JPH0619295B2 - Temperature measuring instrument - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermometer and a temperature measuring device for observing and maintaining a device, and in particular, a function for confirming a previous temperature measurement result prior to a temperature measurement operation. The present invention relates to an electronic temperature measuring instrument equipped with.

[Conventional technology]

This kind of electronic measuring instrument has been adopted in many fields in recent years, and in particular, it is rapidly becoming popular for household use in place of the conventional mercury thermometer because of its simple use.

However, since it does not have a function to check the previous temperature measurement result prior to the temperature measurement operation like the mercury thermometer, it is necessary to make a note of the previous temperature measurement value for each temperature measurement. There was complexity.

In order to solve such a problem, an electronic temperature measuring device has been proposed which has a memory function and holds the temperature measurement result even after the power is turned off so that the temperature measurement result can be read and displayed as needed. : Electronics Digest, Inc., December 10, 1975, "CMOS IC Handbook", pages 287 to 293).

[Problems to be solved by the invention]

In the above conventional technology, a dedicated memory switch for reading the temperature measurement result from the memory unit is provided in addition to the switch for starting the temperature measurement, which complicates the circuit configuration and reduces the entire device. Since the size is increased and the two switches have to be operated separately, the operation is complicated and erroneous, and it is not suitable for home use mainly by women and girls.

[Means for solving problems]

The present invention has been made in view of the above circumstances,
Temperature measurement is started with the operation of the switch, and the current temperature measurement value obtained from the temperature measurement unit is held in the first storage unit, and
Before the temperature measurement is started, the previous temperature measurement value obtained by the previous measurement stored in the first storage unit is written in the second storage unit, and the operation duration of the switch is determined to determine the length of the operation duration. In accordance with the above, it is possible to selectively perform the display corresponding to the current temperature measurement value held in the first storage and the display corresponding to the previous temperature measurement value held in the second storage unit. The present invention realizes the simplification of the circuit configuration and the miniaturization of the entire device, simplifies the operation, and facilitates the handling.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a temperature measuring device according to the present invention, in which 1 is a switch, 2 is an oscillator, 3 and 4 are counters, 5 and 6 are RS type latch circuits, and 7 and 8 are Counter, 9 control unit, 10 temperature measuring unit, 11 and 12 storage unit, 13 multiplexer, 14 display decoder, 15
Is a display, 16 is an RS type latch circuit, 17 and 18 are falling edge detection units, 19 and 20 are NAND gates, and 21 to 25.
Is an inverter.

In the figure, the oscillator 2, the counters 3, 4, 7, and 8, the latch circuits 5, 6, and 16, the control unit 9, the temperature measurement unit 10, the display decoder 14, and the falling edge detection units 17 and 18 are reset respectively. When the signal supplied to the terminal R is at a high level (hereinafter referred to as "H"), it is in the reset state.

The switch 1 is a normally open switch that can be operated from the outside, such as a push button switch, a slide switch, or a switch that operates a reed switch provided in a main body case (not shown) from the outside with a magnet or the like. When the switch 1 is not operated (that is, when it is not closed), the counter 4 and the latch circuit 6 are reset because their reset inputs are "H", and one of the NAND gates 19 is reset. Input is “H”.

The oscillator 2 is, for example, a CR oscillator or a crystal oscillator, and generates the reference clock MCK. The reference clock MCK is divided into a predetermined frequency by the counter 3 and supplied to the counters 4, 8 and the display decoder 14. The oscillator 2 and the counter 3 are switched between the operating state and the non-operating state by the MCK.N signal obtained by inverting the output of the NAND gate 19 by the inverter 21.

The counter 4 and the latch circuit 5 constitute a determination unit for determining that the switch 1 has been operated. In this determination unit, the counter 5 counts the clock from the counter 3 when the switch 1 is operated and the reset is released. When the counter 4 counts the first n, its Qn output is inverted from a low level (hereinafter referred to as “L”) to “H”, and thereafter, every time the counter 4 counts n, the Qn output is inverted. . The counter 4 continues to count, and when the Qn output is inverted k times, the Q output is inverted from "L" to "H". That is, the counter 4 further divides the clock from the counter 3, but the division ratio for the Q output is set to k times the division ratio for the Qn output. In the following description, k = 16.

On the other hand, the latch circuit 5 is
Set on the rising edge of Qn output and its output is “H”
To "L".

