JP2013148373A - Distribution type temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distribution type temperature sensor which can be manufactured at a low cost.SOLUTION: A distribution type temperature sensor 1a includes a temperature-sensing element 2a cylindrically formed to allow a conductive liquid 3a to be charged thereto and electrical resistivity of which varies depending on temperature, a first electrode 67 electrically connected to one end of the temperature-sensing element 2a and a second electrode 68 electrically connected to the other end of the temperature-sensing element 2a as an approximate configuration. The distribution type temperature sensor 1a further includes a measurement part 71 for measuring a temperature in a one-dimensional direction between the first electrode 67 and the second electrode 68 corresponding to a position of the conductive liquid 3a on the basis of the electrical resistivity measured through the first electrode 67 and the second electrode 68 as an approximate configuration.

Description

  The present invention relates to a distributed temperature sensor.

  As a conventional technique, there is known a temperature distribution measuring instrument that measures a temperature distribution in the length direction of an optical fiber using Raman scattered light generated when pulsed light enters an optical fiber (for example, Patent Document 1). reference.).

  This Raman scattered light includes anti-Stokes light that is generated on the short wavelength side with respect to the wavelength of the light pulse and has high temperature dependence, and Stokes light that is generated on the long wavelength side and has low temperature dependence. ing. Therefore, the intensity ratio changes in proportion to the temperature change. The temperature distribution measuring device measures the temperature distribution of the measurement object based on this intensity ratio.

JP 2011-242142 A

  However, since the conventional temperature distribution measuring instrument is weak in Raman scattered light, measurement errors are likely to occur, and in order to reduce the errors, it is configured using a microcomputer having a high processing capacity. is there.

  Accordingly, an object of the present invention is to provide a distributed temperature sensor that can be manufactured at low cost.

  According to one embodiment of the present invention, a temperature sensing element which is formed in a cylindrical shape so that a conductive liquid can be put therein and whose electric resistivity changes with temperature, and a first electrode which is electrically connected to one end of the temperature sensing element And a second electrode electrically connected to the other end of the temperature sensing element.

  According to this invention, it can manufacture at low cost.

FIG. 1A is a longitudinal sectional view of a distributed temperature sensor according to an embodiment, and FIG. 1B is a sectional view taken along line I (b) -I (b) in FIG. It is sectional drawing seen from the arrow direction. Fig.2 (a) is a schematic diagram regarding the experimental apparatus for confirming the temperature dependence of the temperature sensing body of the distributed temperature sensor which concerns on embodiment, (b) is the temperature and electrical resistance of a temperature sensing body. It is a graph which shows the relationship. FIG. 3A is a schematic diagram of an experimental apparatus for experimenting the temperature dependence of the temperature sensing element according to the present embodiment, and FIG. 3B is a schematic view of III (b) -III in FIG. (B) It is sectional drawing which looked at the cross section cut | disconnected by the line from the arrow direction. FIG. 4A is a block diagram of the experimental apparatus according to the present embodiment, and FIG. 4B is a circuit diagram of the measurement circuit. FIG. 5A is a graph showing a result of measuring the electrical resistance of the distributed temperature sensor according to the embodiment, and FIG. 5B is a result of moving and numerically differentiating the resistance value of FIG. 5A. It is a graph which shows. FIG. 6A is a graph showing a temperature change of the frozen temperature sensor according to the embodiment, and FIG. 6B is a block diagram of a measurement circuit according to a modification.

[Embodiment]
(Summary of embodiment)
The distributed temperature sensor according to the embodiment is formed in a cylindrical shape so that a conductive liquid can be put therein, and is electrically connected to one end of the temperature sensing element whose electric resistivity changes depending on the temperature. A first electrode and a second electrode electrically connected to the other end of the temperature sensing element.

