JPS61117425A - Manufacture of thermistor temperature sensor - Google Patents

Abstract

PURPOSE:To manufacture a temperature sensor of economical constitution efficiently by measuring the resistance value of a thermistor at specific temperature, checking which prescribed group the value belongs to, and connecting a corresponding fixed resistance with a specific value. CONSTITUTION:The thermistor temperature sensor consists of the thermistor 1 and the fixed resistance 2 for correction connected thereto in series. The thermistor 1 is held in a thermostatic chamber whose internal temperature is held at, for example, 37 deg.C to measure its resistance value and then it is checked which predetermined group the resistance value of the thermistor belongs to. Then, the fixed resistance corresponding to the group is connected to the thermistor in series to form the temperature sensor which meets requirements of the measurement precision of a clinical thermometer, and a variable resistance need not be adjusted unlike before, so the manufacture is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a thermistor temperature sensor used in an electronic thermometer.

BACKGROUND OF THE INVENTION In recent years, electronic thermometers that electrically measure body temperature have come into widespread use.

Conventionally, the temperature sensor used in this type of electronic thermometer has a thermistor Th and a variable resistor Rv connected in series, as shown in Fig. 8, and this is embedded in a probe made of synthetic resin or the like. is common.

Here, the reason why the variable resistor Rv is connected in series with the thermistor Th is as follows. That is, each thermistor T
There are variations in the characteristics (resistance value, B constant, etc.) of h, and in electronic body temperature needles, the center temperature Tc''C (for example, 3
This is because the combined resistance value Rs (combined resistance of the thermistor Th and variable resistor Rv) of the temperature sensor at 7° C.) is determined. In other words, the conventional thermistor temperature sensor shown in FIG. 8 adjusts the variable resistance Rv-t so that the combined resistance value Rs of the sensor at the center temperature Tc'C becomes a predetermined value. However, in this case, it is necessary to place the temperature sensor in a constant temperature bath and adjust the variable resistor Rv, which has the disadvantage of increasing the working time. Furthermore, since a variable resistor Rv is used,
It is difficult to miniaturize the shape and also has the disadvantage that sufficient reliability cannot be obtained.

Problems to be Solved by the Invention The present invention has solved the above-mentioned problems, and its purpose is to make it possible to manufacture a thermistor temperature sensor with an economical construction with high work efficiency.

Embodiment FIG. 1 is a circuit diagram showing the configuration of a thermistor temperature sensor manufactured according to the present invention, which is composed of a thermistor 1 and a fixed resistor 2 for correction connected in series with the thermistor 1.

The operating temperature range of electronic body temperature needles is generally 32°C to 42°C, and the measurement accuracy is generally ±0.1°C for 35°C to 39°C, and ±0.1°C for 32°C to 35°C and 39°C to 42°C.
0.2°C is required. Since the temperature sensor shown in Figure 1 detects body temperature based on changes in the resistance value of the thermistor 1 due to temperature changes, it is necessary to set the temperature-resistance characteristics of the temperature sensor as a reference in advance. be. For example, if the combined resistance value Rs (thermistor 1 and fixed resistor 2) of the temperature sensor required at the center temperature Tc'C (37°C in this case) is A (KΩ),
As mentioned above, the required measurement accuracy at 37℃ is ±
O, l'C, the combined resistance value Rs of the temperature sensor at 37'c needs to satisfy the relationship shown in the following equation (1).

A (1+71'/10)≦Rs≦A(1-α/10)
−・−−−−−(1) In addition, α is the temperature coefficient of the resistance value of thermistor 1 defined by the following formula (2), and B in formula (2) is the B constant of thermistor 1. , T represents absolute temperature.

α= −B / T 2 −−−−−−−−− (2
) In this case, measurement accuracy of ±0.1°C is required not only at the center temperature Tc°C of 37°C, but also at 35°C to 39°C, so Figure 1 When actually manufacturing a temperature sensor as shown in Fig. 1, it is desirable that the error be ±0.05°C at 37°C. That is, the combined resistance value Rs of the temperature sensor at 37°C
It is desirable that the following equation (3) be satisfied.

