JP3118621B2 - Capsule type strain gauge with temperature measurement function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capsule type strain gauge having a temperature measuring function, and more particularly, to a capsule type strain gauge having a temperature measuring function for detecting strain under high temperature conditions such as vibration measurement of a turbine blade with high accuracy. It relates to a capsule type strain gauge.

[0002]

2. Description of the Related Art When measuring strain in a high temperature environment of several hundred degrees, a strain detector is placed in the high temperature environment,
It is necessary to electrically connect the output terminal of this detector to various measuring instruments placed at room temperature through a cable.

[0003] This cable must be a heat-resistant cable, for example, MI cable (minera).
l insulated metal sheath
dtable).

In this MI cable, a powder of magnesium oxide (MgO) is tightly packed in a metal tube (generally, a stainless steel tube) as a so-called sheath, and a signal line, for example, a copper core wire is provided in the core. Since a plurality of tubes are inserted and held and do not use a burning material, they are very suitable for use in places exposed to high temperatures of several hundred degrees, such as near a furnace.

FIG. 18 is a plan view of a welded high-temperature strain gauge in a state where a flexible cable is connected via such a MI cable and a lead wire connecting portion. This strain gauge is generally fixed to an object to be measured by spot welding, and detects strain generated in the object to be measured at a high temperature as a change in the resistance value of the gauge element.

In FIG. 1, a workpiece 1 is welded with a high-temperature strain gauge (hereinafter referred to as a “capsule gauge”).
2 is placed. The detailed configuration of the capsule gauge 2 is shown in FIG.

In FIG. 19, a strain-sensitive resistor 4 made of a nickel-chromium alloy wire or the like for converting a change in strain into a change in resistance in response to strain is placed in the center of a tube 3 made of a stainless steel tube. It is arranged in a bent shape. An insulator 5 made of a powder of magnesium oxide (MgO) is firmly filled in the tube 3 in which the strain-sensitive resistor 4 is provided.

Further, one end of the tube 3 is sealed, and a lead wire 6 as an input / output terminal wire connected to the strain-sensitive resistor 4 is led out from the other end, and a ceramic heat-resistant adhesive 7 is used. Sealed by.

In such a capsule gauge 2, a base 8 for fixing the sensing part 2a to the object 1 to be measured is fixed. This base 8 is, as shown in FIG.
Flange portions 8a protruding on both sides of the capsule gauge 2,
8b, on which a weld 9 is firmly fixed by spot welding.

Returning to FIG. 18, one end of the lead wire 6 in the tube 3 extending from the capsule gauge 2 and one end of the MI cable 11 are welded, and the welded portion is hermetically sealed with the outside. The connecting portion 10 is formed.

In this connection part 10, two lead wires 6 electrically connected to the strain-sensitive resistor 4 and two conductors inside the MI cable 11 are electrically connected.

A signal line led out from the other end of the MI cable 11 is connected to one end of a lead wire 14 covered with a flexible cable 13 made of a flexible insulating material such as polyethylene. A hermetically sealed connection portion 12 is formed.

Reference numeral 15 denotes a coating formed around the lead wire 14 with a flexible insulating material such as polyethylene. The lead wire 14 is connected to a strain detection circuit via a bridge box (not shown) in which a bridge circuit and the like are formed.

In general, in strain measurement at a high temperature, it is important to know the temperature at the strain measurement point, and correct the strain measurement data based on the measured temperature to obtain an accurate strain corresponding to the true strain. Measurement data can be obtained. This specific example is shown in FIG. In FIG. 21, the object to be measured 1 placed under high temperature
The above-mentioned capsule gauge 2 is attached to the above, and a sheath type thermocouple 20 is attached near the capsule gauge 2.

The change in the resistance value caused by the change in the strain generated in the capsule gauge 2 is converted into a change in the voltage value or the change in the current value by the bridge box 16 and amplified by the amplifier 17 at the next stage. At the same time, the data is recorded in the recorder 18 and the data processing circuit 19 processes the strain data to obtain the data of the measured strain.