(Operation principle of distributed temperature sensor)
FIG. 1A is a longitudinal sectional view of a distributed temperature sensor according to an embodiment, and FIG. 1B is a sectional view taken along line I (b) -I (b) in FIG. It is sectional drawing seen from the arrow direction. In each drawing according to the embodiment, the ratio between parts may differ from the actual ratio.

  A distributed temperature sensor (DTS) is a temperature sensor that can acquire temperature information inside a linear sensor one-dimensionally along each part of the sensor. Since this distributed temperature sensor is linear, it is possible to measure the temperature distribution in a wide space by laying it on the object.

  For example, as shown in FIGS. 1A and 1B, the distributed temperature sensor 1 includes a temperature sensing body 2 formed in a cylindrical shape so that the conductive liquid 3 can be placed therein.

  The temperature sensing element 2 can pass an electric current, and its electrical resistivity is given by ρ (x) for the position x.

ここで、ｒ_１は、図１（ｂ）に示すように、感温体２の内径であり、ｒ_２は、感温体２の外径である。 The electrical resistivity of the conductive liquid 3 is sufficiently smaller than ρ (x), and when the conductive liquid 3 is located from the position 1 to the position L, the electrical resistance at both ends of the temperature sensing element 2 is approximated by the following equation. Can do.

Here, r ₁ is the inner diameter of the temperature sensing element 2 and r ₂ is the outer diameter of the temperature sensing element 2 as shown in FIG.

従って、電気抵抗率が温度により変化する材料を感温体２に用いることにより、感温体２に沿った温度分布を測定することができる。 For example, when the conductive liquid 3 is injected into the through-hole 20 of the temperature sensing body 2 at a speed v, the temperature sensing element 2 represents the electrical resistivity of the temperature sensing element 2 at each point x by the following equation. Can do.

Therefore, the temperature distribution along the temperature sensing element 2 can be measured by using a material whose electrical resistivity varies with temperature for the temperature sensing element 2.

(Confirmation of temperature dependence of electrical resistivity)
Fig.2 (a) is a schematic diagram regarding the experimental apparatus for confirming the temperature dependence of the temperature sensing body of the distributed temperature sensor which concerns on embodiment, (b) is the temperature and electrical resistance of a temperature sensing body. It is a graph which shows the relationship.

  For example, as shown in FIG. 2A, the experimental apparatus 4 includes a container 40 in which water 41 is placed, a heater 42 for raising the temperature of the water 41, and a power supply 43 that supplies power to the heater 42. A test tube 44 in which the temperature sensing element 21 is placed, a first electrode 46 and a second electrode 47 inserted in the temperature sensing element 21, and a temperature sensor 48 for measuring the temperature of the temperature sensing element 21. In general, it is structured.

  As the heater 42, a carbon film resistor was used.

  The first electrode 46 and the second electrode 47 are electrically connected to a power source 49 (AG-203A manufactured by Kenwood). Further, the current flowing through the first electrode 46 and the second electrode 47 is measured by an ammeter 50 (Agilent 34401A), and the voltage between the first electrode 46 and the second electrode 47 is measured by a voltmeter 51. (Agilent 34401A). The first electrode 46 and the second electrode 47 are formed using a copper wire having a diameter of about 1 mm.

  The temperature sensor 48 (LM35DZ manufactured by National Semiconductor) is electrically connected to, for example, a data logger (OR1400 manufactured by Yokogawa Electric Corporation). For example, the data logger calculates the temperature of the temperature sensing body 21 based on temperature information output from the temperature sensor 48.

  In this experiment, saline solution (NaCl solution) gelled with agar is used as the temperature sensor 21 of the distributed temperature sensor.

  It is known that the electrical resistivity of a 7.1352 wt% KCl solution varies approximately linearly with respect to temperatures in the range of 0-25 ° C., and its temperature coefficient is −1.6% / ° C. .

  Because of the chemical similarity between the NaCl solution and the KCl solution, it is desirable that the electrical resistivity and temperature coefficient of the saline solution have characteristics similar to those of the KCl solution. Therefore, in this experiment, it was decided to confirm the temperature dependence of the electrical resistivity.

