JP5451142B2 - Electronic thermometer and operation control method - Google Patents

Description

  The present invention relates to an electronic thermometer and an operation control method thereof.

  Conventionally, in the field of electronic thermometers, temperature measurement values are obtained by measuring resistance changes of the thermistors accompanying temperature changes. As a technique for measuring the resistance change of such a thermistor, there is a method of configuring a CR oscillator including the thermistor and measuring its oscillation frequency, a method using a single input integrating A / D converter circuit, and the like. (Patent Document 1).

  In temperature measurement using a single input integration type A / D conversion circuit, an integration circuit in which a thermistor and a capacitor are connected in series is used. The temperature value can be calculated by measuring the transient period (capacitor charging time or discharging time) of the integrating circuit that changes in accordance with the resistance change of the thermistor.

JP 2003-75263 A

  However, in the configuration in which the resistance change of the thermistor is measured using the transmission circuit and the integration circuit as described above, when the temperature acquisition value fluctuates due to external noise or the like, the predicted temperature value or the actual measurement value is affected. In particular, in an electronic thermometer using a single-input integration type A / D conversion circuit, it is required to measure the transient period of the integration circuit with high accuracy, and therefore, the occurrence of errors due to mixing of external noise is more serious. . Further, in a prediction formula for predicting the temperature in a thermal equilibrium state using temperature measurement values at a plurality of sampling timings, an error included in the sampled temperature value affects the prediction result.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide an electronic thermometer that can appropriately correct a temperature measurement value with respect to mixing of external noise and is not easily affected by external noise. To do.

In order to achieve the above object, an electronic thermometer according to the present invention has the following configuration. That is,
An integrating circuit in which a thermistor and a capacitor are connected in series;
A comparison means for outputting a comparison signal indicating a comparison result between the voltage of the capacitor and a predetermined voltage in the integration circuit;
Clock means for generating a clock signal;
Based on the count value of the clock signal and the frequency of the clock signal during the period from the start of charging or discharging of the capacitor of the integrating circuit to detection of the change of the comparison signal, the charging time or discharging of the capacitor A measuring means for measuring time;
A calculating means for calculating a temperature measurement value indicating an ambient temperature of the thermistor based on the charging time or the discharging time measured by the measuring means at each predetermined sampling timing;
Whether or not the temperature measurement value needs to be corrected is determined based on another temperature measurement value in sampling that is continuous with the temperature measurement value, and the temperature measurement value determined to be abnormal is corrected based on the other temperature measurement value Correction means ,
The estimation means detects the start of body temperature measurement based on the calculated temperature value, and calculates the temperature measurement value calculated by the calculation means in a predetermined period after a predetermined time has elapsed since the start of measurement. To estimate the equilibrium temperature,
The correction means performs a first correction process for determining whether or not the temperature measurement value calculated at the previous sampling timing needs to be corrected outside the predetermined period, and correcting the current sampling timing within the predetermined period. to run a second correction processing of correcting the necessity of in the calculated temperature measurement value of the correction determination to.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to correct a temperature measurement value appropriately with respect to mixing of external noise, and can provide the electronic thermometer which is hard to receive the influence of external noise.

It is a figure which shows the external appearance structure of the electronic thermometer 100 concerning one Embodiment of this invention. 3 is an internal block diagram illustrating a functional configuration of the electronic thermometer 100. FIG. 3 is a flowchart showing a flow of a body temperature measurement process in the electronic thermometer 100. It is a figure which shows the detailed structure of the temperature measurement part 210. FIG. It is a flowchart which shows the flow of a general temperature measurement process. FIG. 6 is a diagram illustrating a time change of a voltage across a capacitor 403 and a time change of a digital signal output from an A / D conversion unit 420. It is a flowchart which shows the flow of the temperature measurement process in 1st Embodiment. FIG. 6 is a diagram illustrating a time change of a voltage across a capacitor 403 and a time change of a digital signal output from an A / D conversion unit 420. It is a flowchart which shows the flow of the temperature measurement process in 3rd Embodiment. FIG. 6 is a diagram illustrating a time change of a voltage across a capacitor 403 and a time change of a digital signal output from an A / D conversion unit 420. It is a flowchart which shows the correction process of the temperature measurement value by embodiment. It is a figure which shows an example of the correction process by embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
1. Appearance Configuration FIG. 1 of the electronic thermometer is a diagram showing an external configuration of the electronic clinical thermometer 100 according to an embodiment of the present invention, FIG. 1 (a) is a plan view, FIG. 1 (b) shows a side view respectively ing. Reference numeral 101 denotes a main body case in which an electronic circuit such as an arithmetic control unit 220 described later, a battery (power supply unit) 250, and the like are accommodated.

  Reference numeral 102 denotes a stainless steel metal cap in which a thermistor (details will be described later) for measuring the temperature is housed. A power ON / OFF switch 103 is turned on when the power supply unit 250 is pressed once, and turned off when pressed again. In an electronic thermometer for hospitals or the like, a magnet reed switch is provided without providing a manual ON / OFF switch such as the power ON / OFF switch 103 in order to provide liquid tightness. For this reason, when the electronic thermometer 100 is taken out of the storage case, the magnet reed switch is turned on, and the electronic thermometer 100 is transferred from the power supply unit 250 to the electronic circuit such as the arithmetic control unit 220, the temperature measurement unit 210, the display unit 230, and the like. The power is continuously supplied until it is stored, and the power is turned on.

  Reference numeral 104 denotes a display unit that displays the body temperature of the subject. Reference numeral 105 denotes an audio output unit that outputs audio based on processing in the arithmetic control unit 220.

2. Functional Configuration of Electronic Thermometer FIG. 2 is an internal block diagram showing the functional configuration of the electronic thermometer 100 according to the present embodiment.