On the other hand, the temperature measuring contact portion of the sheath type thermocouple 20 is fixed near the capsule gauge 2, and its reference contact portion is maintained at the reference temperature. In this reference junction, the cold junction compensator 21 is formed by keeping the ends of the two conductors forming the thermocouple circuit at, for example, ice temperature of 0 ° C. Alternatively, the end of the above-described conductor is placed in an arbitrary (for example, normal temperature) temperature environment, and the temperature in this temperature environment and the reference temperature (for example, 0
The cold junction compensator 21 is configured to electrically compensate for a change in thermoelectromotive force caused by the difference between the cold junction compensator 21.

Accordingly, the cold-junction compensator 2 serving as the reference junction is
To the thermal potential (thermal electromotive force) generated between
The voltage to which the compensation voltage compensated by the cold junction compensator 21 is applied is detected by the voltmeter 22 so that the temperature of the object 1 to be measured (the temperature in the vicinity of the capsule gauge 2).
Is detected. This temperature data is input to the data processing circuit 19 as necessary, so that the change in the detected data corresponding to the temperature can be corrected.

[0018]

In the conventional capsule-type strain gauge, the temperature of the output can be corrected in the strain measurement under a high temperature by using a sheath-type thermocouple together, but the position of the temperature-measuring element can be corrected. And the position of the element for strain measurement does not coincide with each other, so that when there is a temperature difference between the two positions, there is a problem that the temperature of the output cannot be accurately corrected.

When a strain measuring element is attached to each of a plurality of locations on the object to be measured and the distribution of strain within a predetermined range is to be measured, the strain measuring element is placed near each of the strain measuring elements. Ideally, an element for temperature measurement should be provided, but in reality it is difficult to install due to dimensional restrictions, or if many elements for temperature measurement are attached, mechanical There is a problem that the properties may be changed, which causes a decrease in the accuracy of strain measurement.

Further, providing temperature detecting elements in the vicinity of each of a plurality of strain detecting elements is extremely poor in workability. For this reason, since the temperature detecting element has to be provided at a position representative of the temperature distribution of the plurality of strain detecting elements, the problem that the output temperature cannot be accurately corrected remains. Become.

The present invention has been made in view of the above circumstances, and is capable of efficiently and accurately detecting the temperature itself of a strain detecting element placed at a high temperature, and is small and inexpensive. It is an object of the present invention to provide a capsule type strain gauge with a temperature measuring function which is excellent in workability, heat resistance , moisture resistance and durability .

[0022]

In order to achieve the above object, a capsule type strain gauge with a temperature measuring function according to the present invention comprises a heat resistant insulating material filled in a sealed sheath tube. A sensor section comprising a strain-sensitive resistor held in the sheath tube by a body and two leads connected to the strain-sensitive resistor and led out of the sheath tube; and a sensor section led out of the sheath tube. One end of each of the two leads and two conductors made of dissimilar metal derived from the MI cable is connected by brazing, the periphery thereof is surrounded by a metal cylinder, and the sheath tube is provided inside the cylinder. the terminal and the terminal of the MI cable, a first connecting portion formed by seals also seal the cylindrical body itself with sealed with ceramic adhesive having heat resistance, the MI cable The two other end and the core wires of the cold-type flexible cable conductor connecting the other terminal of at least the MI cable around surrounded by the tubular body and inside the cylindrical body of the inner hermetically with a resin And a second connection portion that is sealed, and by selectively connecting each other end of the flexible cable to one side of a bridge circuit, the strain-sensitive resistor is output from the output end of the bridge circuit. The flexible cable is selectively disconnected from one side of the bridge circuit and connected to an input terminal of a thermometer, so that the input terminal is used as a reference contact portion. First
The connection point between the sensor section and the heat-resistant cable in the connection section is used as a temperature measuring contact section so that the temperature at the temperature measuring contact section can be detected.