  The temperature sensing element 21 was a polymer composed of a 5 wt% NaCl solution and 3 wt% agar used to maintain the shape.

  The temperature sensing element 21 was produced by injecting a NaCl solution into a test tube, dissolving the agar with a hot water bath, and returning to room temperature (28 ° C.) for gelation.

  The first electrode 46, the second electrode 47, and the temperature sensor 48 are inserted into the hole provided in the lid 45 of the test tube 44 and then the temperature sensing body 21 is gelled before the temperature sensing body 21 is gelled. Inserted.

  In this experiment, electric power is supplied from the power source 43 shown in FIG. 2A to the heater 42, and electric power is supplied when the temperature of the temperature sensing body 21 reaches about 45 ° C. based on temperature information obtained from the temperature sensor 48. The temperature of the temperature sensing element 21 was changed by natural cooling.

  Here, in this experiment, the power source 49 was an AC power source to prevent electrolysis of NaCl. The power supply 49 has a power supply frequency of 300 Hz, and its waveform is a sine wave.

  In this experimental apparatus 4, the electrical resistance between the first electrode 46 and the second electrode 47 is proportional to the electrical resistivity of the polymer, that is, the saline solution gelled with agar. Dependencies can be measured. The result of the measurement is a graph shown in FIG.

  From this experiment, it was confirmed that the temperature coefficient of the electric resistance of the temperature sensing element 21 was about −1.3% / ° C. as shown in FIG. That is, the electrical resistivity of the temperature sensing element 21 changes linearly with the temperature of the temperature sensing element 21 even though the temperature sensing element 21 is formed using an NaCl solution having an electrolyte different from that of the KCl solution. I was able to confirm. In addition, the temperature coefficient of the electric resistance of the temperature sensing element 21 substantially coincided with the temperature coefficient of the KCl solution.

  In the temperature measurement experiment of the distributed temperature sensor described below, a part of the distributed temperature sensor was set to a low temperature of 0 ° C. or lower.

  Here, it is known that the electrolyte contained in pork is involved in the temperature dependence of the electrical resistivity, similar to the polymer formed using agar.

  Pork has a monotonous decrease in electrical conductivity with a decrease in temperature from a normal temperature range (20 ° C.) to a low temperature range (−30 ° C.). That is, the electrical resistivity is determined if the temperature is determined. The reverse is also true, and the temperature can be determined from the electrical resistivity.

  Therefore, this experiment confirmed that the temperature could be read from the electrical resistivity of the temperature sensing element 21 formed using agar.

(Operation check of distributed temperature sensor)
FIG. 3A is a schematic diagram of an experimental apparatus for experimenting the temperature dependence of the temperature sensing element according to the present embodiment, and FIG. 3B is a schematic view of III (b) -III in FIG. (B) It is sectional drawing which looked at the cross section cut | disconnected by the line from the arrow direction. FIG. 4A is a block diagram of the experimental apparatus according to the present embodiment, and FIG. 4B is a circuit diagram of the measurement circuit.

  For example, as shown in FIGS. 3A and 3B, the distributed temperature sensor 1 a in this experiment is formed in a cylindrical shape so that the conductive liquid 3 a can be put therein, and the temperature sensitivity in which the electrical resistivity changes depending on the temperature. A body 2a, a first electrode 67 electrically connected to one end of the temperature sensing element 2a, and a second electrode 68 electrically connected to the other end of the temperature sensing element 2a. It is configured.

  In addition, the distributed temperature sensor 1a further includes the first electrode 67 and the first electrode corresponding to the position of the conductive liquid 3a based on the electrical resistivity measured through the first electrode 67 and the second electrode 68. And a measuring unit 71 that measures the temperature in a one-dimensional direction between the two electrodes 68.

  The temperature sensing element 2a includes a polymer (eg, agar) containing a conductive material (eg, saline). The temperature sensing element 2a is a porous body containing a polymer.

