JPH08122166A - Method and instrument for measuring temperature - Google Patents

Abstract

PURPOSE: To provide a temperature measuring instrument which can accurately measure temperature even if the temperature greatly changes and may take any value. CONSTITUTION: In the temperature measuring instrument with a temperature sensor 1 for varying resistance according to temperature, a resistance-voltage conversion part 2 for converting resistance to a voltage value by supplying a constant current to the temperature sensor, a zero point adjustment part 5 for adjusting zero point in reference to a voltage value applied to the temperature sensor when temperature is a lower-limit temperature of a measurement temperature span, a span adjustment part 6 for adjusting span so that the span matches with the width of the conversion range of an A/D conversion part, an A/D conversion part 3 for converting the voltage value into a digital value, and an operation processing part for converting the digital value into a measurement temperature value, temperature is measured in the maximum measurement temperature span, the measurement temperature span is set so that the measurement temperature is within the measurement temperature span, and temperature is measured again based on the measurement temperature span.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring device for measuring temperature using a temperature sensor whose resistance value changes according to temperature.

[0002]

2. Description of the Related Art A temperature measuring device measures an air temperature or a water temperature and outputs a display or the like. A conventional technique will be described with reference to FIG. FIG. 3 is a block diagram of the temperature measuring device.

In FIG. 3, reference numeral 1 denotes a temperature sensor whose resistance value changes according to temperature, and a resistance-voltage converter 2 supplies a constant current to the temperature sensor 1 to convert the resistance value into a voltage value.

The zero point adjustment unit 5 performs zero point adjustment of the voltage value, and the span adjustment unit 6 performs span adjustment. The control unit 7 controls the adjustment of the zero point adjusting unit 5 and the span adjusting unit 6 based on the measured temperature span input by the operator at the measured temperature span input unit 4. The range of voltage value that changes according to the temperature within the range of measurement temperature span is A / D after zero point adjustment and span adjustment.
It is associated with the conversion range of the voltage value of the conversion unit 3.

The A / D conversion section 3 converts the voltage value into a digital value, and the arithmetic processing section 8 converts the digital value into a measured temperature value. The temperature value is displayed by the output unit 9 or output as a signal to the outside.

Since the resolution of the A / D converter 3 is constant, if the operator sets a wide measurement temperature span, the resolution will be low, and if the measurement temperature span is set narrow, the resolution will be high.

[0007]

However, in the temperature measuring device as shown in FIG. 3 described above, when it is known in advance that the measured temperature always falls within a certain range, the measured temperature span is narrowed. Although it can be set and the temperature can be measured with high accuracy, it is necessary to set a wide measurement temperature span if there is a large change in the temperature to be measured and it is uncertain what value to take. If the temperature span is set wide, the resolution becomes low, so there is a problem in that the temperature cannot be accurately measured even if the operator once sets the measurement temperature span.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method even when the temperature to be measured has a large change and the value to be taken is uncertain. Another object of the present invention is to provide a temperature measuring device capable of measuring temperature with high accuracy.

[0009]

In order to solve the above problems, the present invention provides a temperature sensor whose resistance value changes according to temperature by supplying a constant current to the temperature sensor. In the temperature measuring method of converting the resistance value into the voltage value, converting the voltage value into the digital value, and calculating the measured temperature value from the digital value, the temperature is measured in the maximum measurement temperature span and based on the measurement result. Adjust the zero point and span so that the measured temperature is within the measured temperature span.
In this method, the temperature is measured again with the set measurement temperature span.