The counter 4 and the latch circuit 5 are in the reset state when the switch 1 is in the open state, and the reset is released when the switch 1 is in the closed state. Therefore, the latch circuit 5 is reset every time the switch 1 is operated to be in the closed state. The output is inverted from “H” to “L”. Therefore, this output indicates that the switch 1 is operated by inverting it from "H" to "L".

The latch circuit 6 is in the reset state when the output of the latch circuit 5 is "H", in the reset release state when the output is "L", and is set at the rising edge of the Q output of the counter 4 after the reset release. When the latch circuit 6 is set, its Q output is inverted from "L" to "H". However, even if the switch 1 is operated, if the operation duration is shorter than the 16n counting period of the counter 4, Counter 4
Is reset before its Q output is inverted from "L" to "H", so the counter 6 is not set. On the other hand, when the operation duration of the switch 1 is longer than the 16n counting period of the counter 4, the latch circuit 6 is set. Therefore, the latch circuit 6 has a function as a determination circuit for determining whether the operation duration of the switch 1 is longer or shorter than the 16n count period of the counter 4. The Q output of the latch circuit 6 is used as an SA signal for switching control of the multiplexer 13.

The counter 7 is a 1-bit binary counter, which counts one at the rising edge of the output of the latch circuit 5,
Each time it counts, its Q output is inverted. The Q output of the counter 7 is inverted by the inverter 22, and as a GRST signal, the counter 8, the control unit 9, the temperature measuring unit 10, the display decoder 1
4, the latch circuit 16 and the falling edge detector 17 are supplied to the reset terminals R of the respective latch gates 16 and the NAND gate 19
Also, the NAND gate 20 is inverted by the inverter 23 and supplied.

The counter 8 further divides the clock from the counter 3. The Ql output having the predetermined frequency division ratio is supplied to the control unit 20 to control the temperature measurement timing in the temperature measurement unit 10. Ql output 2
The output of Qm having a frequency division ratio of twice is supplied to the latch circuit 16 as a set input. The latch circuit 16 is set at the first rising edge of the Qm output of the counter 8 after releasing the reset,
Its output is inverted from “H” to “L”. The falling edge of this output is detected by the falling edge detector 17, and a MAX.R signal representing the falling edge is formed. This MAX. The R signal is composed of a D-type flip-flop and resets the storage unit 11 to erase the previously measured temperature value held so far. The output of the latch circuit 16 is also supplied to the NAND gate 20.

When the temperature measuring unit 10 is released from the reset, the temperature measuring unit 10
Temperature measurement (that is, temperature measurement) is performed once for each cycle of Ql output. Each temperature measurement is completed immediately before the rising edge of the Ql output of the counter 8. Then, in synchronization with the rising edge of this Ql force, the temperature measurement value obtained at that time (hereinafter referred to as the current temperature measurement value) is compared with the temperature measurement value stored in the storage unit 11, and the current temperature measurement value When is large, a MAX.phi. Signal is generated, and the current temperature measurement value is written in place of the temperature measurement value held so far. Therefore, the temperature measuring unit 1 is stored in the storage unit 11.
Among the temperature measurement values obtained so far after the reset release of 0, the maximum value is held.

In the storage unit 12, the temperature measurement value held in the storage unit 11 is written by the MEM / φ signal of “L” obtained by inverting the Q output of the falling edge detection unit 18 by the inverter 25. At the reset terminal R of the falling edge detector 18,
The MCK · N signal obtained by inverting the output of the NAND gate 19 by the inverter 21 is supplied. After the reset is released, the falling edge detector 18 detects the GR from the inverter 22.
The falling edge of the ST signal is detected, and the inverter 25 generates the MEM.phi. Signal of "L" representing this falling edge.

The multiplexer 13 is controlled by the SA signal from the latch circuit 6, selects the temperature measurement value from one of the storage units 11 and 12 and sends it to the display decoder 14.

Although not shown, the multiplexer 13 is provided with a measurement range outside detection means, and when the selected temperature measurement value is outside the predetermined measurement range, the temperature is measured by the display unit 15 to display that fact. The display decoder 14 is supplied with data representing fixed numerical values, symbols, patterns, etc., instead of the values.

