JPH0394131A - Electronic thermometer - Google Patents

Abstract

PURPOSE:To execute the self-diagnosis of a circuit function whenever the thermometer is used by constituting it so that a display testing circuit and a function testing circuit are actuated at the time of operating a switch for measuring a temperature. CONSTITUTION:When a push-button switch which is not shown in the figure, for instructing to start a temperature measurement is operated, a switch circuit 14 is turned on, an oscillation start signal is outputted to an oscillator 1 and a clock oscillator 5, and a function test start signal is outputted to a function testing circuit 15. The circuit 14 outputs a display test signal to a driver 12 and allows an indicator 13 to turn on all the lamps for a prescribed time after the push-button switch is depressed, and an operation check of the indicator 13 is executed. The circuit 15 receives the function test start signal, and a clock signal from the oscillator 5, and resets an FF1 through an OR circuit 16. Accordingly, a switch SW is connected to a reference resistance R side, and the oscillator 1 is oscillated by the resistance R. Since the resistance R is set to a reference temperature value, a function test is executed by confirming whether a temperature display of the indicator 13 is the reference temperature or not.

Description

[Detailed description of the invention] (a) Technical field to which the invention relates The present invention relates to an electronic thermometer K such as an electronic thermometer.

(b) Disadvantages of conventional technology Conventional electronic thermometers immediately enter measurement mode when the power switch is turned on, and have only the normal measurement mode as the b1 operation mode. However, with such a thermometer, if the circuit function is not normal, it may lead to incorrect measurements.Moreover, there is no way to indicate that the displayed value is an incorrect measurement value when making an incorrect measurement. . Therefore, conventional electronic thermometers have a problem of poor reliability in temperature measurement accuracy.

(c) Purpose of the Invention The purpose of the present invention is to provide an electronic thermometer that can self-diagnose circuit functions in a short time each time it is used.

(d) Structure 3 and Effects of the Invention To summarize, the present invention provides: a display test circuit that performs a display test of a display means for displaying temperature; and a function test that performs a function test that causes the display means to display a reference temperature value. a circuit, and a switch circuit that includes a switch that specifies the start of measurement, starts the display test circuit and the function test circuit when the switch is operated, and shifts to the measurement start state after a certain period of time; The present invention is characterized in that when the display test button and the function test are performed, the measurement is started after a certain period of time.

According to this invention, since the circuit function is automatically shut off in a short time when temperature measurement is started, failures in the circuit function can be known in advance before use, improving the reliability of measurement results. It has the advantage of improving

(e) Description of Embodiment FIG. 1 is a block diagram of an electronic thermometer showing an embodiment of the present invention. In the same figure, thermistor (temperature-sensitive resistance) R
x and -@ of the reference resistor R are commonly connected and connected to a power source voltage (not shown), and the other ends of each are connected via a switch SW to a capacitor C whose one end is grounded. The switch SW is a switch that is switched by the output of the flip-flop FFI, and is a switch that is switched by the output of the flip-flop FFI.
When there is a Q output of I, it is switched to the thermistor RX side, and when there is no Q output, it is switched to the reference resistor R side. For example, if the reference resistance R and temperature-sensitive resistance Rx are 37.0°C
It has a resistance value when . The switch circuit 14 includes a push button switch (not shown) that instructs to start measurement, and when this push button is operated, an oscillation start signal is output to the oscillator 1 and the clock oscillator 5, and the first functional test W! r
A function test start signal is output to l5. The switch circuit 14 then outputs a display test (4Ni) to the driver 12 for a certain period of time from when the pushbutton switch is pressed to turn on all the lights of the display 13. The functional test circuit 15 receives the clock signal from the clock oscillator 5, and outputs the output for a certain period of time as a reset signal to the pretub FFI via the OR circuit 16.

The oscillator 1 is an oscillator that oscillates at a frequency that is approximately constant depending on the time constant of the capacitor C, thermistor Rx, or the reference resistor R, and its output is given to the capacitor 2. Kakuunta 2 is a NO counter that can count by a predetermined number Not, and its output is given to latch circuit 3.
The low output is given to delay circuit 4 and latch circuit 7. On the other hand, the output of the clock oscillator 5, which oscillates at a predetermined clock frequency fc, is given to the counter 6. The output of the kakuunta 6 is applied to a latch circuit 7 and a comparator circuit 8.