  The electronic thermometer 100 calculates a body temperature of the subject by performing various processes based on the temperature measurement unit 210 that outputs an ON signal for a time corresponding to the temperature, and the ON signal output from the temperature measurement unit 210. The calculation control part 220 which controls operation | movement of the whole electronic thermometer 100, the display part 230 which displays the calculated body temperature of the subject, the audio | voice output part 240 which outputs audio | voice data, and the power supply part 250 are provided.

  The temperature measurement unit 210 includes a thermistor (measuring resistance element) and a reference resistance element connected in parallel to each other, and a single input integration type A / D conversion circuit, and an ON signal (temperature) corresponding to the temperature. In response to the above, a digital signal whose ON time changes) is output. The detailed configuration of the temperature measurement unit 210 and the flow of temperature measurement processing will be described later.

  The arithmetic control unit 220 includes a timer 222 that measures the ON time of the digital signal output from the temperature measurement unit 210. The timer 222 counts the clock generated by the clock generator 228 in the control circuit 221, and measures the ON time based on the obtained count value and the frequency of the clock.

  The arithmetic control unit 220 includes an arithmetic processing unit 223. The arithmetic processing unit 223 calculates the temperature data based on the time measured by the timer 222 by executing a program stored in the ROM 224, and stores the calculated temperature data in the RAM 226 in time series. The body temperature of the subject is predicted and calculated based on the time change of the temperature data. The EEPROM 225 stores predetermined audio data, and the arithmetic processing unit 223 outputs audio data from the audio output unit 105 using the audio data.

  Further, the calculation control unit 220 includes a display control unit 227 for controlling the display unit 230 that displays the calculation result in the calculation processing unit 223.

  Further, the arithmetic control unit 220 includes a control circuit 221 that controls the timer 222, the display control unit 227, the arithmetic processing unit 223, and the temperature measurement unit 210.

3. Flow of temperature measurement process in electronic thermometer
3.1 Overall Flow of Temperature Measurement Processing in Electronic Thermometer Next, the flow of temperature measurement processing in the electronic thermometer will be described. In addition, although the flow of the body temperature measurement process of the electronic thermometer 100 of an equilibrium temperature prediction type | formula is demonstrated here, this invention is not limited to this, The measurement type | formula electronic thermometer and the electronic thermometer of the type which uses prediction / measurement together are demonstrated. Is also applicable.

  When attached to the measurement site of the subject, the electronic thermometer 100 starts temperature measurement at a predetermined cycle of sampling timing, and predicts and calculates the body temperature of the subject based on the temporal change of the acquired temperature data.

  FIG. 3 is a flowchart showing the flow of the body temperature measurement process in the electronic thermometer 100. Hereinafter, the flow of the body temperature measurement process in the electronic thermometer 100 will be described with reference to FIG. Note that the processing illustrated in FIG. 3 is executed by the arithmetic processing unit 223, for example.

    When the power source 250 of the electronic thermometer 100 is turned on by manual operation of the power ON / OFF switch 103 or a magnet reed switch (not shown) being turned on, in step S301, the electronic thermometer 100 is initialized. The temperature measurement by the thermistor is started. For example, the arithmetic processing unit 223 calculates temperature data at a predetermined interval, for example, every 0.5 seconds.

  In step S302, it is determined whether a body temperature measurement start condition is satisfied. Specifically, the degree of increase from the value of the temperature data calculated by the previous temperature measurement (that is, the value of the temperature data 0.5 seconds before) has become a predetermined value (for example, 1 ° C.) or more. Judge whether or not.

  When it is determined that the degree of increase is equal to or greater than a predetermined value, it is determined that the body temperature measurement start condition is satisfied, and the timing at which the temperature data is measured is set as a reference point (t = 0) for predicted body temperature calculation. . That is, in the electronic thermometer 100, when a rapid temperature rise is measured, it is considered that the subject wears the electronic thermometer 100 at a predetermined measurement site (for example, armpit).

  If it is determined in step S302 that the body temperature measurement start condition is satisfied, the process proceeds to step S303, and temperature data acquisition is started. Specifically, the output temperature data and the timing at which the temperature data is measured are stored in the RAM 226 as time series data.

  In step S304, the predicted body temperature is calculated by a predetermined prediction formula using the temperature data stored in step S303. That is, the temperature (thermal equilibrium temperature) in a thermal equilibrium state with the external temperature of the thermistor is estimated from the measured temperature data. This estimation process uses the establishment of the body temperature measurement start condition as a reference point (t = 0), and a predetermined period (for example, t = 25 seconds to 45 seconds) after a predetermined time (for example, 25 seconds) has elapsed from the reference point. For 20 seconds).

  In step S305, whether the predicted value over the predetermined interval (for example, 5 seconds) calculated in step S304 satisfies the preset prediction establishment condition in the predetermined period (t = 25 to 45 seconds in this example). Judge whether or not. Specifically, it is determined whether or not the estimated value of the thermal equilibrium temperature in a certain section is within a predetermined range (for example, 0.1 ° C.).

  If it is determined in step S305 that the prediction establishment condition is satisfied, the process immediately proceeds to step S306, the temperature measurement is terminated, the process proceeds to step S307, and a sound indicating that the calculation of the predicted body temperature is completed is output and displayed. The calculated predicted body temperature is displayed on the unit 230.

  On the other hand, if it is determined in step S305 that the predetermined period has passed without satisfying the prediction establishment condition, the process proceeds to step S309. In step S309, it is determined that the estimated value has not been obtained even after a predetermined time (t = 45 seconds in this example) has elapsed, and the temperature measurement is forcibly terminated. In addition, when forcedly ending, the predicted body temperature calculated at that time is displayed on the display unit 230 (step S307). At this time, you may make it alert | report that the body temperature measurement was forcibly terminated using the display part 230 or the audio | voice output part 240. FIG.

  In step S308, it is determined whether a body temperature measurement end instruction has been accepted. If it is determined in step S308 that a body temperature measurement end instruction has not been received, the process returns to step S302.