[0023]

The capsule strain gauge with the temperature measuring function constructed as described above holds the strain-sensitive resistor insulated at the core in the sheath tube by filling the powder made of heat-resistant insulating material. Then, the two leads connected to the strain-sensitive resistor are led out from the end of the sheath tube.

One end of each of two conductive wires as a heat-resistant cable is connected to the two lead portions, and the other end is electrically connected to each core wire of a normal-temperature flexible cable.
At this time, the two conductors function as one conductor and the other conductor of the thermocouple forming circuit, and a connection point between the sensor unit and the heat-resistant cable functions as a temperature measuring contact part of the thermocouple.

Then, by selectively connecting the other end of the flexible cable to one side of the bridge circuit and inserting the sensor section into one side of the bridge circuit, distortion generated in the sensor section from the output end of the bridge circuit is obtained. Can be detected.

By selectively disconnecting the flexible cable from one side of the bridge circuit and connecting the flexible cable to the input terminal of the thermometer, this input terminal is used as a reference contact point, and the connection point between the sensor unit and the heat-resistant cable is connected. The temperature measuring contact portion is configured to detect the temperature.

[0027]

FIG. 1 to FIG. 17 show an embodiment of the present invention.
This will be described in detail with reference to FIG.

FIG. 1 is a plan view showing an external configuration of a capsule type strain gauge with a temperature measuring function according to one embodiment of the present invention.

In the figure, the whole is composed of a sensor part 30 composed of a strain sensitive part 31 and a sheath tube 32, a first connecting part 33, an MI cable 34, a second connecting part 35, and a flexible cable 36. I have.

That is, the strain sensing section 31 of the sensor section 30
As shown in detail in FIG. 2, a large-diameter portion 40 of a sheath tube 32 is fixed to a center along the longitudinal direction of a band-shaped flange portion 37 with a thin plate attached to an object to be measured. The strain-sensitive resistor 38 is firmly held by densely filling a heat-resistant insulating material, for example, a powder 39 of magnesium oxide (MgO).

When the maximum operating temperature is about 550 ° C., a nickel-chromium-based or platinum tungsten-based alloy is used as the strain-sensitive resistor 38. When the maximum temperature is about 800 ° C., an iron-chromium-aluminum-based alloy is used. Nickel-chromium-iron alloys and nickel-chromium-aluminum alloys are used.

The material of the flange portion 37 of the sensor portion 30 and the material of the sheath tube 32 are N, which is excellent in corrosion resistance and heat resistance.
Since CF600 (JIS symbol) is used, the maximum operating temperature is secured up to 800 ° C.

The outer diameter of such a sheath tube 32 is formed in two steps, that is, a large diameter portion 40 and a small diameter portion 41, and a distal end portion of the large diameter portion 40 is fixed to the flange portion 37. The end of 41 is connected to the first connection part 33 made of the NCF 600 described above.

As shown in detail in FIG. 3, the first connecting portion 33 connects the small diameter portion 41 of the sheath tube 32 and the MI cable 34 via a cylindrical body 42. The base of the lead portion of the strain sensitive resistor 38 protruding from the tip of 41 is terminal-treated with a ceramic adhesive 43 sufficiently resistant to a high temperature of about 800 ° C.

On the other hand, the bases of the alumel wire 45 and the chromel wire 46 projecting from the end of the MI cable 34 are terminated with a ceramic adhesive 44 sufficiently resistant to a high temperature of about 800 ° C., and the maximum use temperature is about 550 ° C. In the case of the above, when each of the "strain-sensitive resistor 38 and alumel wire 45" and the "strain-sensitive resistor 38 and chromel wire 46" are joined by silver brazing at the connection point a, and the maximum operating temperature is about 800 ° C. Are joined by nickel brazing at the connection point a.

A flexible cable 36 is connected to the other end of the MI cable 34 having one end connected to the first connection portion 33 via a second connection portion 35 shown in detail in FIG.

