Temperature measuring device and temperature measuring method

Abstract

To provide a solution to a conventional radiation thermometer in which a drift portion due to the ambient temperature must be allocated in the input range of an AD converter, and therefore, there is a problem that the allocation of the input range to the sensor output is relatively small and the resolution is reduced.SOLUTION: In order to solve the problem, a temperature measurement device is provided that generates an analog correction signal which is an analog correction signal by DA converting a digital correction signal corresponding to the ambient temperature of a photo detection part, performs offset correction of an output signal obtained by receiving light by the photo detection part by using the analog correction signal, amplifies the corrected output signal, and calculates the temperature of a measurement object based on the amplified output signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radiation thermometer that detects radiant energy from an object to be measured and measures the temperature of the object. [Background technology]

[0002] A radiation thermometer is a device that measures the intensity of infrared or visible light emitted from an object and measures the temperature of the object based on the relationship between the intensity of the emitted light and the temperature. Radiation thermometers are equipped with a light detection sensor that detects infrared light, etc., but fluctuations in the ambient temperature of this light detection sensor cause offset drift, which leads to errors in the temperature measurement of the object.

[0003] Various techniques have been proposed to suppress the effects of offset drift. For example, Patent Document 1 discloses a technique in which a chopper is operated and the light intensity is measured when the chopper is open and when it is closed, thereby suppressing errors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-237322 Summary of the Invention [Problem to be solved by the invention]

[0005] As disclosed in Patent Document 1, there is a technology for suppressing the effects of offset drift due to fluctuations in ambient temperature without providing a device with mechanical means such as a chopper or motor, which attempts to absorb errors by allocating the offset drift amount within the input range of the AD converter when AD converting the sensor output of a light detection sensor.

[0006] Figure 7 is a conceptual diagram illustrating the problems with the above-mentioned conventional technology. In Figure 7, the solid line indicates the sensor output, and convex parts indicate high sensor output. The dashed line indicates the sensor output when drift occurs (drift can occur both positively and negatively). As shown in the figure, in order to keep the input range even when drift occurs, an amount corresponding to the drift is allocated within the limited input range of the AD converter. As a result, the amount allocated to the sensor output becomes relatively small, resulting in a problem of reduced resolution. [Means for solving the problem]

[0007] Therefore, in order to solve the above problems, the present invention provides the following temperature measuring device etc. That is, the temperature measuring device has a light receiving unit that outputs a signal corresponding to the radiant energy of light received from an object to be measured, an ambient temperature measuring unit that measures the ambient temperature of the light receiving unit, a digital correction signal generating unit that generates a digital correction signal that is a digital signal for offset correction corresponding to the measured ambient temperature, a correction signal DA converting unit that performs DA conversion on the generated digital correction signal and outputs an analog correction signal that is an analog correction signal, an amplifying unit that offset-corrects and amplifies an output signal resulting from light received by the light receiving unit using the DA-converted analog correction signal, an AD converting unit that performs AD conversion on the output signal amplified by the amplifier unit, and a temperature calculating unit that calculates the temperature of the object to be measured based on the output signal converted by the AD converting unit. [Effects of the Invention]

[0008] According to the present invention, by correcting the offset, most of the input range of the AD converter can be allocated to the sensor output, thereby making it possible to increase the resolution. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of the functional configuration of a temperature measurement device according to a first embodiment. [Figure 2]A conceptual diagram showing the effect of the temperature measurement device of the first embodiment. [Figure 3] FIG. 1 is a flowchart showing an example of a processing flow of the temperature measuring device according to the first embodiment. [Figure 4] FIG. 10 is a block diagram showing an example of the functional configuration of a temperature measurement device according to a second embodiment. [Figure 5] Conceptual diagram showing the output signal from the amplifier section input to the AD conversion section [Figure 6] Conceptual diagram showing the state of the signal from the light receiving unit until it is used to calculate the temperature [Figure 7] Conceptual diagram showing the problems with conventional temperature measurement devices DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention should not be limited to these embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention.

[0011] <Embodiment 1> <Summary> The temperature measurement device of this embodiment is characterized in that the output signal of the optical sensor is offset-corrected using an offset correction signal corresponding to the ambient temperature of the optical sensor, and is then supplied to the AD converter. This reduces the allocation of drift in the input range of the AD converter, and increases the allocation of the output signal of the optical sensor.

