JPH0217423A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To prevent the occurrence of errors in replacement of temperature sensitive elements for detection by providing the temperature sensitive elements which measure temperature and the installation temperature of a device, and providing a nonvolatile ROM in which the data of the resistance values with respect to the temperature of the temperature sensitive element are stored. CONSTITUTION:A first temperature sensitive element 12 measures the temperature of a place where a measuring device is used. A second temperature sensitive element 15 measures the temperature of, e.g. human body. Standard value data which are measured in the constant temperature oven in the element 12 and the operation value data which are obtained when the value of a current flowing through the element 12 is changed for self-heating are stored in a nonvolatile ROM 22 beforehand. The data can be rewritten by sending control signals into the ROM 22. An operating means 24 computes the resistance values of the temperature sensitive elements 12 and 15, and the results are stored in the ROM 22. A comparing means 25 compares the measured value data from the means 24 with the standard value data of the ROM 22. Correction is performed by using a correcting value obtained from the standard value data and the operational value data, and the result is displayed on a display device 23. Even if there are slight dispersions in the shapes and the resistance values of the temperature sensitive elements for measurements, approximately accurate measurement and display can be performed by replacement of probes.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for measuring temperature, and particularly to a device for measuring internal temperature of a human body.

<Prior Art> As part of the treatment of humans and animals, it may be necessary to measure the internal temperature of the body, such as the rectum or bladder.

As shown in FIG. 5, the conventional device connects a thermistor and a resistor 3 in series across a constant current source 1, and converts the analog voltage between the thermistor 2 and the resistor 3 into an analog-to-digital conversion diagram M (AD conversion circuit). )4 into a digital signal,
This signal is processed by a microcomputer (CPU) 5 and the temperature detected by the thermistor 2 is displayed on a display device 6.

In this device, since the thermistor 2 is configured in the shape of a probe, the probe is often damaged during use, requiring replacement of the probe.

<Problems to be Solved by the Invention> Generally, a thermistor has a resistance value and a thermistor constant determined by the material or purpose of use. When replacing the above-mentioned probe, it is necessary to keep the error with respect to the previously used thermistor to be extremely small, for example, the resistance value of the thermistor must be kept within ±0.01 kQ, and the thermistor constant must be kept within ±10°. This is to ensure consistency with previous measurement data, and as a general rule, it is undesirable for errors to occur due to probe replacement. This makes manufacturing the thermistor probe extremely difficult and has the disadvantage of being expensive.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a temperature measuring device in which almost no error occurs even if the temperature sensing element to be detected is replaced.

Means for Solving the Problems> The present invention comprises a first temperature sensing element that measures temperature, a second temperature sensing element that measures the installed temperature of the device, and a common constant current source that supplies current to these elements. , an AD conversion circuit that converts the voltage across each temperature sensing element into a digital signal, and a nonvolatile ROM that stores data on resistance values of the temperature sensing elements with respect to temperature;
arithmetic means for calculating the resistance value of the temperature sensing element from the digital signal and storing the data in a nonvolatile FLOM;
It consists of a comparing means that compares and corrects the data stored in the OM and the measured data of the calculation means, and a display device that displays the corrected data.

Function> The first temperature sensing element measures the temperature at the location where the measuring device is used. The second temperature sensing element measures, for example, the internal temperature of a human body. The non-volatile generation ROM contains in advance the standard value data measured using a constant temperature bath for the first temperature sensing element and the operating value data when the first temperature sensing element generates self-heating by changing the current value of the current flowing through the first temperature sensing element. Stored. These data are volatile ROM
Rewriting is possible by sending a control signal to.

The output of the 2r6 temperature element is converted into a digital signal by an AD conversion circuit and inputted to the calculation means.

The calculation means calculates the resistance value of the temperature sensing element and stores it in the non-volatile ROM.
Store in. The comparison means compares the measured value data of the calculation means with the standard value data stored in the non-volatile FtOM,
The corrected data is corrected using the correction value obtained from the standard value data and the operating value data, and the corrected data is displayed on the display device.

The correction value gives the net temperature coefficient of the temperature sensing element, but when measuring a special place such as inside the body, a correction value based on experience is added.

<Example> Embodiments of the device of the present invention will be described with reference to the drawings.

In FIG. 2, a first temperature sensing element, for example a thermistor 12, is connected to both ends of the constant current source 10 via an on/off switch 11.
A series circuit of resistor 13 is connected, and a current limiting resistor 1
4. A second temperature sensing element, for example a series circuit of a thermistor 15 and a resistor 16, is connected. The first thermistor 12 is arranged inside the measuring device, and the second thermistor 16
is provided on a probe and inserted into the body, for example into the rectum or bladder. The current limiting resistor 14 is provided with an open/close switch that short-circuits both ends and is normally closed, and the relay 18 opens and closes this switch.

Both ends of the first thermistor 12 are connected to a microcomputer (hereinafter referred to as CPU) 20 via a first analog-to-digital conversion circuit 19. Also, the second
Both ends of the thermistor 15 are connected to the CPU 20 via a second analog-to-digital conversion circuit 21. Analog-to-digital conversion circuits 19.21 convert analog signals into digital signals.

The CPU 20 includes a nonvolatile ROM, such as EEP RO.
M (Electrically Erasable
and Program-mable Read 0n
ly Memory) 22 is attached.

This EEPROM 22 is a memory element in which information can be freely written and erased electrically.