That is, the terminal portion of the MI cable 34 is supported by the cylindrical body 48 and an alumel wire 45 protruding from the end thereof.
And the chromel wire 46 are hermetically sealed with an adhesive 47. The terminal portion of the flexible cable 36 is supported by the cylindrical body 48, and the protruding core wires 50, 52.
Are covered with coatings 49 and 51 made of plastic such as polyethylene.

Then, the alumel wire 45 and the chromel wire 46
Are coated in advance with silver soldering to improve soldering, and "Alumel wire 45 and core wire 50" and "Chromel wire 46 and core wire 52" are soldered at connection point b. Are electrically connected. It should be noted that the interior of the cylinder 48 is filled with an epoxy resin after the connection work.

As shown in FIG. 5, the flange portion 37 is fixed to the object 1 by spot welding, and the first connecting portion 33 is provided with a metal band 53 as shown in FIGS. Is wound about half a turn, and both sides (flange) are spot-welded 5
At 4, it is fixed on the measured object 1. Further, the fixing of the MI cable 34 is performed in the same manner as described above using the metal band 55.

Next, an electric circuit to which the capsule strain gauge with a temperature measuring function according to the present embodiment configured as described above is connected will be described with reference to FIG. The capsule type strain gauge 100 is connected to an input terminal of a switch 56 that switches one input to two systems, and one system of an output terminal of the switch 56 is connected to a bridge box 57, an amplifier 58,
The recorder 59 is connected to a strain detection system circuit configured by sequentially connecting the data processing circuit 60 to the recorder 59. The other system at the output end of the switch 56 is connected to a temperature measurement system circuit configured by sequentially connecting a cold junction compensator 61 and a voltmeter 62.

When measuring dynamic strain at a high temperature using the capsule strain gauge with a temperature measuring function according to the present embodiment configured as described above, the switch 56 is connected to the bridge box 57 side of the strain detection system circuit side. Switch. In this case, the circuit is as shown in FIG.

That is, the resistance component r of the strain sensitive resistor 38
_g and MI cable 34, flexible cable 36
Is inserted into one side of the bridge. The other three sides of the bridge circuit are formed with fixed resistors R1, R2, and R3 having extremely small temperature coefficients.

Accordingly, a predetermined input voltage (bridge voltage) is provided between the connection point between the fixed resistor R1 and the resistance component r _g (including the internal resistance of the cables 34 and 36) and the connection point between the fixed resistors R2 and R3. Is supplied, an output voltage is generated between the connection point of the fixed resistors R1 and R2 and the connection point of the resistor R3 and the resistance component r _g according to the change of the resistance component r _g of the strain sensitive resistor 38. This output voltage follows the strain that the strain-sensitive resistor 38 receives from the object 1 to be measured.

This output voltage is an output voltage from which a DC component and a low frequency component have been cut by a CR type high pass filter circuit formed by a capacitor Cf and a resistor Rf. The characteristic of this cutoff frequency, that is, Eout / Ein
Is given by the following equation, where the capacitance of the capacitor Cf shown in FIG.

[0045]

(Equation 1) Therefore, the capacitance Co of the capacitor Cf is set to 1 μm.
F, 2.2 μF, and 10 μF, the respective cutoff frequencies are 16H as shown in FIG.
z, 7.23 Hz and 1.6 Hz. For this purpose, the capacity Co may be selected in accordance with the mode of the frequency of the dynamic strain to be measured. The output voltage of the bridge box 57 obtained in this manner is amplified by the amplifier 58, recorded in the recorder 59, and subjected to desired data processing in the data processing circuit 60.

Now, when the switch 56 is switched to the temperature measuring circuit system, the resistance component r _g of the strain sensitive resistor 38 becomes
A circuit is inserted between one ends of the alumel wire 45 and the chromel wire 46 as shown in FIG. The other end of the alumel wire 45 is connected to one core wire 50 of the flexible cable 36 at a connection point b, and the cold junction compensator 6
1 will be connected.

