JPS63191934A - Electronic clinical thermometer - Google Patents

Abstract

PURPOSE:To shorten a measurement time and to improve accuracy by detecting temperature variation after rising as a step response, and applying an oiler method and a corrected oiler method to the prescribed transfer function of a measurement system and predicting and calculating balanced bodily temperature. CONSTITUTION:A means which measures actual temperature at a specific sampling period is formed of a temperature sensor 1, an A/D converter 2, a CPU 3, and a ROM 4 and measured temperature data is stored in a RAM 5. A rising point is detected from the inclination of measured temperature per unit time and a temperature rise value is calculated from the measured temperature at the time of sampling. Then the oiler method and corrected oiler method are applied to the prescribed transfer function of the measurement system to predict and calculate the balanced temperature based upon the rising point, and the bodily temperature is predicted and calculated according to the temperature. Consequently, the prediction result with high accuracy is obtained by the simple calculation and the measurement time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an electronic thermometer, and particularly to an electronic thermometer that can measure body temperature quickly and with high precision after starting measurement.

(b) Conventional technology In general, electronic thermometers detect the temperature of the temperature sensor by applying the temperature sensor to the area to be measured and paying attention to the fact that the temperature of the temperature sensor tracks the body temperature and changes. Many are designed to measure body temperature. With this type of electronic thermometer, it takes about 5 to 10 minutes for the temperature sensor to reach the temperature of the part to be measured. On the other hand, in recent years, there has been a demand for electronic thermometers that can take measurements at an early stage.
, JP-A-56-46440, etc. These applications process transient response characteristics during body temperature measurement using, for example, step response characteristics, calculate a focused value from measurement data of a minimum number of multiple points, or calculate a constant value with a first derivative value of the measured body temperature. When this happens, the convergence value is determined by adding a certain bulk increase value to the temperature at that time, or by performing complex calculations using the -th order differential and second-order differential values.

(c) Problems to be solved by the invention Among the above-mentioned conventional electronic thermometers, those that calculate a focused value at a limited number of points or perform differential operations are greatly affected by noise and add a bulk value. This method cannot reflect individual differences, environmental differences, etc., and cannot obtain accurate prediction results.

An object of the present invention is to solve the above-mentioned problems and to provide an electronic thermometer that can measure body temperature quickly and with high accuracy after the start of measurement.

(d) Means and operation for solving the problems First, the principle of adoption of the electronic thermometer of the present invention will be explained.

Generally, when measuring body temperature, even if the detection part of the thermometer is inserted into the measurement area (e.g. axilla, sublingual area), the temperature value cannot be obtained instantly, and it is not until the thermometer and the body part reach a state of thermal equilibrium. , it takes a certain amount of time. In other words, the detected body temperature y (
t) increases exponentially, as shown in FIG. 5, and eventually equilibrates to the temperature x(t) of the body part.

Here, a method for predicting the equilibrium temperature x (tl) from the measured value Y (t) in a short time will be explained.

The body temperature measurement system is a fusion system of a thermometer (temperature sensor) and a living body, which is treated as a black box, the transfer function of this black box is determined, and the equilibrium value (body temperature) is determined from the actual measured values every moment.

Generally, the step response is treated using a transfer function as shown in FIG.
(t), and the transfer function of the system G (S), -= G
(S) ・・・・・・(1) Here, X=L (x(t)), Y=L (y(t
)) and L-' represent Laplace transform and inverse Laplace transform, respectively.

In this way, a step response is generally obtained using a transfer function and Laplace transform.

In this invention, the body temperature measurement system is represented by a transfer function, and the step response, that is, the equilibrium body temperature is determined using the above principle.

When the sensor part of the thermometer is placed in the atmosphere at a temperature of Qa,
If the heat transfer coefficient between the atmosphere and the thermometer is h, then the transfer heat MkQ
is, Q=hA (Q'a-Qt) --(4) where A
:Surface area of sensor part.

Qt: Sensor part temperature.

If the heat capacity of the sensor part is Cw, then t From equations (4) and (5) above, if h is constant, CwSe t(s)=hA (ea(sl-Qt (S
) ) −・−・−・(71 Therefore, it becomes the transfer function indicating the delay of the −th order response.

