JPH07260596A - Temperature measuring method - Google Patents

Abstract

PURPOSE:To provide a temperature measuring method enabling the reduction of the scale of various circuit and the realization of an electronic thermometer low-priced with high performance. CONSTITUTION:This temperature measuring method uses a resistance value- frequency converting circuit 1 for generating a reference pulse signal with frequency based on the resistance value of a reference resistance 102 and a detection pulse signal with frequency based on the resistance value of a thermistor 101 in such a way as to be freely switched. This temperature measuring method has a first phase of counting reference pulse signals by a dividing circuit 2 until reaching the count truncation value and counting clocking from an oscillating circuit 4 by a dividing circuit 5 until reaching the count truncation value so as to determine the counting time every temperature measuring process, and a second phase of counting the detection pulse signals over the counting time equal to the counting time of the reference pulse signals by the dividing circuit 2 after resetting the dividing circuit 2 and latching the counted result of the detection pulse signals so as to display the temperature on the basis of this result. The count truncation value corresponding to resistance dispersion correcting data is set prior to the first phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital electronic thermometer, and more particularly to a method for adjusting the initial logic of an electronic thermometer that corrects individual differences in resistance values to enable high precision display.

[0002]

2. Description of the Related Art Conventionally, an electronic thermometer using a temperature sensitive resistance such as a thermistor has a reference resistance which shows a substantially constant resistance value without being affected by temperature change in a measurement temperature range,
Ratio of resistance value of reference resistance and resistance value of temperature sensitive resistance (resistance ratio)
Is calculated and converted into a temperature (decode) and displayed. That is, the conventional electronic thermometer has a thermistor, a reference resistance, and a variable resistor for initial adjustment, and switches the thermistor and the reference resistance to generate a pulse signal having a frequency based on each resistance value. A circuit, a counting time limit circuit that divides the source oscillation clock and allows the passage of each pulse signal until it reaches a certain count value, and a reference based on a reference resistance over a certain counting time when the source oscillation clock becomes a certain count value. It has a unique counter (dividing circuit) that counts the detection pulse signals based on the temperature-sensitive resistance for the same counting time after counting the pulse signals and after resetting. The count value of the reference pulse signal and the detection pulse After latching the count value of the signal and each of them, their ratio (resistance ratio)
Is calculated, and the resistance ratio is converted to a temperature in the reference memory to display the temperature.

The electronic thermometer having such a structure operates as follows. First, in the first phase, the resistance value-frequency conversion circuit selects the reference resistance and the initial adjustment variable resistor to generate the reference pulse signal having the series combined resistance value of both. This reference pulse signal is counted by the counter for a constant number of counting time T specified by the counting time circuit,
The count value (first count value N ₁ ) of the reference pulse signal is latched and temporarily stored by the storage means. Then, the counter is reset. Next, in the second phase, the resistance value-frequency conversion circuit selects the thermistor (temperature sensitive resistance) and generates a temperature detection pulse signal having a frequency corresponding to the resistance value of the temperature. This temperature detection pulse signal is also counted by the same counter for the counting time T specified by the counting time circuit, and the count value (second count value N ₂ ) of the temperature detection pulse signal is obtained.

Then, the temporarily stored first count value and second count value are stored.
The ratio (N ₁ / N ₂ ) to the count value of is calculated, and the temperature is displayed by temperature conversion. Such a first phase and a second phase are repeatedly performed many times, and when it is determined that the temperature display value is a peak, the repetition of the phase is stopped.

In order to obtain the temperature display from the ratio between the resistance value of the reference resistance and the resistance value of the thermistor as described above, since the conversion table for each thermometer has constant conversion data, a certain constant temperature is obtained. At room temperature, the resistance ratio must be a constant value for all thermometers, but in reality, there are individual differences in resistance values (manufacturing variations in resistance) between the reference resistance and thermistor. The resistance ratio is not constant. Therefore, in order to make the actual resistance ratio constant, in the inspection process at the manufacturing stage, the initial adjustment variable resistor is moved to increase or decrease the combined series resistance value with the reference resistance so that the resistance ratio becomes constant. (Adjustment of absolute value accuracy). A thermometer using such a variable resistor is found in Japanese Patent Application No. 58-234652.

