JP2017227601A - Standard platinum resistance thermometer and winding structure in temperature-sensitive section of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform precise temperature measurement by reducing influence of change in temperature on expansion and shrinkage of a platinum wire in a standard platinum resistance thermometer.SOLUTION: A standard thermometer 1 includes a winding structure such that a trailer 3a of a platinum wire 3 constituting a temperature sensitive section 4 for inspecting temperature and a tip 5a of an external lead wire 5 are connected, and part of the external lead wire 5 beyond a connection section 6 is extracted after being wound onto a coil 2 in a same direction as a winding direction of the platinum wire 3. Therefore, even when the platinum wire 3 is subjected to shape change caused by expansion and shrinkage in a winding radial direction due to change in temperature at a time of temperature measurement, fluctuations of the connection section 6 caused by influence of the shape change can be suppressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a winding structure of a temperature sensing portion in a standard platinum resistance thermometer used as an interpolating thermometer of an international temperature scale (hereinafter referred to as ITS-90), and a standard including the temperature sensing portion of this winding structure The present invention relates to a platinum resistance thermometer.

  Standard platinum resistance thermometer (hereinafter also referred to simply as “standard thermometer”) is a temperature standard study that requires reproducibility and accuracy of 0.001 ° C. or less, or determines the temperature from the resistance value in ITS-90. Interpolated thermometer, used at about -190 ° C to about 962 ° C.

  As disclosed in Patent Document 1 below, the basic structure of a conventionally known standard thermometer 10 (about 25 ohms at 0 ° C.) has a quartz structure as shown in FIGS. 4 (a) and 4 (b). A temperature sensing portion 13 is provided in which a platinum wire 12 is wound in a coil shape with respect to a cross winding frame 11 made of single crystal sapphire.

  Since the thermal expansion coefficient of quartz or sapphire used as the material of the winding frame 11 and platinum of the platinum wire 12 are greatly different, the platinum wire 12 has a fineness of about 2 mm or less by a double coil method in which non-inductive winding is performed in a strain-free state. A small-diameter coil-shaped platinum resistance wire having a large coil diameter is wound around the cross winding frame 11 at a predetermined pitch. This also has the effect of canceling the parasitic inductance of the winding resistance.

  In addition, since the standard thermometer 10 performs four-wire resistance measurement, two sets of external lead wires 14 made of platinum and two sets (four in total) connected to an external device such as an indicator (not shown). ), And one set (two in total) is welded to the end portion of the platinum wire 12. As shown in FIG. 4, the platinum wire 12 is wound around the cross winding frame 11 in a coil shape with the connection portion 15 as a boundary, and the external lead wires 14 are drawn substantially linearly.

  Further, in order to prevent contamination of the temperature sensing portion 13, the temperature sensing portion 13 is covered with a gas-impermeable protective tube (not shown) such as quartz or sapphire, and the inside of this protective tube is intentionally covered with argon. A mixed gas in which oxygen is added at a predetermined ratio is enclosed.

Japanese Patent No. 3380523

  By the way, when the silver point measurement is performed with the conventional standard platinum resistance thermometer 10, the temperature sensing unit 13 is approximately about 3 to measure the triple point (0.01 ° C.) and the silver point (961.78 ° C.) of water. It is considered that the platinum wire 12 expands and contracts in the winding diameter direction in response to a temperature change close to 1000 ° C. In addition, when the silver point measurement is performed a plurality of times, there is a case where a temperature drift of about 10 mK occurs.

  The inventor of the present application has made extensive studies to elucidate the cause of this temperature drift, and as a result, the connecting portion 15 is finely moved due to the shape change of the platinum wire 12 due to the temperature change, and as a result, the measurement temperature has been found to drift. .

  Therefore, the present invention has been made in view of the above-described problems, and the sensitivity of a standard platinum resistance thermometer that can perform temperature measurement with high accuracy by reducing the influence of expansion / contraction of the platinum wire due to temperature change. The object is to provide a winding structure in the warm zone and a standard platinum resistance thermometer using this winding structure.

In order to achieve the above-described object, a first aspect according to the present invention includes a platinum wire that is non-inductively wound in a coil shape in a strain-free state with respect to the winding frame,
An external lead wire that is connected to the platinum wire and outputs the electrical resistance value of the platinum wire that changes during temperature measurement;
In the winding structure in the temperature sensing part of a standard platinum resistance thermometer equipped with
The external lead wire is characterized in that a part of the external lead wire is wound around the winding frame in the same direction as the winding direction of the platinum wire from the connecting portion connected to the terminal portion of the platinum wire, It is the winding structure in the temperature sensing part of the platinum resistance thermometer for standard.

The second aspect according to the present invention is a standard platinum resistance thermometer equipped with a temperature sensing unit for temperature detection.
The temperature sensing part is
A platinum wire that is non-inductively wound in a coil shape in a strain-free state with respect to the winding frame;
An external lead wire connected to the platinum wire and outputting the electrical resistance value of the platinum wire that changes during temperature measurement to the outside;
The external lead wire is characterized in that a part of the external lead wire is wound around the winding frame in the same direction as the winding direction of the platinum wire from the connecting portion connected to the terminal portion of the platinum wire, This is a standard platinum resistance thermometer.