  As shown in FIG. 3 (b), the temperature sensing element 2 a is schematically configured to include a sponge 22 as a porous body and a polymer 23.

  In this experiment, the sponge 22 was impregnated with a polymer made of agar whose characteristics were confirmed as described above to produce the distributed temperature sensor 1a as the temperature sensing element 2a, and the operation was confirmed.

  The polymer 23 of the distributed temperature sensor 1a used in this experiment was prepared by preparing an agar liquid having the same composition as described above and impregnating the sponge 22 while it was melted. The sponge 22 was used because the shape of the tube cannot be made with agar alone. The sponge 22 was a continuous filter, and a urethane filter sponge having a bubble size of about 1 mm was used.

  The sponge 22 is porous, for example, as shown in FIG. 3B, and is configured so that the pores are filled with the polymer 23.

  The length of the produced temperature sensing element 2a is about 30 cm, the inner diameter r is about 5 mm, and the outer diameter R is about 10 mm.

  The first electrode 67 and the second electrode 68 shown in FIG. 3A are in close contact with the sponge 22 by twisting bare wires before impregnating with the agar liquid.

  A syringe 64 in which the cylinder 65 is filled with the conductive liquid 3a is connected to one end of the temperature sensing element 2a. The piston 66 of the syringe 64 is attached to a head 63 of a scanner 60 for a personal computer as a pump.

  For example, as shown in FIG. 3A, the head 63 is driven at a predetermined speed (constant speed) along a rail 62 attached to the housing 61. The head 63 includes a stepping motor for driving and can determine the moving speed with high accuracy, and is suitable for this experiment.

  For example, as shown in FIG. 4A, the head 63 is connected to a DC power source 63a (E3630A manufactured by Agilent) and is configured to be supplied with DC power and driven.

  The temperature sensing element 2a is connected to an AC power source 69 (AG-203A manufactured by Kenwood) via the first electrode 67 and the second electrode 68, and supplied with AC power.

  The temperature sensing element 2a is electrically connected to a DC converter 70 (T-RM501-1 manufactured by Turtle Industry Co., Ltd.), and the DC converter 70 is electrically connected to a measuring unit 71 (OR1400 manufactured by Yokogawa Electric Corporation). Has been. The measurement unit 71 may be configured to include the DC converter 70, or the DC converter 70 may be omitted as long as a DC voltage is output.

  A saturated saline solution was used as the conductive liquid 3a. The electrical conductivity of the saturated saline solution is unknown, but the solubility is 35.9 wt%, which is considered to be sufficiently larger than 5 wt% of the polymer using agar.

Here measuring circuit 8 for measuring the temperature in, for example, as shown in FIG. 4 (b), a voltmeter voltage V _t of the temperature sensing element 2a and the current detection resistor 80 that are electrically connected in series 81 to measure. The measurement circuit 8 includes a voltmeter 82 that measures the voltage of the temperature sensing element 2 a and the current detection resistor 80.

  The AC power supply 69 has one end grounded and the other end electrically connected to the temperature sensing element 2a. The power supply voltage from the AC power supply 69 is about 200 mV, and the power supply frequency is set to be 300 Hz. The waveform of the power supply voltage is a sine wave.

Current detecting resistor 80, the carbon film resistor is used, the resistance value R _s is 1 k [Omega. The current detection resistor 80 has one end grounded and the other end electrically connected to the temperature sensing element 2a.

In addition, since the measurement unit 71 supports only DC input, the voltage V _{t that} is an AC voltage is converted into a DC voltage by the DC converter 70 and input to the measurement unit 71.

  The experimental apparatus 6 is configured such that the output waveform of the head 63 is used as a measurement start signal (trigger signal), and the moment when the conductive liquid 3a enters the temperature sensing element 2a is the starting point of measurement data.

