JPS59225324A - Electronic thermometer - Google Patents

Abstract

PURPOSE:To enhance the versatility in element selection, by dispensing with strict selection of the accuracy in the reference resistance value of a reference resistor or a temp. measuring resistor by adjusting the resistance value of the reference resistor while strictly selecting the B-constant of a thermister. CONSTITUTION:The temp. of a thermostatic tank 9 is set to a reference temp. T0 and the measured temp. output T0 from a temp. measuring apparatus 7 and the count value N2 from the counter circuit 2 of an electronic thermometer are inputted to a data processing apparatus 8 while a resistance value control apparatus 10 controls the resistance value of the reference resistor RS mounted in an oscillator 1 so as to adjust the input count value N2 to a reference value N20. The ratio of the thermister resistance value Rtho at the reference temp. T0 and the resistance value RS of the reference resistor can be kept constant while the reference temp. T0 can be read by a reference address N20 and an accurate temp. can be measured by formulae.

Description

BACKGROUND OF THE INVENTION Technical Field The present invention relates to an electronic thermometer, and more specifically, by standardizing the temperature-resistance count of a resistance thermometer, a count value-temperature conversion table is created. This invention relates to an electronic thermometer that can standardize the temperature.

Conventional technology and its problems Conventionally, as shown in Figure 1, the output pulse train of an oscillation circuit using a temperature sensing element is counted, and the conversion to obtain a temperature value from this counted value is performed by programming in a non-volatile memory. The digital thermometer was published in Japanese Unexamined Patent Publication No. 50-131576.
proposed by No. However, according to this invention, it is necessary to program each device having different oscillation characteristics, and mass productivity is lacking. This disadvantage can be solved by a utilization technique that provides versatility to the temperature conversion table created based on the original data. What is particularly important is that it has been found that providing flexibility in selecting the components of an oscillation circuit that uses such a table increases the productivity and yield of electronic thermometers that use a conversion table created by replication. This led us to propose the present invention.

Purpose of the Invention The purpose of the present invention proposed under the above-mentioned problem is to eliminate the need to strictly select the accuracy of the reference resistor, and to
We are also proposing an electronic thermometer that requires only a temperature-resistance factor to be selected for the resistance temperature sensor.

Another object of the present invention is to propose an electronic thermometer that can correct errors in resistance ratio caused by non-uniform accuracy of a reference resistor.

Still another object of the present invention is to propose an electronic thermometer that can save memory capacity of a temperature data storage section by correcting errors in resistance ratios.

The object of the present invention is to provide a resistance temperature detector having a predetermined temperature resistance coefficient, a resistance value whose ratio to the resistance value at a reference temperature of the resistance temperature detector is approximately constant, and whose resistance value changes depending on the temperature. An oscillator in which an unchanging reference resistor is used as an element for determining the oscillation frequency of the oscillator, and a set value determined from the ratio of the number of oscillations when the temperature sensing resistor and the reference resistor are alternately connected to the oscillator. Addition and subtraction means for addition or subtraction;
The value determined by the addition/subtraction means is set as an address, and a temperature data storage section is provided in which a temperature correlated to the value is fixed at the address, and the value determined by the addition/subtraction means is set as a readout address of the temperature data storage section. Achieved by a featured electronic thermometer.

Further, according to a preferred embodiment, the deviation from the set value of the resistance ratio of the resistance temperature detector and the reference resistor at the reference temperature is corrected by the addition/subtraction means, and furthermore, the temperature data storage section is corrected by the addition/subtraction means. It includes a table for converting the determined value into temperature, the reference address of the table is accessed by the value at the reference temperature, and the resistance value ratio is approximately 1.

Next, an electronic thermometer as a preferred embodiment of the present invention will be described in detail. FIG. 2 is a block diagram showing the configuration of an electronic thermometer according to an embodiment.