  According to the present invention, the external lead wire is wound around the winding frame by a predetermined number of turns in the same direction as the winding direction of the platinum wire from the connecting portion connected to the platinum wire, so that the triple point of water or the silver point Even if the platinum wire expands and contracts in the winding diameter direction due to a temperature change when the measurement is repeated, the connection portion can be suppressed as much as possible. Therefore, since temperature measurement can be performed with higher accuracy than the conventional product, the function as a standard thermometer based on ITS-90 can be sufficiently achieved.

It is a schematic perspective view which shows the structure of the temperature sensing part of the platinum resistance thermometer for standards which concerns on this invention. (A) is a schematic side view when the same temperature sensing part is viewed from the side in the arrow A direction, and (b) is a schematic side view when the temperature sensing part is viewed from the side in the arrow B direction. It is a graph which shows a temperature change when a silver point measurement is each performed with the standard platinum resistance thermometer which concerns on this invention, and the conventional standard platinum resistance thermometer. (A) is a schematic perspective view which shows the structure of the temperature sensing part of the conventional platinum resistance thermometer for standard, (b) is a schematic side view when the conventional temperature sensing part is seen from the side.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and all other forms, examples, operation techniques, etc. that can be implemented by those skilled in the art based on this form are included in the scope of the present invention. .

  In addition, about each component other than the coil | winding structure in the temperature sensing part 4 of the standard platinum resistance thermometer 1 which concerns on this invention, since it is the same as that of the conventional standard thermometer as disclosed by patent document 1 In the present specification, only the description of the configuration of the temperature sensing section 4 of the standard thermometer 1 and the winding structure of the platinum wire 3 which is a characteristic requirement of the present invention will be described.

  As shown in FIGS. 1 and 2, the standard thermometer 1 according to the present invention includes a temperature sensing unit 4 including a winding frame 2 and a platinum wire 3.

  The reel 2 is a long member made of a material that exhibits a stable material characteristic that does not contaminate the platinum wire 3 in a use temperature range such as quartz or single crystal sapphire.

  In the winding frame 2 of the present embodiment, four standing pieces 2a are radially arranged at equal angular intervals (90 ° intervals) with the main body central portion (shaft portion) as the center. That is, when the winding frame 2 is viewed from the front end side, the standing pieces 2a are arranged at 90 ° intervals along the circumference of a virtual circle connecting the end portions of the four standing pieces 2a of the frame 2. Therefore, the cut surface in the short direction perpendicular to the longitudinal direction of the winding frame 2 has a substantially cross shape.

  Further, on the outer edges of the four standing pieces 2a, fitting grooves 2b (depth of about 0.5 to 1 mm) for fitting the wound platinum wire 3 are formed at a predetermined pitch, and adjacent standing pieces are provided. In the relationship between 2a, the formation position is set so that the fitting grooves 2b are shifted by 1/2 pitch. Thereby, the platinum wire 3 can be smoothly wound with a fixed inclination angle.

  Furthermore, a through hole 2c is formed on the front end side of the winding frame 2 to form a folded portion that becomes a winding start position of the wire 3 through the platinum wire 3, and a connecting hole is connected to the rear end side of the winding frame 2. A plurality of through-holes 2d for fixing the position through the external lead wire 5 drawn out from the portion 6 are formed.

  In addition, although the shape of the winding frame 2 in the present embodiment is substantially cross-shaped in the cross-section in the short direction, for example, three standing pieces 2a are arranged at equal angular intervals of 120 ° with the central portion of the main body as the center. The platinum wire 3 is not particularly limited as long as the platinum wire 3 can be wound by non-inductive winding and functions as the temperature-sensitive portion 4 of the standard thermometer 1.

  The platinum wire 3 is a resistance wire made of platinum (Pt) with high purity (purity of 99.999% or more). In order to cancel the parasitic inductance of the winding resistance, the platinum wire 3 is wound around the fitting groove 2b along the outer periphery of the winding frame 2 by a single coil method in which non-inductive winding is performed in a strain-free state. A pair of external lead wires 5 are welded to each of the terminal portions 3 a of the platinum wire 3. In addition, about the diameter and length of the platinum wire 3, it is prescribed | regulated suitably based on the specification of the standard thermometer 1 to produce.

The external lead wire 5 is made of platinum having a purity lower than that of the platinum wire 3 (purity 99.99% or more), and is an electric wire that outputs the electric resistance value of the platinum wire 3 to an external device (such as a digital indicator). . Since the standard thermometer 1 of this embodiment performs 4-wire resistance measurement, two pairs of external lead wires 5 made of platinum are connected to two external devices (not shown) (four in total). It consists of
In the present embodiment, the end portion 5 a of the pair of external lead wires 5 is welded to the terminal end portion 3 a of the platinum wire 3 to constitute the connection portion 6.