  In this experiment, in order to confirm the operation of the distributed temperature sensor 1a as a temperature sensor, the temperature sensing element 2a is divided into two sections, and different temperatures are set in each section.

  For example, as shown in FIG. 3A, one of the two sections is a room temperature region set to be kept at room temperature (20 ° C.), and the other is on the surface using the low temperature of the air duster. It is a low temperature region that is set to cool to the extent that it forms frost and to be cooler than room temperature. In addition, an air duster is a kind of aerosol spray which discharge | releases gas and blows off dust etc., for example.

  FIG. 5A is a graph showing the result of measuring the electrical resistance of the distributed temperature sensor according to the embodiment, and FIG. 5B is a moving average (average of 500 points before and after the resistance value of FIG. 5A). It is a graph showing the result of numerical differentiation. In FIG. 5A, the vertical axis represents electric resistance (Ω), and the horizontal axis represents elapsed time (s) after the start of injection. In FIG. 5B, the vertical axis is the temperature in arbitrary units, and the horizontal axis is the distance in arbitrary units.

Using this experimental device 6, a result of measuring the electrical resistance R _t at both ends of the temperature sensing element 2a of the distributed temperature sensor 1a, a graph as shown in FIG. 5 (a) was obtained.

  As shown in FIG. 5 (a), the elapsed time up to about 1.2 seconds is the normal temperature region, and up to about 2.0 seconds is the low temperature region. After 2.0 seconds, the temperature sensing element 2a is filled with the conductive liquid 3a, and the conductive liquid 3a overflows from the open end opposite to the one end to which the syringe 64 is connected.

  From the equation (2) described above, FIG. 5B shows a graph reflecting the temperature distribution of the temperature sensing element 2a. As can be seen from this graph, the value is divided into two values in the normal temperature region and the low temperature region, and it can be confirmed that the temperature distribution created by the air duster can be measured by the distributed temperature sensor 1a.

  In addition, the graph shows that the waveform gradually changes at the boundary between the normal temperature region and the low temperature region, which is considered to be because the created temperature distribution is not uniform. That is, it is considered that one of the causes is that the two temperatures cannot be clearly separated because heat is exchanged between the two in the vicinity of the boundary. Another possible cause is that the low temperature region created by the air duster is not uniform.

(Low temperature characteristics of the temperature sensing element)
Fig.6 (a) is a graph which shows the temperature change of the frozen thermosensitive body which concerns on embodiment. In FIG. 6A, the vertical axis represents temperature (° C.) and the horizontal axis represents time (s).

  Here, in order to investigate the cause of the nonuniformity in the temperature distribution, the low temperature characteristics of the temperature sensing element 2a were investigated.

In the above experiment, when the temperature sensing element 2a was cooled with an air duster, if the temperature sensing element 2a was overcooled, the resistance value of the temperature sensing element 2a showed a very large value, and measurement was not possible. Therefore, in the above experiment, the degree of resistance suitable for measurement, i.e., the resistance value R _t of the resistance value R _s and the temperature-sensitive body 2a of the current detection resistor 80 had to cool so that the same degree.

  The freezing of the temperature sensing element 2a can be considered as a cause of the distribution type temperature sensor 1a exhibiting an extremely large resistance value. Therefore, an experiment was conducted to verify the freezing temperature of the temperature sensor.

  This experiment was performed by attaching a temperature sensing element to the surface of the temperature sensor, cooling as much as possible with an air duster, and then heating at room temperature (20 ° C.) to change the temperature of the temperature sensing element. . In this experiment, the freezing temperature was estimated from the state of temperature change of the temperature sensor.

  As shown in FIG. 6A, there is a portion where the temperature change becomes flat in the vicinity of −20 ° C.

  Here, when the saline solution is cooled, as seen in drift ice, water begins to freeze first, and crystals made only of water are generated (that is, ice is formed). This continues up to the eutectic point where ice can no longer be produced, and becomes completely solid when cooled from the eutectic point.

