JPS63195533A - temperature measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a temperature measuring device.

[Prior Art] An electronic thermometer heat-sensitive section that shortens the temperature measurement time by providing a heater in the heat-sensitive section of a thermistor element was disclosed in Japanese Patent Application Laid-Open No. 50-104.
It is disclosed in Japanese Patent No. 680.

This electronic thermometer heat sensitive part is characterized in that a heater is installed in the heat sensitive part to reduce the temperature difference between the heat sensitive part and the body temperature that has been heated in advance, and then measures the body temperature [Problems to be Solved by the Invention] ] However, as mentioned above, in the heat-sensitive part of the electronic thermometer, a heater is provided in the heat-sensitive part for preheating the heat-sensitive part, which complicates the manufacturing process and increases the manufacturing cost. There was a problem in that it was difficult to downsize the heat-sensitive section.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a temperature measuring device that can shorten temperature measurement time, is inexpensive, and has a smaller heat-sensitive section.

C. Means for Solving Problems] The present invention provides a temperature measuring device equipped with a heat-sensitive means whose resistance value changes depending on the temperature of an object to be measured, in which a predetermined voltage is applied to the heat-sensitive means to heat the object. It is characterized by comprising a voltage applying means.

[Function] With the above configuration, the resistance value of the voltage applying means changes according to the temperature of the object to be measured! Since the treasured lightning bolt is applied to the shikogin to heat it, the temperature difference between the heat-sensitive means and the object to be measured is reduced, and the temperature measurement time is shortened to measure the temperature of the object to be measured. can do.

[Example] First Example FIG. 1 shows a thermistor element l which is a first example of the present invention.
It is a block diagram of an electronic thermometer using.

This electronic thermometer detects the thermistor element 1 by applying a predetermined voltage to the thermistor element 1 for temperature detection.
The device is characterized in that the temperature difference between the temperature of the human body (the object to be measured) and the temperature of the thermistor element 1 is reduced, and then the body temperature is measured.

In FIG. 1, a temperature detecting thermistor element l housed in a probe container to be brought into contact with the human body, resistors 2 and 3 having a resistance value r, and a resistor 4 having a resistance value R are connected in a bridge shape, and a temperature measuring It constitutes a stone bridge circuit. Power supply terminal of this bridge circuit 1) t, 1
A battery 6 is connected between m via a switch 10, and
An analog-to-digital conversion (hereinafter referred to as A/D conversion) circuit 7 is connected between the output terminals p3 and 94 of this bridge circuit.
connected to the input end of the Here, by turning on the switch IO, the thermistor element ! is connected between the output terminals p3 and 94 of the bridge circuit. A voltage proportional to the detected body temperature is output, and when the bridge circuit is in an equilibrium state, the potential difference between the output terminals Ps and I)4 becomes zero, as is well known.

Further, a series circuit of a resistor 5 having a resistance value rp and a switch 11 for applying a large voltage during self-heating of the thermistor element l is connected in parallel with the resistor 4, and the bridge circuit and the battery 6 are connected during the self-heating of the thermistor element l. A switch 12 for disconnecting the resistor 2 and the terminal p1 is connected between the resistor 2 and the terminal p1.

The above switch 10. If and 12 are both controlled by the control circuit 8, and when the switches IO and 11 are turned on, the output voltage of the battery 6 is applied to the thermistor element l via the parallel resistance of the resistors 4 and 5, thereby causing the thermistor element ! is heated.

On the other hand, switch 11 is turned off, and switches I0 and 1
2 is turned on, the Wheatstone bridge circuit for temperature measurement is configured.

The output of the A/D conversion circuit 7 is input to the non-inverting input terminal of the comparator 13 and the input terminal of the voltage-to-temperature conversion circuit 14. The voltage-to-temperature conversion circuit 14 converts the input terminal into the temperature of the thermistor element l, and outputs the temperature value to the display 15. The display I5 displays the input temperature value when receiving the display command signal from the control circuit 8. On the other hand, the reference voltage generating circuit 9 generates a predetermined digital reference voltage in response to a control signal from the control circuit 8 and outputs it to the inverting input terminal of the comparator I3. The comparator 13 outputs the differential voltage between the input two sets of pressures to the control circuit 8.