That is, this cold junction compensator 61 has fixed resistances R4, R
5 and R6 are connected to each other, and a bridge circuit is connected to a negative resistance R0 having a characteristic that the resistance value decreases when the temperature rises on one side.
A fixed input voltage is supplied between a connection point of the fixed resistance R6 and the connection point of the negative resistance R0.

The connection point between the fixed resistors R5 and R6 and the fixed resistor R
4. A strain sensitive resistor 3 between the connection point of the negative resistance R0
8 and the resistance component _{r g} of alumel wire 45, chromel wire 46
Voltmeter 6 for detecting the thermoelectromotive force of the thermocouple circuit formed by
2 will be connected.

Originally, as the cold junction compensator 61,
A reference temperature, for example, a constant temperature of 0 ° C.,
In this embodiment, electrical means is used so that the actual temperature is always 0 ° C. even if the temperature of the reference contact portion is an arbitrary temperature.

The thermoelectromotive force of the thermocouple circuit formed by the alumel wire 45 and the chromel wire 46 is, of course, the reference electromotive force since the reference contact point is placed in an arbitrary environment (for example, normal temperature). An output difference occurs with respect to the thermoelectromotive force at a temperature (for example, 0 ° C.).

To compensate for this output difference, a negative resistor R0 is provided on one side of the bridge as shown in FIG. The temperature characteristic of the negative resistance R0 is as follows.
5, approximating the thermoelectromotive force characteristics of the thermocouple circuit formed by the chromel wire 46. Then, based on the negative resistance R0 having such characteristics, a change in thermoelectromotive force due to a change in temperature of the reference contact portion is compensated.

Here, the alumel wire 45 and the chromel wire 46
Strictly speaking, the temperature-measuring contact portion formed by combining the strain-sensitive resistor 38 and the alumel wire 4
5, since it has a resistance component such as the chromel wire 46, it is examined whether or not it is affected by the resistance component.

As shown in FIG. 11, the input terminal of the voltmeter 62 is equivalently provided with a resistance component r _g of the strain sensitive resistor 38, a resistance component R _LA of the alumel wire 45, and a resistance component R _{LC of the} chromel wire 46. Are connected in series. And
A thermoelectromotive voltage Eo is generated by the thermocouple circuit using the alumel wire 45 and the chromel wire 46.

In general, in a circuit as shown in FIG. 12, in a state where C and D are short-circuited, points A and B (cold junction or reference junction) and points C and D (temperature measurement junction) are connected. When a temperature difference is given between them, a thermoelectromotive voltage is generated between A and B by the Seebeck effect.

[0055] For this, the output voltage E shown in Fig. _{11, E = Eo-E LA -E} LC -E g next true thermoelectric voltage Eo and the voltage E is not equal. Here, E _LA is a potential difference caused by the resistance component R _LA , E _LC is a potential difference caused by the resistance component R _LC , and E _g is a potential difference caused by the resistance component r _g .

However, in the embodiment shown in FIG.
The output voltage E is measured while the resistance value of the strain-sensitive resistor 38 is about 120Ω and the resistance value of the internal resistance of the lead wire including the alumel wire 45, the chromel wire 46, the flexible cable 36 and the like is about 80Ω. Input impedance Zi of the voltmeter (thermometer) for the
It is about MΩ. Therefore, the resistance of the entire circuit is represented by the resistance components R _LA , r _g , R _LC and the impedance Z.
If i is added, that is, if Zi = 100KΩ, 1
00.2 KΩ.

For this purpose, the resistance components R _LA , r _g , R _LC
Is very low current flowing through the respective, above-described drop voltage E _{LA, E g,} since a value which each negligible E _LC, so that substantially equal data is obtained truly thermoelectric voltage Eo .

