JP3425638B2 - Measuring method and measuring element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method and a measuring element in which a heat sensitive element is operated by intermittent heating to perform measurement.

[0002]

2. Description of the Related Art It is well known that a thermosensitive element is used as a detector of not only temperature but also flow velocity, pressure, gas, humidity, etc. by self-heating by energization or heating by other heating means. .

Conventionally, as a method for heating a heat sensitive element to detect the flow velocity, pressure, gas, humidity and the like, there is one as shown in FIG.

In the measuring method shown in FIG. 20, two heat-sensitive elements, one for detection and one for temperature compensation, are used, and a heat-sensitive element for detection (hereinafter referred to as detection element) 1 and a heat-sensitive element for temperature compensation (hereinafter referred to as compensation). 2) and the fixed resistors 3 and 4 form a bridge circuit. The detecting element 1 is used only in a heated state, and the compensating element 2 is used in two ways: heating and non-heating. .

That is, when the compensating element 2 is used in a heated state, the characteristics of the detecting element 1 and the compensating element 2 are matched, the compensating element 2 is shielded from the object to be measured, and only the ambient temperature is detected. , The ambient temperature dependence of the detection element 1 is compensated.

When the compensating element 2 is used in a non-heated state, adjustment is performed so that the temperature coefficient and the resistance value of the detecting element 1 when heated and the compensating element 2 when not heating are matched.

[0007]

However, as shown in FIG.
In the measuring method shown in (2), since two heat-sensitive elements are used, the number of parts is increased, and it is difficult to match the temperature coefficients of the heat-sensitive elements, and there is a drawback that a compensation error is likely to occur. Further, since the thermosensitive element is always energized and self-heated, there is a problem in terms of life.

An object of the present invention is to provide a measuring method and a measuring element in which a single heat-sensitive element serves both to detect an object and to compensate for temperature.

[0009]

In order to achieve the above object, the measuring method according to the present invention performs a non-heat treatment and a heat treatment on one thermosensitive element to detect a signal to be detected. And a signal for ambient temperature, the non-heating treatment is performed by applying a non-heating current to the heat-sensitive element to such an extent that a temperature rise due to energization can be ignored, and corresponds to the ambient temperature. Which is a process for outputting the voltage value between terminals of the heat-sensitive element or the voltage value between terminals of the resistor element as an ambient temperature signal, and the heating processing is to pass an overcurrent of the non-heating current value or more to the heat-sensitive element. The heat-sensitive element is caused to self-heat, or the heat-sensitive element is indirectly heated, and the voltage value between terminals of the heat-sensitive element or the voltage value between terminals of the resistor element corresponding to the measurement target is output as a detection signal. Yes, heat treated and unheated The management, is performed repeatedly alternately in time division.

Further, the measuring element for carrying out the measuring method according to the present invention is a combination of one thermosensitive element and two sets of energizing circuits, and by applying different current values to the thermosensitive element. , A measuring element that outputs two signals, a detection signal for measurement and a signal for ambient temperature, wherein one thermosensitive element switches currents of different current values from the two sets of energizing circuits in a time division manner. One of the two sets of energizing circuits energizes the thermosensitive element with a non-heating current whose temperature rise due to energization is negligible, and a voltage value corresponding to the ambient temperature. Is output as a signal for ambient temperature between terminals of the heat-sensitive element or between terminals of a resistor element, and the other current-carrying circuit of the two sets of current-carrying circuits causes the heat-sensitive element to have a non-heating current value or more. Applying an electric current to heat the thermosensitive element Are those output a voltage value corresponding to the measurement object between the terminals of the terminals or between the resistor elements of the heat-sensitive element as a detection signal to be measured.

A measuring element having a switch element, which receives an external command, switches the two sets of energizing circuits in a time division manner and connects them in series to one thermosensitive element.

In the measuring element according to the present invention, one thermosensitive element, one set of energizing circuit and one set of heating circuit are combined, and the thermosensitive element is placed in two states having different temperatures. , A measuring element that outputs two signals, a detection signal for measurement and a signal for ambient temperature, wherein one thermosensitive element is
In combination with one set of energizing circuits, a non-heating current whose temperature rise due to energization is negligible is energized from the energizing circuits, and one set of heating circuits indirectly heats the thermosensitive element. It is controlled in a time-sharing manner, and when energization is off, the thermosensitive element is kept in an unheated state and a voltage value corresponding to the ambient temperature is output from between the terminals of the thermosensitive element or between the terminals of the resistor element to turn on the energization. In this case, the heat sensitive element is indirectly heated from the outside, and the voltage value corresponding to the measurement target is output from between the terminals of the heat sensitive element or between the terminals of the resistor element.