According to the second aspect of the invention, a temperature sensor whose resistance value changes according to temperature, and a resistance-voltage which supplies a constant current to the temperature sensor to convert the resistance value into a voltage value. The conversion unit, a zero point adjustment unit that performs zero point adjustment based on the voltage value applied to the temperature sensor at the lower limit temperature of the measurement temperature span, and the measurement temperature span within the conversion range width of the A / D conversion unit. In a temperature measuring device having a span adjusting section for performing a span adjustment so as to match, an A / D converting section for converting a voltage value applied to a sensor into a digital value, and an arithmetic processing section for converting the digital value into a measured temperature value. , The temperature is measured in the maximum measurement temperature span, and based on the measured temperature, the measurement temperature falls within the measurement temperature span,
It is characterized in that a measurement temperature span setting unit for setting the measurement temperature span is provided.

[0011]

With the above construction, according to the invention of claim 1, first, zero point adjustment and span adjustment are performed at the maximum measurement temperature span, and then the temperature is measured,
Based on the measurement temperature that is the measurement result, the measurement temperature span is set so that the measurement temperature falls within the measurement temperature span,
The zero point adjustment and the span adjustment are performed again, and the temperature is measured again at the set span, so that the measurement temperature span narrower than the maximum measurement temperature span and the conversion range of the A / D converter are associated with each other. be able to.

According to the second aspect of the present invention, the measurement temperature span setting unit sets the maximum measurement temperature span to the measurement temperature span, and the measurement temperature span and the conversion range of the A / D conversion unit match. As described above, the zero point adjustment unit performs the zero point adjustment, the span adjustment unit performs the span adjustment, and then the temperature is measured, and the measured temperature span setting unit determines the measured temperature based on the measured temperature as the measurement result. Set the measurement temperature span again so that it falls within the measurement temperature span, perform zero point adjustment and span adjustment again, and measure the temperature at the set measurement temperature span. The narrow measurement temperature span and the conversion range of the A / D converter can be associated with each other.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the temperature measuring device of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a temperature measuring device. FIG. 2 is a flowchart showing the operation of the temperature measuring device.

In FIG. 1, reference numeral 1 indicates a temperature sensor. The temperature sensor 1 detects an air temperature, a water temperature, and the like, has a resistance value that changes according to the temperature, and can measure a temperature within a maximum measurement temperature span [Tmin ° C to Tmax ° C].

The resistance-voltage converter 2 supplies a constant current to the temperature sensor 1 to change the resistance value at the temperature Tr ° C. to the voltage value Er.
Convert to.

The A / D converter 3 converts a voltage value, which is an analog value, into a digital value.

The measurement temperature span setting unit 11 sets the measurement temperature span [Ta ° C to Tb ° C] based on the measured temperature value output by the arithmetic processing unit 8 described later. The measurement temperature span [Ta [deg.] C. to Tb [deg.] C.] is the range of the measurement temperature specified for use in the measurement within the range of the maximum measurement temperature span [Tmin [deg.] C. to Tmax [deg.] C.) and satisfies the following equation.

Tmin ° ≤Ta ° C <Tb ° C≤Tmax ° C The width of voltage value [Emin to Emax] at the maximum measurement temperature span [Tmin ° to Tmax ° C] and the resolution of the A / D converter 3 (for example, quantum If the number of digitized bits is 8 bits, there are 256 stages), as compared with the case of corresponding to the range of voltage values [Ea to Eb] and A at the measurement temperature span [Ta ° C to Tb ° C].
The accuracy is higher when the resolution of the / D converter 3 is associated.

For example, when the width of the voltage value corresponding to the range of [0 ° C. to 256 ° C.] is A / D converted with a resolution of 8 Bit,
When the digital value 1 corresponds to the voltage value corresponding to the temperature of 1 ° C., and the width of the voltage value corresponding to the range of [0 ° C. to 16 ° C.] is A / D converted with a resolution of 8 Bit, the digital value is obtained. Since 1 corresponds to a voltage corresponding to a temperature of 1/16 ° C., the measurement accuracy will be high if the measurement temperature span is set narrow.

That is, the measurement temperature span [Ta ° C to Tb ° C]
The measurement temperature span [Ta ° C to Tb ° C] corresponding to the resolution of the A / D converter 3 is narrower than the maximum measurement temperature span [Tmin ° C to Tmax ° C]. Even if the resolutions of 3 are the same, the accuracy is relatively improved.