  On the other hand, if it is determined in step S308 that a body temperature measurement end instruction has been received, the power supply unit is turned off. The body temperature measurement end instruction is given by the user, for example, by the power ON / OFF switch 103. Alternatively, it may be determined that the end of the body temperature measurement is instructed when the new body temperature measurement is not performed for a predetermined time. Alternatively, the electronic thermometer 100 is housed in a housing case (not shown) containing a permanent magnet, whereby the magnet reed switch is turned off and the power supply from the power supply unit 250 is turned off.

3.2 Correction of Measured Value In steps S301 to S304 described above, temperature measurement using the temperature measuring unit 210 is repeatedly performed at a predetermined sampling timing. In particular, the temperature measurement unit 210 of the present embodiment includes an integration circuit in which a thermistor and a capacitor are connected in series, and a comparison circuit that outputs a comparison signal indicating a comparison result between a voltage of the capacitor and a predetermined voltage in the integration circuit ( This will be described later with reference to FIG. The timer 222 determines a period from the start of charge or discharge in the capacitor of the integrating circuit (start of transition from the steady state to the transient state) to the detection of the change in the comparison signal as the charge time or discharge time (that is, the transient period). ) And the length of the period is measured by counting the clock signals generated by the clock generator 228. Here, when the temperature measurement value at each sampling timing fluctuates due to external noise, the prediction value or the actual measurement value by the prediction calculation is affected. Therefore, in the present embodiment, measurement value correction processing is executed in order to provide resistance to fluctuations in the predicted value due to external noise or the like. The correction process described below is performed on the temperature measurement values sampled in steps S301 to S304, and is executed in parallel with the processes in these steps.

  FIG. 11 is a flowchart showing correction processing with measurement in the present embodiment. The correction process shown in steps S321 to S325 is executed from the start of temperature measurement in step S301 to immediately before a certain section (eg, t = 25 to 30 seconds) in step S303. Further, the correction process shown in steps S326 to S330 is executed in a period until the predetermined time for calculating the predicted temperature elapses (a period up to t = 25 seconds in this example). In the correction processing in steps S321 to S325, the temperature measurement value (hereinafter referred to as sampling value) at the previous sampling timing is corrected using the previous and next sampling values (two previous sampling values and the current sampling value). Done. Further, in the correction process in steps S326 to S330, the current sampling value is corrected using the past (1 to 3 previous sampling values) sampling value. In FIG. 11, “the process of correcting the current sampling value (the correction process of steps S326 to S330)” is always executed during the prediction calculation, but the present invention is not limited to this. For example, the correction process of steps S326 to S330 may be executed at a specific timing during the prediction calculation, and the correction process shown in steps S321 to S325 may be performed at other timings. Here, the specific timing includes grouping determination (processing for selecting a coefficient used for prediction calculation) and timing for performing forced termination determination. This is because these processes include conditional branching using the current sampling data, and it is preferable to perform “processing for correcting the current sampling value”. In addition, any one of the correction processing shown in steps S326 to S330 and the correction processing in steps S321 to S325 is performed for each sampling.

  In step S321, the arithmetic processing unit 223 sets a first straight line connecting the previous and second previous sampling values. In step S322, the arithmetic processing unit 223 determines whether or not the previous sampling value deviates beyond the predetermined range from the first straight line set in step S321. If the deviation exceeds the predetermined range in step S322, the process proceeds to step S323, and the arithmetic processing unit 223 determines whether the current sampling value deviates beyond the predetermined range from the first straight line. If the current sampling value does not deviate from the first straight line beyond a predetermined range, in step S324, the arithmetic processing unit 223 sets the previous sampling value to the value on the set first straight line. To correct. In other cases, the previous sampling value is not corrected. As described above, in the correction processing in steps S321 to S325, the previous sampling value deviates beyond the predetermined range with respect to the first straight line connecting the previous three sampling values and the previous two sampling values. If the current sampling value does not deviate beyond the predetermined range, the previous sampling value is corrected to a value on the first straight line. This correction process is repeated until the start of a predetermined period (t = 25 to 45 seconds) in which the above-described prediction calculation is performed (NO in step S325).

(A) of FIG. 12 is a figure which shows an example of the correction process of said step S321-S325. In the figure, Oh [n] indicates a sampling value n times before, and Oh [0] indicates a current sampling value. In the correction process shown,
(1) Centered on the previous sampling value Oh ′ [1] estimated from the first straight line 1201 connecting the previous and second previous sampling values (Oh [3] and Oh [2]) The sampling value (measurement value) Oh [1] immediately before the predetermined range 1202 deviates (YES in S322),
(2) The current sampling value Oh [0] exists within a predetermined range 1202 centered on the current sampling value Oh ′ [0] estimated from the first straight line 1201 (NO in S323).
Therefore, the previous sampling value Oh [1] is replaced with the estimated value Oh ′ [1]. Note that the size of the range 1202 and the range 1203 may be the same or different.

  When the predetermined period (t = 25 to 45 seconds) in which the prediction calculation is performed, the process proceeds from step S325 to step S326. In step S326, the arithmetic processing unit 223 sets a first straight line connecting the three previous sampling values and the two previous sampling values. In step S327, the arithmetic processing unit 223 determines whether or not the previous sampling value deviates beyond the predetermined range from the first straight line. If the previous sampling value does not deviate from the first straight line beyond a predetermined range, in step S328, the arithmetic processing unit 223 sets the second sampling value connecting the two previous sampling values and the previous sampling value. A straight line is set, and it is determined whether or not the current sampling value deviates from the second straight line beyond a predetermined range. When the current sampling value deviates from the second straight line beyond a predetermined range, in step S330, the arithmetic processing unit 223 corrects the current sampling value to a value on the second straight line. As described above, in the correction processing in steps S326 to S330, the previous sampling value does not deviate beyond the predetermined range with respect to the first straight line connecting the previous and second previous sampling values. When the current sampling value deviates beyond a predetermined range with respect to the second straight line connecting the two previous sampling values and the previous sampling value, the current sampling value is the second straight line. It is corrected to the above value.