Further, the measuring element has a switching element, and the switching element receives an external command to control ON / OFF of the heating circuit in a time division manner.

[0014]

[Operation] The non-heating operation and the heating operation are repeated in a time-sharing manner for one thermosensitive element, the ambient temperature of the detector is detected during the non-heating operation, and the measurement target such as wind speed and humidity is detected during the heating operation. , The temperature of the measurement target is compensated by the ambient temperature. In this way, one heat-sensitive element serves both as the object detection and the temperature compensation.

[0015]

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

(Embodiment 1) FIG. 1 is a configuration diagram showing a measuring element for carrying out a measuring method according to Embodiment 1 of the present invention.

First, the structure of the measuring element according to the first embodiment of the present invention will be described. In the drawings, the first embodiment of the present invention is shown.
The measuring element according to the present invention combines one thermosensitive element 6 and two sets of energizing circuits 7 and 8 and energizes the thermosensitive element 6 with currents having different current values, thereby detecting the detection signal of the measurement object and the surroundings. It outputs two signals, a temperature signal.

One thermosensitive element 6 has two sets of energizing circuits 7,
A current having a different current value from No. 8 is switched in a time division manner to be energized. In the case of FIG. 1, a variable resistance element such as a thermistor is used as the heat sensitive element 6.

In this embodiment, a constant voltage type having a constant voltage source V is used as a method for heating and driving the heat sensitive element 6, and the two sets of energizing circuits 7 and 8 are resistors 7a and 8a.
Are configured as resistance circuits 7 and 8. In the following description, the two sets of energizing circuits 7 and 8 are replaced with the two sets of resistance circuits 7 and 8. One of the two sets of resistance circuits 7 and 8 supplies a non-heating current to the heat sensitive element 6 to such an extent that the temperature rise due to energization can be ignored, and a voltage value corresponding to the ambient temperature is applied to the heat sensitive element 6. The signal between the terminals 6a and 6b is output as an ambient temperature signal.

The other resistance circuit 8 of the two sets of resistance circuits 7 and 8 corresponds to the object to be measured by causing an overcurrent equal to or more than the non-heating current value to pass through the heat sensitive element 6 to cause the heat sensitive element 6 to self-heat. The voltage value is output between the terminals 6a and 6b of the thermosensitive element 6 as a detection target detection signal. The two sets of resistance circuits 7 and 8 have resistors 7a and 8a, respectively,
The relationship between the resistance value R ₁ of the resistor 7a of the resistance circuit 7 and the resistance value R ₂ of the resistor 8a of the resistance circuit 8 is R ₁ > R ₂
Has become.

In the embodiment of FIG. 1, the voltage value as the ambient temperature signal is output to the terminals 6a and 6b of the heat sensitive element 6, but as shown in FIG. 3, the heat sensitive element 6 and the resistance circuit 7 are provided. , 8 may be reversed, and a voltage value as an ambient temperature signal or a measurement target detection signal may be output to the terminals 11a, 11b of the resistors 7a, 8a.

Although the constant voltage source V is a single power source in the case of FIG. 1, it may be a double power source composed of two sets of constant voltage sources V ₁ and V ₂ as shown in FIG.

Further, according to the present invention, the switching elements S ₁ and S _{2 are}
A switching element S ₁ , S ₂ is a measuring element having
In response to an external command, the two sets of resistance circuits 7 and 8 are switched in time division and connected in series to the heat sensitive element 6. Further, as the switch elements S ₁ and S ₂ , mechanical switches, switches made of semiconductor elements, or the like can be used.

The measuring method of the present invention uses the measuring element shown in FIG. 1 and performs the non-heating process and the heating process on one thermosensitive element 6 to detect a signal to be measured and a temperature compensating object. Two signals, that is, a signal and a signal are output.

That is, in FIG. 1, a circuit for connecting the switch element S ₁ and the heat sensitive element 6 from the constant voltage source V in series with the non-heating resistor 7a is constructed to perform non-heating treatment.
In this case, the switch element S ₂ is left open.