Further, a relay 18 and a display device 23 are connected to the CPU 20.

In the above-mentioned circuit, the temperature resistance characteristics of the thermistor are generally measured at the final stage of the manufacturing process and stored in the data device of the computer.

If such data is not available, the thermistor installed in the measuring device is subjected to standard value measurements in a thermostatic oven before being incorporated into the circuit. That is, a constant current is applied to the thermistor, and the temperature of the thermostatic chamber is set to T 1 as shown in FIG. 3, for example.
+ T 2yTa = ('C), the reference resistance value of the thermistor, Rlt rt2. Obtain R3 (k dishes). These values are read into the EEPROM by a predetermined device such as a data device before or after being incorporated into the circuit and become standard values.

Next, in the circuit shown in FIG. 2, when the switch 11 is closed, a current, for example, 1 mA, determined by the circuit constants flows through each thermistor 12, 15. At this current value, self-heating is small. At this time, the CPU 20 is also started up by a circuit not shown. When the CPU 20 starts up, the thermistor 12.1 is output from the signal input from the AD conversion circuit 19.21.
The initial resistance value R10e R20+ of 5 is calculated by the CPU 20 and stored in the EEFROM 22.

It has a CPU2Of timer, which activates the relay and opens the switch 17 when a certain period of time has elapsed since the start-up, and the capacity of the constant current source is changed to about five times that of normal operation. When the switch 17 opens, tenthly, an overcurrent flows through the three-temperature element to the extent that it will not be damaged, and the resistance value of the thermistor decreases as the temperature rises.The coefficient of the characteristic curve is determined from the initial resistance value and this value, and this data is stored in the EEPROM. is accumulated in

This operation is continued for a predetermined time as shown in FIG.
During this time, Thaumister generates heat and increases its own temperature,
Although the thermistor constant, heat dissipation constant, element form, etc. differ, it generally provides a resistance value against temperature changes.

On the other hand, the CPU 20 calculates the change in resistance value due to self-heating of the thermistor 12, and calculates the change in resistance value at each temperature, for example, T i, T 2
Resistance value at t T 3 R1ot R20t R30
is stored in the EEPROM 22. The resistance value due to heat generation is
This value includes the thermistor constant and heat dissipation constant, and is the operating value. In this case, the data from the thermistor 15 is not considered because it hardly changes.

Differences in operating values from standard values stored in the EEFROM 22, for example temperatures 'r,'r2. The resistance value difference RI R10+R3R30 at 'r3 becomes a correction value when the measuring device is used. Standard value, operating value,
The correction value can be recognized by the CPU 20 as a function.

Next, a case will be described in which the probe for internal temperature measurement is replaced. The thermistor used in the probe is
There are some differences in the shape effect, resistance value, thermistor constant, etc. of the thermistor during the manufacturing of the measuring device. In addition, the current flowing through the thermistor of the probe inserted into the body is
The current is extremely small at around 0.3mA. Therefore, almost no self-heating occurs.

When the probe is inserted into the body, the thermistor is heated to the same temperature as body temperature. When thermistor 15 changes to body temperature,
The amount of change is AD converted, the resistance of the thermistor 15 is calculated by the calculating means 24 of the CPU 20, and a measured value is obtained. The measured value is sent to the comparison means 25 of the CPU 20, and the EEP
It is compared with the standard value stored in the ROM 22, a correction value is added, and the error with respect to the standard value is corrected. The corrected body temperature is displayed on the display device.

Effect> The measuring device of the present invention obtains a standard value for the resistance value of the thermistor with respect to temperature and stores it in a non-volatile ROM, and also obtains an operating value due to temperature change due to self-heating and stores it in the non-volatile ROM. Since a correction value is calculated by comparing it with a standard value and the body temperature measurement value is corrected using this correction value, there may be slight variations in the shape, resistance value, thermistor constant, etc. of the measurement thermistor due to replacement of probes, etc. You can also get a very accurate measurement display.

In addition, since a non-volatile ROM'f is used to store correction value data, it does not disappear when the power is turned off, and can be reused by simply setting -degrees. Measurement errors are taken into consideration when using the measuring device. It has the advantage that you don't have to.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of the device of the present invention, Figure 2 is a configuration diagram showing an embodiment of the device of the invention, Figure 3 is a characteristic diagram of the resistance value versus temperature of the thermistor, and Figure 4 is a diagram of the initial current of the device of the invention. The explanatory diagram, FIG. 5, is a schematic diagram of a conventional device. In the figure, 10 is a power supply, 12.13 is a thermistor, 19.2
1 is an AD conversion circuit, 20 is a CPU, 22 is a non-volatile RO
M, 23 is a display device, 24 is a calculation means, and 25 is a comparison means. Figure 2 Figure 2 Figure 2

Claims (1)

[Claims] (1) A first temperature sensing element that measures temperature, a second temperature sensing element that measures the installed temperature of the device, a common constant current source that supplies current to these, and a voltage across each of the temperature sensing elements. An AD conversion circuit that converts into a digital signal, a non-volatile ROM that stores data on the resistance value of the temperature-sensitive element with respect to temperature, and a non-volatile ROM that calculates the resistance value of the temperature-sensitive element from the digital signal and stores the data in the non-volatile ROM. A temperature measuring device comprising: a calculation means; a comparison means for comparing and correcting data stored in the ROM with data measured by the calculation means; and a display device for displaying the corrected data.