JP2000009539A - Radiation thermometer - Google Patents

Abstract

(57) Abstract: The present invention relates to a radiation thermometer for measuring the temperature of an object in a non-contact manner using infrared rays, and measures the time required for temperature measurement by the size of an error allowed in the measurement result. The purpose is to change it appropriately according to. SOLUTION: The infrared measuring means 5 measures infrared rays by a method in which the magnitude of an error included in the measurement value changes according to the time spent for the measurement, and the measuring time determining means 3 determines the infrared rays based on an allowable error. Then, the temperature of the object to be measured is calculated by the temperature calculating means 7 using the infrared measurement value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the temperature of an object to be measured in a non-contact manner using infrared rays.

[0002]

2. Description of the Related Art As a so-called radiation thermometer that detects infrared rays emitted from an object and measures the temperature of the object in a non-contact manner,
The one described in JP-A-60-6835 was generally used.

This radiation thermometer is configured as shown in FIG. 3, and operates as follows.

[0004] First, infrared rays radiated from an object 20 to be measured are intermittently incident on a pyroelectric infrared sensor 22 by a chopper 21, and the infrared rays are converted into an electric signal that changes at a frequency equal to the operating frequency of the chopper 21. I do.
Next, the electric signal is amplified by an amplifier circuit 23 and detected by a synchronous detection circuit 24, and then converted into a direct current by a filter circuit 25 including a low-pass filter. The value obtained as the output signal of the filter circuit 25 is a measured value of infrared rays having a correlation with the temperature of the object 20. On the other hand, the temperature of the chopper 21 is measured using the chopper temperature measuring means 26 composed of a thermistor. The temperature of the chopper 21 is used as a temperature correction signal when calculating the temperature of the object 20 from the output signal of the filter circuit 25. Finally, the temperature calculation means 2
7 reads the temperature of the chopper 21 and the measured value of the infrared ray obtained as the output signal of the filter circuit 25, and calculates the temperature of the object 20 from the read value. The calculation of the temperature is based on the value obtained as the output signal of the filter circuit 25, that is, the output amplitude of the pyroelectric infrared sensor 22 is the fourth power of the absolute temperature of the object 20 and the fourth power of the absolute temperature of the chopper 21 when considered back. However, when the environmental temperature or the measurement temperature range in which the radiation thermometer is used is narrow, the output amplitude of the pyroelectric infrared sensor 22 is determined by the absolute temperature of the object 20 and the chopper 21. Approximately the same result is obtained even if it is performed in proportion to the absolute temperature difference. The magnitude of the error included in the temperature of the object 20 calculated in this manner cannot be specified by the user as an allowable error, and is previously determined as a specification of the radiation thermometer itself.

[0005]

The size of the error allowed in the radiation thermometer and the time required to measure the temperature differ depending on the purpose of use of the radiation thermometer.

[0006] This will be described by taking, as an example, a case where a living body is to be subjected to temperature measurement, that is, a case where a radiation thermometer is used as a thermometer. As such a so-called radiation thermometer, one that measures body temperature with a nominal accuracy of about ± 0.1 ° C. within a short time of about several seconds is already on the market. Assuming that such a radiation thermometer is used to measure body temperature when an infant becomes ill and gives off heat, it is sufficient if the tolerance of the measurement result is kept to ± 0.1 ° C, There is a great advantage to being able to measure the temperature of an infant who is reluctant to do it in just a few seconds. On the other hand, when assuming that the radiation thermometer is used as a woman's thermometer for grasping the ovulation date of a woman, even if the time required for the temperature measurement is increased by about one digit, the allowable error is smaller, for example, ± specified in the Measurement Law
It is more important to keep the temperature within 0.05 ° C.

As described above, even in the case where the radiation thermometer is used as a thermometer only, depending on whether the radiation thermometer is used as a female thermometer or as a general-purpose thermometer other than the female thermometer, an allowable error may be spent or measured. The length of time varies.

However, in the conventional radiation thermometer, regardless of the user's intention of how much tolerance and within what time the user wants to measure the temperature, the same temperature is always taken for the same amount of time and with the same accuracy. Was measured.

[0009]

In order to solve the above-mentioned problems, a radiation thermometer according to the present invention is capable of indicating the magnitude of an error allowed for a calculated temperature of an object, and based on the indicated allowable error. Infrared is measured by a method that changes the time spent on infrared measurement, and the magnitude of the error included in the measured value changes according to the time spent on the measurement, and calculates the temperature of the object from this infrared measured value. I have.

According to the present invention, the magnitude of the error contained in the measured value of the infrared ray is changed based on the permissible error indicated by changing the time spent for measuring the infrared ray. It becomes possible to measure the temperature of the object in time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radiation thermometer according to a first aspect of the present invention is a radiation thermometer that calculates the temperature of an object based on a measurement value of infrared radiation emitted from the object to be measured. A configuration in which the time spent on infrared measurement is changed based on the magnitude of the error allowed for the temperature of the object to be measured, and the infrared ray is measured by a method in which the magnitude of the error included in the measured value changes according to the time spent on the measurement And

Then, the magnitude of the error included in the measured value of the infrared ray is changed based on the permissible error indicated by changing the time spent for measuring the infrared ray, so that the object can be detected at an appropriate time according to the permissible error. The temperature can be measured.