In the non-heating treatment, a non-heating current is passed through the resistor 7a of the resistance circuit 7 to the heat-sensitive element 6 so that the temperature rise due to energization can be neglected to bring the heat-sensitive element 6 into the non-heated state and the ambient temperature. Between terminals 6a and 6b of corresponding heat-sensitive element 6 (or between terminals 11a and 11b of resistors 7 and 8 of FIG. 3)
The voltage value is output as an ambient temperature signal. The switch element S ₁ is closed (the switch element S ₂ is opened) to bring the thermosensitive element 6 into a non-heated state, and the output V _OUT obtained between the terminals 6a and 6b of the thermosensitive element 6 is V _OUT2 . The output V _{OUT 2} is processed by a microcomputer or the like to obtain the ambient temperature of the detector.

Next, the switch element S ₁ is opened, the switch element S ₂ is closed, and a circuit for connecting the switch element S ₂ and the heat-sensitive element 6 in series with the heating resistor 8a from the constant voltage source V is constructed to perform the heat treatment. I do.

In the heat treatment, an overcurrent larger than the non-heating current is passed through the resistor 8a of the resistance circuit 8 to the heat sensitive element 6 to cause the heat sensitive element 6 to self-heat, and the terminal 6a of the heat sensitive element 6 corresponding to the object to be measured. , 6b (or resistors 7, 8 of FIG. 3)
11a, 11b) between terminals of the voltage value is output as a detection signal for measurement. The switch element S ₂ is closed (the switch element S ₁ is opened) to heat the thermosensitive element 6, and the output V _OUT obtained corresponding to the measurement target under the heated state is V _OUT1
And By calculating from V _OUT2 and V _OUT1 , a target detection output whose ambient temperature dependency is compensated is obtained.

The heat treatment and the non-heat treatment described above are
The measurement is executed by obtaining the target detection output in which the ambient temperature dependency is compensated, by alternately repeating the time division.

Next, a specific example in which the present invention is applied to a liquid level detector will be described with reference to FIGS. Heat sensitive element 6 in the heated state
The characteristics of the ambient temperature and the output V _OUT in the liquid or air of the (NTC thermistor in this example) are shown in FIG.

A circuit including the heat-sensitive element 6 is constructed as shown in FIG. 1, and non-heating, heating, non-heating, heating ... The ambient temperature is obtained from V _OUT in the unheated state by arithmetic processing with a microcomputer or the like. This value is Ta.

Based on the value of V _OUT in the next heating state stored in the memory such as the microcomputer, V _OUT is V _OUT1 or V _OUT
Judge whether it is _OUT2 , and determine whether the detector is in the liquid or in the air. The above processing is also performed in the next heating and heating cycle.

In the first embodiment, the present invention is applied to the liquid level detector, but the present invention is not limited to this, and gas such as flow velocity, pressure, gas, temperature, humidity, etc. that touches the heat sensitive element 6 is used. Alternatively, the invention can be applied to any one as long as it measures changes in the number of molecules of a liquid per unit time or unit area.

(Embodiment 2) FIG. 4 is a block diagram showing a measuring element according to Embodiment 2 of the present invention. In the measurement element according to the first embodiment shown in FIGS. 1 to 3, a resistance variable element was used as the heat sensitive element 6, but in the present embodiment, the resistance variable element such as a thermistor or a metal resistor is used as the heat sensitive element 6. Besides the elements,
A voltage output type element such as a thermocouple can be used.

Referring to FIG. 4, the measuring element according to the second embodiment of the present invention includes one thermosensitive element 6 and one set of energizing circuit 12.
And a set of heating circuits 13 are combined to put the thermosensitive element 6 in two states having different temperatures and output two signals, that is, a detection signal for measurement and a signal for ambient temperature. In this embodiment, a constant voltage type having a constant voltage source V is used as a method for heating and driving the heat sensitive element 6 as in the case of the first embodiment.
It is configured as a resistance circuit 12 having a. In the following description, one set of energizing circuit 12 is replaced with one set of resistance circuit 12.

One heat-sensitive element 6 is combined with a set of resistance circuits 12, and a non-heating current whose current rise due to energization is negligible is supplied from the resistance circuits 12.

