JP2011252771A - Electronic medical thermometer and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic medical thermometer that reduces power consumption when not in use for measuring body temperature while maintaining measuring accuracy by appropriately controlling the frequency of clocks used for measurement.SOLUTION: An electronic medical thermometer, having an integrating circuit in which a thermistor and a capacitor are connected in series and a clock generator that generates clock signals, measures a transitional period of the integrating circuit shifting from a steady state to a transitional state by counting clock signals generated by the clock generator; calculates the temperature value on the basis of the measured transitional period; derives from the calculated temperature value a plurality of predicted values by a plurality of prediction formulas; selects one out of the plurality of prediction formulas on the basis of the variation over time of each value; acquires an equilibrium temperature value as a body temperature measurement result by using the selected prediction formula; and displays the same, wherein the clock generator switches over the frequency of the clock signals on the basis of the calculated temperature value.

Description

  The present invention relates to an electronic thermometer and a 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 the thermistor, a method of configuring a CR oscillator including the thermistor and measuring its oscillation frequency, a method using a single input integration type A / D conversion circuit, and the like can be cited. (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.

  Patent Document 2 describes that an appropriate prediction formula is selected based on a change in an initial actual measurement value at the start of measurement, thereby improving measurement accuracy and shortening time required for body temperature measurement. .

JP 2003-075263 A JP 2007-024530 A

  In general, electronic thermometers for hospitals are not provided with a manual power ON / OFF switch in order to provide liquid-tightness. In addition, since the time from when the patient measures the thermometer until the nurse collects the thermometer and reads the thermometer is indefinite, the hospital electronic thermometer usually does not have an automatic power-off function. . Therefore, this type of electronic thermometer often maintains the power-on state even when the body temperature is not measured, during which time power is wasted and the battery life is shortened.

  In particular, an electronic thermometer using a single-input integrating A / D converter circuit requires a very high frequency clock in order to measure the transient period of the integrating circuit with higher accuracy, which is a waste of time other than during body temperature measurement. Power consumption is more serious.

  The present invention has been made in view of the above problems, and provides an electronic thermometer that reduces power consumption other than during body temperature measurement while maintaining measurement accuracy by appropriately controlling the frequency of a clock used for measurement. With the goal.

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;
Clock means for generating a clock signal;
A measuring means for measuring a transient period when transitioning from a steady state to a transient state in the integration circuit by counting the clock signal;
Calculating means for calculating a temperature value based on the transient period measured by the measuring means;
Predicted value deriving means for deriving a plurality of predicted values from the temperature values calculated by the calculating means according to a plurality of prediction formulas;
A selection unit that selects one prediction formula from the plurality of prediction formulas based on each time-dependent change of the plurality of prediction values;
A display output means for acquiring and displaying an equilibrium temperature value as a body temperature measurement result using the prediction formula selected by the selection means;
The clock means switches the frequency of the clock signal based on the temperature value calculated by the calculation means.

  According to the present invention, since the frequency of the clock used for measurement is appropriately controlled, it is possible to reduce power consumption other than during body temperature measurement while maintaining measurement accuracy, and at least 10,000 temperature measurements can be performed in the case of predictive temperature measurement. A prediction / measurement electronic thermometer can be provided.

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 the general temperature measurement process using an integration circuit. 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 explaining the switching process of the clock frequency by embodiment. It is a figure which shows the example of the change of the temperature actual value by a temperature measuring element. It is a figure explaining the grouping based on the measured value of an electronic thermometer. It is a figure explaining the determination of the group based on the change of a some predicted value. It is a figure which shows the conditions in the case of correct | amending a reference point.

  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 such an external configuration of the prediction / actual electronic clinical thermometer 100 according to an embodiment of the present invention, FIG. 1 (a) is a plan view and FIG. 1 (b) is a side view Respectively. Reference numeral 101 denotes a main body case made of a thermoplastic resin having impact resistance and chemical resistance, in which an electronic circuit such as an arithmetic control unit 220 described later with reference to FIG.

