JP4580562B2 - Non-contact temperature sensor and infrared thermometer using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a temperature sensor for measuring temperature without contact, and an infrared thermometer using the same.
[0002]
[Prior art]
As shown in FIGS. 7 and 8, the conventional non-contact type temperature sensor A includes a thermopile B for measuring a relative temperature with an object to be measured and a thermistor C for measuring the temperature of the thermopile. It has an internal structure. The thermopile B includes an infrared absorbing film G that changes its temperature by absorbing infrared rays from an object E (see FIG. 1) through an infrared filter F provided on the top of the can D, and a cold junction as a heat sink H. The thermopile B is composed of a plurality of thermocouples I that are joined together and the hot junctions are joined to the infrared absorption film G. The output of the thermopile B appears as a combination of the outputs from the plurality of thermocouples I.
[0003]
Such a non-contact type temperature sensor A 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, thereby making the heat sink H serving as a reference temperature. And a temperature difference between the object to be measured E (see FIG. 1). At the same time, the resistance value of the thermistor B is measured to detect the temperature of the non-contact temperature sensor A itself, and the control circuit performs a process of adding the temperature measured by the thermopile B and the temperature measured by the thermistor C. Thus, the temperature of the object to be measured is obtained.
[0004]
The infrared absorption film G of the non-contact temperature sensor A thus configured not only absorbs infrared rays from the object to be measured, but also absorbs infrared rays emitted from the wall surface of the head of the can D. End up. Normally, the wall surface of the head of the can D can be theoretically regarded as the same temperature as the temperature of the non-contact type temperature sensor itself, but in reality, when a sudden temperature change is given due to an external factor, the can D A temperature difference is generated between the head and the infrared 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. 9, the non-contact temperature sensor A is placed 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. Installed, wrapped in heat insulation members K and L such as air and plastic, and provided with a metal waveguide M plated with gold so that the emissivity is as low as possible. It was necessary to configure so that the influence of thermal radiation from the object E (see FIG. 1) was reduced. In addition, the thermistor C used as a cold junction temperature compensation sensor produces a temperature difference if the thermal coupling with the cold junction of the thermocouple I is poor, and accurate measurement cannot be performed. It was installed in D and configured to increase the degree of thermal coupling between the cold junction and the thermistor.
[0006]
In such a conventional infrared thermometer, while the environmental temperature rises, there is a separation distance corresponding to the length of the metal waveguide M between the non-contact temperature sensor A and the object E to be measured. A temperature difference is generated between the sensor A and the tip of the metal waveguide M, and the temperature of the non-contact temperature sensor A is lower than the temperature of the tip of the metal waveguide M, causing a positive error. It was. Further, while the environmental temperature is decreasing, the temperature at the tip of the metal waveguide M is lower than the temperature of the non-contact type temperature sensor A, causing a negative error. In order to reduce such an error, it is conceivable to reduce the influence of temperature change by wrapping the non-contact type temperature sensor A 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 B and the thermistor C is processed in the control circuit N as shown in FIG. 10, but the output from the thermopile B is extremely weak particularly in the case of body temperature measurement. After amplification (N1) is performed with a pre-calibrated amplification degree according to variations in the performance of the thermopile B used to a level where processing is possible, linearization processing (N2) is performed to linearize the non-linear output. The 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. Since the output from the thermistor C is also non-linear, linearization processing (N4) is performed. The outputs from the thermopile B and thermistor C that have been subjected to the respective processes are added to the output of the thermopile B and the output of the thermistor C (N5), and then converted into a temperature (N6), and the temperature is displayed on the display ( N7), the temperature is measured.
[0008]
For this reason, in the conventional infrared thermometer, the thermopile B and the thermistor C had to be individually calibrated. In particular, thermistor C 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 B 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]
An object of the present invention is to provide a non-contact temperature sensor that can substantially reduce the influence of environmental temperature change to zero (0), and by mounting the non-contact temperature sensor on the tip of a probe, An object of the present invention is to provide an infrared thermometer capable of measuring a temperature at a position closer to an object to be measured.