However, the electronic thermometer provided with the above-mentioned variable resistor for initial adjustment has the following problems.

It is troublesome to place an electronic thermometer (thermometer) at a constant temperature in the inspection process and manually adjust the resistance of the variable resistor so that the temperature display value becomes a constant temperature. However, in the case of a thermometer, which requires particularly strict accuracy, fine adjustment work requires skill. Therefore, the productivity remains low, which is an obstacle to cost reduction.

Further, in the above-mentioned electronic thermometer, the variable resistor is inferior to the fixed resistor in environmental resistance, is prone to change over time (change in resistance value), and has poor reliability of temperature display during use.

Furthermore, since the variable resistor has a movable part, it is not suitable for semiconductor integration of the entire circuit system, and cannot be integrated into one chip together with the resistance value-frequency conversion circuit, frequency dividing circuit, and counter. The variable resistor must be mounted on the board as an external discrete component. For this reason,
When it is applied to a thermometer or the like, it becomes an obstacle to miniaturization, and an increase in the number of parts leads to an increase in manufacturing cost.

In order to solve such a problem, the present applicant has already disclosed a technique relating to an electronic thermometer using a digital initial logic adjustment circuit (correction circuit) in Japanese Patent Application No. 59-17499. There is.

3 and 4 show Japanese Patent Application No. 59-17499.
The example disclosed in the issue is shown. In this electronic thermometer, first, the resistance values of the thermistor 101 having the resistance value Rt and the reference resistor 102 having the resistance value R1 are set to the resistance value −
The frequency conversion circuit 1 converts the signal into a frequency signal corresponding to each resistance value, that is, a detection pulse signal and a reference pulse signal. The resistance value-frequency conversion circuit 1 can be configured by a circuit that repeats charging and discharging with a resistance and a capacity, a head portion of a double integration AD conversion circuit, and the like. Since the measurement period is short, the time constant is constant during that period. Then, the detection pulse signal is counted by the frequency dividing circuit 37 for a fixed reference time (counting time = T), and the count value is latched by the latch circuit 12. Then, the latched result is decoded into a temperature value by the decoder 13,
It is displayed on the liquid crystal display panel 14. The reference time T for counting the detection pulse signal is the reference pulse signal converted from the reference resistor 102 to a predetermined frequency by the resistance value-frequency conversion circuit 1 in order to eliminate the individual difference of the resistance value-frequency conversion circuit 1. It is set using. That is, the reference pulse signal is counted by the frequency dividing circuit 37, and it is determined whether or not the count value of the frequency dividing circuit 37 has reached the preset reference count value M in the gate setting output circuit 60. Then, the independent frequency dividing circuit 5 counts and clocks the clock (clock pulse) of the oscillation circuit 4 for a period (reference time T) until the count value of the frequency dividing circuit 37 reaches the reference count value M, and When the count value M is reached, the NOR circuit 1
1 is closed to stop the counting operation of the reference pulse signal, and the determined reference time (counting time) T is stored. In this way, the frequency dividing circuit 37 counts the detection pulse signal over the reference time T determined based on the reference resistor 102, and this time, the variation of the resistance value Rt of the thermistor is detected from the count value N. It becomes possible.

Here, assuming that the count value counted within the reference time T based on the resistance value Rt of the thermistor is N, the resistance value and the count value are in inverse proportion to each other, and the following equation holds.

R1 × N = Rt × M (1) However, the resistance value R1 of the reference resistor has individual differences, and
The resistance value Rt of the thermistor also has individual differences.