A (1+ α/20)≦Rs≦A (1−α/20)
−−１１−−−・−(3) The reason is that when a fixed resistor is connected in series with the thermistor, at one temperature point, the desired combined resistance can be achieved by connecting the fixed resistor. It is possible, but
This is because the combined resistance will not be as desired at other temperature points.

Here, the above will be explained using specific numerical values. For example, it is assumed that a thermistor 1 with a B constant (25° C. to 50° C.) of 3955 is used, and that the combined resistance value A of the temperature sensor required at 37° C. is 30Ω. In this case, the temperature coefficient α of the thermistor 1 at 37° C. is approximately −4% by performing the calculation shown in the following equation (4).

α= −3955/ (273,15+ 37) 2=
-0,041=-4(%)---1111・(4) Also, the required measurement accuracy at 37℃ is ±0.1℃
However, when actually manufacturing a temperature sensor, as mentioned above, it is desirable to have a measurement accuracy of ±0.05°C at 37"C, so the above equation (3) By substituting Ω and α=−0,04 for Rc=30, it can be seen that the composite resistance value Rs of the temperature sensor at 37° C. needs to satisfy the relationship shown in the following equation (5).

29.94 (KΩ)≦Rs≦30.06 (KΩ
) A specific method of manufacturing the temperature sensor shown in FIG. 1 will be described in detail below.

First, the thermistor is held in a constant temperature chamber whose internal temperature is kept at 37°C, and then its resistance value Rt is measured. Check which of #1 to #12 it belongs to. Now, for example, the resistance value Rt of the thermistor measured
is 29.8Ω, then this thermistor is in group #
If the resistance value RL is 29, OKΩ, then this thermistor belongs to group #9.

Here, the combined resistance value Rs of the temperature sensor must satisfy the condition shown in equation (5) at 37°C, and is also equal to the upper and lower limits of the resistance value of the thermistor belonging to group #l. Since the difference between the upper limit value and the lower limit value of the condition shown in equation (5) is 0.06Ω, respectively, group #
For the thermistor belonging to 1, the above conditions can be satisfied by connecting a fixed resistor of 0.06Ω in series. Further, regarding the thermistor belonging to group #2, the difference between its upper limit value and lower limit value and the upper limit value and lower limit value of the above conditions is 0.18Ω, respectively, so 0.18Ω.
The above conditions can be satisfied by connecting a fixed resistor of Ω in series with . Table 2 listed on page 21 lists the fixed resistance values required to satisfy the above conditions for each group, and this is generally expressed as the following equation (6). Become.

R'N = (2N-1) ・A・β/2−・−(6
) However, N indicates the group number, A is the combined resistance value of the temperature sensor required at 37°C (30Ω in this case), and β is the tolerance of the combined resistance of the temperature sensor at 37°C. (0.04 in this case).

As mentioned above, the resistance value of the thermistor at 37°C is measured and the resistance value is determined to which group shown in Table 1 it belongs, and the resistance value is determined according to the group as shown in Table 2. By connecting a fixed resistor, 37”C
Although it is possible to satisfy the above-mentioned required measurement accuracy, inspection is required for other temperature points.

Table 3 shown on page 22 shows the upper and lower limits of the resistance value at each temperature point of thermistors belonging to each group #1 to #12 with a B constant (25°C to 50°C) of 3955. Also, Table 4 on page 23 shows the upper and lower limits of the combined resistance value Rs at each temperature point when thermistors of each group #1 to #12 are connected to the fixed resistor corresponding to the group. It shows the value. As can be seen from Table 4, the difference between the upper limit value (30.06 KΩ) and lower limit value (29.94 KΩ) of the combined resistance value Rs of the temperature sensor at 37'C is 0.12Ω. , at 32°C, the difference is 0.148 KΩ, and at 42°C, the difference is 0.098 KΩ. Furthermore, the combined resistance value Rs
At 32°C, the larger the group number, the smaller it becomes, and at 42°C, the thicker the group number, the larger it becomes. Fig. 2 (A), (
B) illustrates this. In this way, 37℃
Since the combined resistance value Rs of the temperature sensors at other temperature points varies depending on the group, it is necessary to set a standard, that is, a reference value, for the combined resistance value Rs of the temperature sensors at each temperature point.