However, in the case of body temperature measurement, a more complex response is possible, and the thermal time constant is not constant, so we believe that it cannot be expressed by a simple step response.

Therefore, as a model for a body temperature meter, we have developed a transfer function G (S
), (1+T2S)(1+T*S)...(1+T,
Consider S). Here T1, T2,..., T1,...
, T7 is a constant fixed to the system. As an example, consider 1+TtS.

If this G is) is represented in a block diagram, it will be as shown in FIG. 7(a). By further performing equivalent transformation, this can be expressed in a form that includes integrals, as shown in FIG. 7 (bl).

Therefore, if we use the numerical calculation method (Euler's method), (see the margin below), if we apply the modified Euler's method to equation (11), we get
Highly accurate calculation results can be obtained.

To obtain the predicted value, use equation (10) as the denominator and numerator as −
Since the shapes are contrasting in the following, using the above calculation process as is and corresponding to the diagram, X-Y, Y-X,, TI→
The predicted value X is obtained by setting T z and T 2 - T + .

That is, the original step person/crab equilibrium temperature: predicted body temperature value is obtained from the measured data Y (response data).

Next, consider the case where (1+T2S) (1+T4S) is used in order to perform higher prediction, and if this G (S) is represented in a block diagram, it will be as shown in FIG. 8(a). This becomes as shown in Fig. 8(b) by further equivalent transformation, so from this Fig. 8(b), the calculation formula by Euler's method can also be changed to the modified Euler's method in order to obtain numerical calculation accuracy. In equation (13), the denominator and numerator are also symmetrical, so in order to obtain the predicted value, we consider the measured data as input and use the same formula as in equations (11) and (12). Considering this in correspondence with Figure 8, X-4Y, Y→X, T, →T2, T2→T1, T3→T
4. Calculation can be done by replacing T 3 = T 4 . That is, the actual measured value Y is
The initial values of YSZ and Q are set to O. Therefore, the final result is
The measured initial temperature of 70 minutes is increased to give y=yo+x.

The electronic thermometer of the present invention adopts the above principle, and includes a temperature sensor, a temperature measuring means for measuring temperature at every predetermined cycle, and a storage means for storing the obtained temperature data. Means for detecting a rising point at which the temperature data suddenly rises; a temperature change after the rising temperature is taken as a step response; and the Euler's method and modified Euler's method are applied to a predefined transfer function of the measurement system to set the rising point as a reference. It is comprised of means for predicting and calculating the equilibrium temperature, means for adding the temperature at the rising point to the calculated equilibrium temperature, and display means for displaying the added temperature as body temperature.

In this electronic thermometer, the temperature is measured at predetermined intervals by the temperature measuring means, and the temperature before the temperature sensor is attached to the measurement site is the measured temperature in that state (y in FIG. 3). When the measurer attaches the temperature sensor to the measurement site, the measured temperature rises rapidly due to body temperature, and a rising point p is detected. After that, the equilibrium temperature X is determined by y7 obtained by the temperature measuring means every predetermined period. is predicted and calculated, and the initial temperature y.

By adding the equilibrium temperature

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram showing the hardware configuration of an electronic thermometer in which the present invention is implemented.

In the figure, a temperature sensor 1 converts temperature into an electrical signal, which is converted into a digital signal by an A/D converter 2, and then input into a CPU. The ROM 4 stores programs and the like that advance the operation of the cpU 3. These temperature sensors 1
, the A/D converter 2, the CPU 3, and the ROM 4 constitute a temperature measuring means that measures the actual temperature at a predetermined sampling period. The measured temperature data is stored in RAM5. Further, the CPU 3 has a function of executing the Euler method and the modified Euler method described in the explanation of the principle above, and calculating the equilibrium temperature for each temperature measurement cycle. The measurement results are displayed on the display 6. 7 is a power switch.

Next, the software configuration and operation of the electronic thermometer of the above embodiment will be explained with reference to the flowchart shown in FIG.

When the operation starts, first in step ST (hereinafter referred to as ST) ■, the sampling period DT, time constant T + ,
Set constants such as T z, T z, T4, etc. (Example: DT
:1 second, T, = 160, T, = 17Q, T.