[0012] <Functional configuration> Fig. 1 is a block diagram showing an example of the functional configuration of a temperature measuring device according to this embodiment. As shown in Fig. 1, the temperature measuring device 100 includes a light receiving unit 101, an ambient temperature measuring unit 102, a digital correction signal generating unit 103, a correction signal DA converting unit 104, an amplifying unit 105, an AD converting unit 106, and a temperature calculating unit 107.

[0013] The light receiving unit 101 has a function of outputting a signal corresponding to the radiant energy received from the object to be measured. The temperature measuring device 100 of this embodiment is intended to be a radiation thermometer, and specific means for realizing the light receiving unit 101 are photodetectors such as thermoelectric elements such as thermopiles and pyroelectric elements such as PZT (lead zirconate titanate). The photodetector can be appropriately selected depending on the object to be measured, the measurement environment, the temperature range to be measured, etc. For example, in the low temperature range of -50 to 1200°C, InAsSb (indium arsenide antimony) or HgCdTe (cadmium mercury telluride) is used to measure wavelengths of 8 to 13 μm. In addition, in the medium temperature range of 300 to 1300°C, InGaAs (indium gallium arsenide) is used to measure wavelengths of 1.5 to 1.8 μm.

[0014] Measurement targets are diverse, including semiconductors, electronic components, machinery, steel, and metals, and this temperature measurement device can be used in a variety of situations, such as manufacturing, processing, quality control, and equipment monitoring of these measurement targets.

[0015] The ambient temperature measurement unit 102 has the function of measuring the ambient temperature of the light receiving unit 101. The ambient temperature is measured by attaching a thermocouple, resistance thermometer, or the like to the light receiving unit, or if it cannot be attached directly to the light receiving unit, by attaching it to the housing of the temperature measurement device in which the light receiving unit is installed. The light receiving unit not only receives radiant energy from the object to be measured, but also receives radiant energy from itself and its surroundings. Therefore, by measuring the ambient temperature, it is possible to separate the radiant energy from the surroundings contained in the received radiant energy. In other words, it is possible to determine only the radiant energy from the object to be measured.

[0016] The digital correction signal generating unit 103 has a function of generating a digital correction signal, which is a digital signal for offset correction corresponding to the measured ambient temperature. Since the difference between the ambient temperature and the temperature that serves as the reference for the offset causes offset drift, the digital correction signal is generated as a digital output signal corresponding to the output signal from the light receiving unit that corresponds to the radiant energy that corresponds to the difference between the reference temperature and the measured ambient temperature.

[0017] The correction signal DA conversion unit 104 has a function of performing DA conversion on the generated digital correction signal to output an analog correction signal, which is an analog correction signal. The digital correction signal is generated for correction in the amplifier unit described below, but since the output signal from the light receiving unit that is the target of this correction is an analog signal, the correction signal DA conversion unit converts the digital correction signal into an analog signal before providing it to the amplifier unit.

[0018] The amplifier 105 has a function of amplifying the output signal resulting from light reception by the light receiving unit after performing offset correction using the DA-converted analog correction signal. By performing offset correction by subtracting the digital correction signal from the output signal resulting from light reception, it becomes unnecessary to allocate an input range in consideration of offset drift at the input of the AD converter (described later), and the signal can be amplified to the extent that almost the entire input range is used.

[0019] The AD conversion unit 106 has the function of AD converting the output signal amplified by the amplifier unit. Because it receives the output signal from the light receiving unit that has been offset corrected and then amplified, it is not necessary to allocate offset drift due to ambient temperature to the input range, as in the prior art. Therefore, as described above for the amplifier unit, almost the entire input range of the AD conversion unit can be allocated to the output signal from the amplifier unit, thereby improving resolution.

[0020] The temperature calculation unit 107 has a function of calculating the temperature of the object to be measured based on the output signal converted by the AD conversion unit. The temperature is calculated based on a table that defines the relationship between temperature and radiant energy stored in advance, or based on a predetermined formula that shows the relationship between temperature and radiant energy.

[0021] FIG. 2 is a conceptual diagram illustrating the effects of the temperature measuring device of embodiment 1. FIG. 2(a) is a conceptual diagram illustrating how a sensor output is received in AD conversion in the prior art shown in FIG. 6. As shown in the figure, the input range is allocated to account for offset drift, so the sensor output (output signal amplified by an amplifier; the same applies below) is allocated in small amounts, and the degree of amplification of the input sensor output is small. In contrast, in the case of AD conversion in the present temperature measuring device shown in FIG. 2(b), almost the entire input range can be allocated to the sensor output, and accordingly, the sensor output is input that is amplified to the extent that almost the entire input range is used. In this way, the present temperature measuring device can significantly improve the resolution of AD conversion compared to the prior art, contributing to improved accuracy in temperature measurement.