If the ratio between the actual resistance value R1 'of the reference resistance and the actual resistance value Rt' of the thermistor differs from the ratio of the resistance values R1 and Rt by ΔR, the following is obtained.

N ′ = Rt ′ / R1 ′ × M (2) Rt / R1 = Rt ′ / R1 ′ × ΔR (3) Therefore, N indicating the actual temperature is N = Rt ′ / R1 ′ × ΔR × M (4) Therefore, in order to obtain N, M may be converted to ΔR × M.

Therefore, in Japanese Patent Application No. 59-17499, the correction is made as ΔR × M = M−ΔM (5). That is, when the reference time T is counted from the reference pulse signal by the frequency dividing circuit 37, the control circuit (initial value setting circuit) 38 is used to set (preset) the initial value ΔM in the frequency dividing circuit 37, and the frequency dividing circuit 37 37 is the number of times that the reference pulse signal is actually counted (M-ΔM)
I am trying.

By the way, as shown in FIG. 4, the control circuit (initial value setting circuit) 38 includes pull-up P-type MOS transistors 51a to 51a for setting the initial value ΔM.
51d, inverters 52a to 52d, and initial value ΔM
It is configured by NAND gate circuits (setting timing circuits) 53a to 53d that control the timing of the setting. When measuring the reference time T, the control circuit 38
The initial value ΔM is set in advance in the frequency dividing circuit 37 configured using the 1/2 frequency dividing circuits with set priority type reset 55a to 55d, and the reference time T is controlled according to the individual difference.

In such an electronic thermometer, initial logic adjustment is performed without using a variable resistor for resistance value variation correction, and high-precision display without individual difference is possible.

Further, since the temperature can be displayed only on the basis of the count value of the detection pulse signal without obtaining the ratio between the count value of the reference pulse signal and the count value of the detection pulse signal, the division processing is unnecessary and the circuit It is possible to avoid the complexity of the system and the enlargement of the element formation area, and to reduce the size and weight of the thermometer.

[0020]

However, in order to further reduce the size and weight and reduce the cost, a 1/2 frequency divider circuit with a set priority type reset having a large circuit scale, which constitutes the frequency divider circuit 37, is used. The NAND gates 53a to 53 that are a normal 1/2 frequency divider circuit with a small circuit scale and a small number of elements and that control the timing of initial value setting
It is necessary to reduce d etc. as much as possible.

In view of the above problems, an object of the present invention is to provide a temperature measuring method capable of reducing the scale of various circuits and realizing a low-cost, high-performance electronic thermometer. Especially.

[0022]

In order to solve the above problems, the present invention provides a resistance of a detection resistor whose resistance value changes in response to a reference pulse signal having a frequency based on the resistance value of the reference resistor and temperature. In a temperature measuring method using a resistance value-frequency converting means for switchably generating a detection pulse signal having a frequency based on a value, one of the reference pulse signal and the detection pulse signal is used as a first pulse signal. Using the other as the second pulse signal, the counting means counts the first pulse signal until the count cutoff value is reached, and the count value of the first pulse signal of the counting means reaches the count cutoff value. A first phase in which the counting time determining means counts the counting pulses to determine the counting time for each temperature measurement step, and then the counting means is reset, and then the counting A second phase in which the second pulse signal is counted for a counting time equal to the counting time of the first pulse signal by the means, the counting result of the second pulse signal is latched, and the temperature is displayed based on the latched result. Has
Prior to the first phase, the above-mentioned count termination value is set according to the resistance variation correction data.

[0023]

In the first phase, the first pulse signal is counted by the counting means, and the counting operation continues until the count value reaches the count cutoff value, during which the count time determining means counts the count pulse. To determine the counting time. next,
In the second phase, the second pulse signal is counted by the same counting means for the counting time determined by the counting time determining means, the counting result is latched, and the temperature is displayed based on this. ing.

