JP2003028726A - Electronic clinical thermometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify constitution of a counting system for an electronic clinical thermometer to improve cost performance. SOLUTION: This electronic clinical thermometer is provided with a switching oscillation circuit for connecting switchably a temperature detecting element to a reference resistance to output switchingly respective oscillation frequencies, and constituted to count a frequency ratio signal of the first oscillation frequency to the second oscillation frequency by a counter, based on the first oscillation frequency by the first oscillation circuit by the temperature detecting element, and based on the second oscillation frequency by the second oscillation circuit by the reference circuit, so as to correspond to a temperature value. The thermometer is further provided, in a counter circuit, with a ROM circuit for setting variably a counting time to the counter for determining the oscillation frequency of the second oscillation circuit to regulate the frequency ratio signal of the first oscillation frequency to the second oscillation frequency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The electronic thermometer according to the present invention relates to a configuration of a measuring system capable of improving cost / performance.

[0002]

2. Description of the Related Art Regarding the measuring system of an electronic thermometer,
Various proposals have been made conventionally. As a typical conventional example in which a temperature change of the resistance value of a temperature sensitive element, for example, a thermistor is used as a detection means, there is Japanese Patent Publication No. 2504753 (hereinafter referred to as Document A). As we all know,
The change in the electric resistance value due to the temperature of the thermistor is non-linear, and if this is incorporated into a CR oscillator and the value corresponding to the temperature of the oscillation frequency is measured and the temperature is displayed,
It becomes an extremely complicated system. FIG. 2 shows an outline of the basic configuration system of the electronic thermometer disclosed in FIG. 3 of Document A, which approximates the non-linearity of the change in electric resistance value with temperature of the thermistor with a plurality of linear characteristics. FIG. 3 shows a conventional switching oscillator circuit and counter circuit. 2 and 3, the basic system includes a switching oscillator circuit 100, a frequency ratio measuring circuit 110, a B constant input means 80, a temperature conversion circuit 90, and a display device 200. The switching oscillating circuit 100 includes a resistor Rx of a temperature sensitive element and a reference resistor R selectively connected to the oscillating circuit by a semiconductor switch SW to form a first oscillating circuit including a resistor Rx of the temperature sensitive element and a capacitor C. It is composed of a circuit 101 and a second oscillator circuit 102 composed of a reference resistor R and the capacitor C. The frequency ratio measuring circuit 110 includes the clock oscillation circuit 3
0 is connected in parallel to the matching circuit 60 via the timer circuit 40 and the latch circuit 50, and the matching circuit 60
Is connected to the counter circuit 20 and the latch circuit 70. The first oscillator 101 and the second oscillator 101 are input to the counter circuit 20.
The output of the oscillation circuit 102 is selectively connected by a switch SW, for example, every 0.5 seconds. Temperature conversion circuit 90
Is a B constant correction storage circuit 90 that receives the B constant input means 80.
b, the display device 200 via the temperature data calculation circuit 90d
Connected to. Latch circuit 7 of frequency ratio measuring circuit 110
0 is connected to the temperature data calculation circuit 90d in parallel with the sensitivity storage circuit 90a and the offset storage circuit 90c.

The counter circuit 20 is a switching oscillator circuit 1.
The number of output pulses output from 00 is counted and the specified value No
When it counts, an overflow signal is output. The timer circuit 40 counts and outputs the clock signal. The latch circuit 50 stores and outputs the time information when the counter circuit 20 outputs the overflow signal. Then, immediately after the overflow signal is output, the counter circuit 20 and the timer circuit 40 are reset. That is, in the conventional example, the number of pulses of the frequency ratio signal output from the switching oscillation circuit 100 is constant. The matching circuit 60 is
A match between the time information output from the latch circuit 50 and the time information output from the timer circuit 40 is detected and a match signal is output. The latch circuit 70 stores the count value Nx of the counter circuit 20 when the coincidence signal is output as a frequency ratio signal and outputs it. The B-constant input means 80 is set by the variation of the B constant of the resistance Rx of the thermistor.
Output constant information. The B-constant correction storage circuit 90b outputs the B-constant correction value b based on the B-constant information set by the B-constant input means 80. The sensitivity storage circuit 90a and the offset storage circuit 90c receive the frequency ratio signal Nx output from the frequency ratio measurement circuit 110 as an input, and the frequency ratio signal Nx, which will be described later and corresponds to each layer of the frequency ratio signal Nx, is used as a variable to measure the measured temperature. Sensitivity [Slope] of multiple linear equations approximated by the line
Output a and offset value c.

The above-mentioned linear equation is expressed as follows in consideration of the B constant correction value b. T = ab (Nx / No-1) + c (1) Here, T represents temperature. As can be seen from the above equation, the coefficient
Nx so that a, b, and c are expressed as the coefficients of multiple polygonal lines
There is a need to choose.

[0005]

[Problems to be Solved by the Invention] However, Document A
In addition to the variation in the B constant of the thermistor, the variation in the reference resistance value R also results in the need to trim the resistance value of the reference resistance by trimming with a laser etc., resulting in equipment depreciation and increased man-hours, resulting in cost / performance Could not be improved. The object of the present invention is to eliminate the above-mentioned drawbacks and to improve cost / performance.A measurement of an electronic clinical thermometer capable of measuring the variation of the reference resistance value of the switching oscillation circuit without trimming with a laser or the like. Regarding the improvement of the system configuration.