In the figure, ■ is an oscillator that uses a thermistor Rth as a resistance temperature detector, and includes a reference resistor Rs whose resistance value does not change depending on temperature. They are selectively connected to an internal oscillation circuit and output pulse trains of frequencies fs and fth, respectively. 2 is a counter circuit that coefficients these pulse trains, and counts the pulse trains only during a variably controlled gate time width T9 in order to eliminate time-series characteristic fluctuations of circuit elements including the oscillator 1; Always output the correct count value N2 for the detected temperature. 3 is a subtraction circuit that subtracts a predetermined value NDo from the count value N2, and outputs an address output N/ip that is a value obtained by subtracting the predetermined value NDo in order to limit the capacity of the subsequent memory. 4 is standard RO
Temperature data Tt that is addressed by the address output NAD and stored in correlation with the read-only memory (ROM or FROM) that stores the M table.
Read out. 5 is a display circuit, which displays read temperature data Tt.
to be displayed digitally.

Here, the oscillator 1 has two C-Ms as shown in FIG.
OS inverter 11. I2, capacitor C, reference resistor Rs, thermistor Rth as a temperature measuring resistor, and terminal S
When the LO level is input to the reference resistor R
It consists of a switch SW which connects the thermistor Rth to the oscillation circuit and switches the thermistor Rth to the oscillation circuit when the HI level is input, and a fixed protection resistor R of the C-MOS inverter 1.

As shown in FIG. 4, the counter circuit 2 includes a reference oscillator 21 that always outputs a pulse train of a constant frequency fo, and a counter 2 that counts the pulse train of a frequency fs up to a predetermined number N1.
2, and a counter 2 that counts up the pulse train of frequency fO only for the time T required for counting at this time, and continues to count down the same pulse train until the count value reaches 0.
3 and the time required for this DOWN count (the TQ
a counter 24 that counts a pulse train with a frequency fth (equal to ), a flip-flop (hereinafter referred to as FF) 25 for repeatedly performing the above counting operation, and a delay pulse generation circuit (hereinafter referred to as DP circuit) 26. and A
It consists of ND gates 27°28.

The principle of temperature measurement in the second configuration will be explained below. First, when the switch SW of the oscillator 1 is turned to the reference resistor Rs side, the oscillation frequency fs at this time can be obtained as Jj-, where k is a proportionality constant. This oscillation frequency fs hardly changes with respect to temperature changes. Next, when the switch SW is turned to the thermistor Rth side, the oscillation frequency fth is 1, , , (2) ftl)"f< , C, -Rzheng-. Also, the temperature of thermistor Rth at this time -Resistance characteristics are generally given by the following equation:

Rt, b = I or oC11 fine - 甚) ・
(3) Here, Ro: Resistance value of the thermistor at reference temperature To Rth: Resistance value of the thermistor at a certain temperature Tt B: Temperature resistance coefficient of the thermistor (hereinafter referred to as B constant).

From the above, when the thermistor Rth is connected to the oscillator 1, if the temperature-sensitive resistance value of the thermistor Rth changes due to temperature change, the oscillation frequency fth will change correspondingly, and the pulse train generated by this oscillator 1 will be If counting is performed only during the gate time width Tc controlled to a constant value, the count value Nth will change according to the following equation.

N th=-Ninishi~~ , , , (4)k
'CIrith Here, set the count value NO at the reference temperature To as No=-
(5) 1(・C1(0) The general formula for the count value Nth at a certain temperature Tt is Nth=Noe -13(Tt -1'o)
... is given by (6).

Therefore, in a temperature environment that is controlled with high precision, if you know the count value No at the reference temperature TO, the count (function) value Nth that the counter should count at a certain temperature (variable) value Tt can be determined by equation (6). Determined.

Therefore, when measuring a certain temperature, simply count value Nt
It is possible to configure a temperature measuring device that can immediately obtain the temperature to be measured Tt just by obtaining h, but if the gate time width Tc is always controlled to a constant value, C- MOS inverter II,
Since the threshold voltage of I2 and the capacitance of capacitor C also change, the resulting fluctuations in oscillation frequency fth appear as fluctuations in count value Nth. This varied value N th ' no longer depends only on the temperature characteristics of the thermistor Rth.

For this purpose, the configuration of the embodiment obtains a gate time width Tq that is variably controlled by the method described below. First, the variable gate time width T, 7 is determined by the characteristic fluctuation required for the pulse train generated by connecting the reference resistor Rs to the oscillator J to be counted up to a constant count value N, and then the same gate time width is determined. A thermistor Rth is connected to the oscillator 1 for Tq, and the pulse train generated is counted to obtain the count value N2. Therefore, the following holds true between the two count values N, , N2 and the gate time width T, and the two count values N I + N2
Between th N knee survey-9N11. (8) holds true.Here, the count value N2 is the value counted during the gate time width TGr by connecting the thermistor Rth to the oscillator 1, and the count value N2° at the reference temperature T0 is...
・(]0) N1”' k-C-R.

given by.