The operation of the electronic thermometer shown in FIG. 1 will be described below with reference to the temperature characteristics of the thermistor cord I shown in FIG. 2.

Now, assume that at time t0, the heat-sensitive part of the thermistor element 1 is pressed against the human body, which is the object to be measured, and the thermistor element 1 is pressed against the human body. The predetermined time is τ from time t0. Until a later time t, the control circuit 8 continues to turn on the switches 10 and II, while turning off the switch 12. As a result, a predetermined voltage is applied from the battery 6 to the thermistor element 1 through the parallel resistances of the resistors 4 and 5, and the thermistor element 1 is heated. Hereinafter, this mode will be referred to as self-heating mode.

Next, time 1. Until time t after a predetermined time τ1, the control circuit 8 continues to turn off the switches 10 and 11, while turning on the switch 12. This constitutes a Wheatstone bridge circuit for temperature measurement, and the temperature of the thermistor element I is measured. This mode is called temperature measurement mode. At this time, the control circuit 8 outputs a display command signal to the display 15 to
The temperature value input via the D conversion circuit 7 and the voltage-to-temperature conversion circuit 14 is displayed, and the value is higher than the temperature T0 by a predetermined value with respect to the base Q voltage generation circuit 9. i r
l'P T n, l: t+ rnasu HA regular r
A reference voltage Vr corresponding to a temperature Tp higher than +Vr, Br and W↑pl by a predetermined value is sequentially generated and inputted to the inverting input terminal of the comparator 13, corresponding to each reference voltage. The output voltage of comparator 13 is detected. As a result, the control circuit 8 controls the thermistor element l at time t.
Check that the temperature is between Tpt and Tpt.

Next, from time t, τ shorter than time τ1, later time t3
Up to this point, control circuit 8 continues to turn on switches 10 and 2, while turning off switch 12. As a result, the thermistor element 1 is heated in the same manner as described above and enters the self-heating mode.

Furthermore, from time t3 to τ and later time t4,
The control circuit 8 continues in the above-described temperature measurement mode, and similarly as described above, confirms that the temperature of the thermistor element 1 is above Tp7 and below Tp3, which is higher than Tpt by a predetermined value.

Furthermore, from time t4 to time t, which is shorter than τ, the control circuit 8 continues to operate in the double self-heating mode.

Finally, at time t, the control circuit 8 enters the temperature measurement mode described above, and after confirming that the temperature of the thermistor element l exceeds the temperature Tp3, the temperature of the thermistor element l does not exceed the body temperature to be measured. The equilibrium temperature Ts
Continue this temperature measurement mode until the temperature is reached.

As explained above, by sequentially switching between the self-heating mode and the temperature measurement mode of the thermistor element 1, the thermistor cord 1 is self-heated and the temperature of the thermistor element 1 rapidly approaches the equilibrium temperature T8 of the body temperature. Therefore, the time required for body temperature measurement can be shortened. In addition, as described above, by sequentially shortening the time of the self-heating mode and the temperature measurement mode, the equilibrium temperature Ts, which is the body temperature of the object to be measured, can be increased.
Since the temperature of the thermistor element l can be more precisely controlled in the vicinity, the temperature of the thermistor element l can be prevented from exceeding the equilibrium temperature Ts due to self-heating.

As mentioned above, when the object to be measured is a specific object such as a human body, the equilibrium temperature Ts is within a certain range, so the self-dissipation constant of the thermistor element l is taken into consideration, and the battery
Voltage value, resistance value rPq reference temperature T I)+, T
I) and time τ. Alternatively, τ4 can be set to a predetermined appropriate value.

Second Embodiment FIG. 3 is a block diagram of an electronic thermometer equipped with an oscillator 20 using a CMOS inverter, which is a second embodiment of the present invention.

This electronic thermometer repeatedly performs the self-heating mode and temperature measurement mode of the thermistor element 1 described above, and also oscillates the oscillator 20 by switching between the thermistor element 1 and the resistor 26 having a constant resistance value Rp in the temperature measurement mode. It is characterized by measuring a frequency difference and measuring body temperature based on this oscillation frequency difference.

In FIG. 3, three CMOS inverters 21 to 23 are connected in series in the same direction, and a connection point between the inverters 22 and 23 is connected to a connection point 20a via a capacitor 24 having a capacitance Bct.