However, in the calculation, if the measurement temperature span is narrowed infinitely, the accuracy will be improved infinitely, but the accuracy of the temperature sensor is limited, and the measurement temperature span is narrowed to a certain width or less. Even if it is improved, a meaningful value is not output due to the measurement error, so that the measurement temperature span has a minimum temperature width that is not affected by the measurement error. Therefore, the measurement temperature span [Ta ℃ ~ Tb ℃] is the maximum measurement temperature span [T
[min ° C to Tmax ° C] and wider than the minimum temperature range.

The zero-point adjusting unit 5 is composed of a bridge circuit, and is based on the voltage value Ea applied to the temperature sensor 1 at the lower limit temperature Ta ° C. of the measurement temperature span [Ta ° C. to Tb ° C.] and the temperature Tr ° C. Zero point adjustment is performed to remove the reference voltage value Ea from the voltage value Er extracted from the temperature sensor 1 so that the voltage value (Er-Ea) can be obtained at any time.

The span adjusting unit 6 is composed of a negative feedback operational amplifier, and has a measurement temperature span [Ta ° C to Tb ° C].
The width [Ea to Eb] of the voltage value corresponding to is adjusted by amplifying the voltage value so as to match the conversion range of the voltage of the A / D conversion unit 3,
The amplified voltage value Eg is input to the A / D conversion unit 3.

The A / D converter 3 converts the analog voltage value Eg obtained by amplifying the voltage value (Er-Ea) into a digital value D, and inputs the digital value D to the arithmetic processing unit 8.

The control unit 7 inputs the measurement temperature span [Ta ° C. to Tb ° C.] set by the measurement temperature span setting unit 11 to the zero point adjusting unit 5 and the span adjusting unit 6. The zero-point adjusting unit 5 receives the measurement temperature span [Ta ° C ~
Tb [deg.] C.], and the span adjusting unit 6 also adjusts based on the measured temperature span [Ta [deg.] C. to Tb [deg.] C.].

The arithmetic processing unit 8 converts the digital value D into a relative temperature Th ° C from the lower limit temperature Ta ° C of the measurement temperature span [Ta ° C to Tb ° C], and calculates the relative temperature Th ° C and the measurement temperature span. The lower limit temperature Ta ° C is added and finally measured temperature Tr ° C is calculated.

The output unit 9 outputs the measured temperature value calculated by the arithmetic processing unit 8 to the outside and displays it on a liquid crystal display or
Output as a signal. The storage unit 10 stores operation programs for the measured temperature value and the measured temperature span setting unit 11, the arithmetic processing unit 8, and the control unit 7.

The operation of the temperature measuring device configured as described above and the method of setting the measurement temperature span in the measurement temperature span setting unit 11 will be described with reference to the flowchart shown in FIG. Also, set the maximum measurement temperature span to [0 ° C to 25
6 ° C.] and the target temperature at the time of measurement is 150.5 ° C., and the following description will be given.

First, the measurement temperature span setting unit 11 sets the measurement temperature span [Ta ° C to Tb ° C] to the maximum measurement temperature span [0 ° C to 256 ° C] (step 101).

The control unit 7 inputs the measured temperature span [0 ° C to 256 ° C] into the zero point adjusting unit 5 and the span adjusting unit 6,
Based on the measured temperature span [0 ° C. to 256 ° C.], the zero point adjustment unit 5 performs zero point adjustment, and the span adjustment unit 6 performs span adjustment (steps 102 and 103). The measurement temperature span is set to [0 ° C. to 256 ° C.] for the same reason as when the temperature measurement device described in the prior art is used, and the measurement temperature span is set wide when measuring an indefinite temperature. Is.