(B) of FIG. 12 is a figure which shows the example of a position of the correction process of said step S326-S330. In the correction process shown,
(1) Centered on the previous sampling value Oh ′ [1] estimated from the first straight line 1211 connecting the previous and second previous sampling values (Oh [3] and Oh [2]) The previous sampling value Oh [1] exists within the predetermined range 1212 (NO in S327),
(2) A predetermined value centered on the current sampling value Oh ′ [0] estimated from the second straight line 1213 connecting the previous and previous sampling values (Oh [2] and Oh [1]). The current sampling value Oh [0] deviates from the range 1214 (YES in S329),
Therefore, the current sampling value Oh [0] is replaced with the estimated value Oh ′ [0]. Note that the size of the range 1212 and the range 1214 may be the same or different.

  According to the correction processing of the present embodiment as described above, fluctuations in the temperature measurement value due to external noise or the like can be properly determined, and abnormal temperature measurement values affected by external noise or the like are changed to appropriate values. It can be corrected. The measurement value correction process described above can be applied to an electronic thermometer or the like that measures a change in the resistance value of the thermistor and obtains a temperature value. In particular, in a configuration in which a temperature measurement value is obtained by measuring a transient period in an integrating circuit including a thermistor using a single-input integrating A / D converter circuit as described below, the measured transient period is extremely short. Since it is time, it can be said that it is easily affected by external noise. Therefore, a more remarkable effect can be obtained by applying the correction process to such a configuration. Hereinafter, the configuration of temperature measurement using the single input integration type A / D conversion circuit according to the present embodiment will be described.

4). Detailed Configuration of Temperature Measurement Unit and Flow of Temperature Measurement Processing Next, the detailed configuration of the temperature measurement unit 210 and the flow of the temperature measurement processing started in step S301 will be described. In the description of the temperature measurement process, a general flow of the temperature measurement process will be described first in order to clarify the characteristics of the temperature measurement process in the present embodiment.

4.1 Detailed Configuration of Temperature Measuring Unit FIG. 4 is a diagram illustrating a detailed configuration of the temperature measuring unit 210. As shown in FIG. 4, in the temperature measurement unit 210, a thermistor 401 and a reference resistance element 402 connected in parallel with each other are connected in series to a capacitor 403. That is, the thermistor 401 and the capacitor 403 constitute an integrating circuit. Similarly, the reference resistance element 402 and the capacitor 403 constitute an integration circuit, and the reference resistance element 402 and the thermistor 401 are connected in parallel. The voltage V is alternately applied to both ends of the system including the thermistor 401 and the capacitor 403 and to both ends of the system including the reference resistance element 402 and the capacitor 403 via the voltage switching unit 410. Has been. That is, the voltage switching unit 410 applies the voltage V to the terminal T1 to charge the capacitor 403, and then sets the terminal T1 to 0 V and starts discharging the capacitor 403 through the thermistor 401. Further, the voltage switching unit 410 applies the voltage V to the terminal T2 to charge the capacitor 403, and then sets the terminal T2 to 0 V and starts discharging the capacitor 403 through the reference resistance element 402. Note that only one of the terminals T1 and T2 may be used for charging the capacitor 403.

  Here, the reference resistance element 402 is a resistance element having a constant resistance value regardless of variations in ambient temperature. For this reason, when the charging voltage V in the capacitor 403 is constant, the discharge time by the capacitor 403 via the reference resistance element 402 is constant.

  On the other hand, the thermistor 401 is a resistance element whose resistance value varies according to variations in ambient temperature. For this reason, when the electric charge accumulated in the capacitor 403 is discharged through the thermistor 401, the discharge time varies depending on the ambient temperature.

  That is, when the voltage V is constant, the discharge time required to discharge the electric charge accumulated in the capacitor 403 is always constant in the case of discharging through the reference resistance element 402, and the voltage V passes through the thermistor 401. In the case of discharge, it depends on the ambient temperature.

  The comparator 421 that constitutes the A / D conversion unit 420 is used while the capacitor 403 has a voltage equal to or higher than a voltage (here, 0.25 V) of a predetermined ratio of the voltage V applied via the voltage switching unit 410. , A predetermined signal is output. As a result, the A / D converter 420 outputs an ON signal as a digital signal.

  As described above, the capacitor 403 and the A / D conversion unit 420 form a single input integration type A / D conversion circuit.

  Due to the discharge, the voltage across the capacitor 403 gradually decreases. When the voltage drops below a predetermined voltage (0.25 V), the digital signal output from the A / D converter 420 is an OFF signal.

  More generally, the comparator 421 outputs a comparison signal indicating a comparison result between the voltage of the capacitor 403 and a predetermined voltage in the integration circuit. The timer 222 counts the clock signal generated by the clock generation unit 228 during the period from the start of discharging of the capacitor 403 in the integration circuit to the detection of a change in the comparison signal output from the comparator 421. Thus, the timer 222 measures the ON time (discharge time) of the digital signal output from the A / D conversion unit 420 after the start of discharge by the capacitor 403. The clock counted by the timer 222 is generated by the clock generator 228, and the discharge time is obtained from the count value obtained by the timer 222 and the clock frequency.

  Here, as described above, when discharged through the reference resistance element 402 (terminal T2), the amount of charge accumulated in the capacitor 403 is constant and the resistance value is also constant. Time also becomes constant. On the other hand, when discharged through the thermistor 401 (terminal T1), the amount of charge stored in the capacitor 403 is constant, but the resistance value varies depending on the ambient temperature, so the discharge time also varies. .

  Therefore, in the electronic thermometer 100, the discharge time when the charge accumulated in the capacitor 403 is discharged via the thermistor 401 in a state where the ambient temperature is known (reference temperature) in advance, and the capacitor via the reference resistance element 402 The discharge time when the charge accumulated in 403 is discharged is measured.