This connection point 20g is connected to the input terminal of the inverter 21 via the resistor 25 of resistor v1Rs, and the resistor 2
6 to the common side of the changeover switch 27a.

Further, the connection point 20a is connected to the common side of the changeover switch 27b through the thermistor element 1, and is also connected to the negative electrode of the battery 6 through the changeover switch 29a. The output terminal of the inverter 23 is connected to the a side of the changeover switch 27a and the b side of the changeover switch 27b, and is also connected to the input terminal of the counting circuit 35 via the oscillation output terminal 28a. A connection point between the thermistor element l and the common side of the changeover switch 27b is connected to the positive electrode of the battery 6 via the changeover switch 29b and a resistor 30 having a resistance value rp.

Here, the changeover switches 27a and 27b are connected to a central processing unit (hereinafter referred to as CPU).

) 31 via the control signal input terminal 28b, it is switched to the a side or the b side.

If the control signal that controls the changeover switches 27a and 27b is at H level, the changeover switches 27a and 27bh are switched to the <a side; on the other hand, if the control signal is at L level, the changeover switches 27a and 27b 27b is switched to the b side.

Further, the changeover switches 29a and 29b are connected to the CPU 3.
It is switched on or off in conjunction with the control signal output from 1.

In the oscillator 20 configured as described above, when the changeover switches 29a and 29b are turned off and the changeover switches 27a and 27b are switched to the a side, the inverters 21 to 23, the capacitor 24, and the resistors 25, 26
This is the first oscillation mode that oscillates at 3.
The rectangular wave oscillation frequency rP of 20 is given by the following equation.

fp = 1/(2,2XCtXRP) ...-
...(1) Also, selector switches 27a and 27b
When switched to side a, inverters 21 to 23,
A second oscillation mode occurs in which the capacitor 24, thermistor element l, and resistor 25 oscillate, and the rectangular wave oscillation frequency rth of the oscillator 20 at this time is given by the following equation.

rth = 1/(2,2XCtXRth) ・
=・(2) From the above equations (1) and (2), the following equation is obtained.

Therefore, when the resistance value Rp of the resistor 26 is fixed at a predetermined value, by measuring the oscillation frequencies rp and rth,
The resistance value rtth of the thermistor cord I can be determined, and thereby the temperature of the heat-sensitive portion of the thermistor element I can be measured.

Furthermore, when both switches 29a and 29b are turned on, the voltage of the battery 6 is applied to the thermistor element l via the resistor 30, heating it, and the thermistor element l enters a self-heating mode. In this self-heating mode, the selector switch 27b is turned off in order to prevent the output current of the battery 6 from leaking to other circuits. Furthermore, one end of the thermistor element l on the selector switch 29a side and the resistor 2
An opening/closing switch may be provided to disconnect the connection point 20a from the connection point 20a.

The counting circuit 35 counts the pulses of the rectangular wave oscillation output output from the oscillation output terminal 28a of the oscillator 20 only during the counting time based on the counting time data manually input from the CPU 31, and sends the counted value to the CPU 31. Output.

The CPU 31 includes a reference frequency oscillator 32 that outputs a clock of a predetermined frequency, and a read-only memory (hereinafter referred to as RO) for storing the system program of this electronic thermometer.
It's called M. ) 33, a random access memory (hereinafter referred to as RAM) 34 for storing calculated values such as count values output from the counting circuit 35, and a display device for displaying the measured body temperature value calculated by the CPU 31. 36 are connected. The CPU 31 is operated by a clock manually inputted from the reference frequency oscillator 32, and performs a temperature measurement operation, which will be described in detail later, based on a system program stored in the ROM 33.

The operation of the electronic thermometer shown in FIG. 3 will be described below with reference to the temperature characteristics of the thermistor element violet shown in FIG. 4.

Now, time t. , the heat-sensitive part of the thermistor element l is pressed against the human body, which is the object to be measured, and the temperature T of the thermistor element l is
th is T. Suppose it was. It's time. for a predetermined time Δt
Time 1 after o+. Up to this point, the CPO 31 continues to switch the switches 27a and 27b to the a side and turns on the switches 29a and 29b. As a result, a predetermined voltage is applied from the battery 6 to the thermistor element 1 via the resistor 30, and the thermistor element 1 is heated.