The set of heating circuits 13 indirectly heats the heat sensitive element 6, and when the energization is OFF, the heat sensitive element 6 is heated.
Is kept in an unheated state and a voltage value corresponding to the ambient temperature is output from between the terminals 6a and 6b of the heat sensitive element 6, and when energization is ON, the heat sensitive element 6 is indirectly heated from the outside to be measured. The corresponding voltage value is set between the terminals 6 of the heat-sensitive element 6
It is output from a and 6b.

Further, the present invention is a measuring element having a switch element S, and the switch element S receives an external command and controls the energization of the heating circuit 13 by time division ON / OFF control.

Incidentally, in FIG. 4, the voltage value as the ambient temperature signal or the detection signal of the measuring object is shown as a value between the terminals 6 of the thermosensitive element 6.
Although it is configured to output to a and 6b, the positional relationship between the heat sensitive element 6 and the resistance circuit 12 is reversed as shown in FIGS.
Between the terminals 14a, 1 of the elements of the resistor 12a of the resistance circuit 12
4b may be made to output the voltage value as a signal for ambient temperature or a signal for detection of a measuring object. Although the constant voltage source V is a single power source in FIG. 4, it may be a dual power source system including _two constant voltage sources V ₁ and V ₂ as shown in FIGS.

In this embodiment, the heat sensitive element 6 is connected to the heating circuit 13.
Although it is different from the first embodiment in that it is indirectly heated by, the thermosensitive element 6 is placed in two states having different temperatures, and two signals, that is, a detection signal for measurement and a signal for ambient temperature are output. The measurement method of the present invention can be implemented in the same manner as in the first embodiment.

In addition to the liquid level detector, the present embodiment is not limited to the liquid level detector, as long as it measures changes in the number of molecules of the gas or liquid touching the heat-sensitive element 6 per unit time and unit area. , Can be applied to any one.

In the first and second embodiments, a constant voltage type having a constant voltage source was used as a method for heating and driving the heat sensitive element 6. However, as shown in FIGS. Alternatively, a constant current type circuit composed of constant current circuits I ₁ and I ₂ for supplying constant currents having different current values may be used.
In addition, as a method for heating and driving the heat sensitive element 6, as shown in FIG.
As shown in 14, 15, and 16, the heating circuit 13 may have a constant current circuit I. As a method for heating and driving the heat sensitive element 6, as shown in FIG. 17, the heat sensitive element 6 is combined with resistors 15 and 16 and resistance circuits 7 and 8 as a conduction current switching circuit to form a bridge circuit. A constant temperature type may be used in which a voltage value as an ambient temperature signal or a detection target detection signal is output between the terminals 6a and 6b. 18 and 1
As a method for heating and driving the heat sensitive element 6 as shown in 9,
The heating circuit 13 is combined with the resistors 15, 16 and 17 to form a bridge circuit, and the terminals 6a and 6b between the terminals of the heat sensitive element 6 are formed.
Alternatively, a constant temperature type in which a voltage value as an ambient temperature signal or a detection target detection signal is output between the terminals 14a and 14b of the resistor 12a may be used. Reference numeral 18 in FIGS. 17, 18 and 19 denotes an operational amplifier.

[0043]

As described above, according to the present invention, 1
Since the non-heating operation and the heating operation are repeatedly performed in a time-sharing manner with respect to each heat-sensitive element, one heat-sensitive element can serve as both object detection and temperature compensation, thus reducing the number of parts. Therefore, the circuit configuration can be simplified.

Furthermore, when two heat-sensitive elements are used, it is difficult to match the temperature coefficients of the heat-sensitive elements and a compensation error is likely to occur.
Since individual heat-sensitive elements are used, it is not necessary to match the temperature coefficients of the heat-sensitive elements as in the conventional case, and it is possible to prevent occurrence of compensation error and perform accurate measurement.

Further, since the heat sensitive element is intermittently heated, its life can be extended as compared with the case of continuous heating.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a measuring element according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example in which the first embodiment of the present invention is a dual power supply system.

FIG. 3 is a configuration diagram showing an example in which the output format of the output voltage value is changed in the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a measuring element according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example in which a second power supply system is used in a second embodiment of the present invention.

FIG. 6 is a configuration diagram showing an example in which the output format of the output voltage value is changed in the second embodiment of the present invention.

FIG. 7 is a configuration diagram showing an example in which the second embodiment of the present invention is a dual power supply system.