  As a result, only the discharge time when the charge accumulated in the capacitor 403 is discharged via the reference resistance element 402 is compared with the discharge time when the charge accumulated in the capacitor 403 is discharged via the thermistor 401. Thus, it is possible to calculate the fluctuation ratio with respect to the reference temperature, and it is possible to calculate the temperature data of the ambient temperature.

  For example, the temperature data T can be calculated based on the following equation.

T = 37 ° C. × (Tth / Tref) × (Tref37 / Tth37)
In the above formula, the reference temperature is 37 ° C.

  Note that Tref37 is obtained by discharging the capacitor 403 through the reference resistance element 402 after charging the capacitor 403 by applying a voltage V across the system of the reference resistance element 402 and the capacitor 403 at the reference temperature (37 ° C.). It shows the discharge time measured when performing. Tth37 is measured when the capacitor 403 is charged by applying the voltage V across the system of the thermistor 401 and the capacitor 403 at the reference temperature, and then the capacitor 403 is discharged through the thermistor 401. The discharge time is shown.

  Further, Tref was measured when the voltage V was applied across the reference resistor element 402 and the capacitor 403 to charge the capacitor 403 and then discharged through the reference resistor element 402 in the temperature measurement process. The discharge time is shown. Tth represents a discharge time measured when the voltage V is applied to both ends of the thermistor 401 and the capacitor 403 to charge the capacitor 403 and then discharged through the thermistor 401 in the temperature measurement process. ing.

4.2 Flow diagram 5 of a general temperature measurement process is a flowchart showing a flow of a general temperature measurement process, FIG. 6, from the time variation and the A / D converter 420 of the voltage across the capacitor 403 It is a figure which shows the time change of the digital signal output. A general flow of temperature measurement processing will be described with reference to FIGS. 5 and 6.

  In step S501, a voltage V is applied across the system including the reference resistance element 402 and the capacitor 403. Reference numeral 601 in FIG. 6 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S502, the capacitor 403 is discharged via the reference resistance element 402 (discharge period 602). Since the ON signal is output from the A / D converter 420 while the voltage of the capacitor 403 is 0.25 V or higher, the timer 222 measures the time of the ON signal (603) in the discharge period 602. As a result, the time (discharge time 604) Tref from when the discharge is started until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (here, 0.25 V) is measured (see 602 in FIG. 6).

  When the discharge of the capacitor 403 is completed, a voltage V is applied across the system including the thermistor 401 and the capacitor 403 in step S503. Reference numeral 605 in FIG. 6 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S504, the capacitor 403 is discharged via the thermistor 401 (discharge period 606). Since the ON signal is output from the A / D converter 420 while the voltage of the capacitor 403 is 0.25 V or higher, the timer 222 measures the time of the ON signal in the discharge period 606. Thereby, the time (discharge time 608) Tth from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (here, 0.25 V) is measured. Note that Tth varies according to the ambient temperature of the thermistor 401.

  When the discharge of the capacitor 403 is completed, in step S505, T = a × Tth / Tref (where a is a coefficient, where a = 37 ° C. × (Tref37 / Tth37)), thereby calculating the reference temperature. The variation ratio with respect to is calculated, and the temperature is calculated. In step S506, the calculation result T is set as the temperature measurement result.

  Thereby, one temperature measurement is completed. The temperature measurement process is repeatedly performed at a predetermined sampling timing until the end of temperature measurement is instructed. The above-described measurement may be performed a plurality of times at one sampling timing, and the average value of the obtained measurement values may be used as the measurement result at the sampling timing.

4.3 Problems of General Temperature Measurement Processing Here, in the example of FIG. 6, the voltage applied to both ends of the system of the reference resistance element 402 and the capacitor 403 and the voltage applied to both ends of the system of the thermistor 401 and the capacitor 403 It is assumed that the voltage is the same.

  However, the voltage applied across the reference resistor element 402 and capacitor 403 system and the voltage applied across the thermistor 401 and capacitor 403 system are not necessarily the same.

  In general, when a battery is used as the power supply unit 250, there is a characteristic that the internal resistance of the battery increases and the voltage of the power supply unit 250 decreases due to the influence of current consumption caused by the operation of the A / D conversion unit 420. For this reason, whenever the discharge time is repeatedly measured, the voltage of the power supply unit 250 decreases each time (specifically, when the first discharge time is measured, the voltage of the power supply unit 250 greatly decreases and the second time Thereafter, each time measurement is repeated, the voltage of the power supply unit 250 gradually decreases and eventually converges to a predetermined power supply voltage).

  That is, the voltage value applied to both ends of the reference resistor element 402 and the capacitor 403 system is different from the voltage applied to both ends of the thermistor 401 and capacitor 403 system, and the voltage applied later is lower. It has become.

  As a result, the measured discharge time includes a voltage drop of the power supply unit 250 as an error.

  In order to avoid such a situation, it is effective to provide a regulator or the like to stabilize the voltage of the power supply unit. However, in the case where a regulator or the like is provided, there is a problem in that the life of the electronic thermometer is hindered because the battery drains quickly due to the leakage current of the regulator. Moreover, if it is set as the structure which arrange | positions a regulator etc., the cost rise of an electronic thermometer will be inevitable.

  Therefore, in the present embodiment, the measurement accuracy is maintained and the lifetime is increased by adopting a configuration that eliminates as much as possible the error of the voltage drop of the power supply unit 250 included in the measured discharge time without using a regulator. And low price. Hereinafter, the details of the temperature measurement process in the present embodiment will be described.

Figure flow of temperature measurement process in 4.4 present embodiment 7 is a flowchart showing a flow of a temperature measurement process according to this embodiment, FIG. 8, the time change and the A / D converter of the voltage across the capacitor 403 FIG. 6 is a diagram showing a time change of a digital signal output from 420. The flow of the temperature measurement process in the present embodiment will be described with reference to FIGS.