  Reference numeral 102 denotes a stainless steel metal cap in which a thermistor (details will be described later) for measuring temperature is stored in a liquid-tight manner. 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 and the like, a magnet reed switch 251 (FIG. 2) is provided without providing a manual ON / OFF switch such as the power ON / OFF switch 103 in order to provide liquid tightness. Yes. 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 installs a permanent magnet from the power supply unit 250 to the electronic circuit such as the arithmetic control unit 220, the temperature measuring unit 210, the display unit 230, and the like. The power is continuously supplied until it is stored in a built-in storage case (not shown), and the power is turned on. Note that both the power ON / OFF switch 103 and the magnet reed switch 251 may be provided.

  A liquid crystal display 104 displays the body temperature of the subject. Reference numeral 105 denotes a speaker, which outputs sound based on processing in the arithmetic control unit 220. Note that the end of body temperature measurement or the like may be notified by a buzzer or the like instead of voice output. The display 104 is not limited to liquid crystal. The display 104 has impact resistance and chemical resistance, and is covered with a window member formed of a transparent thermoplastic resin. This window member is molded in two colors with the main body case 101 to provide liquid-tightness. Have.

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. Audio data is output by the calculation control unit 220 that controls the operation of the entire electronic thermometer 100, the display unit 230 that displays the calculated body temperature of the subject on the display 104 (for example, a liquid crystal display), and the speaker 105. An audio output unit 240 and a power supply unit 250 are provided. The power supply unit 250 includes a battery, and supplies power to the arithmetic control unit 220 and the like via the magnet reed switch 251.

  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. In addition, predetermined audio data is stored in the EEPROM 225, and the arithmetic processing unit 223 outputs audio data from the audio output unit 240 using the audio data. The clock output from the clock generation unit 228 can be switched to either a low frequency clock or a high frequency clock according to an instruction from the arithmetic processing unit 223.

  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.

<Grouping and prediction formula>
FIG. 12 is a diagram exemplarily showing a change in an actual measurement value by an electronic thermometer measured under the armpit.
As shown in FIG. 12, the actual measurement value approaches the equilibrium temperature with time, but the rate of change differs depending on the measurement condition such as the constitution of the person to be measured and the contact state between the temperature measurement and the body surface. Therefore, case classification (grouping) is performed according to the time-dependent change characteristic of the actual measurement value, and a prediction formula to be used for prediction of the equilibrium temperature is determined.

  Below, grouping based on the characteristic of the measured value detected using the thermistor 401 (it mentions later with FIG. 4) is demonstrated. However, in the present embodiment, as described above, the thermal response characteristics of the temperature sensing element are good, and variations in the time-varying characteristics of measured values are likely to occur. Therefore, an example will be shown in which more grouping (in this case, grouping into 12 groups) is performed as compared with the conventional grouping (for example, 7 groups) to cope with the improved thermal response characteristics.

  FIG. 13 is a diagram illustrating an example of grouping according to the temporal change characteristic of the actual measurement value. FIG. 13 shows an example in which the whole is divided into 12 groups using the temperature rise value for 15 to 20 seconds (horizontal axis in FIG. 13) and the temperature at 20 seconds (vertical axis in FIG. 13). Each point of shows the distribution in the measurement sample. The first group is the group with the fastest thermal response, and is the part where the initial temperature is high but the rise is quickly stopped. Conversely, the eighth group is the group with the slowest thermal response, and is the portion where the initial temperature is low but the temperature rise continues until late. Here, since the ninth group and the tenth group greatly deviate from the normal change in the actual measurement value, for example, it may be configured to end with an error because the prediction is impossible, or the actual measurement value is displayed without performing the prediction. It may be configured to do. In addition, the eleventh group and the twelfth group are groups whose body temperature is 36.5 degrees or more at 20 seconds.

When the grouping as described above is performed, for example, when the actually measured value is a predetermined value (30 ° C.) or more and the temperature increase rate is a predetermined value (0.03 ° C./0.5 seconds) or more, the starting point ( t = 0), the predicted value Y can be approximated by the following equation using the actual measurement value T and the elapsed time t.
U = (a * t + b) * dT + (c * t + d)
Y = T + U where a to d: constant, dT: temperature rise in the past 5 seconds.

  After 20 seconds, as described in the grouping, prediction calculation is performed using the coefficients a to d corresponding to each group. As an example, an example of the values of the coefficients a to d in each group during 20 to 25 seconds is shown below. These coefficients a to d are obtained from a large number of measurement samples, and are a part of the parameters 22b stored in the ROM 22 in advance.