[0006]

According to a first aspect of the electronic thermometer of the present invention made to solve the problems, the temperature sensing element and the reference resistance are switched and connected, and the oscillation frequency is switched and output is switched. A first oscillating frequency for the second oscillating frequency based on a first oscillating frequency of the oscillating circuit and the first oscillating circuit of the temperature sensitive element and a second oscillating frequency of the second oscillating circuit of the reference resistor; In the electronic clinical thermometer configured by measuring the frequency ratio signal of the above with a counter and making it correspond to the temperature value, the measuring time to the counter is adjusted in order to adjust the frequency ratio signal of the first oscillation frequency to the second oscillation frequency. The counter circuit is provided with a ROM circuit for variably setting.

According to another aspect of the present invention, there is provided an electronic thermometer according to the present invention, wherein the ROM circuit according to claim 2 is a fuse ROM circuit for adjusting a frequency ratio signal between the first oscillation frequency and the second oscillation frequency. It is characterized in that it is arranged in a counter circuit as.

The ROM circuit of claim 3 of the electronic thermometer of the present invention made to solve the problem is the ROM of the electronic thermometer.
The circuit is characterized in that the measurement time of the counter circuit is adjusted by varying the input of ± 1 bit or more.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration system diagram showing a connection between a switching oscillator circuit and a counter circuit of an electronic thermometer according to the present invention. The structure of the dotted line part shown in FIG.
The counter circuit 20 connected to the switching oscillator circuit 100 similar to that of FIG. 2 is shown, and the other overall configuration is the same as that of FIG. Is omitted. The basic system of the present invention comprises a switching oscillator circuit 100 and a frequency ratio measuring circuit 1.
10, a B constant input means 80, a temperature conversion circuit 90, and a display device 200. The switching oscillator circuit 100 is
By selectively connecting the resistance Rx of the temperature sensing element and the reference resistance R to the oscillation circuit by the semiconductor switch SW, the first oscillation circuit 101 composed of the resistance Rx of the temperature sensing element and the capacitor C, and the reference resistance It is composed of a second oscillator circuit 102 composed of R and the capacitor C.

1 and 2, a counter circuit 20 connected to the switching oscillator circuit 100 of the electronic thermometer according to the present invention.
In the embodiment, the fuse circuit 21 is connected, and by electrically opening a part of the fuse circuit, the counting time of the counter circuit 20 can be changed by ± 1 bit in the embodiment to set the value. It has become. Of course, it is not necessary to limit to ± 1 bit, but it is connected to the counter 20.
A wide range of adjustments can be made by using ROM circuits with more AND circuits. When the number of output pulses output from the switching oscillation circuit 100 is counted and a predetermined value No is counted, an overflow signal is output. The timer circuit 40 counts and outputs the clock signal. The latch circuit 50 stores and outputs the time information when the counter circuit 20 outputs the overflow signal. Then, immediately after the overflow signal is output, the counter circuit 20 and the timer circuit 40 are reset. The following operation is the same as that of the conventional example, so that the description thereof will be omitted.
Since the counting time of 0 becomes variable, the No. shown in the equation (1) is variably set, so that it is not necessary to trim the reference resistor R and the coefficients a, b, and c can be easily set. it can.

The operation of the electronic thermometer of the present invention described below is similar to that of the conventional example, in that the temperature is displayed on the display device 200 via the frequency ratio measuring circuit 110 and the temperature converting circuit 90, but the details have already been described and therefore omitted. To do.

[0012]

According to the present invention, in order to adjust the variation in the reference resistance, the conventional trimming of the reference resistance by a laser or the like is unnecessary, and therefore, there is no depreciation of the device or increase in the number of steps, and the cost is reduced. / The performance is greatly improved, so the practical effect is remarkable.

[Brief description of drawings]

FIG. 1 is a basic system of a counter circuit of an electronic thermometer according to the present invention.

FIG. 2 is a system configuration of a conventional electronic thermometer.

FIG. 3 is a configuration system of a switching oscillation circuit and a counter circuit of a conventional electronic thermometer.

[Explanation of symbols]

20 counter circuit 21 fuse circuit 30 clock oscillator 40 timer circuit 50, 70 Latch circuit 60 matching circuit 80 B constant input means 90 Temperature conversion circuit 90a Sensitivity memory circuit 90b B constant correction memory circuit 90c offset memory circuit 90d temperature data operation circuit 100 switching oscillator 101 First Oscillation Circuit 102 Second oscillator circuit 110 Frequency ratio measurement circuit 200 display

Claims (3)

[Claims] 1. A switching oscillating circuit for switching and outputting an oscillating frequency by switching and connecting a temperature sensitive element and a reference resistor, a first oscillating frequency by a first oscillating circuit by the temperature sensitive element, and the reference. In the electronic thermometer, the counter measures the frequency ratio signal of the first oscillation frequency to the second oscillation frequency based on the second oscillation frequency of the second oscillation circuit of the resistor, and makes it correspond to the temperature value. A counter circuit is a ROM circuit for varying and setting a measurement time to a counter that determines the oscillation frequency of the second oscillation circuit in order to adjust the frequency ratio signal of the first oscillation frequency to the second oscillation frequency. An electronic clinical thermometer characterized by being provided in. 2. A ROM circuit of the electronic thermometer is arranged in a counter circuit as a fuse ROM circuit for adjusting a frequency ratio signal of the first oscillation frequency to the second oscillation frequency. The electronic thermometer according to claim 1. 3. The electronic clinical thermometer according to claim 1, wherein the ROM circuit of the electronic clinical thermometer adjusts the measurement time of the counter circuit by varying the input of ± 1 bit or more.