Here, the predetermined measurement range is 32.0 ° C to 42.0 ° C.
When the previous temperature measurement value selected from the storage unit 12 by the multiplexer 13 is displayed, when it is less than 32.0 ° C, the above-mentioned measuring range detection means displays "32.0 ° C", and when it exceeds 42.0 ° C, " 42.0 ° C ”is displayed. When displaying the current measured temperature value from the storage unit 11 selected by the multiplexer 13, this is 3
When it is less than 2.0 ℃, it is displayed as "LO ℃" and 42.0 ℃
When it exceeds, "HI ° C" is displayed. As described above, in order to make the display contents of the previous temperature measurement value and the current temperature measurement value outside the predetermined measurement range different, the above-mentioned measurement range detection means is also controlled by the SA signal.

The display decoder 14 and the display 15 constitute a display section. At the time of resetting, the display unit 14 does not send any signal to the display unit 15, so that the display unit 15 displays a blank (that is, nothing is displayed). When the GRST signal becomes “L” and the display decoder 14 is released from reset, the output of the multiplexer 13 is decoded as long as the DisPR signal obtained by inverting the output of the NAND gate 20 by the inverter 24 is “L”, Although the above display is performed on the display unit 15, when the DisPR signal becomes “H”, the display decoder 14 is preset to prohibit the output of the multiplexer 13 and the display unit 11 is lit to turn on all the segments. Supply a signal.

Next, the operation of this embodiment will be described with reference to the timing chart of FIG. 2 when the switch 1 is operated longer than the 16n counting period of the counter 4.

The previous temperature measurement value N _X ′ is held in the storage unit 11 even in the non-use state. When a power source (not shown) is turned on, the display 11 is activated and the counter 7 is reset and released, but the Q output of the counter 7 is "L" and the GRST signal is "H". The display decoder 14 is in the reset state and the display 15 displays a blank. Further, the counter 8, the control unit 9, the temperature measuring unit 10, the latch circuit 16, and the falling edge detection unit 17 are also in the reset state. Further, since the switch 1 is in the open state, the counter 4 and the latch circuit 5 are
And have been reset. Furthermore, Nand Gate 1
Since one input on the switch 1 side of 9 is “H” and the other input which is the GRST signal is also “H”, the MCK • ON signal is “H”, and therefore the oscillator 2, the counter 3 and the falling edge. The edge detector 18 is also in the reset state. Furthermore, since the GRST signal is "H" and the output of the latch circuit 16 is "H", the output of the NAND gate 20 is "H".
Therefore, the DisPR signal is “L”.

In such a state, when the switch 3 is closed, the reset of the counter 4 and the latch circuit 5 is released, and the input of the NAND gate 19 on the switch 1 side is inverted from "H" to "L". Becomes "L", and the oscillator 2, the counter 3, and the falling edge detector 18 are released from reset. Therefore, the oscillator 2 has the reference clock M
CK is generated, and the counter 3 divides the frequency.

The counter 4 counts the clock from the counter 3, but when the count is n, its Qn output is inverted from "L" to "H", and the latch circuit 5 is set at the rising edge of this Qn output. Therefore, the output of the latch circuit 5 is inverted from "H" to "L", the latch circuit 6 is released from reset, and at the falling edge of this output, the counter 7 counts by 1 and its Q output is "1". GR from "L" to "H"
The ST signal is inverted from "H" to "L".

With this inversion of the GRST signal, the counter 8, the control unit 9, the temperature measuring unit 10, the display decoder 14, the latch circuit 1
6 and the fall detection unit 17 are released from reset. Further, the falling edge of the GRST signal is detected by the falling edge detection unit 18, and the ME of "L" representing this falling edge is detected.
The M · φ signal is supplied to the storage unit 12. As a result, the previous temperature measurement value N _X ′ held in the storage unit 11 is stored in the storage unit 12
Written in.

On the other hand, the output of the latch circuit 16 is kept at "H",
Since the T signal becomes "L", the DisPR signal becomes "H", the display decoder 14 is preset, and all the segments of the display 15 are turned on. At this time, since the latch circuit 6 has been released from reset but not set, its Q output, therefore, the SA signal is "L", and the multiplexer 13 causes the temperature measurement value from the storage unit 11 (in this case, The previous temperature measurement value) is selected. However, the display decoder 14
Does not accept the output of the multiplexer 13 since it has been preset.

The switch 1 is continuously closed and the counter 4 is set to n.
The Qn output is inverted each time it is counted, but the latch circuit 5 is kept in the set state as it is, and therefore the SA signal from the latch circuit 6 is kept at "L" and the GRST signal is kept at "L".