[0010]
Another object of the present invention is to provide a non-contact temperature sensor that can be used simply by performing a calibration work on a thermistor, and a thermometer that uses the thermopile. .
[0011]
[Means for Solving the Problems]
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, and the non-contact type temperature sensor according to the present invention. A thermopile for measuring the relative temperature with the object to be measured, a thermistor for measuring the temperature of the cold junction of the thermopile, and a heating and cooling combined element for selectively heating or cooling the cold junction of the thermopile (Hereinafter, referred to as a heating / cooling element) .
[0012]
The heating / cooling element is used to heat or cool the thermopile cold junction so that the thermopile output is zero. When the thermopile output is zero, the temperature of the cold junction of the thermopile is equal to the temperature of the hot junction, and the temperature detected by the thermistor that measures the temperature of the cold junction of the thermopile is the temperature of the object to be measured. Can be handled.
[0013]
The non-contact type temperature sensor according to the present invention can also thermally integrate the cold junction of the thermopile, the thermistor, and the heating / cooling element through the same heat transfer member, which should be measured by the thermistor. The temperature of the cold junction of the thermopile can be accurately measured. Further, the non-contact temperature sensor according to the present invention uses a Peltier element applying a thermoelectric cooling semiconductor to the heating / cooling element, and joins one reversible heat / cold contact of the heating / cooling element to the heat transfer member, The reversible hot / cold junction can also be joined to a heat sink. When a current is applied, the reversible heat / cold junction of the heating / cooling element joined to the heat transfer member generates heat or absorbs heat, while heating or cooling the thermopile cold junction via the heat transfer member, In the reversible heat / cold junction of the heating / cooling element joined to the heat sink, heat absorption or heat generation occurs contrary to the above. The heating / cooling of this heating / cooling element is determined by the direction of the current.
[0014]
An infrared thermometer according to the present invention controls the heating / cooling action of the above-described non-contact type temperature sensor and the heating / cooling element of the non-contact type temperature sensor and processes the output of the thermopile and thermistor to display the temperature. The control measurement circuit heats or cools the thermopile cold junction by energizing the heating / cooling element, and measures the detected temperature of the thermistor when the thermopile output becomes zero. By displaying, the above-mentioned problems are solved.
[0015]
Measuring the temperature by heating or cooling the cold junction of the thermopile actively and reliably avoids the effects of changes in the environmental temperature. Therefore, it is possible to attach to the tip of the measurement probe and use it, and to accurately measure the temperature of the object to be measured. In addition, thermopile is used only to determine whether the output is zero or not regardless of its output voltage characteristics. Therefore, the thermopile uses a special device such as a blackbody furnace for complicated temperature calibration. It is only necessary to perform temperature correction for a thermistor having the performance guaranteed by the manufacturer without having to perform work.