In the present invention, since the counting cutoff value is set in accordance with the resistance value variation correction data, the correction is appropriate for the individual difference (resistance value variation) of the thermometer resistance value-frequency conversion means. If the counting cutoff value is set according to the data, the counting time can be adjusted as a result. Therefore, it is possible to increase or decrease the counting result of the second signal pulse at the same temperature. High-precision display is possible on the product.

The counting means is set not to preset the initial value in the counting means before counting the first pulse signal, but to set the count cutoff value (or count-up value). Since the frequency dividing circuit is not required and the reset function is sufficient, the circuit configuration of the counting means itself can be simplified. As high-accuracy display is achieved by using a counting means having a large number of bits, the effect of reducing the circuit scale becomes remarkable.

In the conventional method of presetting the initial value in the counting means, the initial value is sent from the setting timing circuit to the counting means by the set control signal prior to counting the first pulse signal, but the second pulse signal is used. In counting, it was necessary to perform selective control so that the set control signal was not applied, and the circuit scale of the set timing circuit and the set control signal generation circuit were necessary. However, since the preset method is not used in the present invention, a setting timing circuit and a set control signal generation circuit are not necessary, and the simplification of the circuit configuration can reduce the size, weight, and cost.

In the present invention, one temperature measurement step consisting of the first phase (counting process of the first pulse signal) and the second phase (counting process of the second pulse signal) is repeated many times to measure the temperature change. When observing the transition, since the environmental temperature itself of the electronic thermometer changes, it is necessary to sufficiently consider the temperature compensation of the electronic thermometer including electronic elements such as capacitors having temperature dependence. The counting time determining means in the present invention counts the counting pulses until the first pulse signal reaches the count cutoff value and determines the counting time each time the first phase is reached. Therefore, in all temperature measurement steps. The counting time is not always constant, and basically the counting time differs depending on the environmental temperature in each temperature measurement process. Even if the environmental temperature changes, if the count time is a constant value (uniform value), the count value of the second pulse signal itself does not reflect the temperature. In such a case, temperature display cannot be performed based on only the count value of the second pulse signal, and the ratio between the count value of the first pulse signal and the count value of the second pulse signal must be calculated. However, as in the present invention, even when the time required for the count value of the first pulse signal to reach the count cutoff value changes a little due to the change in the environmental temperature, the count time that changes depending on the environmental temperature remains unchanged. Since it is passed as the counting time in the second phase, the error due to the environmental temperature change does not mix in, and there is no need to calculate the ratio of the count values, and the temperature display is based only on the count value of the second pulse signal. You can Therefore, the division process is not necessary, the complexity of the circuit system and the enlargement of the element formation region can be avoided, and the thermometer can be made compact and lightweight.

[0028]

1 is a block diagram of an embodiment of the present invention. The thermistor 101 and the reference resistor 102 are connected to the resistance value-frequency conversion circuit 1 capable of outputting a signal having a frequency inversely proportional to the resistance value, as in Japanese Patent Application No. 59-17499 described above. The conversion circuit 1 outputs a temperature detection signal based on the resistance value Rs that varies depending on the temperature of the thermistor 101 and a reference signal based on the resistance value R1 of the reference resistance. The temperature detection signal and the reference signal are N
The count value based on the reference signal is counted by the frequency divider circuit 2 via the OR gate 11, and the initial logic adjustment circuit 3 corrects the individual difference between the resistance value of the thermistor and the resistance value of the reference resistor. Judgment value). The frequency dividing circuit 5 uses the constant clock (clock pulse) generated from the oscillation circuit 4 to divide the frequency dividing circuit 2.
It is possible to set the reference time (counting time) by counting at, and the setting is performed when the count value reaches the count abort value in the initial logic adjusting circuit 3. The oscillator circuit 4 and the frequency divider circuit 5 form a counting time determination circuit.

The temperature detection signal is supplied to the frequency dividing circuit 2 during the reference time set in the frequency dividing circuit 5 by the NOR gate 11, and is counted in the frequency dividing circuit 2. The count value is latched by the latch circuit 12, and the result of the latch circuit 12 is converted into the temperature by the decode circuit 13,
It is displayed on the liquid crystal display panel 14.