On the other hand, the counter 8 counts the clock from the counter 3. Then, when the predetermined number l is counted, the Q output is inverted from “L” to “H”, and the rising edge of this Ql output is detected by the control unit 9, but the control unit 9 sends a signal to the temperature measuring unit 10. do not send. Furthermore, when the counter 8 continues counting and the count value becomes 2 l, the Ql output changes from “H” to “L”,
Qm output is inverted from “L” to “H”. The latch circuit 16 is set at the rising edge of this Qm output, and its output is inverted from "H" to "L". The falling edge of this output is detected by the falling edge detection unit 17 to form a MAX.R signal, whereby the storage unit 11 is reset.
As a result, the previously measured temperature value N _X ′ is erased and the value 0 is held in the storage unit 11.

Here, the frequency division ratios for the respective outputs are set so that the 16th inversion time of the Qn output of the counter 4 and the time when the Qm output of the counter 8 first inverts from “L” to “H” are almost the same. It is set. Therefore, almost simultaneously with the setting of the latch circuit 16, the Q output of the counter 4 is inverted from "L" to "H", the latch circuit 6 is set, and the SA signal is changed from "L" to "H". And the multiplexer 13 inverts to the storage unit 12
The temperature measurement value from (that is, the previous temperature measurement value N _X ′) is selected. Therefore, the Qm output of the counter 8 may be used as the set input of the latch circuit 6.

Further, since the output of the latch circuit 16 becomes “L”, the output of the NAND gate 20 becomes “H”, the DisPR signal becomes “L”, and the preset of the display decoder 14 is released.

Therefore, the display decoder 14 decodes the output of the multiplexer 13. In this case, since the multiplexer 13 has selected the previous temperature measurement value N _X ′ from the storage unit 12, the display decoder 14 decodes this and displays it. The instrument 15 displays a numerical value "T _X '° C." corresponding to the previously measured value N _X '. When the previous temperature measurement value N _X ′ is outside the predetermined measurement range, the measurement range outside detection means in the multiplexer 13 indicates “32.0 ° C.” or “42.0 ° C.” on the display 15.
Needless to say, it is displayed as "° C".

This state continues while the switch 1 is closed. Meanwhile, the counter 8 continues the counting operation, and when the count value becomes 3 l, its Ql output is inverted from “L” to “H”, and the control unit 9 detects this inversion and sends a signal to the temperature measuring unit 21. To send.

On the other hand, the temperature measurement unit 10 has completed the first temperature measurement immediately before the rising edge of the Ql output of the counter 8, and upon receiving a signal from the control unit 9, reads the temperature measurement value from the storage unit 11. Then, it is compared with the current temperature measurement value N ₁ obtained by the _first temperature measurement. In this case, since the read temperature measurement value is 0 and the current temperature measurement value N ₁ is larger, the temperature measurement unit 10 uses MAX.φ.
A signal is sent to the storage unit 11 and the current temperature measurement value N ₁ is written in the storage unit 11.

Further, the counter 8 continues to count, and the count value becomes 4
At 1, the Qn output is inverted from "H" to "L", and when the count value is 5l, the Qn output is inverted from "L" to "H".
The rising edge of the output temperature measuring unit 10 compares the temperature measurement values N _1, which is held in the current temperature measurement value N ₂ and the storage unit 11 obtained in the immediately preceding, towards the current temperature measurement value N ₂ Is large, the storage unit 1
Overwrite the current measured value N ₂ with 1.

In this way, the counter 8 continues to count, and at the rising edge of the Ql output every 2l counts, the temperature measurement unit 10 compares the current temperature measurement value with the temperature measurement value held in the storage unit 11,
When the current temperature measurement value is larger, the storage unit 11 rewrites the current temperature measurement value. Therefore, after the reset, the storage unit 11 holds the maximum temperature measurement value obtained so far, and during the period in which the temperature is rising, it is stored in the storage unit 11 for each temperature measurement. The measured temperature value is updated.

After that, when the operation of the switch 1 is completed and the switch 1 is opened, the count 4 and the latch circuit 5 are reset. As a result, the output of the latch circuit 5 is inverted from "L" to "H", so that the latch circuit 6 is reset and the SA signal becomes "L". As a result, the multiplexer 13 selects the temperature measurement value from the storage unit 11.

Even if the output of the latch circuit 5 is inverted from "L" to "H", the counter 7 does not count, so the GRST signal is "L".
The other part continues the above operation.