A radiation thermometer according to a second aspect of the present invention measures infrared radiation radiated from an object whose temperature is to be measured by a method in which the magnitude of an error included in a measured value changes according to the time spent in the measurement. Infrared measuring means, an allowable error indicating means for indicating an allowable error in the temperature measurement result, and a measuring time determining means for determining a time for causing the infrared measuring means to measure infrared light using the allowable error indicated by the allowable error indicating means. And temperature calculating means for calculating the temperature of an object to be temperature-measured using the infrared measurement result of the infrared measuring means.

By changing the time for measuring the infrared light by the infrared measuring means by the measuring time determining means, the magnitude of the error included in the measured value of the infrared light is changed based on the allowable error indicated by the allowable error indicating means. Therefore, the temperature of the object can be measured at an appropriate time according to the allowable error.

In the radiation thermometer according to a third aspect of the present invention, the tolerance indicating means has a certain tendency such that the two kinds of errors included in the temperature measurement result are always calculated larger by a certain value. Of the mechanical errors that can be corrected by the method and the random errors that fluctuate irregularly and whose influence can be reduced only by statistical processing, the probability error is indicated.

By allowing the tolerance error indicating means to indicate only the probability error, the measuring time determining means can accurately determine the measuring time by excluding the influence of an instrumental error whose size changes by calibration.

In the radiation thermometer according to a fourth aspect of the present invention, the measuring time determining means determines the measuring time of the infrared ray so as to have a monotonically decreasing relationship with the tolerance specified by the tolerance indicator. And

The measurement time of the infrared ray determined by the measurement time determination means is short when the permissible error is large, and is long when the permissible error is small. It is possible to freely select whether to measure the temperature or to give priority to the measurement accuracy.

According to a fifth aspect of the present invention, there is provided a radiation thermometer, wherein the infrared measuring means includes a plurality of filter circuits having different time constants for smoothing the measured value of the infrared ray. The configuration is such that a filter circuit to be used is selected in response.

Since the measured value of the infrared ray is smoothed by the filter circuit, the measured value of the infrared ray is averaged over a time corresponding to the time constant of the filter circuit.
By selecting and using a filter circuit having a different time constant according to the permissible error, it becomes possible to measure the temperature according to the specified permissible error at an appropriate measurement time.

In the radiation thermometer according to claim 6 of the present invention, the measuring time determining means determines the measuring time of the infrared ray so as to be inversely proportional to a value represented by a quadratic expression of an allowable error.

The measuring time of the infrared ray determined by the measuring time determining means changes in inverse proportion to the quadratic expression of the permissible error, and becomes shorter when the permissible error is large, and longer when the permissible error is small. Therefore, it is possible to freely select whether to measure the temperature with priority on the short measurement time or to measure the temperature with priority on the measurement accuracy.

In a radiation thermometer according to a seventh aspect of the present invention, the measuring time determining means determines the infrared measuring time so as to be inversely proportional to the square of the permissible error.

If the main error contained in the infrared measurement value obtained by one measurement is a stochastic error according to a Gaussian distribution such as thermal noise, infrared light is measured a plurality of times and the average value is finally measured. Since the S / N ratio of the measurement value can be improved in proportion to the square root of the number of measurements by setting the value, the measurement time determination means determines the measurement time of the infrared ray so as to be inversely proportional to the square of the permissible error. The magnitude of the error contained in the infrared measurement can be made proportional to the specified tolerance.

In the radiation thermometer according to claim 8 of the present invention, the measurement time determination means determines the measurement time of the infrared ray so as to be inversely proportional to the square of a value obtained by subtracting a predetermined value from the allowable error.

If the error contained in the infrared measurement value obtained by one measurement consists of a probability error according to a Gaussian distribution such as thermal noise and a certain amount of mechanical error, infrared light is measured a plurality of times and the average value is obtained. Is the final measured value, the S / N ratio of the measured value can be improved in proportion to the square root of the value obtained by subtracting a constant value corresponding to the instrument noise from the number of measurements. Is determined to be inversely proportional to the square of a value obtained by subtracting a predetermined value from the allowable error, thereby making it possible to make the magnitude of the error included in the infrared measurement value proportional to the specified allowable error. .

According to a ninth aspect of the present invention, there is provided a radiation thermometer comprising an allowable error input means for inputting an allowable error as a numerical value by the allowable error indicating means.

Since the measuring time determining means determines the infrared measuring time based on the numerical value input from the allowable error input means, it is possible to measure the temperature of the object at an appropriate time according to the allowable error. .

A radiation thermometer according to a tenth aspect of the present invention comprises:
The permissible error indicating means includes permissible error selecting means for selecting one of a plurality of predetermined permissible errors.