  The eutectic point of the saline solution is −21.1 ° C. Therefore, at a temperature lower than the eutectic point, there is no heat release associated with the phase transition, so the temperature rises faster.

  From the above, as shown in FIG. 6 (a), the temperature sensitive body also has a eutectic point in the vicinity of −20 ° C., and at temperatures below this temperature, the temperature sensitive body becomes completely solid. Conceivable. Therefore, below the eutectic point, since salt (hydrate) and ice exist separately, electricity hardly flows.

  Moreover, as shown to Fig.6 (a), it turns out that an air duster can be cooled to about -50 degreeC. Therefore, it can be seen that if the air duster is used for cooling too much, the temperature sensitive body easily falls below the eutectic point.

  In other words, the reason why the resistance value of the temperature sensing element 2a of the distributed temperature sensor 1a showed a very large value is considered that the temperature sensing element 2a became equal to or lower than the eutectic point. On the other hand, since the phase transition occurs at the eutectic point, the temperature sensing element 2a is kept at a constant temperature.

  On the other hand, at the eutectic point or higher, the temperature cannot be maintained by phase transition, and it is difficult to make the temperature distribution of the temperature sensing element 2a uniform. It can be considered that the temperature distribution is not constant as a cause of the gentle waveform in FIG.

(Modification)
-Modification of temperature sensing element A temperature sensing element according to a modification is formed from a polymer containing a conductive substance. In addition, this polymer body has, for example, a positive thermistor characteristic in which the resistance value increases as the temperature increases.

  In the above, the temperature sensing body used is a sponge in which a polymer containing saline in agar is contained in a sponge, but is not limited thereto. For example, the temperature sensing body is made of a material having a positive thermistor characteristic. May be formed. As a material having positive thermistor characteristics, for example, a PTC (positive temperature coefficient) polymer can be used.

  This PTC polymer is formed by mixing a conductive powder (for example, carbon black) in a resin and has a positive thermistor characteristic in which the electrical resistivity increases with temperature.

  Since the PTC polymer is a resin, it can be molded or bent into a tubular shape and is suitable for a distributed temperature sensor.

-Modification of conductive liquid In each of the above experiments, saturated saline was used as the conductive liquid. However, the present invention is not limited to this, and for example, an ionic liquid and a liquid metal may be used.

  As an ionic liquid, for example, the cation is a pyridine type, an alicyclic amine type, or an aliphatic amine type, and various structures can be synthesized by selecting the type of anion to be combined therewith. . Examples of the anions to be combined include bromide ions and halogens such as triflate, borons such as tetraphenylborate, and phosphoruss such as hexafluorophosphate.

  As an example of the liquid metal, mercury that is liquid at room temperature, U alloy that is a low melting point alloy, or the like can be used.

  These have properties that do not electrolyze or are difficult to do. Therefore, it is possible to measure with direct current, and it is possible to measure with a simpler circuit.

Modification Example of Measurement Circuit FIG. 6B is a block diagram of a measurement circuit according to a modification example.

In this modification, the measurement unit 71 includes, for example, the second electrode via the band-pass filter 9a when the first electrode 67 is grounded and the second electrode 68 is electrically connected to the fixed resistor 91. based on the voltage V _t which is output from the electrode 68, it is configured to the first electrode 67 corresponding to the position of the conductive fluid 3a and measuring the temperature of the one-dimensional direction between the second electrode 68.

  In the above experiment, for verification of the principle, the resistance value of the distributed temperature sensor was directly measured, and the obtained resistance value was differentiated by numerical processing to obtain temperature information. Depending on the object to be measured, the distributed temperature sensor may require a measuring instrument with better distance accuracy and longer distance than the above experiment. Therefore, as a modification, the following measurement circuit 9 that saves the required dynamic range of the measuring instrument is proposed.

  For example, as shown in FIG. 6B, the measurement circuit 9 is a band composed of a temperature sensing element 2a, a DC power source 90, a fixed resistor 91, a resistor 92, a capacitor 93, an operational amplifier 94, a resistor 95, and a capacitor 96. And a pass filter 9a.

