JPH0514865U - Infrared thermometer - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a highly accurate infrared thermometer with inexpensive parts. [Structure] The output of an infrared sensor 1 and the reference voltage of a reference voltage source 5 are switched by a switching circuit 6, both are taken into a CPU 3 via an A / D converter 2, the ratio thereof is obtained, and a corresponding measured temperature is obtained. .

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an infrared thermometer that measures the temperature of an object using infrared rays emitted from the object.

[0002]

[Prior Art]

 As shown in FIG. 2, a conventional infrared thermometer includes an infrared sensor 21 using a thermopile, a pyroelectric element, and a preamplifier, which amplifies the output v of the infrared sensor 21 and converts it into a digital signal. It is composed of an A / D converter 22 for controlling, a CPU 23 for processing the taken data to calculate the temperature T, and a display 24 for displaying the measured temperature T.

[0003]

[Problems to be solved by the device]

 The infrared sensor used in the above-mentioned conventional infrared thermometer is a thermopile or a pyroelectric element, has a low sensing sensitivity, and the sensor output is very small on the order of μV with respect to 1 ° C. Therefore, in the measurement circuit unit such as the A / D converter 2, it is necessary to reduce the offset voltage and use a high gain operational amplifier or a high resistance element. For example, when the output v of the infrared sensor 21 is amplified to V = gv (g: gain) by the amplifier built in the A / D converter 22 and the temperature T is calculated by the CPU 23, the gain fluctuates, and g + Δg Then, V = (g + Δg) v and the temperature also becomes T + ΔT (Δg · v). Therefore, in order to perform accurate temperature measurement, it is necessary to use the A / D converter 22 in which the fluctuation of the gain g is small, and there is a problem that high precision and expensive components must be used.

The present invention has been made in view of the above problems, and an object thereof is to provide an infrared thermometer capable of highly accurate temperature measurement using inexpensive parts.

[0005]

[Means and Actions for Solving the Problems]

 The infrared thermometer of the present invention comprises an infrared sensor and a measuring circuit section for processing a signal from the infrared sensor to measure the temperature, wherein a reference voltage source, the output of the infrared sensor and the reference voltage are provided. A switching circuit for switching the source voltage and inputting it to the measuring circuit section, and circuit means for obtaining the ratio of the output of the infrared sensor and the voltage from the reference voltage source and obtaining the measured temperature based on this ratio. It has a characteristic.

In this infrared thermometer, a voltage according to the temperature of the object to be measured is output from the infrared sensor, and the output voltage and the voltage from the reference voltage source are switched by the switching circuit and taken into the measurement circuit section. Obtain the ratio, and then obtain the measured temperature based on this ratio. Therefore, even if the gain of the measurement circuit unit fluctuates by Δg, the fluctuation is canceled by the ratio of the output of the infrared sensor and the reference voltage.

[0007]

【Example】

 Hereinafter, the present invention will be described in more detail with reference to examples. FIG. 1 is a block diagram showing a circuit configuration of an infrared thermometer according to an embodiment of the present invention. This infrared thermometer is provided with an infrared sensor 1, an A / D converter 2, a CPU 3 and a display 4, as in the conventional thermometer shown in FIG. Besides, a reference voltage source 5 and a switching circuit 6 are provided. The switching circuit 6 switches between the output of the infrared sensor 1 and the reference voltage from the reference voltage source 5 according to a command from the CPU 3 and inputs it to the A / D converter 2. The switching circuit 6 may be an electronic contactless switch such as an analog switch, a transistor or an FET, or a magnetic contact switch such as a reed switch. Alternatively, a mechanical contact switch such as a slide switch may be used to perform the switching manually.

In the infrared thermometer of this embodiment, at the time of measurement, the switching circuit 6 is first turned on to the infrared sensor 1 side by a command from the CPU 3. Therefore, with respect to the output v of the infrared sensor 1, the measured value V = gv is converted into a digital signal and taken into the CPU 3 when the gain of the A / D converter 2 is g. Next, the switching circuit 6 is turned on to the reference voltage source 5 side by the command from the CPU 3, and the reference voltage v _r is input to the A / D converter 2. Then, it is amplified by V _r = gv _r and A / D converter 2 is taken into CPU3 is converted into a digital signal. The CPU 3 obtains the ratio of the taken-in voltages V and V _r , obtains the temperature value T from this ratio, and displays it on the display 4.

In the infrared thermometer of this embodiment, assuming that the gain of the A / D converter 2 changes by Δg, the voltage V corresponding to the temperature taken into the CPU 3 becomes V = (g + Δg) v, The take-in voltage V _r when applied to the reference voltage source 5 side is V _r = (g + Δg) v _r . Therefore, the ratio of the two voltages determined by CPU3 becomes _{V / V r = v / v} r _{becomes, v = V / V r ·} v r. From this equation, the voltage v depending on the temperature is proportional to V / V _r irrespective of the gain g of the A / D converter 2, and v = f (T). Therefore, the voltage V and the voltage V _The measured temperature T can be obtained from the ratio of _r . The temperature T to be measured may be extracted by storing the temperature T for various V / V _{r in} a table or by calculating it from an arithmetic expression including V / V _r .

[0010]

[Effect of the device]

 According to this invention, the reference voltage source and the switching circuit are provided, the output of the infrared sensor and the reference voltage source are switched, the signal is converted in the same measurement circuit unit, and the temperature is obtained from the ratio of both outputs. As a result, fluctuations in the gain of the measurement circuit section can be canceled, and inexpensive circuit elements can be used. In addition, it is possible to eliminate the influence of the gain variation of the measurement circuit section due to the environmental temperature variation and the like, and it becomes possible to perform highly accurate measurement.

[Submission date] June 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

[0003]

[Problems to be solved by the device]

 The infrared sensor used in the above-mentioned conventional infrared thermometer is a thermopile or a pyroelectric element, has a low sensing sensitivity, and the sensor output is very small on the order of μV with respect to 1 ° C. Therefore, in the measurement circuit unit such as the A / D converter 2, it is necessary to use an operational amplifier or a high-accuracy resistance element having a small offset voltage and a high gain. For example, when the output v of the infrared sensor 21 is amplified to V 2 = gv (g: gain) by the amplifier incorporated in the A / D converter 22 and the temperature T is calculated by the CPU 23, the gain fluctuates, and g + Δg Then, V = (g + Δg) v, and the temperature also becomes T + ΔT (Δg · v). Therefore, in order to perform accurate temperature measurement, it is necessary to use the A / D converter 22 in which the fluctuation of the gain g is small, and there is a problem that high precision and expensive components must be used. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an infrared thermometer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a conventional infrared thermometer.

[Explanation of symbols]

 1 Infrared sensor 2 A / D converter 3 CPU 4 Display 5 Reference voltage source 6 Switching circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Atsushi Nakamura 17 Nakadoji Minami-cho, Shimogyo-ku, Kyoto City Science Center Building Inside the OMRON Life Science Research Institute (72) Shigeru Makida 17th Nakado-ji Minami-cho, Shimogyo-ku, Kyoto Saien Center Center Omron Life Science Research Institute

Claims (1)

[Scope of utility model registration request] 1. An infrared thermometer comprising an infrared sensor and a measuring circuit section for processing a signal from the infrared sensor to measure a temperature, comprising: a reference voltage source; and an output of the infrared sensor and the reference voltage source. A switching circuit for switching the voltage and inputting it to the measurement circuit section; and a circuit means for obtaining the ratio of the output of the infrared sensor and the voltage from the reference voltage source and obtaining the measured temperature based on this ratio. Infrared thermometer characterized by