Therefore, the count value N2 counted at a certain temperature Tt
has a value proportional to -11 of the oscillation frequency of 2'''' generated in the two total tb idle operations, with N1 being a predetermined number.

Now, suppose that two oscillation frequencies fs and ft are applied to temperature changes.
Even if h changes to /zfs', fth', both are common C-MOS inverters Il', I with changed characteristics.
2' and capacitor C' for a short period and only during the variably controlled gate time width Tq, the count value N2' is always accurate and reproducible count value N2. Become.

By this method, the reference resistor Rs and thermistor Rth are removed. In all the configurations of the embodiments, even if there is a gradual change over time in the characteristics of the circuit elements, it is effective in canceling them out.

Detailed Operation of the Invention Next, referring again to FIGS. 3 and 4, the variably controlled gate time width T6 and the count (il
The operation to obtain N 2 will be explained in detail.

In FIG. 4, at the end of the previous counting operation, the DP circuit 2
The pulse output of 6 resets the counts of counters 22 and 24. The count value of the counter 22 becomes O, and the output terminal Qn
The level becomes LO.

This LO level energizes its own count enable terminal (hereinafter referred to as terminal E) so that if there is an input to the count terminal C, it can be counted. Also counter 24
Terminal E of the counter 23 is deenergized to make it impossible to count.
Set to UP count mode. On the other hand, in the oscillator 1 of FIG. 4, since the LO level is input to the terminal S, the reference resistor Rs is connected to the oscillation circuit and outputs a pulse train of frequency fs. Further, in FIG. 4, the DP circuit 26 is the FF2
5 is reset, so the output end is dried, but it becomes HI and AND
Game) Energize the human power of 27 and 28. In the above condition,
First, the counter 22 counts the input pulse train of frequency fs, and at the same time, the counter 23 counts up the pulse train of frequency fo.

Next, when the count value of the counter 22 reaches a predetermined value N, its output terminal Qn becomes HI level and stops its own a-1 number operation, and the terminal E of the counter 24 is turned on. Set to DOWN count mode. The time required for counting up to this point is Tq. On the other hand, in the oscillator l, since the HI level is input to the terminal S, the thermistor Rth is switched and connected to the oscillation circuit and outputs a pulse train of the frequency fth. In this state, the counter 24 counts the input pulse train of frequency fth, and at the same time the counter 23 counts down the pulse train of frequency fo. D until the count value of the counter 23 reaches O.
When OWN is counted, the rising edge of the output terminal Qn sets the FF 25, and the output terminals become LO level, deactivating the counting inputs of the counters 23 and 24. The value N2 counted by the counter 24 at this time is the frequency f at the so-called variably controlled gate time width Tc.
th input pulse train is counted. Next, since the output terminal Q of the FF 25 is HI, the DP circuit 26 outputs a positive pulse after a predetermined period of time and repeats a new counting operation.

Since the pulse trains counted in the UP force direction and the DOWN direction to the counter 23 are clocks of the same frequency f0, according to the above-described operation, the counter 24 is clocked at the frequency A count value N2 is obtained by counting the pulse train of fth. In order to save the memory capacity of the read-on memory 4 for reasons to be described later, a predetermined value Nov is subtracted from this callan I value N2 in the subtraction circuit 3, and the output value N4p is sent to the address line of the read-only memory 4. The corresponding temperature data Tt is read out from NAp and displayed on the display circuit 5.

At the time of manufacturing at least one standard sample of the electronic thermometer of the embodiment, the predetermined value N, .
FROM addressed by the value N4p
The so-called RO with the corresponding correct temperature data written on top
It is necessary to create an M table. The thermistor built into the sample electronic thermometer at this time is referred to as a reference thermistor for convenience.

Here, we will first focus on the count value N2, and the value NAD obtained by subtracting the predetermined value NDO will be described later. Again the above (3
), (9), and (10) to create a general formula for the count value N2 and the measured temperature data Tt. However, the count value N20 at the reference temperature TO is calculated from the above equation (8), where f tho is the reference temperature T. . This is the oscillation frequency when the reference thermistor Rth is connected to the oscillator l.