Based on the output data of the voltmeter 62, the distortion data obtained by the distortion detection circuit composed of the bridge box 57, the amplifier 58, and the recorder 59 is corrected by the data processing circuit 60 to obtain the true distortion data. As a prerequisite, it is necessary to correct the resistance value of the MI cable 34, the change in the resistance value of the sensor unit 30, the gauge factor, and the like by measuring the temperature of the sensor unit 30.

First, as shown in FIG.
1. A part (length L1) of the sheath tube 32, the first connection part 33 and the MI cable 34 is placed under high temperature, and a part (length L2) of the MI cable 34 and the second connection part 35 are flexible. The cable 36 is placed at room temperature and the length L1
Is 0.5 m and the length L2 is 1.5 m, the resistance correction coefficient of the MI cable 34 is obtained from the graph shown in FIG. For example, when the temperature is 800 ° C., the coefficient is 1.
It is 45.

Further, the strain-sensitive resistor 38 itself,
The correction coefficient of the resistance value based on the temperature is obtained according to FIG. For example, when the temperature is 800 ° C., the coefficient is 1.04
It is set to 8.

Further, a correction coefficient of the gauge factor of the strain-sensitive resistor 38 itself based on the temperature is obtained by referring to FIG. For example, when the temperature is 800 ° C., the resistance correction coefficient is set to 0.92. Based on the correction coefficient of the above three items, it is the final gauge factor K _B of the total gauge determined as the following formula.

[0062]

(Equation 2) Here, K ₁ is the gauge factor corrected by the correction coefficient calculated in FIG 17, R _GO is corrected resistance value by the correction factor obtained in FIG. 16, r _g is corrected by the correction coefficient obtained by the FIG. 16 The resistance value obtained by adding the calculated resistance value R _GO and the resistance value corrected by the coefficient obtained in FIG. Therefore, in this embodiment, since the alloy having excellent high-temperature stability is used as the strain-sensitive resistor 38, it can sufficiently withstand a high temperature of about 800 ° C.

Further, since the core wire of the MI cable 34 exposed to a high temperature uses the alumel wire 45 and the chromel wire 46 having excellent durability at a high temperature, it can sufficiently withstand a high temperature of about 800 ° C. .

Further, these strain-sensitive resistors 38,
Since the surface of the MI cable 34 and its first connecting portion 33 and the like which are directly exposed to high temperatures is made of NCF600, it can withstand high temperatures of about 800 ° C.
Even if exposed to an acid or the like, its function is not impaired.

In this embodiment, the temperature measuring function, that is, the alumel wire and the chromel wire forming the thermocouple circuit are sealed in a sheath tube to form a heat-resistant cable. No need to use it,
To that extent, the overall configuration can be simplified, and as a result, costs can be reduced.

Further, since the size is greatly reduced as compared with the conventional capsule type strain gauge, the strain gauge can be mounted in a narrow place where mounting was impossible so far. Strain distribution measurement can be performed at a high density when measuring.

Further, since the mounting of the sensor portion can be easily performed by spot welding, no adhesive is required, and no heating or pressurizing is required at the time of mounting, and measurement can be performed immediately after mounting. . In addition, when the sensor unit 30 is attached to the object to be measured, it is not necessary to connect a lead wire or to perform a coating process, so that there is an advantage that efficient attachment can be performed and no special skill is required.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the strain-sensitive resistor 38 is directly connected to the first connection portion 33. However, the strain-sensitive resistor 38 is provided only in the strain detecting portion, and a heat-resistant conductive wire or the like is used. A connection may be made to the first connection portion 33 via a lead wire, and this lead wire may be electrically connected to the MI cable 34.

The two core wires (for example, the alumel wire 45 and the chromel wire 46) of the MI cable 34 forming the thermocouple circuit are buried inside the capsule portion in which the strain-sensitive resistor 38 is housed. Is also good. With such a configuration, although the outer diameter of the strain-sensitive portion 31 cannot be denied, the strain-sensitive portion and the temperature measurement portion match, and more accurate strain measurement can be realized.