As a result, the display unit 15 displays the temperature measured value from the storage unit 11, but in FIG.
This shows the case where the switch 1 is opened while N ₁ is held, and in this case, the multiplexer 1
Along with the changeover of 3, first, the numerical value "T ₁ ° C" for the temperature measurement value N ₁ is displayed, and then when the temperature measurement value N ₂ is rewritten in the storage unit 11, the numerical value "T ₂ ° C" is displayed. To be done. Hereinafter, every time the temperature value is rewritten in the storage unit 11 to a new temperature value, the numerical value displayed on the display unit 15 is updated.

Next, when the switch 1 is operated to be closed, the reset of the counter 4 and the latch circuit 5 is released, and the output of the latch circuit 5 is inverted from "H" to "L" as described above.
As a result, the counter 7 counts by 1 and the GRST signal is inverted from "L" to "H".

Therefore, the display decoder 14 is reset and the display 15
Is displayed blank, and the counter 8, control unit 9, temperature measuring unit 1
0, the latch circuit 16 and the falling edge detector 17 are also reset, and the temperature measuring operation is completed. At this time, MAX
Since the R signal is not generated, the storage unit 11 is not reset, and the storage unit 11 retains the maximum temperature measurement value N _x so far. This temperature measurement value N _x becomes the previous temperature measurement value for the next temperature measurement. Also, the GRST signal changes from "L" to "H".
Even if the signal is inverted to M, the falling edge detection unit 18 causes an M of "L".
Since the EM · φ signal is not generated, the previous temperature measurement value N _x ′ is held in the storage unit 12 as it is. However, this is not particularly important because the temperature measurement value N _x held in the storage unit 11 is written in the storage unit 12 with the next operation of the switch 1.

Next, when the operation of the switch 1 is completed and the switch 1 is opened, one input on the switch 1 side of the NAND gate 19 becomes "H" and the GRST signal is also "H". Therefore, the MCK / N signal is "H". Then, the oscillator 2, the counter 3 and the falling edge detector 18 are also reset, and all the operations are completed.

In this way, if the operation duration of the switch 1 is longer than the 16n counting period of the counter 4, the previous temperature measurement value is displayed until the operation of the switch 1 is completed, and when the operation of the switch 1 is completed, the current measurement value is displayed. The display for the temperature value is performed.

Next, the operation duration of the switch 1 is 16n of the counter 4.
The operation of this embodiment when it is shorter than the counting period,
This will be described with reference to the timing chart of FIG.

Also in this case, when the switch 1 is operated to be in the closed state, the oscillator 2, the count 3 and the falling edge detection unit 1 are
8 is released from reset, the counter 4 and the latch circuit 5 are released from reset, and the GRST signal changes from "H" to "L".
When the display decoder 14 is reset and released, all the segments of the display 15 are turned on at the same time as the display decoder 14 is reset, and the counter 8, the control unit 9, the temperature measuring unit 10, the latch circuit 16 and the falling edge detecting unit are turned on. Until the reset release of 17 is performed, the operation is the same as that described above.

At this time, since the output of the latch circuit 5 is "L", the latch circuit 6 has been released from the reset state, but has not been set yet. Therefore, the SA signal is "L", and the multiplexer 13 stores in the storage unit 11. The temperature measurement value from (that is, the previous temperature measurement value N _x ′) is selected. However, since the display decoder 14 is preset, the multiplexer 1
Do not accept 3 output.

The operation of the switch 1 is completed and opened before the counter 4 counts 16 n, so that the latch circuit 6 is finally reset without being set. For this reason, the SA signal is held at “L”, and the multiplexer 13 selects the temperature measurement value N _x ′ from the storage unit 11 as it is.

Meanwhile, the counter 8 continues counting, and when the count value becomes 2 l, its Qm output is inverted from “L” to “H” and the latch circuit 16 is set, and the falling edge of the Q output causes a falling edge. The unit 17 generates the MAX.R signal, and the storage unit 11 is reset. As a result, the storage unit 1
The value 0 is held in 1. At the same time, the display decoder 14 cancels the preset and receives the output of the multiplexer 13. In this case, since the measured temperature value from the storage unit 11 selected by the multiplexer 13 is 0, the above-mentioned measuring range outside detection means judges that this value 0 is less than 32.0 ° C. and represents “LO ° C.”. Data to multiplexer 1
3 output. Therefore, this numerical value “LO ° C.” is displayed on the display unit 15.

After that, it is similar to the case where the switch 1 is operated for a long time, and the numerical value displayed on the display unit 15 is sequentially updated as the temperature measurement value of the storage unit 11 is rewritten by the temperature measurement unit 10, and the value of the switch 1 is changed. Along with the operation again, the temperature measurement operation is completed and the operation of all circuits is stopped.