Now, attention is paid to the count value N20 at the reference temperature T0' in the equation (13). This value is the reference thermistor R
It is proportional to the ratio Rs/Rtho between the resistance value Rtho at the reference temperature T0 of th and the resistance value Rs of the reference resistor. In addition, this count 474 N, o corresponds to the range of N20≦N2≦N2□ when the temperature range to be measured is TO≦Tt≦T, and when creating the ROM table, it corresponds to the reference temperature T0. This is the reference address N2°.

The procedure for creating this ROM table will be explained below. FIG. 5 is a block diagram showing a method for creating a ROM table. In the figure, first, the temperature of the constant temperature bath 9 is T o
, TT's two constant temperature points are set sequentially and the count value at each temperature is N2 '' N20 + N2 = N
2-r is input to a data processing device 8 connected to the outside by an appropriate method. The external data processing device 8 simultaneously receives the two constant temperature data T0. T
Since T is taken, the B constant of the reference thermistor Rth can be obtained from the following equation.

This process will be explained in more detail with reference to the flowchart of FIG. 6 showing the ROM table creation procedure. First, constant temperature bath 9
With the set temperature set as the reference temperature T0, the data processing device 8 inputs the measured temperature T sensed by the temperature sensor 6 from the temperature measuring device 7 in step 102.

In step 103, the input temperature T is the reference temperature T.

It is determined whether or not. If the determination is No, the process returns to the height 102 and a new temperature T is obtained. If the determination is YES, the output count value N2° of the counter circuit 2 is inputted in step 104. Next, set the temperature of the constant temperature bath 9 to a predetermined temperature of 1 and 1. In the same state, step 105 is performed.
and 106 are executed. Eventually, the temperature in the thermostatic chamber 9 reaches a predetermined temperature, and the determination in step 106 is Y,...E.
If S, then in step 107, the output count value N2T of the counter circuit 2 at this time is input. Process 1
In 08, the following two constant temperature information T0. The above (I
4) Calculate the B constant of the reference thermistor Rth according to the formula. At this point, the external data processing device uses the B constant just found and the count value N2 previously input from the counter circuit 2.
゜, temperature data T inputted from the temperature measurement device 7 of N2 and other g1' M degrees. , has one knife. Next, in step 109, the required measurement temperature range (for example, To
-TT ) interval T, the temperature (variable) value Tt is increased by temperature measurement accuracy ΔT (e.g. 0.1°C), and the corresponding count (function) value N2 is calculated as above (12
) Calculated according to the formula.

FIG. 5 shows a configuration for creating a correlation table to be replicated in the read-only memory of an electronic thermometer to be manufactured, in which the thermistor Rth disposed in the thermostatic bath 9,
Standard resistance resistance, standard resistance temperature, standard resistance, in the sense that the oscillator creates the original data to be replicated.
It can be compared to a standard oscillator by 11'f.

Generally, the temperature range to be measured is T2 to T3 and T.

In the relationship: <T2<T3 <1, the two-wheel data pair may be calculated as T2 to T3. In any case, the temperature data Tt can be expressed as, for example, T(,1+Toz...
TI)1. If the temperature pitch is increased by △T until l and the calculated result is set as ND, , N, er...NON, the temperature data T is stored in address No. of the ROM table.
DI, temperature data TD2 is at address Np2...
It is sufficient if it is stored as follows. At this time, since the reference address N[) of the ROM table is a large value due to the configuration of the thermometer of the embodiment, in order to save the memory capacity M- of the read-only memory 4, a predetermined value NDO is set from the reference address NDI.
≦MDI is subtracted to make the value smaller, and this is used as the actual reference address NJID.

] In the second step 110, the address data NDI, NI)□...NDN minus the predetermined value NDO calculated as described above, Nゎl+NAD2. ...N
ADN is determined, this is used as the address input to the nonvolatile memory 4, and each corresponding temperature data TD, , TD2.
...TDN is stored in correlation as data input.