=40, T, =38).

Next, it is determined whether the slope of the actual measured temperature per unit time is above a certain value (e.g. 0.5°C/sec), and if it is above a certain value, the temperature characteristic is at the rising point (see (Sr1). Next, set initial values such as 2=0 and Q=O (Sr3), read and store the measured temperature y0 at the rising point p (Sr4), and then set the variable n to 0.
Next, the actual measured temperature value y0 at the start is deleted from the actual measured temperature value y7 at each sampling time, and the temperature rise value y from the rising point p is calculated (Sr1). Putting the value y7 into equation (16), the increment DZ,
, DQ, , DZ2, DQZ, Z, Q, , Xn are calculated (Sr7). As is clear from FIG. 3, since Xn is a step from point p, the equilibrium temperature, that is, the predicted temperature xn, becomes the initial measured temperature y, +Xn (Sr1). The calculated predicted temperature xn is displayed on the display 6 as a body temperature (Sr9). Subsequently, the variable n is incremented by 5 TIO), and the measured temperature value y is obtained at each sampling time. (STII), and it is determined whether n has reached a predetermined value M, that is, whether a predetermined time has elapsed since the rising point p (ST12), and until the predetermined time elapses, Sr1 Return to ST6~5T at each sampling time.
12 is repeated to continue the prediction calculation.

Figure 4 shows the characteristic curve of the measured temperature value and predicted equilibrium value, where ■ is the measured temperature curve, and ■■■ is the parameter T.
1. This is a predicted temperature curve when T2, T1, and T4 are changed, and the curve (■) is the result of selecting the optimal parameters.

(F) Effects of the Invention In this invention, the temperature change after the rise of the measured temperature curve is taken as a step response, and the Euler method or modified Euler method is applied to the predefined transfer function of the measurement system, and the rising point is used as the reference. Since the equilibrium temperature is predicted and calculated and the body temperature is predicted and calculated based on this equilibrium temperature, highly accurate prediction results can be obtained with simple calculations. In addition, since the calculation is simple, a 4-bit microcomputer can perform sufficient processing without using a highly functional CPU, so it can be realized at low cost.

Furthermore, the predetermined period (sampling period) can be set arbitrarily, and predicted body temperature can be obtained at each sampling time.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram for explaining the software configuration and operation of an electronic thermometer according to an embodiment of the present invention, FIG. 2 is a block diagram showing the hardware configuration of an electronic thermometer in which the present invention is implemented, and FIG. is a diagram showing the time-temperature characteristics to explain the operation of the electronic thermometer, Fig. 4 is a diagram showing an example of the characteristics of the measured temperature value and predicted temperature value of the electronic thermometer, and Fig. 5 is a diagram showing the characteristics of a general thermometer. Figure 6 is a diagram for explaining the specific characteristics and equilibrium characteristics of figure(
b) is the transfer function of the measurement system as (1+'r+s)/H+T
2S) and the block diagrams when equivalent transformation is performed, Figures 8(a) and 8(b) show the transfer function of the measurement system as (1+Tl5)(1+T3S)/(1+
FIG. 12 is a block diagram in the case of TZS) (1+T4S) and a block diagram in the case of performing equivalent transformation. 1: Temperature sensor, 2: A/D converter, 3: cPU
, 6: Display device. Patent applicant Tateishi Electric Co., Ltd. Agent
Patent Attorney Shigeru Nakamura Figure 3 Figure 4 Time Figure 5 T (target) Figure 6 X (S) G (S) Y (S)
Figure 7 ((7) Figure 7 (b) Figure 8 (G) Figure 8 (b)

Claims (1)

[Claims] (1) Temperature measurement means that includes a temperature sensor and measures temperature at predetermined intervals, storage means that stores the obtained temperature data, means that detects a rising point at which the temperature data suddenly rises, and Means for predicting and calculating the equilibrium temperature with the rising point as a reference by capturing the subsequent temperature change as a step response and applying Euler's method and modified Euler's method to a predefined transfer function of the measurement system; An electronic thermometer comprising means for adding the temperature at the rising point to the equilibrium temperature, and display means for displaying the added temperature as body temperature.