Figure 3 shows a temperature sensor made by connecting a thermistor that belongs to group #1 with a fixed resistor (0, 06 Ω) in series, and a thermistor that belongs to group #12 and a fixed resistor that corresponds to group #12. (1,38Ω)
It is a diagram showing the combined resistance value Rs at each temperature point of the temperature sensor created by connecting the
It can be seen that the standard may be set based on a thermistor having an intermediate resistance value between the resistance value of the thermistor belonging to group #I2 and the resistance value of the thermistor belonging to group #I2. That is, the upper limit value of group #1 is 30Ω, and group #1
Since the lower limit of 12 is 28.56 KΩ, 37°C
In (30-28,56) / 2 = 29.2
A thermistor having a resistance value of 8 KΩ may be used as the reference thermistor. Also, in 37"c, the temperature sensor is required to have a resistance value of 30Ω, so the value of the fixed resistance connected to the reference thermistor is 30-29.28 = 0. Therefore, by determining the resistance value Rt at each temperature point for the reference thermistor and adding the fixed resistance bone to this, the standard reference value can be determined.

Table 5 on page 24 shows the resistance value RE of the reference thermistor at each temperature point and the combined resistance value of the temperature sensor constructed by connecting a fixed resistance of 0.72Ω to the reference thermistor in series. Fig. 4 shows the standard specifications prepared based on Table 5.

Comparing the standards shown in Figure 4 with the composite resistance value Rs of the temperature sensors shown in Table 4, all the temperature sensors shown in Table 4 satisfy the standards shown in Figure 4. I understand. However, at 32°C and 35°C, group #1
The upper limit value of group #12 and the lower limit value of group #12 are also the lower limit value of group #1 and the lower limit value of group #12 at the points of 39°C and 42°C.
The upper limit value of is closest to the standard. FIG. 5 shows this relationship, and as can be seen from the figure, temperature sensors made using thermistors belonging to group #1 and group #12 are close to the set standards.
It can be seen that temperature sensors made using thermistors belonging to other groups have a considerable margin with respect to the standard.

That is, as in this example, the resistance value Rt of the thermistor at 37°C is measured, and then the measured thermistor is
By checking which of the groups #1 to #12 shown in the table it belongs to, and then connecting the fixed resistor corresponding to the group shown in Table 2 in series with the thermistor, you can create a temperature sensor that fully satisfies the measurement accuracy of the body temperature needle. can be created.

In addition, although the above-mentioned embodiment was explained assuming that the B constants of the thermistors used are all the same, it is possible to make the B constant variation of the thermistors about ±1%, so the variation in the B constant is not a problem. In practice, there is almost no need to do so.

Next, other embodiments of the present invention will be described. In this case, the temperature sensor is required to have the same measurement accuracy as in the above-mentioned embodiment, and the thermistor used has a B constant of 3955, as in the above-mentioned embodiment. do.

First, the thermistor was held in a constant temperature bath whose internal temperature was maintained at 37°C, and then its resistance value Rt was measured, and the measured resistance value Rt of the thermistor was shown in Table 6 on page 25. Check which of groups #1 to #12 it belongs to. Now, for example, the resistance value Rt of the thermistor measured is 30. If it is OKΩ, this thermistor belongs to group #1, and if the resistance value Rt is 29.4Ω, it belongs to group #6.

Here, the combined resistance value Rs of the temperature sensor needs to satisfy the formula (5) at 37°C, as in the above-mentioned embodiment, and is also the upper limit of the resistance value of the thermistor belonging to group #1. Since the value and lower limit value are the same as the upper limit value and lower limit value of the condition shown in equation (5), the thermistor belonging to group #1 can meet the condition of equation (5) without connecting a fixed resistor. can be satisfied. Regarding the thermistor belonging to group #2, the difference between its upper and lower limits and the upper and lower limits of the above conditions is 0.12Ω, respectively, so a fixed resistance of 0.12Ω is connected to the thermistor. The above conditions can be satisfied by connecting in series. Table 7 listed on page 26 lists the fixed resistance values required to satisfy the above conditions in groups, and this can be generally expressed by the following equation (7).
It will be as shown below.