The clock oscillator 5, the kakunta 6, the latch circuit 7, and the comparison circuit 8 constitute a time measuring means for measuring the time until the kakunta 2 overflows. It is a count value holding circuit that uses the over-7 low output of the 7-digit radial circuit 2 as a strobe signal, and its output is given to the comparator circuit 8. Comparison circuit 8 compares these two types of input signals, and generates an output when both inputs match. The output is given to the delay circuit 9, and further given to the latch circuit 3 as a stroke signal. It will be done.

The output of the delay Wj4 is applied to the clip 7 loop FFI as a set signal, and is also applied to the counters 2 and 6 via the OR circuit 10 as a clear signal. The output of the latch circuit 3 is applied to the decoder 11 and further to the read-only memory ROM. It will be done. Read only memo IJR
OM is a memory in which temperature values corresponding to inputs are stored, and the temperature information output is displayed on a display 13 via a driver 12.

FIG. 2 is a circuit diagram showing an example of the oscillator 1 and its peripheral parts. As shown in the same figure, the capacitor C has a discharge resistor R.
1, an inverter 17, 25 and a MOS transistor 18 are connected. Here, it is assumed that the impercator 25 has a hysteresis characteristic, and the imperctor 17 does not have a hysteresis characteristic. Imperter 25.
The output of 17 is 7 limp 7 through gate circuit 19.20.
It is applied to the set input terminal and reset input terminal of the flop FF2. The Q output of the flip-flop FF2 is applied to the above-mentioned capacitor 2 and the gate of the MOS transistor 18. An oscillation start signal from the switch circuit 14 is applied to the CLI terminal of the flip-flop FF2.

FIG. 3 is a block diagram illustrating the switchway 14. In the same figure, the power supply voltage VDD is introduced to the D input terminal of flip-flop FF3, and the flip-flop FF
A frequency-divided clock signal CLS is applied from a clock oscillator 5 to each CLK terminal of FF3 and FF4. The Q output of flipflop FF3 is the D output of flipflop FF4.
given to the input terminal. The Q output of flip-flop FF4 is given to the CLK input terminal of flip-flop FF5 and the NOR circuit M22, and the Q output is applied to the NOR circuit 21.
given to. The D input of the flip-flop FF5 is given from the Q output of the clip-flop FF5, and the Q output is given to the NOR circuits 21 and 22. Noah circuit 2
The output terminal of the flipflop FF6 is connected to the D input terminal of the flipflop FF6, and a clock signal is applied from the clock oscillator 5 to its CLK input terminal. Fritz flop FF3
, 4.6 are connected to the output of the aforementioned pushbutton switch (not shown). flip flop F
The Q output of F6 is applied to the function test circuit 15 as a function test start signal 4Fi, and the output is applied to the clock oscillator 1 as an oscillation start signal. It will be done. Corresponding to this board assembly start signal and the oscillation start signal to the oscillator 1, the Q output is "0"(low),'! The oscillation start signal to the clock oscillator 5 corresponds to the output of "1" (high). Treasure, Noah Road 2
The output of 2 is applied to the driver 12 as a display test signal.

This display test signal corresponds to "1" of the NOR circuit 22 output.

FIG. 4 is a block diagram showing the IA function test circuit 15. In the same figure, Kakunta 24Vi clock oscillator 5
Once the clock signal is input, a function test start signal is received via the inverter 23, and the signal is counted for a certain period of time. Then, the count amplifier signal is sent to the Kakunta 1 of Kakunta 24.
The up output is output to the S input terminal of the b flip 7 flip FF7. The output of the ij7 flip-flop FF7 is also applied to the R input terminal of the input/< 23, and the output of the 7 flip-flop FF7 is applied to the R input terminal of the 7 flip-flop FFI via the OR circuit 16 as described above.

In addition, Fritub FFI,? is a 7-lip flop with reset priority.

Based on the above considerations, the temperature sensitive resistor that constitutes the output U is the thermistor Rx, and the comparison means are the kakuntas 2 and 6, the launch circuit 7, the clock oscillator 5, the delay ports 4 and 9, and the comparison circuit. The display means corresponds to the driver 12 and the display 13, and the display test value corresponds to the display test value generator such as the NOR circuit 22 of the switch circuit 14, respectively.