Since the measuring time determining means determines the infrared measuring time based on the allowable error selected by the allowable error selecting means, the temperature of the object can be measured at an appropriate time according to the allowable error. Become.

[0031] The radiation thermometer according to claim 11 of the present invention comprises:
When the allowable error is selected by the allowable error selecting means, the infrared measuring means starts measuring the infrared light.

The infrared measurement and the calculation of the temperature associated therewith are performed automatically only by operating the allowable error selecting means and selecting the allowable error, so that the temperature can be promptly measured without separately instructing the start of the measurement. Measurement can be performed.

[0033] The radiation thermometer according to claim 12 of the present invention comprises:
The apparatus is provided with measurement start instructing means for instructing start of temperature measurement, and the infrared measuring means starts infrared measurement when receiving an instruction from the measurement start instructing means.

Since the measurement of the infrared ray and the start of the calculation of the temperature associated therewith are performed based on the instruction from the measurement start instructing means, the allowable error is set in advance using the allowable error instructing means, and then the measurement start instructing means is started. By performing the operation twice, it becomes possible to continuously measure the temperatures of a plurality of objects with the same allowable error without resetting the allowable error many times.

A radiation thermometer according to a thirteenth aspect of the present invention comprises:
The temperature measurement target is a human body, and the allowable error selecting means includes a thermometer function selecting means for selecting whether to use the radiation thermometer as a female thermometer or as a general-purpose thermometer having a larger allowable error than the female thermometer.

The allowable error selecting means selects an allowable error depending on whether the radiation thermometer selected by the thermometer function selecting means is used as a female thermometer or a general-purpose thermometer. And the measurement time can be used to measure the body temperature.

A radiation thermometer according to a fourteenth aspect of the present invention comprises:
The allowable error indicating means is arranged so that the user can operate it at any time.

Then, by operating the allowable error indicating means, the allowable error can be set at any time, so that the user can determine the allowable error as needed and the measuring time according to the error at his own will.

A radiation thermometer according to a fifteenth aspect of the present invention comprises:
The tolerance error indicating means is arranged to be operated before shipment and arranged so as not to be operated by the user.

Then, the manufacturer of the radiation thermometer operates the tolerance error indicating means at the time of shipping, so that a plurality of types of radiation thermometers having different errors included in the temperature measurement results and different times required for the measurement can be manufactured in the same process. It can be manufactured.

[0041]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a radiation thermometer according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes an allowable error indicating means for indicating an allowable error. Reference numeral 2 denotes a tolerance selecting means for selecting one of a plurality of predetermined tolerances, and includes a push button 2a and a push button 2b therein.
have. Reference numeral 3 denotes a measuring time determining means for determining a time spent for measuring infrared rays. Reference numeral 4 denotes an object whose temperature is to be measured. Reference numeral 5 denotes infrared measuring means for measuring infrared radiation radiated from the object 4, and includes a chopper 5a for intermittently transmitting infrared light, a pyroelectric infrared sensor 5b for converting the intermittent infrared light into an electric signal, and an amplifier circuit 5c. , A synchronous detection circuit 5d, filter circuits 5e and 5f, and signal selection means 5g. 6 is a chopper temperature measuring means for measuring the temperature of the chopper 5a; 7 is a temperature calculating means for calculating the temperature of the object 4 based on the measured value of the infrared ray obtained by the infrared measuring means 5; .

Each of the filter circuits 5e and 5f is composed of a low-pass filter.
The time constant of the low-pass filter used for the filter circuit 5f
Is smaller than the time constant of the low-pass filter used for. For the sake of convenience in the following description, the time required from the operation of the chopper 5a to the time when the output signal of the filter circuit 5e becomes a stable value is represented by τ1, and
The time required for the output signal of f to reach a stable value is τ
Represented by 2. At this time, since the time constant of the filter circuit 5e is smaller than the time constant of the filter circuit 5f, τ1 <τ2.

The chopper temperature measuring means 6 includes a chopper 5a
And a thermistor that is thermally coupled to the thermistor. The temperature of the chopper 5a measured by the chopper temperature measuring means 6 is used as a temperature correction signal when the temperature calculating means 7 calculates the temperature of the object 4.

Two values of ε1 and ε2 can be selected as the magnitude of the error allowed for the temperature calculated by the temperature calculating means 7, and which of the two is selected by the push button 2a.
Is determined using the push button 2b. The value of ε1 is the magnitude of a stochastic error caused by noise superimposed on the output signal when the temperature calculation means 7 calculates the temperature using the output signal of the filter circuit 5e, and the value of ε2 is When the means 7 calculates the temperature using the output signal of the filter circuit 5f, the magnitude of the probability error generated due to the noise superimposed on the output signal is predetermined. At this time, the time constant of the filter circuit 5e is smaller than the time constant of the filter circuit 5f.
Is compared with the output signal of the filter circuit 5f, the output signal of the filter circuit 5f is based on averaging the output signal of the synchronous detection circuit 5d over a longer period of time and is included. The probability error is small. That is, there is a relationship of ε1> ε2.