RN = (N 1) ・A・β−・−−−−−(
7) However, N indicates the group number, and A is the combined resistance value of the temperature sensor required at 37°C (in this case, 3
0 to Ω), and β is the tolerance of the combined resistance of the temperature sensor at 37° C. (0.04 in this case).

As mentioned above, the resistance value of the thermistor at 37°C is measured, and it is determined to which group the resistance value belongs as shown in Table 6. By connecting a fixed resistor, it is possible to satisfy the above-mentioned required measurement accuracy at 37° C., but inspection is required at other temperature points.

Table 8 shown on page 27 shows the B constant (25°C to 50°C
) shows the upper and lower limits of the resistance value at each temperature point of the thermistors belonging to each group #1 to #12 of 3955, and Table 9 on page 28 shows the resistance values of the thermistors belonging to each group #1 to #12 of 3955. This figure shows the upper and lower limits of the combined resistance value Rs at each temperature point when fixed resistors corresponding to groups are connected to the thermistors #12 to #12.

As can be seen from Table 9, the upper limit (30.06KΩ) and lower limit (
29,94KΩ) is 0.12Ω, but 32
At ℃, the difference is 0.148 KΩ, which is 42°
For C, the difference is 0.098 KΩ. Also,
Further, the combined resistance value Rs also decreases as the group number increases at 32°C, and increases as the group number increases at 42°C.

Figure 6 shows the combined resistance value Rs at each temperature point of a temperature sensor created by connecting a fixed resistor (Ω to L32) corresponding to group #12 to the thermistor belonging to group #1 and the thermistor belonging to group #12. From the diagram, it can be seen that the standard should be set based on a thermistor having a resistance value intermediate between the resistance value of the thermistor belonging to group #1 and the resistance value of the thermistor belonging to group #12. . That is, the upper limit of group #1 is 30.0.
6 and the lower limit of group #12 is 28.62
Since it is KΩ, it is sufficient to use a thermistor having a resistance value of (30,06+28°62)/2=29.34Ω at 37°C as the reference thermistor. Also, 37
Since the temperature sensor is required to have a resistance value of 30Ω at °C, the value of the fixed resistance connected to the reference thermistor is 30-29.34 = 0.
．． 66 becomes Ω.

Figure 7 is a standard diagram created as a standard for a temperature sensor constructed by connecting a fixed resistor of 0.66Ω to the reference thermistor in series, and when comparing Figure 7 and Table 9, it is found that It can be seen that all the temperature sensors shown in Table 9 satisfy the standards shown in FIG. Therefore, as in this example, the resistance value Rt of the thermistor at 37°C is measured, and then the measured thermistor is placed in the group # shown in Table 6.
1 to #12, and then connect fixed resistors corresponding to the groups shown in Table 7 in series to the thermistor to create a temperature sensor that fully satisfies the measurement accuracy of the body temperature needle. can.

In the two embodiments described above, when the thermistors were divided into groups, the width of the resistance value of each group was made equal;
As can be seen from the figure, groups #1 and #12 are closest to the standard, and it can be seen that the group numbers in the center (groups #6, 7, etc.) have more margin than the standard. Therefore, if the group number is #1 or #1
It is conceivable that the closer the group number is to 2, the narrower the range of resistance values, and the closer the group number is to the center, the wider the range of resistance values. Other embodiments based on the above idea will be described below.

In this case, the temperature sensor is required to have the same measurement accuracy as in the above-mentioned embodiment, and the thermistor used also has a B constant of 3955 as in the above-mentioned embodiment.
Suppose you use the one in .