Next, the measurement dr f'+- of this electronic hygrometer will be explained. FIG. 5 is a waveform diagram showing a capacitor-1/-C IZ) terminal voltage ratio waveform. Assuming that the 4-switch SW is on the side of the reference resistor R, the capacitor C is charged via the reference resistor R, and its terminal voltage gradually increases. When the terminal voltage reaches the on-voltage v2 of the inverter 25, the flip-flop FF2 is set, the MOS transistor 18 is turned on, and the b1 capacitor C is discharged through the resistor R1. Pancreatic voltage drops and invert 25
When the off-voltage ■l is reached, the flipflop FF2 is reset and charged again. The charging direction 'rC is expressed by the following equation. Here, if R 1 <1<, Rx, the discharge time can be ignored. Therefore, the oscillation frequency fo of the oscillator is expressed as follows:
Toku as 1-ln-LnieL. ) E-V. It is expressed as The clock pulses 2 and 6 are cleared simultaneously to count the output pulses of the oscillator 1 and the clock oscillator 5, respectively. When the count value of the kakunta 2 reaches a predetermined value &No, the calculated value of the kakunta 6 is held in the launch circuit 7 by its overflow output. By the way, Kakunta 2
Since the time until overflow is No/fo, if the clock frequency loss of the clock oscillator 5 is fc (for example, 33 KHz), the calculated value of the kakuntator 6 held in the latch concave path 7 is expressed as the following equation. be able to. Next, the overflow output of the kakunta 2 is delayed by a minute time by the delay circuit 4, and then the OR circuit 10
, clears Kakunta 2.6, and sets flip-flop FFI. flipflop FF
By inverting I, the switch SW is switched from the reference resistor R side to the thermistor Rx side. Thermistor Rx
is connected, the oscillation frequency of the oscillator l is given by the equation (
2) can be obtained by converting R into Rx (when connected to Pumister Rx). Kakunta 2 has an oscillation frequency of 11k from now on.
Start counting the output pulses of oscillator 1 of fx. Meanwhile, the kakunta 6 counts the output pulses of the clock oscillator 5 again. Here, let the clock frequency be fc. Kakunta 6
When the count reaches the count value shown in equation (3), the comparison lgI circuit 8 detects a coincidence between the two, and the count value of the kakunta 2 at that point is temporarily held by the kucchi circuit 3. If the count value held by the latch circle path 3 is Nx, the count value (/cNx/fx) counted by the kakunta 6 within the time (Nx/fx) that the kakunta 2 counts at Nx t will be Stored measurement value fcNo/fo
(The value of equation (3)) is disturbing. Therefore, the following equation stands out.

Assuming that the clock frequency does not change while switching the reference resistor R and thermistor Rx, fc and fc are equal, so by transforming equation (4) and substituting equation +21 and (2), we get the following equation: Stand up.

By the way, the resistance value of the thermistor Rx can be expressed by the following equation.

Similarity Ro: Resistance at absolute zero To B: Polnmann's constant T: Absolute temperature The switch SW is a semiconductor switch, but the reference resistance R,! :The resistance value of Thermist RX is amazing! If they are equal, the on-resistance of the switch, off-voltage vt1 on-voltage VmO
Since the values are considered to be equal, it can be set as k1. Using this and substituting equation (6) into (2), if Nyd>i is determined, the temperature can be found since everything else is constant. Ride-on V% shown in Figure 1
:The conversion code written in formula (7) is stored in the ROM, and the Nx data held in the receipt and latch circuit 3 is read-only memorized through the decoder 11! It is given to JROM and temperature information is output one after another.

The temperature information is displayed on the display 13 via the driver 12.

Next, the same circuit function test operation that can be performed by pressing the button on this electronic thermometer will be explained.

FIG. 6.7 is a timing chart showing the operations of the switch circuit 14 and the function test circuit 15, respectively. When the pushbutton switch of the switch circuit 14 is pressed, the flip-flop FFs 3, 4.6 are reset at the rising timing of the input. Immediately after the reset, the function test start value button, the oscillation start signal of the oscillator 1, and the oscillation start signal of the clock oscillator 5 are output from the output of the flip-flop FF6. At this time, the NOR circuit 22 outputs a display test signal. That is, by operating this push button, the power-on state is entered. As shown in FIG. 6, the time during which this display test signal is output is the ON time T1 of the pushbutton switch and the time T1 provided to prevent chuckling. It is the sum of By the way, time T! pa2l0/
Since it is about fc seconds, it can be said that 'rt'>”rs.