The initial logic adjusting circuit 3 of this example is composed of the frequency dividing circuit 2.
Of the gate setting output circuit 60 for determining whether or not the count value of 1 has reached a preset reference count value M, and the reference count value M is set to M ′ in order to correct the individual difference between the thermistor 101 and the reference resistor 102. It is composed of an initial setting circuit 61 to be changed. Therefore, in the electronic thermometer of this example, ΔR × M, which is the correction for deriving N indicating the actual temperature, can be directly converted into M ′ in the equation (4) described above. That is, Japanese Patent Application No. 59-
In No. 17499, as shown in equation (5), ΔR
Although × M is realized as M−ΔM, in this example, it is realized as ΔR × M = M ′ (6). As a result, the frequency dividing circuit 2
In addition, it is not necessary to set the initial value before counting the reference signal, and the frequency dividing circuit 2 can be realized by a normal 1/2 frequency dividing circuit with reset.

FIG. 2 shows the configurations of the frequency dividing circuit 2 and the initial logic adjusting circuit 3. The frequency dividing circuit 2 is composed of eight 1/2 frequency dividing circuits 15 to 22 with reset,
2 ⁰ , 2 ¹ , 2 ² , 2 ³ , 2 ⁴ , 2 ⁵ , 2 ⁶ , respectively
In charge of the division of 2 ^7. Therefore, reset terminal 6
After the reset signal input from the input terminal 23
The reference signal and the temperature detection signal input from can be counted and output as an 8-bit signal to the latch circuit 12 and the gate setting output circuit 60.

The initialization circuit 61 has four P channels M
The OS 31 to 34 and the four EXORs 24 to 27 are included. Then, the output of the P-channel MOS 31 and the output of the 1/2 divider circuit with reset 15 are input to the EXOR 24, and the output thereof is the gate setting output circuit 60.
Is connected to the multi-input NAND 29 that constitutes the. Similarly, in the other EXORs 25 to 27, the output of the P-channel MOS 32 and the 1/2 divider circuit with reset 16 are also provided.
Output, P-channel MOS33 output and 1 / with reset
The output of the divide-by-2 frequency divider circuit 17, the output of the P-channel MOS 34, and the output of the 1/2 divider circuit with reset 18 are input, and the outputs of the respective EXORs 25 to 27 are connected to the multi-input NAND 29 constituting the gate setting output circuit 60. Has been done.
P channel MO used in the initialization circuit 61
S31 to S34 are pull-up MOs for setting initial values.
S, the source side of each of the MOSs 31 to 34 is connected to the high potential Vdd, and the gate electrode is connected to the low potential Vss. The data input lines 7-1 are provided on the drain side connected to the EXOR gates 24-27.
0 are connected to each other, and the initial value can be set depending on whether or not the lines 7 to 10 are grounded.

The gate setting output circuit 60 for judging the count value counted by the frequency dividing circuit 2 from the initial value set in the initial setting circuit 61 is composed of a multi-input NAND circuit 29, and EXOR gates 31-34. And the outputs of the 1/2 frequency dividers with reset 20 to 22 are input, and all the values become 1, so that the count value becomes a predetermined value (counting abort value) via the inverter 30.
The signal that has reached is output to the frequency dividing circuit 5.

As described above, in this example, the initial setting circuit 61 changes the reference count value determined by the gate setting output circuit 60 to correct the individual difference between the resistance value of the thermistor and the resistance value of the reference resistance. ing. For example, the resistance value of the thermistor is 2 at the set temperature.
When the resistance value of the reference resistance is 3.0 KΩ and the resistance value of the reference resistance is 22.4 KΩ, the number of counts related to the resistance value of the thermistor is 224.
In order to adjust the count, 224 = 22.4 / 23.0 × M ′ ... (7) from the equations (4) and (6), and M ′ is 230. Therefore, in this example, M is set to M ′, that is, 23 by the initial setting circuit 61.
You can set it to 0.