First, the thermistor was held in a constant temperature bath whose internal temperature was maintained at 37°C, and then its resistance value Rt was measured, and the measured resistance value Rt of the thermistor was shown in Table 10 on page 29. It is determined which of groups #1 to #12 it belongs to, and then a fixed resistor having a value corresponding to the group listed in Table 11 on page 30 is connected in series to the thermistor. Now, for example, the resistance value R of the thermistor measured
If t is 29.75 KΩ, this thermistor belongs to group #3, so a fixed resistance of 0.24Ω is connected.

The relationship between the resistance value RN of the fixed resistor connected to the thermistor of each group and the group number N is generally expressed by the following equation (8).

RN=β9・A/2+Σβ9−1・A′ −−−−−
-(8) However, in the opening formula, A is the combined resistance value of the temperature sensor required at 37° C., and A·βN is the width of the resistance value of each group. Further, β0=0.

In addition, Table 12 shown on page 31 shows the B constant (25°C to 5°C).
0°C) shows the resistance value at each temperature point of thermistors belonging to each group #1 to #12 of 3955, and Table 13 on page 32 shows the resistance value at each temperature point of the thermistor belonging to each group #1 to #1 of 3955.
2 shows the combined resistance value Rs at each temperature point when fixed resistors corresponding to the groups are connected to the thermistor No. 2.

Comparing Table 13 with FIG. 7, it can be seen that all the temperature sensors shown in Table 13 satisfy the standards shown in FIG. Therefore, as in this example, the resistance value Rt of the thermistor at 37°C is measured, and then it is checked to which of groups #1 to #12 shown in Table 10 the measured thermistor belongs. By connecting the fixed resistors corresponding to the groups shown in the table in series with the thermistor, it is possible to create a temperature sensor that fully satisfies the measurement accuracy of a one-body temperature needle.

As in this example, the closer the group number is to #1 or #12, the narrower the resistance value width is, and the closer the group number is to the center, the wider the resistance value width. Since the accuracy can be improved, the yield can be further improved compared to the above-mentioned embodiments.

Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 1'-Grudges lead to lack of honesty.

Table 10 Table 11 Table 12 Table 13 Detailed Description of the Invention As described above, the present invention measures the resistance value of a thermistor at a predetermined temperature, and then determines that the measured resistance value of the thermistor is determined in advance. In this method, the thermistor is checked to see which group it belongs to, and then a fixed resistor with a predetermined value corresponding to the group is connected to the thermistor, so there is no need to adjust the variable resistor as in the conventional example. Since it is a material, it has the advantage that it can be easily manufactured and also has the advantage that reliability can be improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a temperature sensor manufactured by the method of the present invention, and Figures 2 (A) and (B) are 32°C and 42°C, respectively.
A diagram showing the resistance value of each group number-mistor in °C. Figure 3 is a diagram showing the temperature-resistance characteristics of a temperature sensor made using the thermistors belonging to group #1 and group #12. , Fig. 4 is a standard diagram in the first embodiment, Fig. 5 is a diagram showing the relationship between the standard diagram and Table 4, and Fig. 6 uses thermistors belonging to group #1 and group #12. FIG. 7 is a diagram showing the temperature-resistance characteristics of the temperature sensor created in this manner, FIG. 7 is a standard diagram in the second embodiment, and FIG. 8 is a configuration diagram of a conventional temperature sensor. 1, Th is a thermistor, 2 is a fixed resistance, and Rv is a variable resistance. Representative Patent Attorney Gobe Tamamushi (2 others) Figure 1 Figure 2 Figure 6 52 35 37 39 42 ″'C Figure 4 Figure 5 52 35 37 59 42 @c Figure 6 Ω 32 35 37 39 42 6C
Figure 7 Figure 8 Procedural amendment April 16, 1985

Claims (1)

[Claims] In a method of manufacturing a thermistor temperature sensor, the resistance value of the thermistor temperature sensor consisting of a thermistor and a resistor connected in series with the thermistor becomes a predetermined value at a predetermined temperature. , and then find out which of the predetermined groups the resistance value of the thermistor whose resistance value was measured belongs to, and then attach a fixed resistor with a predetermined value corresponding to the group to the thermistor. A method of manufacturing a thermistor temperature sensor, characterized in that the thermistor temperature sensor is connected.