The operation and operation of the radiation thermometer will be described below. The radiation thermometer of this embodiment starts operating when either the push button 2a or the push button 2b is pressed. The allowable error selecting means 2 starts the operation when either the push button 2a or the push button 2b is pressed, and when the push button 2a is pressed, the allowable error is ε1.
Is selected as the allowable error when the push button 2b is pressed. The permissible error indicating means 1 determines the permissible error selected by the permissible error selecting means 2 as a measurement time determining means 3
To supply.

When the allowable error is supplied from the allowable error indicating means 1, the measuring time determining means 3 determines how much time the infrared measuring means 5 should spend for measuring the infrared rays according to the allowable error. . This time is determined as τ1 when the allowable error supplied from the allowable error indicating means 1 is ε1, and is determined as τ2 when the supplied error is ε2. The measuring time determining means 3 supplies the infrared measuring time determined in this way to the infrared measuring means 5.

The infrared measuring means 5 includes the measuring time determining means 3
The operation of the chopper 5a is started when the infrared measurement time is supplied from. The chopper 5a intermittently emits infrared rays emitted from the object 4 at a constant cycle and causes the pyroelectric infrared sensor 5b to enter the pyroelectric infrared sensor 5b. As a result, the pyroelectric infrared sensor 5b
When the chopper 5a transmits infrared rays, the infrared rays radiated from the object 4 enter, and when the chopper 5a blocks the infrared rays, the infrared rays radiated from the chopper 5a itself enter.

The pyroelectric infrared sensor 5b outputs an electric signal indicating the change of the infrared light. When the temperature of the object 4 is higher than the temperature of the chopper 5a, the output signal rises when the infrared ray radiated from the object 4 is incident and falls when the infrared ray radiated from the object 4 is cut off. It becomes a repetitive signal having the same cycle as the operation cycle of 5a. Conversely, when the temperature of the object 4 is lower than the temperature of the chopper 5a, the chopper 5a rises when the infrared ray radiated from the object 4 is incident and rises when the infrared ray radiated from the object 4 is cut off. The repetition signal has the same cycle as the operation cycle. However, since the output signal of the pyroelectric infrared sensor 5b is a voltage excited by the pyroelectric effect on the insulator constituting the sensor element, the output signal is not so large, and thermal noise of a magnitude that cannot be ignored is superimposed thereon. are doing.

The amplifying circuit 5c amplifies the output signal of the pyroelectric infrared sensor 5b on which the thermal noise is superimposed, and amplifies the output signal of the pyroelectric infrared sensor 5b.
d. The synchronous detection circuit 5d detects this repetitive signal and supplies it to the filter circuits 5e and 5f.

The filter circuit 5e smoothes the signal supplied from the synchronous detection circuit 5d using a low-pass filter and supplies the signal to the signal selection means 5g. On the other hand, the filter circuit 5f smoothes the signal supplied from the synchronous detection circuit 5d using a low-pass filter, and supplies the signal to the signal selection means 5g. At this time, the time constant of the filter circuit 5e is smaller than the time constant of the filter circuit 5f.
Is compared with the output signal of the filter circuit 5f, the output signal of the filter circuit 5f is based on averaging the output signal of the synchronous detection circuit 5d over a longer period of time and is included. The probability error is small. However, the time τ2 required for the output signal of the filter circuit 5f to reach a stable value is larger than the time required for the output signal of the filter circuit 5e to reach a stable value than τ1.

The signal selecting means 5g is connected to the measuring time determining means 3
If the measurement time supplied by the chopper 5 is τ1, the output signal of the filter circuit 5e is selected when the time has elapsed by τ1 after the operation of the chopper 5a, and the temperature calculation means Supply to 7. If the measurement time supplied from the measurement time determination means 3 is τ2, the output signal of the filter circuit 5f is selected when the time has elapsed by τ2 after the operation of the chopper 5a,
The measured value of the infrared ray is supplied to the temperature calculating means 7.

The chopper temperature measuring means 6 includes a chopper 5a
Is measured using a thermistor, and the temperature obtained as a result of the measurement is supplied to the temperature calculating means 7. Temperature calculation means 7
Calculates the temperature of the object 4 by using the measured value of the infrared ray supplied from the signal selection means 5 g and supplies it to the temperature display means 8. At this time, the temperature of the chopper 5a supplied from the chopper temperature measuring means 6 is used for calculation as a correction signal.
The temperature display means 8 displays the supplied temperature.

According to the present embodiment, the measurement time is determined so that the probability error included in the temperature calculated by the temperature calculating means 7 becomes equal to the allowable error selected by pressing the push button 2a or the push button 2b by the user. The means 3 changes the time for measuring the infrared radiation and spends a short time τ1 if the selected tolerance is a large value ε1 and a long time τ2 if the selected tolerance is a small value ε2. Therefore, the temperature of the object 4 can be measured in the minimum necessary measurement time according to the tolerance selected by the tolerance selection means 2.

Further, since the temperature of the object 4 is automatically measured only by selecting the tolerance by pressing either the push button 2a or the push button 2b, it is necessary to wait for a separate instruction to start the measurement. Temperature measurement can be performed promptly without the need.