FIG. 8 is a diagram showing characteristics of ambient temperature and output in a specific example in which the present invention is applied to a liquid level detector.

FIG. 9 is a configuration diagram showing an embodiment in which a method of heating and driving a thermosensitive element is a constant current type in the present invention.

FIG. 10 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant current type in the present invention.

FIG. 11 is a configuration diagram showing an embodiment in which a method of heating and driving a thermosensitive element is a constant current type in the present invention.

FIG. 12 is a configuration diagram showing an embodiment in which a method of heating and driving a heat sensitive element is a constant current type in the present invention.

FIG. 13 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant current type in the present invention.

FIG. 14 is a configuration diagram showing an embodiment in which a method of heating and driving a thermosensitive element is a constant current type in the present invention.

FIG. 15 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant current type in the present invention.

FIG. 16 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant current type in the present invention.

FIG. 17 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant temperature type in the present invention.

FIG. 18 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant temperature type in the present invention.

FIG. 19 is a configuration diagram showing an embodiment in which the method of heating and driving the thermosensitive element is a constant temperature type in the present invention.

FIG. 20 is a configuration diagram showing a conventional example.

[Explanation of symbols]

6 Thermal element 7, 8 Resistance circuit 7a, 8a Resistor S, S ₁ , S ₂ Switch element

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Claims (5)

(57) [Claims] 1. A measurement method for outputting two signals, a detection signal for a measurement target and a signal for ambient temperature, by performing a non-heat treatment and a heat treatment on one thermosensitive element, The non-heating treatment is performed by applying a non-heating current to the heat-sensitive element such that a temperature rise due to energization is negligible, and measuring the voltage value between terminals of the heat-sensitive element or the voltage value between terminals of the resistor element corresponding to the ambient temperature. It is a process of outputting as a signal for ambient temperature, the heating process, the thermosensitive element is caused to self-heat by passing an overcurrent of the non-heating current value or more, or the thermosensitive element is indirectly heated, This is a process of outputting the voltage value between terminals of the heat-sensitive element or the voltage value between terminals of the resistor element corresponding to the measurement target as a detection signal. The heating process and the non-heating process are alternately repeated in a time-sharing manner. Measuring method characterized by . 2. A thermosensitive element and two sets of energizing circuits are combined to energize the thermosensitive elements with electric currents having different current values, whereby a detection target signal for measurement and an ambient temperature signal are combined. A measuring element that outputs two signals, wherein one heat-sensitive element is one in which currents of different current values are switched by time division from the two sets of energizing circuits to be energized. One of the energizing circuits energizes the heat-sensitive element with a non-heating current whose temperature rise due to energization is negligible, and applies a voltage value corresponding to the ambient temperature between the terminals of the heat-sensitive element or between the terminals of the resistor element. In the other energizing circuit of the two sets of energizing circuits, the thermosensitive element is caused to self-heat by applying an overcurrent equal to or more than the non-heating current value to the thermosensitive element, The voltage value corresponding to the measurement target is measured between the terminals of the thermal element. Alternatively, a measuring element characterized in that it is output as a detection signal of a measurement target between terminals of a resistor element. 3. A measuring element having a switch element, wherein the switch element receives an external command and switches between two sets of energizing circuits in a time division manner to connect them in series to one thermosensitive element. The measuring element according to claim 2, which is characterized in that. 4. A thermosensitive element, a set of energizing circuits,
A measuring element which combines a set of heating circuits to put the thermosensitive element in two states having different temperatures and outputs two signals, a detection signal for measurement and a signal for ambient temperature, wherein: The individual heat-sensitive elements are combined with a pair of energizing circuits, and a non-heating current whose temperature rise due to energization is negligible is energized from the energizing circuits. The element is indirectly heated, and is controlled in a time-sharing manner, and when the energization is OFF, the thermosensitive element is kept in an unheated state and the voltage value corresponding to the ambient temperature is applied between the terminals of the thermal element or between the terminals of the resistor element. When the energization is turned on, the thermosensitive element is indirectly heated from the outside and the voltage value corresponding to the measurement target is output from between the terminals of the thermal element or between the terminals of the resistor element. element. 5. The measuring element having a switch element, wherein the switch element receives an external command to control ON / OFF of the heating circuit in a time-sharing manner. Measuring element.