Hereinafter, this mode will be referred to as self-heating mode, as described above.

Next, time 1. , the CPU 31 switches the changeover switches 27a and 27b to the a side, causes the oscillator 20 to oscillate in the first oscillation mode in which the inverters 21 to 23, the capacitor 24, and the resistor 25 and 26 oscillate, and the oscillator 20 outputs an oscillation signal. The oscillation frequency "p" of the oscillator 20 is calculated from the output count value of the counting circuit 35 that counts the rectangular wave pulses.Then, the CPU 31 switches the changeover switches 27a and 27b to the b side, and the inverters 2 to 23
, the oscillator 20 is caused to oscillate in the second oscillation mode in which the capacitor 24, thermistor element l, and resistor 25 oscillate, and the oscillation frequency nh of the oscillator 20 is calculated in the same manner as described above. Further, the CPU 31 calculates the temperature Tth of the heat-sensitive portion of the thermistor cable 1 from the calculated oscillation frequencies rp and rth, and displays the value on the display 36. The temperature Tth of the heat sensitive part of the thermistor element 1 at this time is T1
Hereinafter, the mode for measuring the temperature Tth of the heat-sensitive portion of the thermistor element l described above will be referred to as a temperature measurement mode.

Then, a time t after a predetermined time of 6111 seconds from time t1,
, the CPU 31 repeats the temperature measurement mode described above, and at this time the temperature TLh of the heat sensitive part of the thermistor cord l
'rt,! :do. At this time, the CPU 31 is at a temperature T
A temperature coefficient ΔT expressed by the following equation is calculated from I, T and time Δtit.

ΔT = (T!-T t)/Δt1. ...
(4) From this temperature coefficient ΔT, the CPU 31 determines that the temperature of the heat-sensitive portion of the thermistor element 1 will more quickly reach the equilibrium temperature Ts, which is equal to the body temperature, by the above-mentioned self-heating, and Calculate the duration of the self-heating mode not exceeding Δ[, , . As a result, the CPU 31 moves from time t to the set time Δt1. The above-described self-heating mode is executed until a later time t.

Furthermore, the CPU 31 executes the temperature measurement mode described above at time t and time t4 after a predetermined time Δj44 after that time t, and calculates the temperature Tth of the heat-sensitive part of the thermistor element at each time t3 and t4. Then, as above, (4
) The temperature coefficient ΔT of the equation is calculated, and the next self-heating mode duration Δt41i is calculated.

Similarly, by repeating the self-heating mode and temperature measurement mode performed for an optimized duration, the thermistor element is self-heated to an equilibrium temperature T equal to body temperature.
The temperature difference with s can be gradually reduced.

Figure 5 is a block diagram showing another configuration example 20a of the oscillator 20 of the electronic thermometer shown in Figure 3, and in Figure 5, the same components as in the above-mentioned drawings are given the same reference numerals. ing.

The oscillator 20a in FIG. 5 differs from the oscillator 20 in FIG.
This is because inverters 41 to 44 are used, and below,
The above differences will be explained in detail.

In FIG. 5, the output terminal of the inverter 22 is a CMOS
It is connected to the oscillation output terminal 28a via inverters 41 and 42 and CMOS inverters 43 and 44. The control signal input terminal 28b is connected to the enable terminals of the inverters 41 and 42, and the CMO
It is connected to enable terminals of inverters 43 and 44 via an S inverter 40. In addition, inverters 41 and 4
The connection point between the inverters 43 and 44 is connected to one end of the resistor 26', and the connection point between the inverters 43 and 44 is connected to one end of the thermistor element l.

With the above configuration, when a 14-level signal is input to the control signal input terminal 28b, the inverters 41 and 42 enter the operating state, while the inverter 4
3 and 44 are inactive. This results in the above-mentioned first oscillation mode in which the inverters 21, 22, 41 and 42, the capacitor 24, and the resistor 25, 26 oscillate. Furthermore, when an L level signal is input to the control signal input terminal 28b, inverters 41 and 42 become inactive, while inverters 43 and 44 become active. This results in the above-mentioned second oscillation mode in which the inverters 21, 22, 43 and 44, the capacitor 24, and thermistor element 11 and resistor 25 oscillate.

