JPH0823510B2 - Thermometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermometer such as an electronic thermometer and a thermometer, and a thermometer that displays a temperature based on a ratio of resistance values of a reference resistance and a temperature sensitive resistance. Relates to correction technology for correcting display errors in.

[Conventional technology]

Conventionally, an electronic thermometer that uses a temperature-sensitive resistor such as a thermistor has a reference resistance that shows a substantially constant resistance value within the measurement temperature range without being affected by temperature changes. The ratio (resistance ratio) of the temperature resistance to the resistance value is obtained and converted (decoded) into temperature. FIG. 3 is a block diagram showing a conventional electronic thermometer. Thermistor
The resistance value-frequency conversion circuit 1 having 101, the reference resistor 102 and the initial adjustment variable resistor 103 switches the thermistor 101 or the reference resistor 102 to generate a signal having a frequency based on each resistance value. The clock oscillated by the oscillator circuit 5 is divided by the divider circuit 4, the divider circuit 4 outputs a low level signal for a predetermined counting time, and the NOR gate 44 outputs the signal from the resistance value-frequency converter circuit 1. Are passed for the predetermined counting time. The frequency dividing circuit 2 is a counter, counts the signal from the resistance value-frequency conversion circuit 1, and is reset by the reset signal on the reset signal line 6.

The electronic thermometer having such a configuration operates as follows.
First, in the first phase, the resistance value-frequency conversion circuit 1 selects the reference resistor 102 and the initial adjustment variable resistor 103 to generate a reference signal having a frequency corresponding to the series combined resistance value of both. This reference signal is counted by the frequency dividing circuit 2 for a constant counting time determined by the frequency dividing circuit 4, and the count value of the reference signal is temporarily stored. Then, the reset signal is input to the reset signal line 6, and the count value of the frequency dividing circuit 2 is reset.

Next, in the second phase, the resistance value-frequency conversion circuit 1 selects the thermistor 101 and generates a temperature detection signal having a frequency corresponding to the resistance value. This temperature detection signal is also counted by the frequency dividing circuit 2 for a constant counting time determined by the frequency dividing circuit 4, and is converted into a temperature from the ratio between the count value of the temporarily stored reference signal and the count value of the temperature detecting signal. The temperature value is displayed by.

In order to obtain the temperature display from the ratio of the reference resistance 102 and the resistance value of the thermistor 101 in this way, since the conversion table for each thermometer has constant conversion data, any thermometer (any product) It must have a constant resistance ratio at a certain temperature, but in practice, there are individual differences in resistance values (variations in resistance value) between the reference resistor 102 and the thermistor 101 depending on the product, so the resistance ratio should be kept constant. Can not do it. Therefore, in order to make the resistance ratio a constant value, the initial adjustment variable resistor 103 is moved to adjust the combined series resistance value with the reference resistor 102 for each product in the inspection process before product shipment.

[Problems to be Solved by the Invention] However, the above-mentioned electronic thermometer has the following problems.

Placing the electronic thermometer under a constant temperature in the inspection process, and manually adjusting the variable resistor 103 so that the temperature display value becomes the constant temperature value requires complicated labor,
Particularly for a thermometer that requires strict accuracy, fine adjustment work requires skill. Therefore, the productivity remains low, which is an obstacle to cost reduction.

In addition, the above-mentioned electronic thermometer requires the mounting of the variable resistance value 103, but in general, the variable resistance value is inferior to the fixed resistance value in environmental resistance, and it is easy to cause a change over time (change in resistance value). The reliability of the temperature display at time is poor.

Furthermore, since the variable resistance value 13 has a movable portion, it is not suitable for semiconductor integration, and the resistance value-frequency conversion circuit 1
The variable resistor 103 must be mounted as an external discrete component because it cannot be integrated into one chip together with the frequency dividing circuits 2 and 4. Therefore, when it is applied to a thermometer or the like, it hinders miniaturization, and an increase in the number of parts leads to an increase in product cost.

Therefore, in view of the above problems, an object of the present invention is to use an initial adjustment variable resistor, and to use a reference resistance and a temperature-sensitive resistance having a variation in resistance value to make the resistance ratio apparently constant. By doing so, it is an object to provide a thermometer capable of facilitating the initial adjustment work, suppressing the temporal change of the display accuracy, integrating the semiconductor, and reducing the cost.