The resistance-voltage converter 2 converts the resistance value of the temperature sensor into a voltage value (step 104). Since the zero point adjustment and the span adjustment have already been performed, the range of the voltage value can be the same as the range of the voltage that the A / D converter 3 can convert into the digital value.

Therefore, the A / D converter 3 changes the voltage value to 8
It is converted into a digital value of bit (256 steps) (step 105). Since the temperature range of the measurement temperature span [0 ° C to 256 ° C] is 256 ° C, 256 stages of digital values correspond,
A digital value of 1 indicates a temperature of 1 ° C. Therefore, the digital value 150 is obtained from the voltage value corresponding to the temperature of the temperature measurement object of 150.5 ° C.

Since the ratio of the temperature of 1 ° C. to the digital value of 1 can be calculated from the measurement temperature span, the arithmetic processing unit 8 uses this ratio to convert the digital value 150 to obtain the temperature of 150 ° C. . Since the temperature of 150 ° C. is a relative temperature from the lower limit temperature of 0 ° C. of the measurement temperature span [0 ° C. to 256 ° C.], the relative temperature of 150 ° C. and the lower limit temperature of the measurement temperature span of 0 ° C. are added to obtain the final temperature. Measured temperature 150
Calculate ° C (step 106).

The measuring temperature of 150 ° C. is measured span setting section 11
Is input to the measurement span setting unit 11 and the measurement temperature is set to 12
It is determined whether the temperature is 8 ° C. or higher (step 107).

If the measurement temperature is lower than 128 ° C., the measurement span setting section 11 sets the measurement temperature span to [0 ° C. to 128 ° C.].
(Step 108). If the measurement temperature is 128 ° C or higher, the measurement span setting unit 11 sets the measurement temperature span to [128 ° C to 256 ° C] (step 10).
9). Since the temperature currently measured is 150 ° C,
The measurement temperature span is set to [128 ° C to 256 ° C].

Next, zero point adjustment (step 110) and span adjustment (step 111) are performed according to the newly set measurement temperature span [128 ° C. to 256 ° C.].

The resistance-voltage converter 2 converts the resistance value of the temperature sensor 1 into a voltage value (step 112). Since the zero point adjustment and the span adjustment are already performed according to the newly set measurement temperature span [128 ° C. to 256 ° C.], the range of the voltage value can be converted into a digital value by the A / D conversion unit 3. Voltage range.

Therefore, the A / D converter 3 converts the analog voltage value into an 8-bit digital value (step 11).
3). That is, the A / D conversion unit 3 measures the measurement temperature span [12
The voltage value obtained by converting from the resistance value corresponding to the measured temperature at 8 ° C. to 256 ° C.] is converted into a digital value of 8 bits (256 stages). Measurement temperature span [128 ℃ -25
6 ° C.] temperature range of 128 ° C. corresponds to 256 digital values, so a digital value of 1 indicates a temperature of 0.5 ° C. Therefore, if the temperature of the temperature measurement object is 150.5 ° C., the digital value 45 is obtained from the voltage value corresponding to 22.5 ° C., which is the temperature from 128 ° C.

The arithmetic processing unit 8 converts the digital value 45 at a ratio of 0.5 ° C. to 1 of the digital value to obtain the temperature of 2
Obtain 2.5 ° C. The temperature 22.5 ° C. is a relative temperature from the lower limit temperature 128 ° C. of the measurement temperature span [128 ° C. to 256 ° C.]. The relative temperature of 22.5 ° C. and the lower limit temperature of the measured temperature span of 128 ° C. are added together to finally calculate the measured temperature of 150.5 ° C. (step 114).

The measured temperature is stored in the storage unit 10 or is output to the outside by a liquid crystal display or the like (steps 115 and 116).

Although the maximum measurement temperature span is described as [0 ° C. to 256 ° C.] in this embodiment, the maximum measurement temperature span is determined by the performance of the temperature sensor, and therefore, [0 ° C. to 256 ° C.]. ] Is not limited thereto.

Further, in resetting the measurement temperature span,
Although a measurement temperature span having a temperature range of [0 ° C to 128 ° C] and [128 ° C to 256 ° C] of 128 ° C is used, the measurement temperature span is not limited to 128 ° C. For example, 5
A measurement temperature span such as 0 ° C. or 10 ° C. may be used.

In this embodiment, the resetting of the measurement temperature span is 1
Although it is performed only once, the measurement temperature span may be performed several times, for example, after the measurement temperature span of 128 ° C. is measured and then the measurement temperature span of 64 ° C. is further performed.

Further, in the present embodiment, the resistance value indicated by the resistance sensor 1 and the voltage value converted by the resistance-voltage conversion unit 2 are in a proportional relationship, so that the relationship between the temperature of the object and the digital value is also proportional. However, the relationship between the resistance value indicated by the resistance sensor and the voltage value converted by the resistance-voltage conversion unit is not limited to the proportional relationship, and a constant relationship is sufficient. For example, when the above relationship is represented by a function such as a curve formula, the temperature of the object and the digital value after A / D conversion have the same relationship, and therefore the inverse function is used in the arithmetic processing unit. The measured temperature value may be calculated from the digital value.

[0045]

Since the temperature measuring device of the present invention is constructed as described above, according to the invention of claim 1, first, zero point adjustment and span adjustment are performed at the maximum measurement temperature span. After that, the temperature was measured, the measurement temperature span was set again so that the measurement temperature was within the measurement temperature span, and the zero point adjustment and the span adjustment were performed again based on the temperature as the measurement result. Since the temperature is measured in the span and the narrower measurement temperature span than the maximum measurement temperature span and the conversion range of the A / D conversion unit can be associated with each other, the change in the temperature to be measured is large. It is possible to provide a temperature measuring method capable of accurately measuring the temperature even when it takes an uncertain value.

According to a second aspect of the present invention, the invention of the first aspect is embodied, and even when the temperature to be measured is greatly changed and it is uncertain what value to take,
It is possible to provide a temperature measurement device that can measure temperature with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a temperature measuring device of the present invention.

FIG. 2 is a flowchart showing the operation of the temperature measuring device of the above embodiment.

FIG. 3 is a block diagram of a conventional temperature measuring device.

[Explanation of symbols]

 1 Temperature Sensor 2 Resistance-Voltage Converter 3 A / D Converter 5 Zero Point Adjuster 6 Span Adjuster 8 Calculation Processor 11 Measurement Temperature Span Adjuster

Claims (2)

[Claims] 1. A constant current is supplied to a temperature sensor whose resistance value changes according to temperature, the resistance value is converted into a voltage value, the voltage value is converted into a digital value, and the measured temperature value is calculated from the digital value. In the temperature measuring method, the temperature is measured in the maximum measurement temperature span, and based on the measurement result, the zero point adjustment and the span adjustment are performed so that the measurement temperature falls within the measurement temperature span, and the setting is performed. A temperature measuring method characterized in that the temperature is measured again in a measurement temperature span. 2. A temperature sensor whose resistance value changes according to temperature, a resistance-voltage conversion unit which supplies a constant current to the temperature sensor to convert the resistance value into a voltage value, and a lower limit temperature of a measurement temperature span. Sometimes, a zero point adjustment unit that performs zero point adjustment based on the voltage value applied to the temperature sensor, and a span adjustment unit that performs span adjustment so that the measured temperature span matches the width of the conversion range of the A / D conversion unit. In a temperature measuring device having an A / D conversion unit for converting a voltage value applied to a sensor into a digital value and an arithmetic processing unit for converting the digital value into a measured temperature value, temperature measurement is performed in a maximum measurement temperature span. The temperature measuring device is provided with a measurement temperature span setting unit that sets the measurement temperature span so that the measurement temperature falls within the measurement temperature span based on the measurement temperature.