In the circuit configuration of the embodiment shown in FIG.
In order to correctly read the temperature table created in step 11O, the predetermined value No. is calculated from the output count value N2 of the counter circuit 2. It has a subtraction circuit 3 from which is subtracted.

With this in mind, the reference address of the ROM table will be described as N20 again for convenience of explanation below.

In principle, if temperature tables are created on the FROM according to the procedure shown in FIG. 7 for a plurality of other electronic thermometers, a single electronic thermometer with high accuracy can be manufactured.

However, the saving of FROM memory capacity, usage efficiency,
Furthermore, considering the ease of manufacturing electronic thermometers, it is desirable that the created temperature table always start from a predetermined address and end at a predetermined address (with the same standard content). When manufacturing another electronic thermometer according to the embodiment in order to obtain this advantage, the following manufacturing steps are used.

The ROM table created in step 109 of FIG. 7 is a so-called standard ROM table created under the use of a reference thermistor, and after that, it is shown by the dotted line with respect to other electronic thermometers in the manufacturing process. Like simply step 1
Only 10 are executed. That is, the contents of the standard ROM table are copied to a non-volatile memory that is either integrated with the electronic thermometer or provided separately.

However, not only the thermistor Rth that is actually available for constructing other electronic thermometers, but even the reference resistor Rs has variations in its resistance value.

According to equations (12) and (13) above, this is the reference temperature T
This causes a change in the count output value N20 at the maximum value of the measured temperature range due to variations in the characteristics of the temperature gradient, since there are variations in the B constant of the thermistor.
2D also changes, which can lead to incorrect access to the temperature table. As mentioned above (the reference address N20 of the ROM table is dependent on the ratio of the thermistor resistance value Rtho and the resistance value Rs of the reference resistor at the reference temperature T), if this ratio is kept constant, the reference temperature T0 can be read out. In this case, it is not necessary that Rs=Rtho, but in order to keep the ratio RS/Rtho constant, the resistance (I!Rs) can be adjusted to match.

This embodiment utilizes the configuration shown in FIG.

In the figure, the constant temperature bath 9 is set in advance to a reference temperature T0. The data processing device 8 receives the measured temperature output T from the temperature measuring device 7. to monitor. At the same time, the count value N2 from the counter circuit 2 of the electronic thermometer placed at the reference temperature TO is monitored. The resistance value adjusting device 10 is controlled based on these monitored data, and the resistance value of the reference resistor Rs built in the oscillator I is automatically adjusted. The specific steps of this adjustment method will be explained according to flowchart 1 in FIG. 8. In step 202, the data processing device 8 inputs the measured temperature output T. Step 203
Then, it is determined whether the input temperature T is the reference temperature To or not. If the determination is NO, the process returns to step 201. Also, the discrimination is Y
When it comes to ES, is it a process? 04, the count value N2 from the counter circuit 2 is input. In step 205, it is determined whether the input count value N2 is the reference value N20.

If l'1 is different or NO, proceed to step 206 and set the reference resistance R.
s is adjusted so that the input count value N2 approaches the reference value N2'O. Step 207 is a step in which the operation of the oscillator 1 is delayed for a predetermined time so that the operation of the oscillator 1 is sufficiently stabilized at the new resistance value. When the predetermined time has elapsed, the process returns to step 202 and repeats the two consecutive operations. Further, if the determination becomes YES in step 205, the adjustment of the reference resistor Rs is completed.

In addition to keeping such a resistance ratio constant, there is a method of controlling and fixing the fixed input NDO of the subtraction circuit 3.

In this case, the determination in step 203 of FIG. 8 is YES.
If so, proceed to step 208. In step 208, the output count value N2 from the counter circuit 2 is input. Process 2
In 09, the subtraction value Noo is calculated by N/IDO-N2. Here, NAD (the reference address of the temperature table stored in the II beam only memory 4,
A reference temperature To is written there. Usually NA
D(+< N 2, so l NADON2 I
It is sufficient to use the value as it is as a fixed input to the subtraction circuit 3. Further, if a situation such as NAoo > N 2 occurs, the subtraction circuit 3 is switched to addition. Such switching can be easily performed if the configuration of the addition/subtraction circuit is prepared in advance. Further, as a method for setting and fixing the value of NApO mentioned above, for example, by controlling the laser beam spot, the input register 1 of the subtraction circuit 3
There are methods such as burning out 1 in a predetermined pattern. Step 20
Step 9 only needs to be done once and does not need to be repeated.