1 group a = 0.554: b = -6.5185: c = -0.1545: d = 2.8915
Group 2 a = 1.1098: b = -15.446: c = -0.244: d = 4.5294
3 groups a = 0.7187: b = -6.9876: c = -0.0571: d = 1.0682
4 groups a = 0.8092: b = -7.8356: c = -0.0448: d = 0.8609
5 groups a = 0.8555: b = -9.2469: c = -0.0697: d = 1.5205
6 groups a = 0.4548: b = -2.1512: c = 0.0083: d = 0.2872
Group 7 a = 0.378: b = -1.3724: c = 0.0027: d = 0.8912
8 groups a = 0.378: b = -1.3724: c = 0.0027: d = 0.8912
11th group a = -0.0148: b = 1.9438: c = 0.0282: d = 0.142
12 groups a = 0.468: b = -4.794: c = -0.06: d = 1.2593

<Body temperature measurement operation of electronic thermometer>
FIG. 3 shows a flowchart of a procedure for measuring body temperature in the electronic thermometer of the first embodiment. The following operation is triggered by, for example, pressing the power ON / OFF switch 103 or turning on the power by the magnet reed switch 251. The following steps are realized by the arithmetic processing unit 223 executing a program stored in the ROM 224.

  In step S301, the arithmetic processing unit 223 sets the clock output from the clock generation unit 228 to a low frequency clock. In step S <b> 302, the arithmetic processing unit 223 initializes the electronic thermometer and starts detecting the temperature value by the thermistor 401. For example, the temperature value is detected using a sensor every 0.5 seconds.

  In step S303, the arithmetic processing unit 223 starts prediction when the degree of temperature change is equal to or greater than a predetermined value. For example, the time point when the temperature value at which the increase from the previous actual measurement value (that is, the actual measurement value before 0.5 seconds) becomes a predetermined value (for example, 1 ° C.) or more is measured as the reference point (t = 0) of the prediction formula. The data is set and stored in the RAM 226 as specific timing and measured value data (time-series data). In other words, by detecting a rapid temperature rise, it is considered that the measurement person wears a predetermined measurement site.

  In step S304, the arithmetic processing unit 223 determines whether or not a measured temperature drop is observed during the measurement. When the predetermined decrease is observed, the process proceeds to step S314, and when the predetermined temperature decrease is not observed, the process proceeds to step S305.

  In step S305, the arithmetic processing unit 223 changes the clock output from the clock generation unit 228 to a high frequency clock. That is, S301 to S304 are standby states for detecting the start of body temperature measurement, and high measurement accuracy is not required. Therefore, temperature measurement is performed using a low-frequency clock to save power. Then, with the start of body temperature measurement, the clock is set to a high frequency, and highly accurate body temperature measurement is performed. In step S306, the arithmetic processing unit 223 uses the data stored in step S303 to derive a sequential (predetermined period) prediction value (for example, every 0.5 seconds) using the prediction formula described above. However, the arithmetic processing unit 223 of the present embodiment performs prediction calculations in parallel based on prediction formulas corresponding to each of the plurality of groups shown in FIG. That is, a predicted value derivation process is performed to derive a plurality of predicted values from the calculated temperature value according to a plurality of prediction formulas. Note that computation may be performed in parallel for all the groups (here, 10 types of 1 to 8, 11 and 12), or an approximate group is set based on some actually measured values, and some of the surrounding groups are set. The calculation may be performed only for.

  In step S307, the arithmetic processing unit 223 changes each predicted value corresponding to the plurality of groups derived in step S306 after a predetermined time (predetermined second; for example, 20 seconds) has elapsed from the reference point (t = 0). The grouping determination is performed based on the above. Details of this group determination operation will be described later.

  In step S308, the calculation processing unit 223 stops calculations other than the group determined in step S307, and continues to derive the prediction calculation in the determined group for a predetermined time. As described above, in steps S307 and S308, one prediction formula is selected from the plurality of prediction formulas based on the respective temporal changes of the plurality of prediction values, and the equilibrium temperature as the body temperature measurement result using the selected prediction formula. The value is obtained.

  In step S309, the arithmetic processing unit 223, when a predetermined time (predetermined second; for example, 25 seconds) elapses from the reference point (t = 0), the fixed section (for example, t = 20 to 20) derived as a result of step S308. It is checked whether or not the predicted value at 25 seconds) satisfies a preset prediction establishment condition. For example, it is a check as to whether or not it falls within a predetermined range (for example, 0.1 ° C.). If the prediction establishment condition is satisfied, the process proceeds to step S310. If the prediction establishment condition is not satisfied, the process proceeds to step S316.