  In step S701, the voltage V is applied across the system including the reference resistance element 402 and the capacitor 403. Reference numeral 801 in FIG. 8 indicates a period during which electric charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S702, the capacitor 403 is discharged via the reference resistance element 402 (terminal T2 is connected to 0V). At this time, the timer 222 measures a time (discharge time 802) Tref0 from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25V). In step S702, only discharging is performed, and Tref0 need not be measured.

  When the discharge of the capacitor 403 is completed, in step S703, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 again. Reference numeral 803 in FIG. 8 indicates a period during which electric charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, the capacitor 403 is discharged via the reference resistance element 402 in step S704. At this time, the timer 222 measures a time (discharge time 804) Tref1 from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V).

  When the discharge of the capacitor 403 is completed, a voltage V is applied across the system including the thermistor 401 and the capacitor 403 in step S705. Reference numeral 805 in FIG. 8 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S706, the capacitor 403 is discharged via the thermistor 401 (terminal T1 is connected to 0V). At this time, the time (discharge time 806) Tth from the start of discharge until the voltage of the capacitor 403 becomes a predetermined voltage (0.25 V) or less is measured. Note that Tth varies according to the ambient temperature of the thermistor 401.

  When the discharge of the capacitor 403 is completed, in step S707, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 again. Reference numeral 807 in FIG. 8 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, the capacitor 403 is discharged via the reference resistance element 402 in step S708. At this time, the timer 222 measures a time Tref2 (discharge time 808) from when the discharge is started until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25V).

  When the discharge of the capacitor 403 is completed, Tref = (Tref1 + Tref2) / 2 is calculated in step S709.

  In step S710, T = a × Tth / Tref (where a is a coefficient) is calculated to obtain a variation ratio with respect to the reference temperature, thereby calculating temperature data. In step S711, the calculation result T is set as the temperature measurement result.

  Thereby, one temperature measurement is completed. The temperature measurement process is repeatedly performed until the end of temperature measurement is instructed. The above-described measurement may be performed a plurality of times at one sampling timing, and the average value of the obtained measurement values may be used as the measurement result at the sampling timing.

  As described above, the electronic thermometer according to the present embodiment is configured such that the first discharge time Tref0 at the time of temperature measurement at each sampling timing is not used for calculation of temperature data. As a result, it is possible to reduce the influence of a significant voltage drop of the power supply unit 250 due to the first discharge. Needless to say, the first discharge may be the discharge by the thermistor, and the first discharge time Tth0 may not be used for the calculation of the temperature data. In the above example, charging / discharging that is not used for calculating the temperature data is performed only once, but charging / discharging that is not used for calculating the temperature data may be performed twice or more.

  In the electronic thermometer according to the present embodiment, the charge is accumulated in the capacitor via the reference resistance element immediately before and immediately after the discharge time when discharging the charge accumulated in the capacitor via the thermistor. The discharge times Tref1 and Tref2 when discharging the accumulated charges are measured. Further, the average value of the discharge times Tref1 and Tref2 measured immediately before and after is used for the calculation of temperature data.

  As described above, by using the average value of the discharge time in the calculation of the temperature data, it is possible to reduce the influence of the voltage drop of the power supply unit due to repeated measurement of the discharge time as much as possible.

  That is, even when a regulator is not used, highly accurate temperature measurement can be realized. As a result, it is possible to provide an electronic thermometer with a long lifetime and low cost and high measurement accuracy. In addition, more accurate temperature measurement can be realized in cooperation with the correction processing described above.

[Second Embodiment]
In the first embodiment, the configuration is such that one temperature measurement process is completed by repeating charging / discharging of the capacitor four times immediately after the start of the temperature measurement process, but the present invention is not limited to this. For example, the temperature measurement process may be completed once by repeating charging / discharging of the capacitor three times.

  Specifically, the order of discharge is the first time: discharge through the reference resistance element, the second time: discharge through the reference resistance element, and the third time: discharge through the thermistor. The first discharge time Tref0 is not used for calculating the temperature data, while the second discharge time Tref1 and the third discharge time Tth are compared to calculate the temperature data. It is good.

  Alternatively, the order of discharge is the first time: discharge through the reference resistance element, the second time: discharge through the thermistor, and the third time: discharge through the reference resistance element. The first discharge time Tref0 may be used for calculating the temperature data, while the average value of the second discharge time Tth and the third discharge time Tref1 may be used for calculating the temperature data. According to this procedure, unnecessary charge / discharge can be avoided in a configuration in which the voltage drop of the power supply unit 250 due to the initial discharge is not so great at the time of temperature measurement at each sampling timing.

[Third Embodiment]
In the first embodiment, the temperature measurement process is completed once by repeating charging / discharging of the capacitor four times immediately after the start of the temperature measurement process. However, the present invention is not limited to this. For example, a configuration in which one temperature measurement process is completed by repeating charging / discharging of the capacitor after the voltage drop of the power supply unit due to repeated measurement of the discharge time has converged within a certain threshold value. .

  FIG. 9 is a flowchart showing the flow of the temperature measurement process in the present embodiment, and FIG. 10 shows the time change of the voltage across the capacitor 403 and the time change of the digital signal output from the A / D converter 420. FIG. The flow of the temperature measurement process in the present embodiment will be described with reference to FIGS.

  First, in step S901, 1 is input to the counter n. In step S902, a voltage V is applied across the system including the reference resistance element 402 and the capacitor 403. Reference numeral 1001 in FIG. 10 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S903, the capacitor 403 is discharged through the reference resistance element 402. At this time, the timer 222 measures a time (discharge time 1002) Tref0 from when discharge is started until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V).

  When the discharge of the capacitor 403 is completed, in step S904, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 again. Reference numeral 1003 in FIG. 10 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, in step S905, the capacitor 403 is discharged again via the reference resistance element 402. At this time, the timer 222 measures a time (discharge time 1004) Tref1 from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V).