The technique of adjusting the fixed input NDo of the subtraction circuit 3 so that the resistance ratio is constant is that the temperature-resistance coefficient (B constant) of the thermistor Rth has a certain accuracy, but the resistance ratio due to variations in the resistance value at the reference temperature It is clear that it is also possible to correct the error of .

Furthermore, the B constant of the thermistor is carefully selected within a range that does not impair the desired temperature measurement accuracy. Therefore, in view of the above points, rather than creating a ROM table specific to each electronic thermometer, for example, by adjusting the resistance value Rs of the IF reference resistor and carefully selecting the B constant of the thermistor,
It is rather easy to manufacture an electronic thermometer that always correctly accesses a standard ROM table with a single standard and content without compromising temperature measurement accuracy.

In this way, the electronic thermometer shown in FIG. 3 has a thermistor Rth whose B constant is carefully selected within a range that provides the desired temperature measurement accuracy, and a reference temperature T of this thermistor. The ratio between the resistance value Rth and the resistance value Rth is constant and the resistance value hardly changes depending on the force and temperature l/) is the same as the standard ROM table created according to the predetermined procedure for the reference resistor Rs and the specific sample of the electronic thermometer. RO reproduced with standards and content
M or FROM.

Concrete Effects of the Invention Since the present invention is configured as described above, even if there is a variation in the resistance ratio between the temperature measuring resistor and the reference resistor at the reference temperature, the variation is corrected and the temperature data storage section temperature conversion data can be used correctly. Therefore, there is no need to carefully select the accuracy of the reference resistor or all warm body antibody quasi-resistance values, and flexibility is provided in selecting each element.

Further, according to the present invention, errors in the reference resistance value are corrected, so the yield of products is improved, and the correct temperature can be measured.

Furthermore, according to the present invention, the error in the resistance ratio is corrected,
Since the reference address is unified, it is possible to use the correct count value (or ratio) temperature conversion table, and by starting the reference address from address zero, the memory capacity of the temperature data storage unit that stores conversion data can be minimized. It can be made into

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a conventional digital thermometer, Figure 2 is a block diagram showing the configuration of an electronic thermometer according to an embodiment of the present invention, and Figure 3 is a circuit diagram of an oscillation circuit using a thermistor. , Fig. 4 is a block diagram showing the counter circuit in Fig. 2 in detail, Fig. 5 is a program diagram showing the method for creating a ROM table, Fig. 6 is a flowchart showing the procedure for creating a ROM table, and Fig. 7 8 is a block diagram showing a method for matching the reference resistance value, and FIG. 8 is a flowchart showing the procedure for matching the reference resistance value. Here, ■...oscillator, 2...counter circuit, 3...
...Subtraction circuit, 4...Read-only memory, 5...
Display circuit, 6... Temperature sensor, 7... Temperature measuring device, 8... Data processing device, 9... Constant temperature chamber, 10...
-Resistance value adjustment device, 11...input register.

Claims (4)

[Claims] (1) A resistance temperature detector having a predetermined temperature resistance coefficient, and a reference resistor having a resistance value whose ratio to the resistance value at a reference temperature of the resistance temperature detector is almost constant, and whose resistance value does not change depending on temperature. an oscillator that determines the oscillation frequency of the oscillator, and an addition/subtraction means for adding or subtracting a set value to a value determined from the ratio of the number of oscillations when the temperature measuring resistor and the reference resistor are alternately connected to the oscillator. and a temperature data storage section in which a value determined by the addition/subtraction means is set as an address, and a temperature correlated to the value is fixed at the address, and the value determined by the addition/subtraction section is set as a read address of the temperature data storage section. An electronic thermometer featuring (2) The deviation from the set value of the resistance value ratio of the resistance temperature detector and the reference resistor at the reference temperature is an additional g3! 2. The electronic thermometer according to claim 1, wherein the electronic thermometer is corrected by means. (3) The temperature data storage section includes a table for converting the value determined by the addition/subtraction means into temperature, and the reference address of the table is accessed by the value at the reference temperature. electronic thermometer. (4) The electronic thermometer according to claim 1, wherein the resistance value ratio is approximately 1.