[Means for solving the problem]

In order to solve the above problems, the means taken by the present invention are:
The counting means is a counting means with a set, and the resistance value variation correction data for each product is set in the counting means with a set as an initial value prior to the counting operation of the reference signal.

That is, the present invention provides a resistance that is switchable between a reference signal having a frequency based on the resistance value of a reference resistance and a temperature detection signal having a frequency based on the resistance value of a temperature-sensitive resistance that changes in resistance value in response to temperature. A value-frequency conversion means, a counting means with a set, which counts the reference signal for a predetermined counting time, is reset by a reset signal, and counts the temperature detection signal for the predetermined counting time, and the reference signal. Prior to the counting operation, the initial value setting means for setting resistance value variation correction data to the counting means with set as an initial value, and the count value of the reference signal and the temperature detection by the counting means with set. In the thermometer that displays the temperature based on the ratio of the signal count value, the initial value setting means creates the resistance value variation correction data as a logical signal. Positive data creating means and initial value setting control means for setting and controlling the logical signal output from the correction data creating means as an initial value by a set timing signal prior to the counting operation of the reference signal. It is characterized by

[Action]

As in the conventional case, the thermometer according to the present invention also needs to be adjusted so that the ratio of the reference resistance count value and the temperature sensitive resistance count value at a constant temperature is a constant value without variation among products. However, instead of keeping the ratio (resistance ratio) between the reference resistance and the temperature-sensitive resistance constant by adjusting the variable resistor as in the past, the ratio of the count values in the same set counting means is set to be constant. As described above, the resistance value variation correction data peculiar to the product is sent to and set in the counting means with a set prior to the counting operation of the reference signal.

Whereas the conventional correction method for eliminating the variation of the resistance value is to increase or decrease the resistance value itself in the inspection process, the method of the present invention is to match the actual temperature value and the display temperature value in the inspection process. It is to determine resistance value variation correction data peculiar to the product, and to set the correction data to the counting means with set as an initial value at the time of temperature measurement (at the time of use).

In the inspection step, the temperature is measured under a constant temperature, and the specific resistance value correction data whose temperature display value matches the constant temperature value is determined. In the process of determining the correction data, the logical signal of the correction data created by the correction data creating means is changed to set different initial values in the counting means with the set, and the unique correction data is eventually found. You can If the logic signals are changed in descending or ascending order, the correction data can be easily found. In such a case, the initial value setting means sets the logical signal output from the correction data creating means as an initial value by the set timing signal prior to the counting operation of the reference signal, in addition to the correction data creating means. Since it is provided with the means, the correction data creating means does not immediately set the logic signal, but the initial value is set only by the set timing signal. Therefore, even if the logic signal partially changes while the correction data is being changed, it is not set as the initial value, and the correction data determination operation can be performed without any trouble.

In the present invention, at the time of temperature measurement, the determined correction data is output as a logical signal from the correction data creating means, and the initial value is set by the initial value setting control means.
Since the timing for setting the correction data as the initial value can be determined by the set timing signal of the initial value setting control means, the initial value can be set prior to the counting operation of the reference signal. Since the set timing signal is not added when counting the temperature detection signal, the initial value of the correction data is not set.

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an electronic thermometer according to an embodiment of the present invention. In the electronic thermometer of this example, the resistance value-frequency conversion circuit 1 selects the reference resistor 102 in the first phase to generate a reference signal having a frequency corresponding to the resistance value, and the switching phase controls the second phase. Selects the thermistor 101 and generates a temperature detection signal having a frequency corresponding to its resistance value. In the first phase, the reference signal is counted by the frequency divider 2 with a set for a fixed time determined by the frequency divider 4, and the count value is temporarily stored. Then, the count value of the divider circuit with set 2 is reset by the reset signal applied to the reset signal line 6.