Therefore, the display test signal is output approximately while the pushbutton switch is being pressed. When this display test signal is given to the driver 12, all the lights of the display device 13 are turned on. Thereby, the operator can check the normal operation of the display 13 by visually checking whether all the lights on the display 13 are lit. After 11 hours have elapsed since the pushbutton switch was turned off, at the falling edge b timing of the clock signal 9CLS, the flip-flop 7
The lobe FFs 4 and 5 are set, the output of the NOR circuit 22 is inverted, and the display test signal is no longer output.

On the other hand, while this display test signal is being output, the function test circuit 15 receives the function test start signal and the clock signal from the clock oscillator 5 via the inverter 23, and the counter 24 starts counting. At the same time,
A reset signal is given to flip 7 lop FF7,
The page output of clip 7 lop FF7 becomes "1". This page output is sent to the flip 7 lob FFI via the OR circuit 16.
, and the flip-flop FFI is reset. Therefore, the switch SW is a temperature sensitive resistor R
1 connected to the reference resistor R side without switching to the x side
Becomes a box. Therefore, the oscillator 1 is forced to oscillate with the reference resistance R. Then, as mentioned above, the reference resistance l or 37
．． The feeling you had at O'C? ! Since the resistance value is set to the resistance value of the III resistor Rx, 37.0° C. is displayed as the reference temperature value on the display 13 for a certain period of time until the kakunta 24 goes up.

That is, the operator can check the circuit function by checking with the naked eye whether 37.0° C. is displayed on the display 13. This test is performed even when the pushbutton switch is pressed while the display test signal is being output, but since all the lights on the display 13 are lit during that TI time, it is actually 37 seconds.
, Display O℃? You can move lIkm only after pressing the pushokun switch.

Next, when the kakuunta 24 steps up, the kakunt-up output is applied to the 7-rip, 7-lop FF7, and the 7-rip, 7-lop FF7 is set.

Therefore, the routine moves on to the aforementioned normal measurement operation in which the reset signal to flip-flop FF1 is released.

After the measurement is completed, when the pushbutton switch is pressed, the 7-rig flops FF3 and FF4 are reset at the rising timing of the input. Then, after the time Ta set for chattering prevention has elapsed since the end of pressing the pushbutton switch, the 7-rip 7-lob FF4 is set at the fall timing b of the clock signal CLS, and the flip 7-lob FF5 is set. will be reset. Therefore, grip 7
The Q output of FF6 is set to ``1'', and the output of FF6 is set to ``0''.
”, and the situation suddenly became worse. That is, the oscillation of the oscillator 1 button and the clock oscillator 5 is stopped due to the inversion of the output of the 7-rip FF 6.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an electronic thermometer showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing the periphery of the oscillator 1 of the electronic thermometer, and Fig. 4/3 is a switch concave path of the electronic thermometer. 14 circuit diagram, tJ; Figure 4 is the functional test circuit 15 of the same electronic thermometer.
5 is a waveform diagram showing the terminal voltage waveform of capacitor C of the electronic thermometer, and FIG.
This is a timing chart showing the delivery of the product. 1... Oscillator, 13... Display device, 14
...Switch circuit, 15...Function test one way,
R...Reference resistance, Rx...Temperature-sensitive resistance. Departer: Tateishi Im Board Co., Ltd.

Claims (1)

[Claims] (1) an oscillator configured such that the resistance constituting the time constant number can be switched between a reference resistance and a temperature-sensitive resistance; a comparison means for switching the two types of resistance of the oscillator and comparing the respective oscillation frequencies; a display means for displaying a temperature value based on the output of the comparison means; a display test circuit for performing a display test on the display means; a function test circuit for performing a function test for displaying a reference temperature value on the display means; and a switch circuit that starts the display test circuit and the function test circuit when the switch is operated, and shifts to a measurement start state after each test is completed, and when the switch is operated, the display test circuit and the function test circuit are activated. , an electronic thermometer that performs the display test and the function test and starts measurement after a certain period of time.