  In step S310, the arithmetic processing unit 223 switches the clock generated by the clock generation unit 228 to a low frequency clock. In step S <b> 311, the arithmetic processing unit 223 notifies the prediction establishment by the audio output unit 240 (may be a buzzer sounding), and proceeds to step S <b> 312.

  In step S312, the arithmetic processing unit 223 displays the derived predicted value on the display unit 230.

  In step S313, the arithmetic processing unit 223 determines whether or not an instruction to end the temperature detection process has been received. For example, it may be determined whether or not the power ON / OFF switch 103 has been pressed, or the temperature measurement process may be automatically terminated when a predetermined time has elapsed after the predicted temperature display. Alternatively, when the new body temperature measurement is not executed for a predetermined time, it may be determined that the end of the body temperature measurement is instructed, and the predicted temperature display may be ended. Alternatively, the predicted temperature display may be continued until the magnet reed switch 251 is turned off and the power supply from the power supply unit 250 is turned off. For example, the magnet reed switch 251 is turned off when the electronic thermometer 100 is housed in a housing case (not shown) containing a permanent magnet.

In step S314, the arithmetic processing unit 223 corrects the measured data. If the correction process is normally performed, the process returns to step S303. On the other hand, if the correction process does not end normally, the process proceeds to step S315. In the correction process of the reference point (t = 0), for example, when all of the following conditions are satisfied, a temperature drop before being attached to a predetermined measurement site, for example, contact with clothes or skin, and pinching Accordingly, a correction process for subtracting Δt1 + Δt2 from the starting point time shown in FIG.
[Condition 1] The time (Δt1) from the reference point of the prediction formula to the temperature drop detection is within a predetermined time (seconds) (for example, 5 seconds).
[Condition 2] The measured value before the temperature drop is not more than a predetermined value (for example, 34 ° C.).
[Condition 3] The time (Δt 2) from when the temperature drop is detected until the temperature rises again is within a predetermined time (second) (eg, 8 seconds).
[Condition 4] The temperature drop (ΔT) is within a predetermined range (for example, 1.5 ° C.).

  In step S315, the arithmetic processing unit 223 notifies the error by the audio output unit 240 (the buzzer may sound) and ends the temperature measurement. In the case of notification by buzzer ringing, it is desirable that the buzzer sound is different from that in step S311.

  In step S316, when a predetermined time (for example, 45 seconds) has elapsed from the start of measurement, the arithmetic processing unit 223 forcibly establishes a prediction, and the process proceeds to step S310. That is, the prediction value derived at that time is regarded as the final prediction value as it is.

  Through the above steps, the temperature measuring operation is completed.

<Determination of groups based on predicted values>
Hereinafter, processing (corresponding to step S307) when determining a group corresponding to the prediction formula used for the final prediction value from a plurality of prediction values derived based on the plurality of prediction formulas will be described.

  FIG. 14 is a diagram exemplarily showing changes with time of predicted values based on actual measurement values and a plurality of prediction formulas. In this figure, along with the actual measurement value detected by the thermistor 401, changes in predicted values corresponding to the five groups of the first group to the fifth group derived in step S306 are shown. In the following, the group is determined based on the temporal change of these predicted values. That is, it is determined whether the most accurate predicted value is obtained when the prediction formula corresponding to which group is used.

Here, as an example, a group in which both of the following two points are established is selected.
(1) The change in 10-second regression is less than a predetermined value (for example, 0.1 degree).
(2) The above condition corresponding to the predicted value derived every 0.5 seconds is continuously evaluated five times.

  That is, as a result, it is considered that the group corresponding to the time series in which the fluctuation of the predicted value is small selects the optimum group in the main measurement. In this way, by performing prediction calculation for a plurality of groups and comparing the predicted values with time to determine the group, a more accurate prediction can be made by 30 seconds using the reference point as the measurement start point. It is possible.

  In the above, in order to improve the accuracy of prediction, the predicted value is continuously derived for a predetermined time after the group is determined (steps S308 to S309), and the final predicted value is determined. However, if the change is sufficiently small (for example, less than 0.05 degrees) at the time of group determination, the predicted value corresponding to the determined group can be regarded as sufficiently accurate, so it is immediately determined as the final predicted value. May be.