Further, the respective materials such as the strain-sensitive resistor 38, the sheath tube 32, the first connecting portion 33, the outer surface coating of the MI cable 34, and the core wires of the MI cable 34 (almer wire 45 and chromel wire 46) are as follows. Of course, it may be changed according to the temperature actually used and the state of special conditions such as high-pressure gas and steam.

The present invention can be applied only to a capsule type strain gauge in which only one strain sensitive resistor 38 is embedded and held in a sheath tube 32 by powder 39 as shown in FIG. In addition, in addition to the above-described strain-sensitive resistor 38, a dummy resistor provided in an insulated state so as to be wound therewith is placed in the sheath tube 32 together with the powder 3.
The present invention can also be applied to a capsule-type strain gauge of the type buried and held by No. 9.

In this case, the dummy resistor is made of the same material as the strain-sensitive resistor 38, and
A structure in which the periphery of the strain-sensitive resistor 38 is wound so as to be insensitive to the strain of the object to be measured received from 7 and to change its resistance value, gauge factor and the like in response to temperature change. do it.

In this case, when measuring the temperature,
One end of the strain sensitive resistor 38 and one end of the dummy resistor
The first connection 33 connects the other end of the strain-sensitive resistor 38 and the other end of the dummy resistor to the one end of the alumel wire 45 and the chromel wire 46 at the first connection 33, respectively. do it.

[0074]

As is apparent from the above description, the capsule type strain gauge with a temperature measuring function according to the present invention firstly comprises :
Since the two core wires of the cable are made of a material that forms a thermocouple circuit as a heat-resistant cable for guiding the detection output of the strain gauge to the measurement circuit, a sheath-type heat-resistant thermocouple is used.
There is no need to use it separately, and the overall configuration is simplified accordingly.
Can be simplified, resulting in cost reduction
You. Second, the sensor is filled in a sealed sheath tube.
The sheath is filled with heat-resistant insulating powder.
Hold the strain sensitive body and two leads in the tube
Configuration, compared to conventional capsule-type strain gauges.
In a narrow space that could not be mounted until now
It can be installed in places, and by installing multiple
Strain distribution with high density when measuring strain distribution
A measurement can be made.

Third, according to the present invention, the sheath tube
From two leads and M1 cable
Connect one end of each of the two lead wires made of dissimilar metals to the first
Connected by brazing at the connection part, and the surrounding area is a metal cylinder
At the end of the sheath tube inside the tubular body.
A ceramic having heat resistance between the end and the end of the M1 cable
And sealed with a rubber-based adhesive.
Each of the other ends of the two conductors and a room-temperature flexible cable
The core wire is connected at the second connection portion, and its periphery is surrounded by a cylindrical body.
At least the other end of the M1 cable inside the cylindrical body
Since the end is hermetically sealed with resin,
Outside air is prevented from entering the M1 cable.
Suppose that the outside air slightly entered from the other end from the M1 cable
However, at the first connection point, the terminal at one end of the M1 cable is
When sealed with a heat-resistant ceramic adhesive,
Since the cylindrical body itself is also sealed, the first connecting portion
It does not reach the cylinder, and the first connection part also seals the cylinder itself.
Because it is stopped, intrusion of outside air into the cylinder is also prevented.
The end of the sheath tube is also connected to the first connection
After all, it is eventually sealed into the sheath tube.
Does not allow outside air to enter. Therefore, the intrusion of outside air
The strain gauge in the sheath tube is not oxidized
Also, since insulation deterioration due to moisture absorption does not occur at all,
Extremely durable capsule type strain gauge with temperature measurement function
Can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view of a capsule type strain gauge with a temperature measuring function according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a sensor unit shown in FIG.

FIG. 3 is an enlarged sectional view of a first connection portion shown in FIG.

FIG. 4 is an enlarged sectional view of a second connecting portion shown in FIG.