The electronic thermometer using the oscillator 20a of FIG. 5 has the same effects as the device of the second embodiment described above, and
As mentioned above, the analog changeover switches 27a and 27
Since a CMOS inverter is used instead of b, the device can be made smaller, and since there are no moving parts, it has the unique effect of improving the reliability of the circuit.

Fourth Embodiment FIG. 6 is a block diagram showing another example of the configuration of the oscillator shown in FIG. 5. In FIG. 6, the same parts as in the above-mentioned drawings are given the same reference numerals. This oscillator 20 in FIG.
The difference between a and the oscillator 20b in FIG. 5 is that a three-state CM is used instead of the CMOS inverters 21 and 22.
Using OS inverters 51 to 54, and CMOS
CMOS inverter 5 replaces inverter 40
5 and further uses CMOS inverters 56 and 57, and the above differences will be explained in detail below.

In FIG. 6, one end of the resistor 25 is connected to a connection point 61 at one end of the capacitor 24 via inverters 51 and 52 and inverters 53 and 54, and the control signal input terminal 28b is connected to the inverter 55. It is connected to connection point 62 via. This connection point 62 is connected to each enable terminal of inverters 41, 42, 51, and 52 via an inverter 56, and is connected to each enable terminal of inverters 41, 42, 51, and 52, and
It is connected to each enable terminal of inverters 43, 44, 53 and 54 via. Here, the inverters 41 to 44, 51 to 54, 56 and 57 can be constructed of general-purpose integrated circuits, such as Motorola's 74 HC240 type integrated circuit.

By configuring as described above, the control signal input terminal 2
8b1. - When the H level signal is input, the inverters 41, 42, 51 and 52 become operational, and on the other hand,
Inverters 43, 44, 53, and 54 become inactive, and the above-mentioned first oscillation mode is entered. Furthermore, when an L level signal is input to the control signal input terminal 28b, the inverters 43, 44, 53 and 54 are in the operating state, while the inverters 41, 42, 51 and 52 are in the non-operating state, and the above-mentioned 2 oscillation mode.

The electronic thermometer using the oscillator 20b shown in FIG. 6 has the same effect as the electronic thermometer using the oscillator 20a shown in FIG. Since it can be constructed using a general-purpose integrated circuit, it has the unique effect of being able to reduce the number of components mounted on the device and also making the device smaller.

Other Embodiments In the above embodiments, the thermistor element l is used as the heat-sensitive means of the object to be measured, but the present invention is not limited to this, and other elements whose resistance value changes with temperature changes may be used.

In the above embodiments, an electronic thermometer has been described, but the present invention is not limited to this, and can be widely applied to a temperature measuring device that measures an object to be measured whose temperature is lower than the normal temperature of the heat-sensitive means.

[Effects of the Invention] As described in detail above, according to the present invention, since the voltage applying means for applying a predetermined voltage to the heat sensitive means whose resistance value changes depending on the temperature of the object to be measured to heat it, After reducing the temperature difference between the heat-sensitive means and the object to be measured, the temperature of the object can be measured by shortening the temperature measurement time. Therefore, unlike the conventional example, it is not necessary to provide the heat sensitive means with a heater, so the heat sensitive means can be made smaller and manufactured at low cost.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an electronic thermometer using a thermistor element according to the first embodiment of the present invention, Figure 2 is a diagram showing the temperature characteristics of the thermistor element of Figure 1, and Figure 3 is a diagram showing the temperature characteristics of the thermistor element of the present invention. FIG. 4 is a diagram showing the temperature characteristics of the thermistor element in FIG. 3; FIG. 5 is a diagram showing another first configuration of the oscillator in FIG. 3. Block Diagram Showing an Example FIG. 6 is a block diagram showing another example of the second configuration of the oscillator shown in FIG. 3. l... Thermistor element, 2.3.4.5... Resistance, 6... Battery, 8... Control circuit, 10.11.12... Changeover switch, 14... Voltage-temperature conversion circuit. Patent applicant Ricoh Co., Ltd. Attorney Patent attorney Aoyama Baka 1 person, 2nd ward, Figure 4A

Claims (1)

[Claims] (1) A temperature measuring device equipped with a heat-sensitive means whose resistance value changes depending on the temperature of the object to be measured, characterized by comprising a voltage application means for applying a predetermined voltage to the heat-sensitive means to heat it. Temperature measuring device.