  When the discharge of the capacitor 403 is completed, in step S906, the voltage V0 when Tref0 is measured is compared with the voltage V1 when Tref1 is measured, and the difference between the voltage V0 and the voltage V1 is calculated (actually). Calculate the difference between Tref0 and Tref1). If it is determined that the difference between the voltage V0 and the voltage V1 is not less than or equal to the predetermined value, the value n is incremented in step S907, and the process returns to step S904.

  In this case, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 again. Reference numeral 1005 in FIG. 10 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, the capacitor 403 is discharged in step S905. At this time, the timer 222 measures a period (discharge time 1006) Tref2 from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V).

  When the discharge of the capacitor 403 is completed, in step S906, the voltage V1 when Tref1 is measured is compared with the voltage V2 when Tref2 is measured, and the difference between the voltage V1 and the voltage V2 is calculated (actually). , Calculate the difference between Tref1 and Tref2). If it is determined that the difference between the voltage V1 and the voltage V2 is not less than or equal to the predetermined value, the value n is incremented in step S907, and the process returns to step S904.

  Thereafter, a process of applying the voltage V to both ends of the system including the reference resistance element 402 and the capacitor 403 until the voltage drop due to repeated measurement of the discharge time becomes a predetermined value or less, The process of discharging the charge accumulated in the capacitor 403 is repeated.

  If it is determined that the voltage drop (1007) due to repeated measurement of the discharge time has become a predetermined value or less, the process proceeds to step S908.

  In step S906, a voltage V is applied across the system including the thermistor 401 and the capacitor 403. Reference numeral 1008 in FIG. 10 indicates a period during which charges are gradually accumulated in the capacitor 403 (charging period).

  When the charging of the capacitor 403 is completed, the capacitor 403 is discharged via the thermistor 401 in step S909. At this time, the time (discharge time 1009) Tth from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V) is measured.

  When the discharge of the capacitor 403 is completed, in step S910, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 again. 1010 in FIG. 10 shows a period (charge period) in which charges are gradually accumulated in the capacitor 403.

  When the charging of the capacitor 403 is completed, the capacitor 403 is discharged via the reference resistance element 402 in step S911. At this time, the timer 222 measures a time (discharge time 1011) Tref_n + 1 from the start of discharge until the voltage of the capacitor 403 becomes equal to or lower than a predetermined voltage (0.25 V).

  When the discharge of the capacitor 403 is completed, Tref = (Tref_n + Tref_n + 1) / 2 is calculated in step S912.

  In step S913, T = a × Tth / Tref (where a is a coefficient) is calculated to obtain a variation ratio with respect to the reference temperature, and temperature data is calculated. In step S914, the calculation result T is set as the temperature measurement result.

  Thereby, one temperature measurement is completed. The temperature measurement process is repeatedly performed until the end of temperature measurement is instructed.

  As described above, in the electronic thermometer according to the present embodiment, charging / discharging of the capacitor through the reference resistance element until the voltage drop of the voltage unit due to repeated measurement of the discharge time converges within a certain threshold value. It was set as the structure which repeats. Thereby, it becomes possible to reduce the influence of the significant voltage drop of the power supply part accompanying discharge.

  In the electronic thermometer according to the present embodiment, the charge is accumulated in the capacitor via the reference resistance element immediately before and immediately after the discharge time when discharging the charge accumulated in the capacitor via the thermistor. The discharge times Tref_n and Tref_n + 1 when discharging the accumulated charge are measured. Further, the average value of the discharge times Tref_n and Tref_n + 1 measured immediately before and immediately after is used for temperature measurement.

  As described above, by using the average value of the discharge time, it is possible to reduce the influence of the voltage drop of the power supply unit by repeatedly measuring the discharge time as much as possible.

  That is, even when a regulator is not used, highly accurate temperature measurement can be realized. As a result, it is possible to provide an electronic thermometer with a long lifetime and low cost and high measurement accuracy. In addition, more accurate temperature measurement can be realized in cooperation with the correction processing described above.

Claims (10)