  On the other hand, the group may be determined based on the change over time of the actually measured values. That is, the time series data of the actual measurement values may be associated with the grouping table shown in FIG. 13, and the group with the most corresponding points may be selected and determined.

  As described above, the electronic thermometer of the present embodiment can realize an electronic thermometer with high prediction accuracy in a short measurement time, and can reduce the burden on the measurer. In addition, since the measurement time is shortened by selecting an appropriate prediction formula, the period in which the high-frequency clock is used is shortened, and highly accurate body temperature measurement is realized while realizing power saving.

3.2 Power Saving by Controlling Operation Clock As described above, in the present embodiment, both power saving and high-accuracy measurement are achieved by switching the frequency of the clock output from the clock generator 228. The temperature measurement unit 210 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. The timer 222 determines a period from the start of charging or discharging (starting transition from the steady state to the transient state) in the capacitor of the integrating circuit until the detection of the change in the comparison signal as the charging time or The discharge time (that is, the transition period) is set, and the length of the period is measured by counting the clock signal generated by the clock generator 228. Since the charging time or discharging time changes according to the change in resistance value of the thermistor, the arithmetic processing unit 223 can obtain the resistance value of the thermistor, that is, the temperature value from the measurement result of the charging time or discharging time. . As the frequency of the clock counted by the timer 222 increases, the measurement accuracy increases, but the power consumption increases. If the clock frequency is kept low, power consumption can be reduced, but the measurement accuracy is reduced. In the present embodiment, by switching the frequency of the clock signal generated by the clock generator 228, measurement accuracy is maintained and power saving is achieved. That is, it is determined whether or not the body temperature is being measured. If the body temperature is being measured, the high frequency clock is used to maintain the measurement accuracy of the transient period by the timer 222. If the body temperature is not being measured, the low frequency clock is Use it to save power. In the above example, as a determination of whether or not the body temperature is being measured, a high frequency clock is used from the start of the predicted temperature calculation (S306) to the end of the predicted temperature calculation (before S311), and other periods are set. Power is saved by operating with a low-frequency clock as a standby state.

  Note that the clock frequency switching method is not limited to the above-described method. For example, clock frequency switching control by the arithmetic processing unit 223 as shown in FIG. 11 may be executed, and S301, S305, and S310 in FIG. 3 may be omitted. In the process shown in FIG. 11, it is determined whether or not the standby state is established by comparing the temperature measurement value with the threshold value, and it is determined whether to use the high frequency clock or the low frequency clock.

  In step S321 in FIG. 11, when the power source of the electronic thermometer is turned on by manual operation of the power ON / OFF switch 103 or a magnet reed switch (not shown) being turned on, the arithmetic processing unit 223 is turned on in step S322. The clock generator 228 is set to generate a clock with a high frequency (for example, 1 MHz). In this step, setting may be made so that the clock generator 228 operates at either a high frequency or a low frequency, and the setting is not limited to a high frequency as shown in the figure.

  Next, in step S 323, the arithmetic processing unit 223 acquires a temperature measurement value (actual measurement value) using the temperature measurement unit 210 and the timer 222. As described above, the timer 222 counts the clock generated by the clock generation unit 228 for the charge time or discharge time of the capacitor forming the integration circuit together with the thermistor in the temperature measurement unit 210. The arithmetic processing unit 223 calculates the charging time or discharging time from the clock count value obtained from the timer 222 and the frequency of the clock, and acquires the temperature measurement value. In this embodiment, the discharge time in the capacitor is measured.

  In step S324, when the temperature measurement value acquired in step S323 is smaller than the predetermined value (Th1) and the current clock frequency is a high frequency, the arithmetic processing unit 223 does not measure from the body temperature measurement state. It is determined that the state has been changed. When it is determined that the state has shifted to the non-measurement state, the arithmetic processing unit 223 controls the clock generation unit 228 to generate a clock having a low frequency (for example, 100 kHz) in step S326. In step S325, when the temperature measurement value acquired in step S323 is larger than the predetermined value (Th2) and the current clock frequency is a low frequency, the arithmetic processing unit 223 moves from the non-measurement state. It is determined that the body temperature measurement state has been entered. If it is determined that the state has shifted to the body temperature measurement state, the arithmetic processing unit 223 controls the clock generation unit 228 to generate a high-frequency clock in step S327.