M ′ = 230 = 128 + 64 + 32 + 4 +2 = 2 ⁷ +2 ⁶ +2 ⁵ +2 ² +2 ¹ (8) Therefore, in the initialization circuit 61, EXOR2
Of the data applied to 4-27, 2 ⁰ , 2 ³ , 2 ⁴
Data input line 7 so that the data of
Lines 8 and 9 of 10 may be set to a low level. In this example, 2 ⁴ data, that is, 1/2
The signal of the frequency dividing circuit 19 is inverted by the inverter 28 so that it becomes a high level at the time of determination. Under such settings, the 1/2 divider circuit with reset 16, 1
The value of 7 is directly input to the multi-input NAND 29 without being inverted by the EXORs 25 and 26, and the values of the 1/2 divider circuits with reset 15 and 18 are inverted by the EXORs 24 and 27 and input to the multi-input NAND 29. Then, the value of the 1/2 frequency divider circuit with reset 20 is inverted by the inverter 28, and the values of the 1/2 frequency divider circuits with reset 21 and 22 are directly input to the multi-input NAND 29. For this reason,
In this example, the 1/2 divider circuits with reset 15, 18, 20, 21, 2 representing 2 ¹ , 2 ² , 2 ⁵ , 2 ⁶ , 2 ⁷ ,
The value of 2 is directly input to the multi-input NAND 29, and the other values are inverted and input to the multi-input NAND 29.
Therefore, in the frequency dividing circuit 2, the multi-input NAND 29 becomes low level when 230 is counted, and the time spent for this counting is set in the frequency dividing circuit 5 as a reference time (counting time). Then, the frequency detection signal is counted by the frequency dividing circuit 2 for the reference time (counting time), whereby the corrected count value is latched in the latch circuit 12, and the accurate temperature is displayed.

As described above, in this embodiment, since the reference count value for comparing the count values of the frequency dividing circuit 2 is changed, it is not necessary to set the initial value for correction in the frequency dividing circuit 2. Therefore, a 1/2 divider circuit with reset can be adopted as the divider circuit 2, and a set-priority-type 1/2 divider circuit with reset, which has been adopted to set an initial value, can be adopted.
The frequency divider circuit can be omitted. Therefore, the number of elements such as the set-priority type 1/2 divider circuit with reset is large, and a circuit having a large circuit scale can be eliminated, and the electronic thermometer can be miniaturized and manufactured at low cost. In addition, the EXOR used in this example compares the output from the frequency dividing circuit 2 in the conventional electronic thermometer with an inverter or the like provided to invert the output according to the characteristics of the thermistor, This is not a gate circuit with a large circuit scale, and this has little effect on the circuit area.

Further, in this example, since the set control signal is unnecessary, the NAN of the conventional setting timing circuit is used.
The D gate can be omitted, and the cost can be reduced and the measuring operation of the electronic thermometer can be simplified.

Furthermore, as compared with the prior art, temperature display can be performed based only on the count value of the second pulse signal (detection pulse signal), so division processing is not required, which contributes to simplification of the circuit system. There is.

[0039]

As described above, the temperature measuring method according to the present invention uses the resistance value-frequency conversion means for switchably generating the reference pulse signal and the detection pulse signal, and uses the reference pulse signal and the detection pulse signal. One is used as the first pulse signal and the other is used as the second pulse signal.
In the phase, the first pulse signal is counted until the count cutoff value is reached, and the counting time is determined by the counting time determining means. In the second phase, the counting means is reset and then the first pulse signal The second pulse signal is counted for a counting time equal to the counting time, and the temperature is displayed only by the counting result, and the counting cutoff value according to the resistance variation correction data is set prior to the first phase. It is characterized by doing. Therefore, the following effects are obtained.