[0016]
Infrared thermometers according to the present invention also provide that when the temperature of the cold junction of the thermopile is equal to the temperature of the hot junction by heating or cooling the cold junction of the thermopile with at least a heating / cooling element, When the temperature of the cold junction of the thermopile becomes equal to the temperature of the hot junction again by cooling or heating the cold junction, the control measurement circuit measures the detected temperature of the thermistor and displays the average value of each. This can also minimize the measurement error. In addition, the infrared thermometer according to the present invention uses a Peltier element applying a thermoelectric cooling semiconductor as a heating / cooling element, and the control measurement circuit determines the direction of the current first supplied to the heating / cooling element according to the output of the thermopile. It can also be configured. Usually, when the temperature of the cold junction of the thermopile is lower than the environmental temperature (temperature of the hot junction), the output of the thermopile indicates minus (−), and when it is high, it indicates plus (+). Therefore, when the thermopile output is negative at the start of temperature measurement, the control measurement circuit causes the heating / cooling element to flow a current so that the heating / cooling element heats the cold junction of the thermopile, and the thermopile output is positive. When the heating / cooling element cools the cold junction of the thermopile, a reverse current is passed through the heating / cooling element so that the thermopile output is always zero.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 1, an infrared thermometer according to an embodiment of the present invention is provided with a non-contact temperature sensor 1 at the tip of a probe 2 constituting the body of the thermometer. A control measurement circuit 3 (see FIG. 4) described later is provided. As shown in FIGS. 2 and 3, the non-contact type temperature sensor 1 of the present invention includes a thermopile 10 for measuring a relative temperature between an object to be measured E (see FIG. 1), and a cold junction of the thermopile 10. a thermistor 11 functioning as a temperature sensor for measuring the temperature of the heating and cooling combined element 12 for selectively heating or cooling the cold junctions of the thermopile 10 (hereinafter, referred to as a heating / cooling element 12), but An infrared filter 13 a is provided on the top of the can 13.
[0018]
The thermopile 10 includes an infrared absorption film 14 that generates heat by receiving infrared rays from the object E (see FIG. 1) that has passed through the infrared filter 13a, and a plurality of thermocouples 15. Each thermocouple 15 is provided with its warm junction 15 a joined to the infrared absorption film 14 and each cold junction 15 b joined to the heat transfer member 16, and the combined output from the plurality of thermocouples 15 is provided in the thermopile 10. Processed as output.
[0019]
The thermistor 11 is provided by being joined to the heat transfer member 16, and measures the temperature of the cold junction 15 b of each thermocouple 15 constituting the cold junction of the thermopile 10 via the heat transfer member 16. As the heating / cooling element 12, a plurality of Peltier elements using thermoelectric cooling semiconductors are used. Each heating / cooling element 12 is provided with two reversible heat / cold contacts 12a and 12b, which are first and second reversible contacts for heating or cooling the cold junction of the thermopile 10, separated into one and the other. The two reversible heat / cold junctions 12a and 12b absorb heat at the other reversible heat / cold junction when the heating / cooling element 12 is energized and generates heat at one reversible heat / cold junction. Produces an effect. The heat generation or heat absorption action at the reversible heat / cold junction is determined by the direction of the current passed through the heating / cooling element 12. The reversible heat / cold junctions 12a and 12b of the heating / cooling element 12 are respectively connected to a heat transfer member 16 to which the cold junction of the thermopile 10 and the thermistor 11 are connected, and a heat sink 17 as a member for heat dissipation or heat storage or heat absorption. It is joined. The infrared absorbing film 14, the heat transfer member 16, and the heat sink 17 are insulated by a thermal insulating material 18 so as not to be affected by heat.
[0020]
The hot junction (15a) and cold junction (15b) of the thermopile 10 are connected via terminals 19a and 19a, the thermistor 11 is connected via terminals 19b and 19b, and the reversible hot / cold contacts 12a and 12b of the heating / cooling element 12. Are connected to the control measurement circuit 3 via terminals 19c and 19c, respectively.
[0021]
As shown in FIG. 4, the control measurement circuit 3 sends a control signal to the heating / cooling element 12 according to the output from the comparator 20 for determining the output of the thermopile 10 and the comparator 20, and outputs the thermopile 10. When the temperature becomes zero, the microcontroller 21 for measuring the temperature detected by the thermistor 11, the A / D converter 22 for converting the resistance value of the thermistor 11 into a temperature value, and the temperature detected by the thermistor 11 are displayed. Display 23 for the purpose.