In this embodiment, the case where the number of the filter circuits of the infrared measuring means 5 and the number of the push buttons of the allowable error selecting means 2 are two has been described as an example. Of course, it doesn't matter.

When the radiation thermometer of this embodiment is used as a thermometer with the temperature of the living body as the temperature of the eardrum of the living body, ± 0.05 ° C. is selected as the allowable error when the push button 2a is pressed. However, when the push button 2b is pressed, ± 0.1 ° C. is selected as the allowable error, so that one thermometer requires a long temperature measurement time of ± 0.1 ° C.
Of course, it can be used by switching between using it as a female thermometer capable of measuring body temperature with an accuracy of 05 ° C. or using it as a general-purpose thermometer capable of measuring body temperature in a shorter time although the temperature measurement accuracy is not as high as that of a female thermometer.

(Embodiment 2) FIG. 2 is a configuration diagram of a radiation thermometer according to Embodiment 2 of the present invention. In FIG. 2, reference numeral 11 denotes an allowable error indicating means for indicating an allowable error. Numeral 12 denotes an allowable error input means for inputting a numerical value of the allowable error. Numerical keys 12a for instructing the input of a numerical value from 0 to 9 and a decimal point and canceling the already input numerical value, the numerical value of 0 to 9 and a decimal point Is displayed. Reference numeral 13 denotes a measurement time determination unit that determines a time spent for measuring infrared rays. Reference numeral 14 denotes a measurement start instructing unit for instructing the start of temperature measurement, and includes a push button 14a therein. Reference numeral 15 denotes an infrared measuring means for measuring infrared radiation radiated from the object 4 to be subjected to temperature measurement. The infrared measuring means 15 has a filter circuit 15a therein, a sampling means 15b for sampling an analog signal, and an infrared measuring means based on the sampled signal value. An arithmetic unit 15c for calculating a value is provided. In addition, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

The filter circuit 15a is constituted by a low-pass filter that does not pass a signal having a frequency higher than a predetermined frequency.

The arithmetic means 15c uses the concept of the discrete Fourier transform, and based on the value sequence sampled by the sampling means 15b, the chopper 5c of the signal components of various frequencies contained in the output signal of the filter circuit 15a.
The magnitude of a signal component having a frequency equal to the operating frequency of “a” is calculated.

Hereinafter, the operation and operation of the radiation thermometer will be described. The radiation thermometer of this embodiment starts preparations for temperature measurement when the push button 14a in the measurement start instruction means 14 is pressed after the allowable probability error is input using the allowable error input means 12. I do.

The probability error allowed by the user is input as a numerical value via the numeric keypad 12 a of the allowable error input means 12. The value of the input permissible error is indicated by the permissible error display means 12.
b. The user confirms the numerical value of the allowable error once input by the allowable error display means 12b, and if the numerical value is incorrect, operates the numeric keypad 12a to cancel the value and input the correct allowable error value again. be able to. Hereinafter, the value of the permissible error input from the numeric keypad 12a is referred to as ε3 for convenience of explanation.

The permissible error indicating means 11 supplies the permissible error value ε 3 inputted to the permissible error input means 12 to the measuring time determining means 13. The measurement time determining means 13 uses the value ε3 supplied from the allowable error indicating means 11 and a positive constant K,

[0064]

(Equation 1)

The time τ 3 determined as is calculated and supplied to the infrared measuring means 15. The measurement start instructing means 14 waits for the push button 14a to be pressed, and supplies a measurement start command to the infrared measuring means 15 when the push button 14a is pressed. The infrared measuring means 15 is provided with a measuring start instructing means 14.
, The operation of the chopper 5a is started as preparation for temperature measurement.

The chopper 5a intermittently emits infrared rays emitted from the object 4 at a constant cycle and makes the infrared rays incident on the pyroelectric infrared sensor 5b. As a result, the pyroelectric infrared sensor 5b includes:
When the chopper 5a transmits infrared light, the object 4
When the chopper 5a blocks infrared rays, the infrared rays emitted from the chopper 5a itself enter. Hereinafter, for convenience of explanation,
The operating cycle of the chopper 5a is represented by T.

The pyroelectric infrared sensor 5b outputs an electric signal indicating the change of the infrared light. When the temperature of the object 4 is higher than the temperature of the chopper 5a, the output signal rises when infrared rays radiated from the object 4 enter and falls when the infrared rays radiated from the object 4 are cut off. It becomes a repetition signal of T. Conversely, when the temperature of the object 4 is lower than the temperature of the chopper 5a, the period T falls when the infrared light emitted from the object 4 is incident and rises when the infrared light emitted from the object 4 is cut off. It becomes a repeated signal. However, since the output signal of the pyroelectric infrared sensor 5b is a voltage excited by the pyroelectric effect on the insulator constituting the sensor element, the output signal is not so large, and thermal noise of a magnitude that cannot be ignored is superimposed thereon. are doing.