[0022] In addition, InAsSb (indium arsenide antimonide) and InSb (indium antimonide), which are used as light-receiving elements when measuring low temperatures such as -50 to 1200°C, are easily affected by ambient temperature and have large offset drift. As a result, during AD conversion, approximately 60% of the input range is allocated to the drift, and only approximately 40% is allocated to the output signal. For this reason, the technology described above in this temperature measurement device is very effective for radiation thermometers that measure low-temperature ranges.

[0023] <Hardware configuration> The hardware configuration of the temperature measuring device of this embodiment is realized by an arithmetic processing device such as a microcomputer having a processor, main memory, ROM, and other non-volatile memory, which realizes each functional configuration of a digital correction signal generating unit, a correction signal DA conversion unit, an amplifier unit, an AD conversion unit, and a temperature calculation unit, and the processor expands the programs for realizing each functional configuration stored in the ROM onto the main memory and performs arithmetic processing, causing the temperature measuring device to operate.

[0024] <Processing flow> 3 is a flow chart showing an example of the processing flow of the temperature measuring device according to this embodiment. As shown in the figure, the temperature measurement method first outputs a signal corresponding to the radiant energy of light received from the object to be measured (S301: light receiving step). Then, the ambient temperature during the light receiving step is measured (S302: ambient temperature measurement step). Then, a digital correction signal, which is a digital signal for offset correction corresponding to the measured ambient temperature, is generated (S303: digital correction signal generation step). Then, the generated digital correction signal is DA converted to output an analog correction signal, which is an analog correction signal (S304: correction signal DA conversion step). Then, an output signal resulting from the light reception during the light receiving step is offset corrected and amplified using the DA converted analog correction signal (S305: amplification step). Then, the output signal amplified during the amplification step is AD converted (S306: AD conversion step). Then, the temperature of the object to be measured is calculated based on the output signal converted during the AD conversion step (S307: temperature calculation step). The amplifying step may be a step of offset-correcting the output signal resulting from light reception in the light receiving step using the DA-converted analog correction signal, and amplifying the signal to such an extent that almost the entire input range in the AD conversion step is used.

[0025] <Effects> By correcting the offset with the temperature measuring device of this embodiment, most of the input range of the AD converter can be allocated to the sensor output, thereby making it possible to increase the resolution.

[0026] <Embodiment 2> <Summary> This embodiment is based on the first embodiment and is a temperature measuring device characterized in that the quantization error occurring in the sensor output signal is cancelled out by correcting it with a digital correction signal.

[0027] <Functional configuration> Fig. 4 is a block diagram showing an example of the functional configuration of the temperature measuring device of this embodiment. As shown in Fig. 4, the temperature measuring device 400 includes a light receiving unit 401, an ambient temperature measuring unit 402, a digital correction signal generating unit 403, a correction signal DA converting unit 404, an amplifying unit 405, an AD converting unit 406, and a temperature calculating unit 407, and the temperature calculating unit 407 includes a canceling means 408. Each component except the canceling means 408 has the same function as the corresponding component in the first embodiment, and therefore a description thereof will be omitted.

[0028] The cancellation means 408 calculates the temperature of the object to be measured based on the output signal obtained by canceling the quantization error due to DA conversion of the digital correction signal of the output signal converted by the AD conversion unit with the digital correction signal provided for offset correction in the amplification unit of the output signal.

[0029] The output signal from the amplifier 405 and input to the AD converter 406 is a signal obtained by subtracting the analog correction signal that has been DA-converted by the correction signal DA converter 404 from the analog signal from the light receiving unit. Here, the analog correction signal is a signal that has been DA-converted from an originally digital signal, and therefore has steps according to the resolution of the DA converter. Therefore, as shown in FIG. 5, the output signal 501 from the amplifier 405 and input to the AD converter 406 is not an ideal, purely analog output signal 502, but an output signal 503 that has steps. The error caused by such steps is called a quantization error.

[0030] If the temperature calculation unit 407 calculates the temperature based on the output signal 503 in which the step remains, this will have an effect on the temperature measurement. Therefore, when calculating the temperature, the cancellation means 408 subtracts the digital correction signal that is the source of the step remaining in the output signal from the amplifier 405. In other words, by adding the signal amount subtracted for correction when calculating the temperature, it is possible to remove the step (quantization error) contained in the signal used for temperature calculation.