[0022]
Next, the operation of the control measurement circuit 3 will be described with reference to FIG. The output of the thermopile 10 shows a positive value when the cold junction temperature of the thermopile 10 is lower than the hot junction temperature, that is, the temperature of the object to be measured, and a negative value when the cold junction temperature is higher than the hot junction temperature. The output is zero when the cold junction temperature is equal to the hot junction temperature. The comparator 20 outputs “0” when the output of the thermopile 10 is positive, outputs “1” when it is negative, and outputs “1” or “1” from “0” when it is zero. Transition to. When the output of the comparator 20 is “0”, the microcontroller 21 sends a heating signal to the heating / cooling element 12 to increase the cold junction temperature of the thermopile 10. When the output of the comparator 20 is “1”, A cooling signal is sent to the cooling element 12 to lower the cold junction temperature of the thermopile 10.
[0023]
When the output of the comparator 20 transitions from “0” to “1” or “1” to “0”, the microcontroller 21 detects the temperature detected by the thermistor 11 converted from a resistance value into a temperature value by the A / D converter 22. Is displayed on the display 23. Here, the detection temperature of the thermistor 11 may be read only once when the output of the comparator 20 transitions from “0” to “1” or “1” to “0”. A heating or cooling signal is sent to the heating / cooling element 12 in response to a transition of “0” → “1” or “1” → “0” of the output of the comparator 20, and the output transition of the comparator 20 is transitioned within a short time. The measurement error can be further reduced by sampling the detected temperature of the thermistor 11 a plurality of times and calculating and displaying the average value thereof.
[0024]
When the cold junction temperature and the hot junction of the thermopile 10 change at the same or approximate values at the start of measurement (for example, when the thermometer is equal to the body temperature as in the case of a midsummer day), it is shown in FIG. As described above, the output of the comparator 20 becomes unstable, and “1” → “0” → “1” → “0” may be repeated, but the detected temperature of the thermistor 11 at any transition of the output of the comparator 20 The temperature can be measured by sampling. However, if necessary, a heating or cooling signal is sent to the heating / cooling element 12 for a certain period of time based on the value “0” or “1” first output from the comparator 20 at the start of temperature measurement. It can also be configured to start the temperature measurement operation. It will be readily appreciated by those skilled in the art that the relationship between the output of the comparator 20 and the heating or cooling signal sent to the heating / cooling element 12 can be made in the opposite relationship to that described above.
[0025]
【The invention's effect】
According to the present invention, since the thermopile and the thermistor are integrated, the thermal coupling degree between the cold junction of the thermopile and the thermistor can be increased, and the non-contact temperature sensor can be miniaturized. In addition, since the thermopile cold junction is heated or cooled to the object temperature by the heating / cooling element and the temperature of the object is measured, the non-contact temperature sensor is not affected by the external temperature. Thus, a non-contact temperature sensor can be formed on an infrared thermometer attached to the tip of the probe, and the temperature can be measured at a position closer to the measurement object. In addition, the temperature detected by the thermistor can be measured and displayed when the cold junction of the thermopile reaches the temperature of the object to be measured, so the temperature of the cold junction and the temperature of the object to be measured are the same for a thermopile with relatively large variations. The temperature of the object to be measured is measured depending on a thermistor that is used only as a means for determining whether or not there is relatively uneven, and the temperature calibration operation can be minimized. Further, since the average value can be displayed by sampling the detected temperature of the thermistor a plurality of times, the temperature measurement error 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 a non-contact temperature sensor according to an embodiment of the present invention.
3 is a cross-sectional view of the non-contact temperature sensor shown in FIG.
4 is a block diagram of a control measurement circuit used with the non-contact temperature sensor shown in FIG.
5 is a diagram for explaining the relationship between temperature and output during measurement in the control measurement circuit shown in FIG. 4; FIG.
6 is a diagram showing a comparator output when the thermopile cold junction temperature and the measured object temperature in the control measurement circuit shown in FIG. 4 are the same. FIG.
FIG. 7 is a partial perspective view showing a non-contact type temperature sensor used in a conventional infrared thermometer.
8 is a cross-sectional view of the non-contact temperature sensor shown in FIG.