The amplification circuit 5c amplifies the output signal of the pyroelectric infrared sensor 5b on which the thermal noise is superimposed, and amplifies the output signal of the pyroelectric infrared sensor 5b.
5a. For a predetermined natural number N, the filter circuit 15a outputs a signal component having a frequency N / 2T or higher corresponding to N / 2 times the operating frequency 1 / T of the chopper 5a among the signals supplied from the amplifier circuit 5c. Without passing through, a signal component having an operating frequency of 1 / T or less of the chopper 5a is passed without attenuating and supplied to the sampling means 15b.
It is desirable to set the value of N to 10 or more. The signal supplied to the input of the filter circuit 15a is a signal obtained by superimposing thermal noise on a repetitive signal having a period T, so that the influence of the initial response of the pyroelectric infrared sensor 5b, the amplifier circuit 5c, and the filter circuit 15a is eliminated. Is such that the waveform of the signal appearing at the output of the filter circuit 15a is such that the band-limited thermal noise is superimposed on the repetitive signal having the period T.

The infrared measuring means 15 considers that the preparation for the measurement is completed when the influence of the initial response is eliminated, and the chopper 5a, the pyroelectric infrared sensor 5b, the amplifier circuit 5c, and the filter circuit 15a While the operation of (1) is performed, the sampling means 15b and the arithmetic means 15c are newly added.
The operation of is started. When the influence of the initial response is eliminated is determined in advance from the physical characteristics of the chopper 5a, the pyroelectric infrared sensor 5b, the amplifier circuit 5c, and the filter circuit 15a. The sampling means 15b is a measuring time determining means 1
3 and the operation cycle T of the chopper 5a.
From

[0070]

(Equation 2)

With respect to the minimum natural number M, T / T corresponding to 1 / N of the operation cycle of the chopper 5a over the time of the M cycle of the operation of the chopper 5a, that is, over the time of M × T. The signal supplied from the filter circuit 15a is sampled at the cycle of N, in other words, at the frequency of N / T, and the sampled signal value sequence is supplied to the calculating means 15c. Hereinafter, for convenience of explanation, the sampling means 15b
S are the values sampled in the order
(0), s (1), s (2),..., S (M × N−
1).

The calculating means 15c uses this sequence of sampling values to calculate

[0073]

(Equation 3)

Then, the measured value of the infrared ray radiated from the object 4 is calculated. Thereafter, the operations performed by the chopper temperature measuring means 6, the temperature calculating means 7, and the temperature displaying means 8 are exactly the same as those in the first embodiment, and therefore detailed description is omitted.

Here, the output signal of the filter circuit 15a after the influence of the initial response is eliminated becomes a repetitive signal having a period T when the superposed thermal noise component is ignored. Further, the output signal of the filter circuit 15a has a frequency of N / 2T.
The above signal components are not included, and the sampling means 1
Since the sampling frequency N / T of 5b satisfies the so-called Nyquist condition, the chopper 5 out of signal components of various frequencies included in the output signal of the filter circuit 15a.
A signal component having a frequency equal to the operating frequency 1 / T of a, that is, a peak-to-peak amplitude voltage of a signal component representing a measured value of infrared radiation emitted from the object 4 is expressed by s using a discrete Fourier transform. (0), s (1), s
From (2), ..., s (N-1)

[0076]

(Equation 4)

Can be calculated as In actuality, thermal noise is superimposed on the output signal of the filter circuit 15a, so that even when the temperature of the object 4 and the chopper 5a is constant, the fluctuation of the calculated infrared measurement value due to this thermal noise is included. Occurs and for each cycle of the chopper operation, equation (4)
The value calculated by applying the formula fluctuates slightly. This variation width can be reduced in inverse proportion to the square root of M by taking an average value over the time of M cycles of the operation of the chopper 5a. Due to the periodicity of the trigonometric function, the calculation formula of equation (3) performs the same processing as that for calculating the average value. Therefore, the magnitude of the error contained in the infrared measurement value calculated by the calculation means 15c is M Is inversely proportional to the square root of.

When the operation cycle T of the chopper 5a is constant, M is proportional to τ3 according to the equation (2). On the other hand, from equation (1), τ3 is inversely proportional to the square of the allowable error ε3. That is, the magnitude of the error included in the infrared measurement value calculated by the calculation means 15c is proportional to ε3.

Therefore, according to the present embodiment, the temperature calculating means 7 determines the proportionality constant K of the equation (1) by taking into account the arithmetic equation used when calculating the temperature of the object 4. It is possible to measure the temperature of the object 4 in a minimum measurement time according to ε3 while suppressing the error included in the temperature calculated by the error to the allowable error ε3 input by the user using the allowable error input unit 12. .

Further, the infrared measuring means 15 does not start its operation only when the permissible error instructing means 11 instructs the permissible error, but starts the infrared measurement only when the push button 14a in the measuring start instructing means 14 is pressed. Therefore, by pressing the push button 14a a plurality of times after setting the allowable error in advance, it is possible to continuously measure the temperatures of a plurality of objects with the same allowable error without resetting the allowable error many times. Become.