Since the cutoff value can be changed, if the cutoff value is set according to the correction data corresponding to the individual difference (resistance value variation) of the resistance value-frequency conversion means of the thermometer, the count cutoff value can be obtained. Since the counting time of can be adjusted to be shorter or longer, it is possible to increase or decrease the counting result of the second signal pulse at the same temperature, and it is possible to display with high accuracy in all products by correcting the individual resistance difference. First
Since the initial value is not preset in the counting means prior to the counting of the pulse signal, the counting means does not need a frequency divider with a set, and the circuit configuration can be simplified. As the number of bits of the counting means increases, the circuit scale will be significantly reduced.

Since the set control signal is unnecessary, it is possible to omit the initial value setting timing circuit and the set control signal generating circuit, and it is possible to reduce the size, weight and cost by simplifying the circuit configuration.

In the present invention, the counting time determining means determines the counting time for each temperature measurement process. As a result, even when the time required for the count value of the first pulse signal to reach the count cutoff value changes to some extent due to the change in the environmental temperature, the count time that has changed to a shorter value depending on the environmental temperature is used as it is for the second pulse signal. Since it is passed as the counting time in, the error due to the environmental temperature change is not mixed up, and it is not necessary to calculate the ratio of the count values, and the temperature can be displayed only based on the count value of the second pulse signal. It has become. Therefore, the division process is not necessary, the complexity of the circuit system and the enlargement of the element formation region can be avoided, and the thermometer can be made compact and lightweight.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing configurations of a frequency dividing circuit and an initial logic adjusting circuit shown in FIG.

FIG. 3 is a block diagram of an example of Japanese Patent Application No. 59-17499, which is a conventional example.

FIG. 4 is a circuit diagram showing a configuration of a frequency dividing circuit and a control circuit of a conventional example of Japanese Patent Application No. 59-17499.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Resistance value-frequency conversion circuit 2 ... Frequency divider circuit (counting means) 3 ... Initial logic adjustment circuit for correcting resistance values of reference resistance and thermistor 4 ... Oscillation circuit for generating constant clock 5 ... Counting time is determined Frequency dividing circuit 6 ... Reset signal input line for resetting the frequency dividing circuit 7-10 ... Logical adjustment data input line for inputting adjustment data 11 ... NOR circuit 12 ... Latch circuit 13 ... Decoder 14 ... Liquid crystal display (LCD) 15 -22 ... 1/2 divider circuit with reset 23 ... Input signal line of divider circuit 24-27 ... EXOR circuit 28, 30, 39-45 ... Inverter 29, 44 ... Multi-input NAND gate 31-34 ... Pull-up P-channel MOS transistor 35 ... Terminal connected to power supply Vss 36 ... Terminal connected to power supply Vdd 37 ... Initial logic adjustment data A frequency dividing circuit 38 capable of performing initial setting of the data 38 ... Control circuits 47 to 50 ... Control set signal input line 60 ... Gate setting output circuit 61 ... Initial value setting circuit 101 ... Thermistor 102 ... Reference resistance.

Claims (1)

[Claims] 1. A resistance value which is switchably generated between a reference pulse signal having a frequency based on the resistance value of the reference resistance and a detection pulse signal having a frequency based on the resistance value of the detection resistance whose resistance value changes in response to temperature. In the temperature measuring method using the frequency conversion means, one of the reference pulse signal and the detection pulse signal is used as a first pulse signal and the other is used as a second pulse signal, and the counting means reaches the count cutoff value. Counting the first pulse signal until
The first phase in which the counting time is determined by the counting time determining means to determine the counting time for each temperature measurement step until the count value of the pulse signal reaches the counting cutoff value, and then the counting means is reset. From the above, the counting means counts the second pulse signal for a counting time equal to the counting time of the first pulse signal, latches the counting result of the second pulse signal, and displays the temperature based on this. A temperature measurement method, which has two phases, and sets the count-off value according to the resistance variation correction data prior to the first phase.