Calculation means for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
Estimating means for estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on a plurality of temperature values calculated by the calculating means;
The necessity of correction for the temperature value calculated by the calculating means is determined based on the temperature value calculated at another sampling timing, and when it is determined that correction is required, the temperature value is set to be higher than the temperature value. Correction means for correcting based on the temperature value calculated at the previous sampling timing,
The estimation means detects the start of body temperature measurement based on the calculated temperature value, and calculates the temperature measurement value calculated by the calculation means in a predetermined period after a predetermined time has elapsed since the start of measurement. To estimate the equilibrium temperature,
The correction means performs a first correction process for determining whether or not the temperature measurement value calculated at the previous sampling timing needs to be corrected outside the predetermined period, and correcting the current sampling timing within the predetermined period. in calculated temperature measurement correction necessity determination to features and to that electronic thermometer to perform a second correction processing for correcting the. Calculation means for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
Estimating means for estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on a plurality of temperature values calculated by the calculating means;
The necessity of correction for the temperature value calculated by the calculating means is determined based on the temperature value calculated at another sampling timing, and when it is determined that correction is required, the temperature value is set to be higher than the temperature value. Correction means for correcting based on the temperature value calculated at the previous sampling timing,
The estimation means detects the start of body temperature measurement based on the calculated temperature value, and calculates the temperature measurement value calculated by the calculation means in a predetermined period after a predetermined time has elapsed since the start of measurement. To estimate the equilibrium temperature,
The correcting means is
In the timing for selecting the prediction coefficient for the estimation in the predetermined period and determining the censoring of the estimation, the second determination is made by determining whether or not the temperature measurement value calculated at the current sampling timing needs to be corrected. corrective action is performed, wherein the to that electronic performing a first correction process of correcting determines the necessity of correction temperature measurement value calculated in the previous sampling timing at another timing Thermometer. In the first correction process, the correction means includes:
Deviation between the estimated temperature value at the previous sampling timing estimated from the temperature values calculated at the previous and third sampling timings, and the temperature value at the previous sampling timing calculated by the calculation means Exceeds the predetermined range, and the estimated temperature value at the current sampling timing estimated from the temperature values calculated at the previous and second previous sampling timings, and the current sampling timing calculated by the calculating means When the deviation of the temperature value at is within a predetermined range, it is determined that the correction of the temperature measurement value at the previous sampling timing is necessary,
If the fix is determined to be necessary, electrons according to claim 1 or 2, characterized in that to correct the temperature measurement value in the preceding sampling timing to the estimated temperature value in the preceding sampling timing Thermometer. In the second correction process, the correction means includes:
The estimated temperature value at the previous sampling timing estimated from the temperature measurement values calculated at the previous and second previous sampling timings, and the temperature value at the previous sampling timing calculated by the calculation means Is within a predetermined range, and the estimated temperature value at the current sampling timing estimated from the temperature values calculated at the previous and previous sampling timings, and the current value calculated by the calculating means When the deviation from the temperature value at the sampling timing exceeds a predetermined range, it is determined that the temperature measurement value at the current sampling timing needs to be corrected,
If the modification is determined to be necessary, the temperature measurement value at the current sampling timing, to any one of claims 1 to 3, characterized in that to correct the estimated temperature value of the current sampling timing Electronic thermometer as described. Calculation means for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
Estimating means for estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on a plurality of temperature values calculated by the calculating means;
A capacitor connected in series with the thermistor and constituting an integrating circuit;
Clock means for generating a clock signal;
A comparison means for outputting a comparison signal indicating a comparison result between the voltage of the capacitor and a predetermined voltage in the integration circuit;
Measuring means for measuring the discharge time of the electric charge accumulated in the capacitor by counting the clock signal in a period from the start of discharge in the capacitor of the integration circuit until the change of the comparison signal is detected ; Bei example,
The integrating circuit further includes a reference resistor connected in series with the capacitor and in parallel with the thermistor;
The measuring means accumulates in the capacitor immediately before and immediately after the measurement of the first discharge time obtained by discharging the charge accumulated in the capacitor through the thermistor and the measurement of the first discharge time. Measuring the second and third discharge times obtained by discharging the charged charges through the reference resistor,
Said calculation means, said second and third average value of the discharge time, the first discharge time and you wherein electronic thermometer to calculate a temperature value used. 6. The electronic thermometer according to claim 5 , wherein the measuring means performs at least one charge and discharge to the capacitor prior to the start of the measurement of the discharge time at each of the sampling timings. The measurement means repeats the discharge from the capacitor through the reference resistor a plurality of times, and when the difference between the previous discharge time and the current discharge time becomes a predetermined value or less, the current discharge time is As the second discharge time, immediately after the current discharge time is measured, the capacitor is discharged through the thermistor to measure the first discharge time. Further, the first discharge time is measured. 6. The electronic thermometer according to claim 5 , wherein immediately after the capacitor is discharged through the reference resistor, the third discharge time is measured. A calculation step for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
An estimation step of estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on the plurality of temperature values calculated by the calculation step;
The necessity of correction for the temperature value calculated by the calculation step is determined based on the temperature value calculated at another sampling timing, and when it is determined that correction is required, the temperature value is set to be higher than the temperature value. possess a correcting step for correcting, based on the temperature value calculated in the previous sampling timing,
In the estimation step, the measurement start of the body temperature is detected based on the calculated temperature value, and the temperature measurement value calculated in the calculation step in the predetermined period after the predetermined time has elapsed since the start of the measurement is detected. To estimate the equilibrium temperature,
In the correction step, a first correction process for determining whether or not to correct the temperature measurement value calculated at the previous sampling timing other than the predetermined period is performed, and the current sampling timing is determined within the predetermined period. A control method for an electronic thermometer, comprising: performing a second correction process for determining whether or not the temperature measurement value calculated in step 1 is to be corrected .   A calculation step for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
  An estimation step of estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on the plurality of temperature values calculated by the calculation step;
  The necessity of correction for the temperature value calculated by the calculation step is determined based on the temperature value calculated at another sampling timing, and when it is determined that correction is required, the temperature value is set to be higher than the temperature value. A correction step of correcting based on the temperature value calculated at the previous sampling timing,
  In the estimation step, the measurement start of the body temperature is detected based on the calculated temperature value, and the temperature measurement value calculated by the calculation step in the predetermined period after the predetermined time has elapsed since the start of the measurement is detected. To estimate the equilibrium temperature,
  The correction step includes
  In the timing for selecting the prediction coefficient for the estimation in the predetermined period and determining the censoring of the estimation, the second determination is made by determining whether or not the temperature measurement value calculated at the current sampling timing needs to be corrected. An electronic thermometer characterized by executing a correction process and executing a first correction process for determining whether or not the temperature measurement value calculated at the previous sampling timing needs to be corrected at other timings. Control method.   A calculation step for calculating a temperature value based on a resistance value change of the thermistor at each sampling timing;
  An estimation step of estimating a temperature value in a temperature equilibrium state with an external temperature of the thermistor based on the plurality of temperature values calculated by the calculation step;
  A comparison step of outputting a comparison signal indicating a comparison result between the voltage of the capacitor and a predetermined voltage in an integration circuit in which the thermistor and the capacitor are connected in a special manner;
  Measurement for measuring the discharge time of the electric charge accumulated in the capacitor by counting the clock signal generated by the clock means in the period from the start of the discharge in the capacitor of the integration circuit until the change of the comparison signal is detected. And having a process
  The integrating circuit further includes a reference resistor connected in series with the capacitor and in parallel with the thermistor;
  In the measuring step, the charge accumulated in the capacitor is accumulated in the capacitor immediately before and immediately after the measurement of the first discharge time obtained by discharging the charge through the thermistor and the measurement of the first discharge time. Measuring the second and third discharge times obtained by discharging the charged charges through the reference resistor,
  In the calculating step, a temperature value is calculated using an average value of the second and third discharge times and the first discharge time.

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