As described above, when the operation duration of the switch 1 is shorter than the 16n counting period of the counter 4, the display according to the current temperature measurement value is immediately performed without passing through the display according to the previous temperature measurement value.

As described above, in this embodiment, either the display according to the previous temperature measurement value or the display according to the current temperature measurement value can be selected depending on the length of the operation duration of the single switch 1. Therefore, as a criterion for determining the duration of the operation,
The lighting period of all the segments of the display unit 15 (the 16n counting period described above) can be used, and by completing the operation of the switch 1 in the lighting period, the display corresponding to the current temperature measurement value can be immediately obtained. However, by continuing the operation of the switch 1 even after the lighting period, the display according to the previous temperature measurement value is immediately obtained, and it is extremely easy to select the both, and the switch 1 is operated. As long as the display according to the previous temperature measurement value is continued, for example, for comparison with the current temperature measurement value, sufficient time can be taken to store the previous temperature measurement value and the operation can be performed. It is easy and easy to handle, and even if it is used by women and women, no accidental operation will occur.

Further, in both the display according to the previous temperature measurement value and the display according to the current temperature measurement value, all the segments of the display unit 15 are turned on immediately before the display, so that the display section operates normally. It is possible to confirm whether or not to do so, and the reliability of the displayed content is improved.

In addition, when the measured temperature value is outside the measurement range, fixed values, symbols, patterns, etc. are displayed, so meaningless temperatures outside the measurement range are displayed to allow the user to make unnecessary judgments. This can be prevented, and in this case, since different numerical values, symbols, and patterns are displayed for the previous temperature measurement value and the current temperature measurement value, the display according to which temperature value is displayed. It is possible to clearly distinguish whether it is the period being conducted.

In the above-mentioned embodiment, if the period for counting 1 by the counter 8 is about 0.7 seconds, the lighting period of all the segments of the display unit 15 is about 1.4 seconds, and all the segments are lit at this level. Can be fully recognized. However, the numerical values and the specific numerical values used in the above description are merely examples, and the present invention is not limited to these numerical values.

〔The invention's effect〕

As described above, according to the present invention, not only can the temperature measurement operation be started and stopped by operating a single switch, but the previous measurement can be performed according to the length of the operation duration of the switch. The display according to the temperature value and the display according to the current temperature value can be selected, and the operation is extremely simple and the handling is extremely easy. Moreover, the configuration is simple and the size can be reduced. That is an excellent effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a temperature measuring device according to the present invention, and FIGS. 2 and 3 are timing charts for explaining the operation of FIG. 1 ... Switch, 4 ... Counter, 5,6 ... Latch circuit, 7,8 ... Counter, 10 ... Temperature measuring section, 11,12
... storage unit, 13 ... multiplexer, 14 ... display decoder, 15 ... display unit.

Continuation of front page (72) Inventor Isao Imagawa 4680 Ikata, Hachijo-machi, Tagawa-gun, Fukuoka Prefecture Kyushu Hitachi Maxell Co., Ltd. (56) Reference JP-A-58-46723 (JP, A)

Claims (1)

[Claims] 1. A switch that can be operated from the outside, a first determination unit that determines the opening / closing operation state of the switch, and a measurement that starts measurement in response to the determination of the operation of the switch by the first determination unit. A temperature section, a first storage section that holds measurement data of the temperature measurement section, and a measurement stored in the first storage section according to the determination of the operation of the switch by the first determination section. The operation duration length of the switch is determined based on the determination of the second storage unit in which the data is written and the first determination unit, and when the operation duration length is equal to or less than a preset reference length, the first
And a second determination unit which outputs a signal which becomes a second level when the operation duration exceeds the reference length and which becomes the first level when the operation of the switch is completed,
When the output level of the second determination unit is the first level, the measurement data read from the first storage unit is selected, and when the output level is the second level, the second storage unit is selected. Multiplexer to select the measurement data read from the unit,
A display unit for displaying the measurement data selected by the multiplexer, the first storage unit holds the current measurement data by the temperature measurement unit, and the second storage unit the temperature measurement unit. By holding the previous measurement data by the unit, it is possible to selectively perform the display according to the current measurement data and the display according to the previous measurement data according to the length of the operation duration of the switch. A temperature measuring instrument characterized by being configured as described above. Temperature measuring instrument.