  In the DC power supply 90, the negative side is grounded, and the positive side is electrically connected to one end of the fixed resistor 91.

The other end of the fixed resistor 91 is electrically connected to one end of the temperature sensing element 2a. The resistance value of the fixed resistor 91 is, for example, _{R M.}

  The other end of the temperature sensing element 2a of the distributed temperature sensor 1a is grounded. Between the fixed resistor 91 and the temperature sensing element 2a, one end of the resistor 92 of the band pass filter 9a is electrically connected.

The other end of the resistor 92 is electrically connected to one electrode of the capacitor 93. The resistance value of the resistor 92 is, for example, _{R 1.}

The other electrode of the capacitor 93 is electrically connected to the inverting input terminal of the operational amplifier 94. The capacitance of the capacitor 93 is, for example, _{C 1.}

The non-inverting input terminal of the operational amplifier 94 is grounded. The output voltage V _out is output from the output terminal of the operational amplifier 94.

One end of the resistor 95 is electrically connected to the inverting input terminal of the operational amplifier 94, and the other end is electrically connected to the output terminal of the operational amplifier 94. The resistance value of the resistor 95 is, for example, _{R 2.}

One end of the capacitor 96 is electrically connected to the inverting input terminal of the operational amplifier 94, and the other end is electrically connected to the output terminal of the operational amplifier 94. The capacitance of the capacitor 93 is, for example, _{C 2.}

この式（３）より、抵抗値Ｒ_ｔ＜＜Ｒ_Ｍであるとき、次の式が成り立つ。

式（４）は、微分項以外は定数項（Ｒ_Ｍ／Ｖ_ｓ）となっているため、分布型温度センサ１ａの感温体２ａの抵抗値Ｒ_ｔの変化によりレンジが大きく変化することはない。従って、この測定回路９から出力される出力電圧Ｖ_ｏｕｔを測定する測定器に必要なダイナミックレンジは、∂Ｒ_ｔ／∂ｔが取りうる値の範囲のみ、つまり温度変化の幅のみである。 Here, when the voltage across the temperature sensing element 2a of the distributed temperature sensor 1a is V _t, the following equation holds.

From this equation (3), when the resistance value is _R t << _{R M,} the following equation holds.

Since the expression (4) is a constant term (R _M / V _s ) other than the differential term, the range greatly changes due to the change of the resistance value R _t of the temperature sensing element 2 a of the distributed temperature sensor 1 a. Absent. Therefore, the dynamic range necessary for the measuring instrument that measures the output voltage _Vout output from the measuring circuit 9 is only the range of values that can be taken by ∂R _t / ∂t, that is, only the width of the temperature change.

この測定回路９は、高周波領域では積分回路となり、ノイズを抑制する。従って、測定回路９の全体の入出力特性は、次の式で表すことができる。

As shown in FIG. 6B, the circuit after the resistor 92 is a differentiating circuit, and the following equation is established by appropriately selecting the resistance value and the capacitance.

The measurement circuit 9 becomes an integration circuit in a high frequency region and suppresses noise. Therefore, the entire input / output characteristic of the measurement circuit 9 can be expressed by the following equation.

・ Applications other than temperature measurement Since the distributed temperature sensor according to the embodiment only needs to be related to the physical quantity to be measured and the electrical resistivity, a wide variety of distributed temperature sensors are configured in addition to temperature measurement. can do. For example, when the temperature sensitive part is a sponge, the electrical resistivity changes due to the attached moisture, and thus a water leakage detection sensor can be configured. In addition, the application to a corrosion detection sensor, a humidity distribution sensor, etc. can be considered.

(Effect of embodiment)
The distributed temperature sensor according to the present embodiment calculates the temperature distribution in the one-dimensional direction from the electrical resistivity of the temperature sensing element measured with the conductive liquid injected into the through hole of the temperature sensing element formed in a cylindrical shape. Since it can be measured, the configuration is simple, and it can be manufactured at low cost.