  By executing the clock frequency switching process as described above in parallel with the body temperature measurement process shown in FIG. 3, the clock frequency can be kept low when the body temperature is not being measured, and the power consumption of the electronic thermometer can be reduced. be able to. Further, the clock frequency may be set to a low clock frequency when the equilibrium temperature value as the body temperature measurement result is acquired (that is, the process of FIG. 11 and the process of step S310 may be used in combination). . In addition, the measurement accuracy is maintained because it operates with a high-frequency clock during body temperature measurement. In particular, if the above configuration is applied to an electronic thermometer for hospitals equipped with a magnet reed switch without a power on / off switch by manual operation or an automatic power off function, the power saving effect will be more prominent. Become. As described above, according to the present embodiment, by controlling the switching of the clock frequency used for measurement, it is possible to maintain measurement accuracy and save power, such as hospitals with high daily measurement frequency. In the case of predictive temperature measurement, power consumption is about 10 mW, and body temperature can be measured at least about 10,000 times from the beginning of use.

  That is, in the clock frequency switching process in the present embodiment, it is determined whether or not the body temperature is being measured from the temperature value measured using the thermistor, and if it is determined that the body temperature is not being measured, the clock frequency is kept low. Reduce power consumption. Note that power consumption can be further reduced by switching the frequency of the operation clock in the arithmetic processing unit 223 in the same manner as the clock for measurement described above. The frequency switching process described above can be applied to an electronic thermometer that acquires a temperature value by measuring a resistance value change of the thermistor. In particular, an integration circuit such as a temperature measurement using a single input integration type A / D conversion circuit. By applying to a configuration that requires a high-frequency clock in order to measure the transition period, a more remarkable effect can be obtained. 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. As described above, there are at least two types of frequencies. Therefore, the discharge time is obtained from the count value by the timer 222 and the clock frequency at that time.

  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). In this example, voltage is applied to the capacitor 403 by applying a voltage to the capacitor 403 for a preset charging time (the charging time can be determined from the capacitance of the capacitor 403 and the resistance values of the thermistor 401 and the reference resistance element 402). It is assumed that the charging of has been completed. 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 this embodiment, by using a configuration that eliminates as much as possible the voltage drop error of the power supply unit 250 included in the measured discharge time without using a regulator, it is possible to maintain measurement accuracy and save power. Longer lifespan can be realized, and when performing predictive temperature measurement in hospitals where daily measurement frequency is high, power consumption is about 10 mW, and body temperature can be measured at least about 10,000 times from the start of use. To achieve 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. Moreover, a remarkable power saving effect can be obtained by cooperation with the switching of the clock frequency.

[Second Embodiment]
In the first embodiment, one temperature measurement process is completed by repeating charging / discharging of the capacitor 403 four times immediately after the start of the temperature measurement process. However, the present invention is not limited to this. For example, one temperature measurement process may be completed by repeating charging / discharging of the capacitor 403 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 first discharge: discharge through the reference resistance element, the second: discharge through the thermistor, the third: discharge through the reference resistance element, and the first discharge time Tref0 is calculated as temperature data. You may make it use for. That is, the average value of the first discharge time Tref0 and the third discharge time Tref1 and the second discharge time Tth 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, 0 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) Tref_0 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) Tref_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, 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 Tref_0 and Tref_1). 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 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 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) Tref_2 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 Tref_1 is measured is compared with the voltage V2 when Tref_2 is measured, and the difference between the voltage V1 and the voltage V2 is calculated (actually, , Calculate the difference between Tref_1 and Tref_2). 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, the voltage V is applied to both ends of the system including the reference resistance element 402 and the capacitor 403 until the voltage drop (difference between Tref_n and Tref_n + 1) due to repeated measurement of the discharge time becomes a predetermined value or less. The process and the process of discharging the electric charge accumulated in the capacitor 403 via the reference resistance element 402 are repeated (S904 to S907).

  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 S908, 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 + 2 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 + 1 + Tref_n + 2) / 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 + 1 and Tref_n + 2 when discharging the accumulated charges are measured. Further, the average values of the discharge times Tref_n + 1 and Tref_n + 2 measured immediately before and after are 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. Moreover, a remarkable power saving effect can be obtained by cooperation with the switching of the clock frequency.