[0031] FIG. 6 is a conceptual diagram showing the state of an output signal from a light receiving unit in a temperature measurement device having a cancellation means until it is used to calculate temperature. First, FIG. 6(a) shows an output signal 601 amplified by an amplifier unit to the extent that it uses most of the input range of the AD conversion unit without performing offset correction (the steps are exaggerated). In this case, the output signal does not fit within the input range because offset correction is not performed. Therefore, by performing offset correction and then amplifying the signal, as shown in FIG. 6(b), the output signal fits within the input range while using most of the input range of the AD conversion unit. Then, by adding and canceling the amount subtracted by the offset correction using the cancellation means, the quantization error in the output signal is removed, and temperature can be calculated based on an output signal without steps.

[0032] <Hardware configuration> The temperature measuring device of this embodiment can be realized in accordance with the hardware configuration of the temperature measuring device of the first embodiment.

[0033] <Processing flow> The processing flow of the temperature measuring device of this embodiment is basically the same as the processing flow of the temperature measuring device of Embodiment 1. The temperature measuring device of this embodiment further includes a cancellation substep of calculating the temperature of the object to be measured based on an output signal obtained by canceling a quantization error due to DA conversion of the digital correction signal of the output signal converted in the AD conversion step, with the digital correction signal that has been subjected to offset correction in the amplification step of the output signal.

[0034] <Effects> The temperature device of this embodiment can eliminate quantization errors caused by offset correction using a digital correction signal. [Explanation of symbols]

[0035] 100, 400: Temperature measuring device 101, 401: Light receiving section 102, 402: Ambient temperature measurement unit 103, 403: Digital correction signal generation unit 104, 404: Correction signal DA conversion section 105, 405: Amplification section 106, 406: AD conversion section 107, 407: Temperature calculation section 408: Countervailing measures

Claims

1. a light receiving unit that outputs a signal corresponding to the radiant energy received from the measurement object; an ambient temperature measuring unit that measures the ambient temperature of the light receiving unit; a digital correction signal generating unit that generates a digital correction signal, which is a digital signal for offset correction according to the measured ambient temperature; a correction signal DA conversion unit that converts the generated digital correction signal into an analog correction signal by DA conversion; an amplifier that amplifies an output signal from the light receiving unit by performing offset correction using the DA converted analog correction signal; an AD conversion unit that performs AD conversion on the output signal amplified by the amplification unit; a temperature calculation unit that calculates the temperature of the object to be measured based on the output signal converted by the AD conversion unit; A temperature measuring device having

2. 2. The temperature measuring device according to claim 1, wherein the amplifier performs offset correction on the output signal from the light receiving unit using the DA converted analog correction signal, and amplifies the signal to such an extent that almost the entire input range of the AD converter is used.

3. The temperature calculation unit a canceling means for calculating the temperature of the object to be measured based on an output signal obtained by canceling a quantization error due to DA conversion of the digital correction signal of the output signal converted by the AD conversion unit with the digital correction signal provided for offset correction in the amplification unit of the output signal, 3. The temperature measuring device according to claim 1, further comprising:

4. a light receiving step of outputting a signal corresponding to the radiant energy received from the measurement object; an ambient temperature measuring step of measuring an ambient temperature in the light receiving step; a digital correction signal generating step of generating a digital correction signal which is a digital signal for offset correction according to the measured ambient temperature; a correction signal DA conversion step of converting the generated digital correction signal into an analog correction signal; an amplifying step of amplifying an output signal resulting from the light reception in the light receiving step by performing offset correction using the DA converted analog correction signal; an AD conversion step of AD-converting the output signal amplified by the amplification step; a temperature calculation step of calculating a temperature of the object to be measured based on the output signal converted by the AD conversion step; A temperature measurement method comprising:

5. 5. The temperature measurement method according to claim 4, wherein the amplifying step performs offset correction on the output signal generated by the light reception step using the DA converted analog correction signal, and amplifies the signal to such an extent that almost the entire input range in the AD conversion step is used.

6. The temperature calculation step a cancellation substep of calculating the temperature of the object to be measured based on an output signal obtained by canceling a quantization error due to DA conversion of the digital correction signal of the output signal converted in the AD conversion step with the digital correction signal that has been subjected to offset correction in the amplification step of the output signal; 6. The temperature measuring method according to claim 4 or 5, further comprising:

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