FIG. 9 is a diagram for explaining an outline of a conventional infrared thermometer.
FIG. 10 is a block diagram of a control circuit used in a conventional infrared thermometer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Non-contact-type temperature sensor 2 Probe 3 Control measurement circuit 10 Thermopile 11 Thermistor 12 Heating / cooling element 12a, 12b Reversible heat / cold junction 13 Can 13a Infrared filter 14 Infrared absorption film 15 Thermocouple 15a Hot junction 15b Cold junction 16 Heat transfer Member 17 Heat sink 18 Thermal insulation material 19a, 19b, 19c Terminal 20 Comparator 21 Microcontroller 22 A / D converter 23 Display A Non-contact temperature sensor B Thermopile C Thermistor D Can E Measured object F Infrared filter G Infrared absorbing film H Heat sink I Thermocouple J Metal holder K, L Thermal insulation member M Metal waveguide N Control circuit

Claims (3)

From a plurality of thermocouples each having a cold junction joined to a heat transfer member provided for thermopile attachment and a hot junction joined to an infrared absorption film provided to absorb infrared rays from the object to be measured A thermopile for measuring a relative temperature with the object to be measured , using a composite output of
The cold junction is provided when the temperature of the cold junction reaches the temperature of the hot junction where the temperature of the cold junction reaches the temperature of the object to be measured because the temperature of the cold junction reaches the temperature of the object to be measured. A thermistor for measuring the temperature of
A heat sink attached to the heat transfer member so as not to be thermally affected by a thermal insulation material;
A first reversible contact for heating or cooling the cold junction is joined to the heat transfer member, and a second reversible contact opposite to the first reversible contact is joined to the heat sink; while the temperature of the cold junction is pressurized heat the cold junction by applying a unidirectional current when less than the temperature of the hot junction, in one direction when the temperature of the cold junction is higher than the temperature of the hot junction A heating and cooling combined element for cooling the cold junction by flowing a current in the opposite direction ;
A non-contact type temperature sensor comprising: From a plurality of thermocouples each having a cold junction joined to a heat transfer member provided for thermopile attachment and a hot junction joined to an infrared absorption film provided to absorb infrared rays from the object to be measured A thermopile for measuring a relative temperature with the object to be measured, using a composite output of
The cold junction is provided when the temperature of the cold junction reaches the temperature of the hot junction where the temperature of the cold junction reaches the temperature of the object to be measured because the temperature of the cold junction reaches the temperature of the object to be measured. A thermistor for measuring the temperature of
A heat sink attached to the heat transfer member so as not to be thermally affected by a thermal insulation material;
A first reversible contact for heating or cooling the cold junction is joined to the heat transfer member, and a second reversible contact opposite to the first reversible contact is joined to the heat sink; When the temperature of the cold junction is lower than the temperature of the hot junction, current flows in one direction to heat the cold junction, while when the temperature of the cold junction is higher than the temperature of the hot junction, Is a heating and cooling combined element for cooling the cold junction by flowing a current in the reverse direction;
Temperature measurement control means for controlling the thermopile, the thermistor, and the heating and cooling combined element to measure the temperature of the object to be measured,
The temperature measurement control means includes
A comparator for binaryly discriminating between a first state where the temperature of the cold junction is lower than the temperature of the hot junction and a second state where the temperature of the cold junction is higher than the temperature of the hot junction;
When the comparator determines that the first state is present, the heating and cooling element is used to heat the cold junction, while when the comparator determines that the second state is the second state. A controller that measures and displays the detected temperature of the thermistor when the output of the thermopile becomes zero while controlling the thermopile output to be zero by cooling the cold junction with a cooling combined element;
Infrared thermometer not include you characterized the Rukoto a. 3. The infrared thermometer according to claim 2, wherein a temperature detected by the thermistor is measured after a heating signal or a cooling signal is sent to the heating / cooling combined element for a predetermined time via the controller .

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