FIG. 5 is a perspective view showing an attached state of the capsule type strain gauge with a temperature measuring function shown in FIG. 1;

FIG. 6 is a side view showing only the MI cable of the first connection portion shown in FIG. 5 in a cutaway manner.

FIG. 7 is a perspective view showing a fixed state of a first connecting portion shown in FIG. 5;

8 is a circuit diagram of a measuring unit to which the capsule type strain gauge with a temperature measuring function shown in FIG. 1 is connected.

9 is a detailed circuit diagram of the bridge box circuit shown in FIG.

FIG. 10 is a frequency characteristic diagram showing cutoff characteristics of the circuit shown in FIG. 9;

FIG. 11 is an equivalent circuit diagram showing a relationship between a thermoelectromotive force and a line resistance.

FIG. 12 is an equivalent circuit diagram for explaining the operation of the circuit shown in FIG. 8;

FIG. 13 is a detailed circuit diagram of the circuit shown in FIG. 8;

FIG. 14 is a plan view showing a relationship between MI cable lengths exposed to high temperatures.

FIG. 15 is a characteristic diagram showing a resistance correction coefficient with respect to the temperature of the MI cable.

FIG. 16 is a characteristic diagram showing a resistance correction coefficient with respect to a temperature of the strain-sensitive resistor.

FIG. 17 is a characteristic diagram showing a gauge factor correction coefficient of the strain-sensitive resistor.

FIG. 18 is a plan view showing the appearance of a conventional capsule-type strain gauge.

FIG. 19 is an enlarged sectional view of the capsule portion shown in FIG.

20 is an enlarged plan view showing a state in which the capsule section shown in FIG. 18 is fixed on an object to be measured.

FIG. 21 is a circuit diagram showing a conventional temperature measurement circuit and a distortion detection circuit.

[Explanation of symbols]

 Reference Signs List 30 sensor part 31 strain sensitive part 32 sheath tube 33 first connection part 34 MI cable 35 second connection part 36 flexible cable 37 flange part 39 powder 40 large diameter part 41 small diameter part 42, 48 cylindrical body 43, 44, 47 adhesive 45 alumel wire 46 chromel wire 49,51 coating 50,52 core wire 53,55 metal strip 54 point weld 56 switch 57 bridge box 58 amplifier 59 recorder 60 data processing circuit 61 cold junction compensator 62 voltmeter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B ⁷ /00-7/34 G01D 21/02 G01K 13/00

Claims (1)

(57) [Claims] 1. A strain-sensitive resistor held in a sheath tube by a powder of a heat-resistant insulating material filled in a sheath tube to be hermetically sealed, and the sheath connected to the strain-sensitive resistor and connected to the strain-sensitive resistor. 2 derived from the tube
One end of each of two sensor wires consisting of two lead portions, two lead wires derived from the sheath tube, and two lead wires made of dissimilar metal derived from the MI cable are connected by brazing, and the periphery thereof is connected. Surrounded by a metal tubular body, and inside the tubular body, the end of the sheath tube and the end of the MI cable are sealed with a heat-resistant ceramic-based adhesive, and the tubular body itself is also sealed. A first connecting portion, and the other ends of the two conductors in the MI cable are connected to the respective core wires of a room-temperature-type flexible cable, the periphery thereof is surrounded by a cylinder, and at least inside the cylinder. A second connection portion in which the other end of the MI cable is hermetically sealed with resin, and by selectively connecting each other end of the flexible cable to one side of a bridge circuit, The said And an output corresponding to the strain received by the strain-sensitive resistor from the output end of the bridge circuit, and selectively disconnecting the flexible cable from one side of the bridge circuit to the input end of the thermometer. By connecting, the input end serves as a reference contact portion, and a connection point between the sensor portion and the heat-resistant cable in the first connection portion serves as a temperature measuring contact portion, so that the temperature at the temperature measuring contact portion can be detected. Capsule type strain gauge with temperature measurement function, characterized in that: