JPH07286913A - Differential heat sensor - Google Patents

Abstract

PURPOSE:To reduce the amount of microcomputer arithmetic processing to reduce the processing time for temperature data detection by referring to a temperature data conversion table according to an identified resistance type potential divider circuit, and retrieving the temperature data digitized. CONSTITUTION:A microcomputer MC closes either of switches SW1-SW3 to suit the outside air temperature sensed by a temperature sensing portion, digitizes the outputs of a resistance type potential divider circuit using an A/D converter CV, and stores the digitized values in ROM as temperature data Dx1'-Dx3'. The data are determined as being within either of the following temperature measuring ranges: -10-20 deg.C (low range), 20-50 deg.C (medium range), and 50-80 deg.C (high range). From a temperature data conversion table TBA (A)-TBA(C) to be referred to which is selected on the basis of the determined measuring range, either of the data Dx1'-Dx3' that serve as the outputs of the resistance type potential divider circuit are retrieved, and the temperature data corrected into linear form Dx1-Dx3 that correspond to the retrieved data are read. The temperature data Dx1-Dx3 can thus be obtained without performing arithmetic processing using the microcomputer MC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a differential thermal sensor using a thermistor as a temperature detecting element, and more specifically, by using a microcomputer and an A / D converter, even in a wide temperature measuring range. The present invention relates to a differential heat sensor equipped with a temperature detection unit capable of obtaining and processing linearly and continuously changing temperature data.

[0002]

2. Description of the Related Art In a differential thermal sensor using a thermistor as a temperature sensing element, the relationship between the outside air temperature and the temperature data is linear over a wide temperature range (for example, -10 to 80 ° C.) in which the thermal sensor is used. However, the conventional products do not sufficiently meet such requirements.

Therefore, the present applicant has filed Japanese Patent Application No. 4-32017.
In No. 7, using a microcomputer and A / D converter,
Divide the measurement temperature range into three areas of high, medium and low in advance,
Differential thermal sensor equipped with a temperature detector that obtains linearly corrected continuous output by obtaining temperature data that retains linearity only in each temperature region and performing arithmetic processing. Proposed.

That is, as shown in FIG. 6, the temperature detecting portion of this differential type heat sensor has a constant voltage source VIN,
One thermistor RTH and three resistance elements R having different resistance values prepared in advance for sharing the temperature measurement region.
A, RB, RC are switching means SW1, SW2, S
By selectively switching and connecting with W3, three resistance voltage dividing circuits are independently formed, and the outputs of the three resistance voltage dividing circuits formed independently are converted into A / D converters 10.
After being input to the digital signal and converted into a digital signal, the microcomputer MC performs arithmetic processing to linearly correct the digitized temperature data to obtain temperature data showing a continuous change in all temperature regions. ing.

The operation of this differential thermal sensor will be described below.
Three switching means SW1, S by microcomputer MC
Switching between W2 and SW3 in sequence, one thermistor RTH
In contrast, by connecting three resistance elements RA, RB, RC, the thermistor RTH and the resistors R1, R in each case are connected.
Output of resistance divider circuit formed by 2 and R3 (divided value)
Is converted into a digital signal by the A / D converter CV, and the temperature data at that time is stored in the memory M such as the RAM of the microcomputer MC as Dx1 ′, Dx2 ′, Dx3 ′. Here, the three resistors RA, RB, and RC share a temperature region obtained by dividing the whole measurement region that can be measured by the sensor into three, and the resistance voltage dividing circuit when only SW1 is closed is −10. ~
20 ° C temperature range (low range), when only SW2 is closed, 20-50 ° C temperature range (middle range), when only SW3 is closed, 50-80 ° C temperature range (high range) is shared Then
The resistances RA, RB, RC are set so that only the characteristics of the digitized temperature data Dx1 ', Dx2', Dx3 'measured in the respective measurement areas have linearity.
However, even if the temperature data Dx1 ', Dx2', and Dx3 'obtained in these measurement areas are used as the temperature data as they are, the linearity is obtained in the entire measurement area that can be measured by the differential sensor. Is not retained.

Therefore, in the microcomputer MC, for the temperature data Dx1 ', Dx2', Dx3 'obtained by converting the output of each resistance voltage dividing circuit into a digital signal by an A / D converter,
Further calculation is performed, as shown in FIG. 4, temperature data Dx1, Dx2, and Dx3 that are linearized over the entire measurement temperature region and continuously change are calculated, and this is processed.

For example, the linear correction calculation performed in this case is Dx1 = Dx1'x in the temperature range of -10 to 20 ° C.
3 / 4-15 In the temperature range of 20 to 50 ° C., Dx2 = Dx2 ′ × 7 /
8 + 42 In the temperature range of 50 to 80 ° C., Dx3 = Dx3 ′ + 10
5 is required.

However, when the calculation is performed in the microcomputer MC in this way, a program for the calculation is required. Further, after the temperature data is converted into a digital signal by the A / D converter, the above-mentioned calculation is adjusted. In addition to this, multiplication and division are also necessary. However, since the multiplication / division of digital data is generally carried out by shifting the bits of the data to the left or right, the lower several bits of the data (3 bits for 1/8 multiplication, 2 bits for 1/4 multiplication) Is omitted. Therefore, the temperature data obtained by calculation has a slight difference from the ideal value obtained by actual calculation.
Steps 200 to 213 in FIG. 7 show the operation procedure at this time with a flowchart. FIG. 8 and FIG. 9 show a calculation process when linearly correcting the temperature data digitized to 8 bits (256 stages), and therefore, the values in the middle of calculation for the temperature data in the low range and the high range are shown as a table. It is a thing.

[0009]

SUMMARY OF THE INVENTION In the present invention, the conventional differential thermal sensor is linearly corrected in the entire temperature range by performing the digital arithmetic processing including the addition, subtraction, multiplication and division as described above. The present invention has been made in view of the situation of obtaining temperature data, and its purpose is to reduce the calculation processing in the microcomputer to reduce the processing time for detecting the temperature data.

[0010]

DISCLOSURE OF THE INVENTION The present invention, which is proposed to achieve the above object, does not perform arithmetic processing of addition / subtraction and multiplication / division for linear correction on temperature data converted into a digital signal. The present invention provides a microcomputer-operated differential thermal sensor that obtains linearly corrected temperature data only by referring to a temperature data conversion table that stores linearly corrected values in advance. The differential thermal sensor proposed in Section 1 is connected to a voltage power source.
A plurality of resistance elements, which are divided into a plurality of temperature measurement regions and are preliminarily divided, are selectively connected to one thermistor by switching a corresponding number of switching means, and output when the switching means is switched. This is an improvement of the differential thermal sensor in which the output of the resistance voltage dividing circuit is sequentially converted into a digital signal by the A / D converter and then linearly corrected temperature data is obtained in the entire measurement area of the thermal sensor. The characteristic of the temperature data conversion is that the temperature data obtained by A / D converting the output of the resistance voltage dividing circuit selected by the switching operation of the switching means is stored in advance with the temperature data linearly corrected. A table is prepared for each type of resistance voltage dividing circuit, and the output of the resistance voltage dividing circuit obtained by switching each of the switching means is sequentially A
The temperature data is temporarily stored in the memory as A / D-converted temperature data by the A / D converter, and a resistance voltage dividing circuit sharing the temperature measurement area is selected according to the value of any of the temperature data stored in this memory. From the conversion table, the linearly corrected temperature data corresponding to the temperature data stored in the memory is read and processed.

[0011]

According to the differential heat sensor of the present invention, the switching means is switched to sequentially read the temperature data converted into the digital signal by the A / D converter and store it in the memory. Then, the value of any digitized temperature data thus obtained is read, and the resistance voltage dividing circuit that shares the temperature measurement region is discriminated based on the value.

As a result of this judgment, the temperature data conversion table corresponding to the resistance voltage dividing circuit is referred to from the linear correction temperature data conversion table prepared in advance, and the digitized temperature data is searched for. The linearly-corrected temperature data corresponding to is read and is processed as temperature data by the heat sensor.

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 2 shows an example of the linear correction temperature data conversion table used in the present invention. This temperature data conversion table is formed for each resistance voltage dividing circuit that can be selected by the switching means. For each resistance voltage dividing circuit, the temperature is converted into a digital signal by the A / D converter and digitized. Data Dx '[column]
Of the temperature data and the value of the temperature data Dx [stage] linearly corrected by performing a predetermined calculation.

In the example shown in the figure, three resistance voltage dividing circuits that share a low band T1, a middle band T2, and a high band T3 of the entire temperature measurement region of the differential sensor are shown in tables TAB (A) to TAB (C). )
And each table TAB (A) to T
For AB (C), the temperature data [0 to 255 stages] converted into a digital signal with 8 bits is Dx1 ′, Dx.
2 ', Dx3', and temperature data [0 to 255 steps] corrected linearly are shown as Dx1, Dx2, and Dx3.

FIG. 3 is a view showing a temperature detecting portion A which is a main portion of the differential heat sensor of the present invention. Temperature detector A
As shown in this figure, is the constant voltage power supply VIN
Is applied to one thermistor RTH, three types of resistance elements R1, R2, R3 are switchably connected by switching means SW1, SW2, SW3, and input of each resistance R1, R2, R3. The end is input to the A / D converter CV and converted into a digital signal,
The other ends of the switching means SW1, SW2 and SW3 are connected to the negative terminal of the battery E.

Here, the resistance voltage dividing circuit includes the resistance elements R1 and R1.
Switching means SW1, provided corresponding to R2 and R3
Each of the three resistive voltage divider circuits formed independently by selectively closing SW2 and SW3 has a total temperature measurement area (-) that can be measured by the thermal sensor.
Low temperature T1 (-10 to 20 ° C) of 10 to 80 ° C,
Mid range T2 (20-50 ° C), high range T3 (50-80 ° C)
Are shared.

The output of the resistance voltage dividing circuit is the switching means SW1. A / when closing SW2 and SW3
The temperature data that is input to the D converter CV, converted into a digital signal, and digitized at this time has the low range T1 (-10 to 20 ° C.) and the middle range T2 as shown in FIG.
(20 to 50 ° C.), a linear change is exhibited only in a high temperature region T3 (50 to 80 ° C.).

Next, an execution procedure for obtaining linearly corrected temperature data by the differential heat sensor of the present invention will be described. According to the present invention, the outside air temperature is detected by the temperature detecting unit A, and the temperature data Dx1 ′, Dx2 ′, Dx3 ′ digitized by the A / D converter CV are processed by the microcomputer MC without being processed by the microcomputer MC. ROM of
Stored in a memory such as, and referring to the temperature data conversion tables TAB (A) to TAB (C) prepared in advance,
Linearly corrected temperature data Dx1, Dx2, Dx3
Can be obtained. [Procedure 1] Each of SW1, SW2 and SW3 is closed, and the output of the resistance voltage dividing circuit formed by the thermistor RTH and the resistors R1, R2 and R3 is A / D converted by the A / D converter CV in the microcomputer MC. Then, the digitized values are stored in the RAM as temperature data Dx1 ′, Dx2 ′, Dx3 ′. [Procedure 2] Temperature data Dx acquired by procedure 1
Of 1 ', Dx2', Dx3 ', the current outside air temperature is -10 to 20 ° C (low range), 20 to 50 ° C (medium range) based on the value of the temperature data Dx2' that shares the middle range T2. ), 5
It is determined which of the temperature measurement regions of 0 to 80 ° C. (high range) is the temperature measurement region.

The criterion in this case is that if Dx2 '<72, the temperature measurement region is the low region T1, that is, -10 to 20.
If ℃ 72 ≦ Dx2 ′ <152, the temperature measurement area is the middle area T
2, that is, 20 to 50 ° C. 152 <Dx2, it is determined that the temperature measurement region is the high region T3, that is, 50 to 80 ° C. [Procedure 3] The temperature data conversion tables TAB (A) to TAB (C) to be referred to are selected according to the temperature measurement area determined by the temperature data Dx2 ′, and the digital data which becomes the output of the resistance voltage dividing circuit is selected from the conversion table. Of the converted temperature data Dx1 ', Dx2', or Dx3 ', and the linearly corrected temperature data Dx corresponding to the searched temperature data
Read 1, Dx2 and Dx3. For example, in the procedure 1, the temperature data digitized by the A / D converter CV is Dx1 ′ = 170 [stages], Dx2 ′ = 84.
When [step] and Dx3 ′ = 30 [step], the digitized temperature data Dx2 ′ sharing the middle range is
Since 72 ≦ Dx2 ′ = 84 <152, it is determined that the temperature measurement region is the middle region T2, the temperature data conversion table TAB (B) sharing the middle region is referred to, and Dx2 ′ = 84 [steps]
Linearly corrected temperature data Dx2 = 12 corresponding to
Read 0 [column] and process it. The above operation is shown in steps 100 to 118 of FIG.

According to the present invention, the temperature data thus digitized and the temperature data linearly corrected corresponding to the temperature data are stored in the ROM of the microcomputer MC in advance separately for each resistance voltage dividing circuit. By preparing the linear correction temperature data conversion table in advance, the temperature corrected linearly over the entire measurement temperature range as shown in FIG. 4 can be obtained only by referring to the conversion table without performing calculation in the microcomputer. You can get the data.

Therefore, according to the present invention, since the arithmetic program in the microcomputer is remarkably omitted, the program can be shortened, the processing in the microcomputer can be speeded up, and a differential thermal sensor with good responsiveness can be provided. Further, since the processing speed of the microcomputer is increased, the operation time of the microcomputer can be shortened and the current consumption of the differential operation type heat sensor can be reduced.

Further, since all linearly corrected temperature data in the temperature data conversion table can be set to ideal values, the difference between the temperature data and the ideal values calculated can be eliminated and the accuracy of the temperature data can be improved.

[0023]

According to the differential thermal sensor of the present invention, A /
When linearly correcting the temperature data digitized by the D converter, there is no need to perform arithmetic processing, and it is possible to respond only by referring to the temperature data conversion table prepared in advance, so the program in the microcomputer can be shortened and the operating time of the microcomputer can be shortened. Can be shortened and the current consumption of the microcomputer can be reduced.

[Brief description of drawings]

FIG. 1 is a flow chart showing an operation procedure executed to obtain linearly corrected temperature data in a whole measurement temperature region in a differential heat sensor of the present invention.

FIG. 2 is a diagram showing an example of a linear correction temperature data conversion table used in the present invention.

FIG. 3 is a block diagram showing a configuration of a basic circuit of a temperature detection unit used in the present invention.

FIG. 4 is a graph showing linearly corrected temperature data obtained in the differential thermal sensor of the present invention over the entire measurement temperature range.

FIG. 5 is a graph of temperature data showing temperature data (8 bits) digitized by an A / D converter for each resistance voltage dividing circuit sharing a temperature measurement region.

FIG. 6 is a block diagram showing the configuration of a basic circuit of a temperature detection unit of a differential thermal sensor for obtaining linearly corrected temperature data in the entire measurement temperature region.

FIG. 7 is a flowchart showing an operation procedure executed in a conventional differential thermal sensor when linearly correcting temperature data.

FIG. 8 is a table (low range) showing calculation values in the process of linearly correcting temperature data digitized by an A / D converter.

FIG. 9 is a table (high range) showing calculation values in the process of linear correction of temperature data digitized by an A / D converter.

[Explanation of symbols]

A ... Temperature detection unit TAB (A) to TAB (C) ... Linearly corrected temperature data conversion table RTH ... Thermistor RA, RB, RC ... Resistor element SW1, SW2, SW3 ... Switching means T1 ... Temperature measurement region (low region) T2 ... Temperature measurement region (middle region) T3 ... Temperature measurement region (high region) MC ... Microcomputer CV ... A / D converter VIN. ..Constant voltage power supply

Claims (1)

[Claims] 1. A plurality of resistance elements, which are divided into a plurality of temperature measurement regions in advance, are selectively connected to one thermistor connected to a constant voltage power source by switching a corresponding number of switching means. Then, when the switching means is switched, the output of the resistance voltage divider circuit is
In a differential thermal sensor, which is adapted to obtain linearly corrected temperature data in the entire measurement region of the thermal sensor after being sequentially converted to a digital signal by a / D converter, selected by the switching operation of the switching means. For each type of resistance voltage dividing circuit, for the temperature data obtained by converting the output of the resistance voltage dividing circuit into a digital signal, there is prepared a linear correction temperature data conversion table storing temperature data that has been linearly corrected in advance. The temperature data obtained by sequentially converting the output of the resistance voltage dividing circuit obtained by switching each of the switching means into a digital signal by an A / D converter is temporarily stored in a memory, and one of the temperatures stored in this memory is stored. After the resistance voltage divider circuit that shares the temperature measurement area is determined by the value of the data, it is stored in the memory from the temperature data conversion table. A differential thermal sensor for reading and processing linearly corrected temperature data corresponding to the stored temperature data.