  In the above embodiment, when charging the capacitor 403, charging through a reference resistance element is used when measuring Tref, and charging via a thermistor is used when measuring Tth. Is not something For example, charging of the capacitor 403 may always be performed via either the reference resistance element or the thermistor, or may be performed via both the reference resistance element and the thermistor.

  As described above, according to each of the above embodiments, the frequency of the clock for temperature measurement is switched based on the measured value of the temperature in the electronic thermometer that obtains the measured value by the thermistor and the integrating circuit. For this reason, it is possible to achieve power saving by using a low-frequency clock in a standby period in which the predicted temperature calculation is not performed, and it is possible to realize highly accurate measurement using the high-frequency clock in a measurement period in which the predicted temperature calculation is performed. Also, if the measurement period is from the start to the end of the predicted temperature calculation (until the predicted temperature value is displayed), the clock is switched to a lower frequency as the predicted temperature calculation ends, thus achieving more effective power saving. it can. Further, in the predicted temperature calculation, the time required for the predicted temperature calculation can be shortened by selecting an appropriate prediction formula from the initial actual measurement values. Therefore, the measurement period can be shortened, and more effective power saving can be achieved.

  DESCRIPTION OF SYMBOLS 100: Electronic thermometer 101: Main body case 102: Gold cap 100: Power ON / OFF switch 104: Liquid crystal display 105: Speaker

Claims (7)

An integrating circuit in which a thermistor and a capacitor are connected in series;
Clock means for generating a clock signal;
A measuring means for measuring a transient period when transitioning from a steady state to a transient state in the integration circuit by counting the clock signal;
Calculating means for calculating a temperature value based on the transient period measured by the measuring means;
Predicted value deriving means for deriving a plurality of predicted values from the temperature values calculated by the calculating means according to a plurality of prediction formulas;
A selection unit that selects one prediction formula from the plurality of prediction formulas based on each time-dependent change of the plurality of prediction values;
A display output means for acquiring and displaying an equilibrium temperature value as a body temperature measurement result using the prediction formula selected by the selection means;
The electronic thermometer characterized in that the clock means switches the frequency of the clock signal based on the temperature value calculated by the calculating means.   The clock means sets the frequency of the clock to the first frequency when the temperature value calculated by the calculating means is a predetermined temperature or higher, and when the temperature value is lower than the predetermined temperature. The electronic thermometer according to claim 1, wherein the frequency of the clock is set to a second frequency, and the first frequency is higher than the second frequency.   3. The electronic thermometer according to claim 2, wherein the clock means sets the frequency of the clock to the second frequency when the equilibrium temperature value as a body temperature measurement result is acquired. The predicted value deriving unit starts derivation of the plurality of predicted values when the temperature value calculated by the calculating unit is equal to or higher than a predetermined temperature and the degree of temperature change is equal to or higher than a predetermined value.
The clock means sets the frequency of the clock to a first frequency in a period from the start of the derivation by the predicted value derivation means until the display output means obtains the equilibrium temperature value, and in other periods, the clock frequency The electronic thermometer according to claim 1, wherein a clock frequency is set to a second frequency, and the first frequency is higher than the second frequency. A power supply for supplying power to each part of the electronic thermometer;
The electronic thermometer according to any one of claims 1 to 4, further comprising a magnet reed switch that turns on and off power supply from the power supply unit to each unit.   The electronic thermometer according to claim 1, wherein the electronic thermometer is liquid-tight. An integrating circuit in which a thermistor and a capacitor are connected in series;
A method for controlling an electronic thermometer comprising clock means for generating a clock signal,
A measuring step of measuring the transition period by counting the clock signal when transitioning from the steady state to the transient state in the integration circuit;
A calculation step of calculating a temperature value based on the transient period measured in the measurement step;
A predicted value deriving step of deriving a plurality of predicted values from the temperature value calculated in the calculating step according to a plurality of prediction formulas;
A selection step of selecting one prediction formula from the plurality of prediction formulas based on each time-dependent change of the plurality of prediction values;
A display output step of acquiring and displaying an equilibrium temperature value as a body temperature measurement result using the prediction formula selected in the selection step;
And a switching step of switching a frequency of the clock signal generated by the clock means based on the temperature value calculated in the calculation step.

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