Next, in the second phase, the temperature detection signal is counted by the frequency divider 2 with a set for a fixed time determined by the frequency divider 4, and the count value based on the temporarily stored reference resistor 102 and the thermistor 101 are stored. Although the temperature is displayed based on the ratio with the count value based on this, the frequency division ratio of the frequency divider 2 with a set can be changed by the output from the control circuit (initial value setting means) 3 in this example. That is, the frequency dividing ratio of the frequency dividing circuit 2 when the reference resistor 102 is used and the frequency dividing ratio of the frequency dividing circuit 2 when the thermistor 101 is used are varied by the set output from the control circuit 3 to correct the count value. Is.

FIG. 2 is a circuit diagram showing a specific configuration of the frequency dividing circuit 2 and the control circuit (initial value setting means) 3 shown in FIG.

In FIG. 2, the set-priority type 1/2 divider circuit with reset 11, 12, 13, 14 and the 1/2 divider circuit with reset 15 are connected in cascade, and the reference signal input from the input line 36 or It counts the temperature detection signals, and corresponds to the frequency divider 2 with a set shown in FIG. Input line
The output of the NOR gate 44 of FIG. 1 is supplied to 36, and the temperature is displayed using the frequency division output line 37 which is the output of the 1/2 frequency divider circuit with reset 15. A reset signal input line 38 (6) is connected to the reset terminal R of each of the 1/2 frequency divider circuits 11 to 15, and the reset signal is added at the timing matched with each temperature measurement to obtain the 1/2 frequency divider circuit 11. Reset ~ 15.

The output of the NAND circuits 19, 18, 17, 16 is connected to the set input terminals of the 1/2 divider circuit with set priority type reset 11, 12, 13, 14 and the NAND circuit 19, 18, 17, 16 is connected. The set timing signal input line 39 is connected to one input, and the correction data signal input lines 32, 33, 34 and 35 (7 in FIG. 1 are supplied to the other input through the inverter circuits 20, 21, 22 and 23. Equivalent to 8,9,10) are connected respectively. The set timing signal is added when the correction data is set to the initial value, but the set timing signal is not added when counting the temperature detection signal, and the line 39 is fixed to the low level. Correction data signal input line 32,3
The source terminals of P-channel type MOS transistors 27, 26, 25, 24 for line pull-up are connected to 3, 34, 35, and the gate of each MOS transistor is V _SS (ground potential).
And the drains are connected to V _DD (power supply potential), respectively. P-channel MOS transistor 2 when power is turned on
7,26,25,24 function as high resistance, line 32,33,34,35
Is pulled to high potential V _DD . Here, the correction data signal input lines 32, 33, 34, 35, the P-channel type MOS transistors 27, 26, 25, 24 and the inverters 20, 21, 22, 23 constitute the correction data creating means of the initial value setting means. Set timing signal input line 39 and NAND gates 19, 18, 17, 16
Constitutes the initial value setting control means of the initial value setting means.

At the time of counting the first phase reference signal, the set timing signal input line 39 temporarily becomes high level before the counting is started, and the correction data signal input lines 32, 33, 3
Logic signal of correction data generated on 4,35 (4 bits)
Is supplied to the set input terminals of the 1/2 divider circuits 11, 12, 13, 14 with set priority type reset and is set as the initial value. After the initial value is set, the reference signal input to the input line 36 is counted and added to the initial value. When the counting of the reference signal is completed, a reset signal is applied to the reset signal input line 6 to reset the count value of the frequency divider 2 with a set. Next, in the second phase, the set timing signal line 39 remains at the low level, the correction data is not set as the initial value, and the temperature detection signal is counted.

In the inspection process (initial adjustment process) that determines the unique correction data for each manufactured electronic thermometer, measure at a specific temperature, change the logical signal of the correction data until the temperature display matches, and then Fix the correction data. As a procedure to determine the correction data, for example, first set all 1/2 divider circuits 11, 12, 13, 14 and then measure the temperature, and then release the set in descending order to reduce the display error. Repeatedly, when the measured temperature display reaches the measured temperature, the correction data is determined. Here, in order to set the logical signal of the correction data as the initial value, it is necessary to apply the set timing signal, so the 1/2 frequency dividing circuit 11, before the change of the logical signal is completed in the inspection process, The inconvenience that the initial value is set to 12,13,14 can be eliminated. Therefore, the correction data determination operation can be performed without any trouble.