  In addition, this distributed temperature sensor is a device that measures the resistance of a temperature sensor, for example, compared to a device that separates Stokes light and anti-Stokes light from weak Raman scattered light that scatters in an optical fiber, for example. Since advanced processing is not required, it can be manufactured at low cost.

  Furthermore, the distributed temperature sensor according to the present embodiment has a substantially linear relationship between the electrical resistivity and the temperature, and it is necessary to perform advanced processing for removing noise and correcting measurement errors due to external factors. And can be manufactured at low cost. Therefore, the distributed temperature sensor has a simple configuration and the measurement target is electrical resistivity, so that it is possible to easily determine a fault location and improve measurement accuracy.

  In the present embodiment, the temperature sensing element has a negative thermistor characteristic. However, the temperature sensing element is not limited to this and may have a positive thermistor characteristic depending on the application.

  As mentioned above, although some embodiment and modification of this invention were demonstrated, these embodiment and modification are only examples, and do not limit the invention based on a claim. These novel embodiments and modifications can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the scope of the present invention. In addition, not all combinations of features described in these embodiments and modifications are necessarily essential to the means for solving the problems of the invention. Furthermore, these embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1, 1a ... Distributed temperature sensor 2, 2a ... Temperature sensor 3, 3a ... Conductive liquid 4, 6, ... Experimental apparatus, 8, 9 ... Measurement circuit, 9a ... Band pass filter, 20 ... Through-hole, 21 DESCRIPTION OF SYMBOLS Temperature sensor, 22 ... Sponge, 23 ... Polymer, 24 ... Through-hole, 40 ... Container, 41 ... Water, 42 ... Heater, 43 ... Power source, 44 ... Test tube, 45 ... Lid, 46 ... First electrode, 47 ... second electrode, 48 ... temperature sensor, 49 ... power supply, 50 ... ammeter, 51 ... voltmeter, 60 ... scanner, 61 ... housing, 62 ... rail, 63 ... head, 63a ... DC power supply, 64 ... Syringe, 65 ... Cylinder, 66 ... Piston, 67 ... First electrode, 68 ... Second electrode, 69 ... AC power source, 70 ... DC converter, 71 ... Measuring unit, 80 ... Current detection resistor, 81, 82 ... Voltmeter, 90 ... DC power supply, 91 ... fixed resistor, 92 ... resistor, 93 ... condenser Service, 94 ... op-amp, 95 ... resistance, 96 ... capacitor

Claims (7)

A temperature sensing element that is formed in a cylindrical shape so that a conductive liquid can be put therein, and whose electric resistivity changes with temperature,
A first electrode electrically connected to one end of the temperature sensing body;
A second electrode electrically connected to the other end of the temperature sensing element;
A distributed temperature sensor. Further, based on the electrical resistivity measured through the first electrode and the second electrode, a one-dimensional direction between the first electrode and the second electrode according to the position of the conductive liquid A measuring unit for measuring the temperature of
The distributed temperature sensor according to claim 1, comprising:   The distributed temperature sensor according to claim 1, wherein the temperature sensing element includes a polymer containing a conductive substance.   The distributed temperature sensor according to claim 1, wherein the temperature sensing body is a porous body containing the polymer.   The distributed temperature sensor according to claim 1, wherein the temperature sensing body is a polymer body containing a conductive substance.   The distributed temperature sensor according to claim 5, wherein the polymer body has a positive thermistor characteristic in which a resistance value increases as the temperature increases.   The measurement unit is based on a voltage output from the second electrode via a band-pass filter when the first electrode is grounded and the second electrode is electrically connected to a fixed resistor. The distributed temperature sensor according to claim 1, wherein a temperature in a one-dimensional direction between the first electrode and the second electrode corresponding to the position of the conductive liquid is measured.

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