In the second embodiment, only the probability error is described assuming that the instrument error can be ignored. However, when it is necessary to expect a certain value ε0> 0 as the instrument error, the measurement time of the infrared ray is reduced. Since the value allowed for the probability error that can be reduced by changing the value may be limited to ε3−ε0, instead of Expression (1),

[0082]

(Equation 5)

The infrared measurement time may be determined. However, in that case, the machine error ε0
Needless to say, only larger values can be entered.

In the above embodiment, the case where the user operates the allowable error indicating means to set the allowable error has been described as an example. However, the allowable error is written in the EPROM or the radiation temperature is set by using a jumper wire. It is also possible to adopt a configuration in which the setting is made at the time of manufacture or shipping of the meter, and is not operated by the user thereafter. According to such a configuration, it becomes possible to manufacture radiation thermometers of a plurality of specifications having different temperature measurement accuracy and measurement time in exactly the same process except for setting of information on an allowable error.

[0085]

As described above, according to the first aspect of the present invention,
The radiation thermometer according to the is a radiation thermometer that calculates the temperature of the object based on the measurement value of the infrared radiation emitted from the object to be measured temperature, the infrared thermometer based on the magnitude of the error allowed in the temperature measurement result Since the time spent for measurement is changed, and the size of the error included in the measured value is changed according to the time spent for measurement, infrared rays are measured,
There is an effect that the temperature of the object can be measured at an appropriate time according to the tolerance.

In the radiation thermometer according to the second aspect of the present invention, the time for measuring the infrared rays by the infrared measuring means is changed by the measuring time determining means, and the infrared thermometer is measured based on the permissible error indicated by the permissible error indicating means. Since the magnitude of the error included in the value is changed, there is an effect that the temperature of the object can be measured in an appropriate time according to the allowable error.

Further, in the radiation thermometer according to the third aspect, the allowable error indicating means indicates only the probability error, and the measuring time determining means eliminates the influence of the instrumental error whose size changes due to calibration. The effect is that the time can be determined accurately.

In the radiation thermometer according to the fourth aspect, the measuring time of the infrared ray determined by the measuring time determining means is short when the allowable error is large and is long when the allowable error is small. In addition, there is an effect that it is possible to freely select whether to measure the temperature with priority to the short measurement time or to measure the temperature with priority to the measurement accuracy.

Further, the radiation thermometer according to claim 5 is provided with a plurality of filter circuits having different time constants for smoothing the measured value of the infrared ray by the infrared ray measuring means, and responding to the permissible error indicated by the permissible error indicating means. By selecting the filter circuit to be used, the infrared measurement value will be averaged over the time corresponding to the allowable error.Therefore, measure the temperature according to the specified error at the appropriate measurement time. There is an effect that can be.

In the radiation thermometer according to the sixth aspect, the measurement time of the infrared ray determined by the measurement time determination means changes in inverse proportion to the quadratic expression of the allowable error, and becomes shorter when the allowable error is large. Conversely, when the allowable error is small, the length becomes longer, so that there is an effect that it is possible to freely select whether to measure the temperature with priority on the short measurement time or to measure the temperature with priority on the measurement accuracy.

The radiation thermometer according to the seventh aspect of the present invention is characterized in that when the main error contained in the infrared measurement value obtained by one measurement is a probability error according to a Gaussian distribution such as thermal noise, infrared radiation is measured a plurality of times. Since the S / N ratio of the measured value can be improved in proportion to the square root of the number of measurements by measuring and averaging the average value as the final measured value, the measuring time determining means can reduce the infrared measuring time by the square of the permissible error. Is determined so as to be inversely proportional to the error tolerance, it is possible to make the magnitude of the error included in the infrared measurement value proportional to the specified allowable error.

The radiation thermometer according to the eighth aspect of the present invention is characterized in that the error contained in the infrared measurement value obtained by one measurement consists of a probability error following a Gaussian distribution such as thermal noise and a certain amount of instrument error. To improve the signal-to-noise ratio of the measured values in proportion to the square root of the value obtained by subtracting a constant value corresponding to the instrument noise from the number of measurements, by measuring the infrared light multiple times and taking the average value as the final measured value Since the measurement time determination means determines the measurement time of the infrared light so as to be inversely proportional to the square of a value obtained by subtracting a predetermined value from the allowable error, the magnitude of the error included in the infrared measurement value is designated. It becomes possible to make it proportional to the allowable error.

In the radiation thermometer according to the ninth aspect, since the measuring time determining means determines the infrared measuring time based on the numerical value input from the allowable error input means, the object can be measured at an appropriate time according to the allowable error. This has the effect that the temperature of the sample can be measured.

In the radiation thermometer according to the tenth aspect, the measuring time determining means determines the measuring time of the infrared ray based on the allowable error selected by the allowable error selecting means. There is an effect that the temperature of the object can be measured.

Further, in the radiation thermometer according to the eleventh aspect, when the allowable error is selected by the allowable error selecting means, the infrared measuring means automatically starts measuring the infrared ray, so that the start of the measurement is separately instructed. There is an effect that the temperature can be measured promptly without the need.