In this example, a set priority type reset for correction is included.
The 1/2 frequency dividing circuits 11, 12, 13, and 14 have four stages, and the correction data has 4 bits = 16 ways, but the number of stages can be appropriately increased or decreased according to the target accuracy and the variation of the resistance ratio. Further, the application range of the present invention can be applied not only to thermometers but also to initial adjustment of various measuring instruments such as pressure gauges and cryometers, and can be used for logical adjustment of clocks and the like.

〔The invention's effect〕

As explained above, in the thermometer according to the present invention, the initial adjustment variable resistor is not used, and the resistance value variation correction data is initially set to the set counting means prior to the reference signal counting operation. Since there is an initial value setting means for setting as a value, it is possible to simplify the initial adjusting means, suppress the change in display accuracy over time, realize semiconductor integration, and reduce the cost. The means is a correction data creating means for creating resistance value variation correction data as a logic signal, and an initial setting control for setting the logic signal output from the correction data creating means as an initial value by the set timing signal prior to the counting operation of the reference signal. The present invention is characterized by having a value setting control means, and has the following unique effects.

In the adjustment process for determining the correction data, since the initial value setting control means is provided, it is not set immediately after the logical signal is created by the correction data creation means, and the initial value is set only by the set timing signal. It is supposed to be done. Therefore, even if the logic signal partially changes while the correction data is being changed, it is not set as the initial value, and the correction data determination operation can be performed without any trouble.

The correction data is not set as an initial value before the counting operation of the temperature detection signal, but the correction data is set as an initial value before the counting operation of the reference signal by the set timing signal. Even if an initial value is set in the counting process of the temperature detection signal, no display error is shown at the temperature during inspection, but since the temperature-sensitive resistance has a large temperature-resistance characteristic, the display error is large at the other temperatures. Will end up. On the other hand, in the present invention, since the initial value of the correction data is set prior to the counting operation of the reference signal, the temperature change of the reference resistance can be ignored, and therefore, the temperature display error over a wide temperature range. Can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electronic thermometer according to an embodiment of the present invention. The second is a circuit diagram showing a specific configuration of the frequency dividing circuit and the control circuit shown in FIG. FIG. 3 is a block diagram showing a conventional electronic thermometer. [Description of symbols] 1 ... Resistance value-frequency conversion circuit 2 ... Dividing circuit with set 3 ... Control circuit (initial value setting means) 4 ... Dividing circuit 5 ... Oscillation circuit 6,38 ... Reset Signal input line 7,8,9,10 (32,33,34,35) …… Correction data signal input line 11,12,13,14 …… 1/2 divider circuit with set priority type reset 15 …… Reset With 1/2 divider circuit 16,17,18,19 …… NAND circuit (initial value setting control means) 20,21,22,23 …… Inverter circuit 24,25,26,27 …… Line pull-up P channel type M
OS transistors 28,29,30,31 …… Terminals connected to power supply potential V _DD 39 …… Set timing signal input lines 40,41,42,43 …… Terminals connected to ground potential V _SS 101… … Thermistor (temperature sensitive resistor) 102 …… Reference resistor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Hosaka 390 Shiojiri-cho, Shiojiri-shi, Nagano Shiojiri Industrial Co., Ltd. (56) References JP-A-58-15134 (JP, A) JP-A-55- 160823 (JP, A) JP-A-52-57857 (JP, A) JP-A-58-124921 (JP, A) JP-A-54-52583 (JP, A)

Claims (1)

[Claims] 1. A resistance value switchably generated between a reference signal having a frequency based on the resistance value of a reference resistance and a temperature detection signal having a frequency based on the resistance value of a temperature-sensitive resistance that changes in resistance value in response to temperature. -Frequency conversion means, counting means with a set, which counts the reference signal for a predetermined counting time, and is then reset by a reset signal, and counts the temperature detection signal for the predetermined counting time; Prior to the counting operation, there is provided an initial value setting means for setting resistance value variation correction data as an initial value to the set counting means, and the count value of the reference signal and the temperature detection signal by the set counting means. In a thermometer that displays the temperature based on the ratio with the count value of the correction value, the initial value setting means corrects the resistance value variation correction data as a logical signal. Data creating means, and initial value setting control means for setting and controlling the logical signal output from the correction data creating means as an initial value by a set timing signal prior to the counting operation of the reference signal,
A thermometer characterized by comprising.