction via the thermistor and the heat sink when the temperature of the cold junction is lower than the temperature of the hot junction, When the thermopile output becomes zero, heating by the heating element is stopped, and when it is detected that the thermopile output becomes zero again, the detected temperature of the thermistor is measured and displayed. infrared thermometer shall be the feature.

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