A radiation thermometer according to a twelfth aspect of the present invention comprises:
It is provided with measurement start instructing means for instructing the start of temperature measurement, and when receiving an instruction from the measurement start instructing means, the infrared measuring means starts measuring infrared rays. By operating the measurement start instruction means a plurality of times later, there is an effect that the temperatures of a plurality of objects can be continuously measured with the same allowable error without setting the allowable error many times.

In the radiation thermometer according to the thirteenth aspect, the allowable error selection means selects an allowable error according to whether the radiation thermometer selected by the thermometer function selection means is used as a female thermometer or as a general-purpose thermometer. Therefore, there is an effect that the body temperature can be measured with the measurement error and the measurement time according to the purpose of use.

In the radiation thermometer according to the fourteenth aspect, the tolerance can be set at any time by operating the tolerance indicator, so that the user can determine the required tolerance and the measurement time according to his / her own will. There is an effect that can be determined by.

The radiation thermometer according to the fifteenth aspect is characterized in that a company that manufactures the radiation thermometer operates the tolerance error indicating means at the time of shipment, so that the error included in the temperature measurement result and the time required for the measurement are different. There is an effect that various kinds of radiation thermometers can be manufactured in the same process.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a radiation thermometer according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a radiation thermometer according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a radiation thermometer according to a conventional technique.

[Explanation of symbols]

 1, 11 allowable error indicating means 2 allowable error selecting means 3, 13 measurement time determining means 5, 15 infrared measuring means 7 temperature calculating means 12 allowable error input means 14 measurement start instructing means

Claims (15)

[Claims] 1. A radiation thermometer for calculating a temperature of an object based on a measured value of an infrared ray radiated from an object to be subjected to temperature measurement, the infrared thermometer being configured to calculate an infrared ray based on a magnitude of an error allowed for the calculated temperature of the object. A radiation thermometer that measures the amount of time spent in the measurement of infrared light, and measures infrared rays in such a way that the magnitude of the error contained in the measured value changes according to the time spent in the measurement. 2. An infrared measuring means for measuring infrared radiation radiated from an object to be subjected to temperature measurement by a method in which a magnitude of an error included in a measured value changes according to a time spent for the measurement.
Tolerance error instructing means for instructing an error to be allowed in the temperature measurement result, measurement time determining means for determining a time for causing the infrared measuring means to measure infrared light by using an allowable error instructed by the allowable error instructing means, and the infrared light The radiation thermometer according to claim 1, further comprising: a temperature calculating unit that calculates a temperature of an object to be subjected to a temperature measurement using a measurement result of the infrared ray by the measuring unit. 3. The radiation thermometer according to claim 2, wherein said allowable error indicating means is configured to indicate an allowable error in the temperature measurement result. 4. The radiation thermometer according to claim 2, wherein the infrared measurement time determined by the measurement time determination means has a monotonically decreasing relationship with respect to the tolerance indicated by the tolerance indication means. 5. An infrared measuring means comprising a plurality of filter circuits having different time constants for smoothing a measured value of infrared light, and selecting a filter circuit to be used in accordance with an allowable error indicated by the allowable error indicating means. The radiation thermometer according to claim 4. 6. The radiation thermometer according to claim 4, wherein the measuring time of the infrared ray determined by the measuring time determining means is inversely proportional to a value represented by a quadratic expression of an allowable error indicated by the allowable error indicating means. 7. The radiation thermometer according to claim 6, wherein the measuring time of the infrared ray determined by the measuring time determining means is inversely proportional to the square of the permissible error indicated by the permissible error indicating means. 8. The infrared measuring time determined by the measuring time determining means is inversely proportional to the square of a value obtained by subtracting a predetermined value from the allowable error indicated by the allowable error indicating means.
Radiation thermometer as described. 9. The radiation thermometer according to claim 4, wherein said allowable error indicating means has an allowable error input means for inputting an allowable error as a numerical value. 10. The radiation thermometer according to claim 4, wherein said allowable error indicating means includes an allowable error selecting means for selecting one of a plurality of predetermined allowable errors. 11. The radiation thermometer according to claim 10, wherein said infrared measuring means is configured to start measuring infrared rays when an allowable error is selected by said allowable error selecting means. 12. The radiation temperature according to claim 10, further comprising measurement start instructing means for instructing the start of temperature measurement, wherein the infrared measuring means starts infrared measurement when receiving an instruction from said measurement start instructing means. Total. 13. A thermometer function selecting means for selecting whether to use the radiation thermometer as a female thermometer or as a general-purpose thermometer having a larger permissible error than the female thermometer, wherein the temperature measuring object is a human body. Item 10. A radiation thermometer according to Item 10. 14. The radiation thermometer according to claim 3, wherein the tolerance error indicating means is arranged so that the user can operate it at any time. 15. The radiation thermometer according to claim 3, wherein said tolerance error indicating means is operated before shipping and cannot be operated by a user.