  Here, the winding structure around the connection portion 6 between the platinum wire 3 and the external lead wire 5, which is a characteristic requirement of the present invention, will be described.

  The temperature sensing part 13 in the conventional standard thermometer 10 has a connection part 15 in which a pair of two external lead wires 14 are welded to each end part 12a of the platinum wire 12, for example, FIG. 4 (b). As shown in FIG. 6, the platinum wire 12 is wound around the cross winding frame 11 in a coil shape with the connecting portion 15 as a boundary, and the external lead wire 14 is drawn out substantially linearly.

  On the other hand, the winding structure around the connection portion 6 to which the end portion 3a of the platinum wire 3 and the distal end portion 5a of the external lead wire 5 according to the present invention are connected is shown in FIGS. 2 (a) and 2 (b). As shown, the terminal portion 3 a of the platinum wire 3 wound around the winding frame 2 and a set of two external lead wires 5 are connected by a connection portion 6, and the external lead wire 5 ahead of the connection portion 6. Is pulled out after being wound around the winding frame 2 by a predetermined number of turns in the same direction as the winding direction of the platinum wire 3. The external lead wire 5 is led out through the through hole 2d formed on the rear end side of the winding frame 2. 2A and 2B show the periphery of the connection portion 6 with the set of external lead wires 5 connected to the respective terminal portions 3a of the platinum wire 3. FIG.

Since the winding structure of the present invention is intended to suppress the fine movement of the connecting portion 6 caused by the shape change of the platinum wire 3 during temperature measurement, at least the connecting portion when the connecting portion 6 is used as a boundary. What is necessary is just to have a structure in which the external lead wire 5 is wound around the standing piece 2a next to the standing piece 2a around which the platinum wire 3 immediately before 6 is wound.
Therefore, if the interval between the standing pieces 2a is 90 ° with respect to the winding direction, the number of turns of the external lead wire 5 is about ¼ or more from the connection portion 6 as a starting point. If it exists, it becomes about 1/3 or more windings from the connection part 6.

  Thus, in the winding structure of the present invention, the external lead wire 5 is wound around the winding frame 2 by a predetermined number of turns in the same direction as the winding direction of the platinum wire 3 from the connecting portion 6 connected to the platinum wire 3. Since the position of the connecting portion 6 is fixed, the platinum wire 3 expands and contracts in the winding diameter direction due to a temperature change of about 1000 ° C. when the triple point or silver point of water is repeatedly measured. Even if the change occurs, the fine movement of the connecting portion 6 due to the influence of the shape change can be suppressed.

[Example]
Next, performance evaluation of the standard thermometer 1 employing the above-described winding structure will be described.
In addition, the following Example is an example, does not limit the present invention, and any appropriate design change in light of the gist of the preceding and following description is included in the technical scope of the present invention.

FIG. 3 shows the evaluation results at the time of silver point measurement between the standard thermometer 1 employing the winding structure of the present invention and the conventional standard thermometer not employing the winding structure of the present invention. . The structure of the temperature sensing unit 4 is as follows.
-Wire diameter of platinum wire 3: 0.35 mm
-The length of the platinum wire 3: 260 mm
-Number of windings of platinum wire 3: 20 turns

  In addition, the silver point measurement step is to measure the triple point of water (0.01 ° C) → insert into an electric furnace at 500 ° C and raise the temperature to 990 ° C at 6 ° C / min. Point measurement (approx. 962 ° C) → Return to 990 ° C electric furnace → Decrease to 500 ° C at 1 ° C / min → Pull out to room temperature, measure water triple point (0.01 ° C) again, and repeat this process 4 times Repeatedly.

As shown in FIG. 3, the average change (mK) of the silver point ratio from the first to the fourth time in the conventional standard thermometer 1 (Δ in the figure) is 15.2 mK, whereas the winding of the present invention The average change (mK) in the silver point ratio from the first time to the fourth time in the standard thermometer 1 employing the line structure (● in the figure) was 2.3 mK.
By adopting the winding structure of the present invention, the influence of the shape change due to the expansion / contraction of the platinum wire 3 is reduced due to the temperature change of about 1000 ° C. by the silver point measurement, and the temperature measurement is more accurate. Proved feasible.

  As described above, the standard thermometer 1 described above is connected to the external portion beyond the connection portion 6 where the terminal portion 3a of the platinum wire 3 and the tip portion 5a of the external lead wire 5 constituting the temperature sensing portion 4 are connected. The lead wire 5 has a winding structure drawn out after being wound around the winding frame 2 in the same direction as the winding direction of the platinum wire 3.

  As a result, even if the platinum wire 3 expands and contracts in the winding diameter direction due to temperature changes when the triple point or silver point measurement of water is repeatedly measured, the external lead wire pulled out from the connecting portion 6 5 also displaces following the shape change of the platinum wire 3, so that the fine movement of the connecting portion 6 can be suppressed as much as possible.

  By the way, in the above-described embodiment, the platinum wire 3 is wound around the winding 2 in a single-coil method in which the platinum wire 3 is non-inductively wound in a strain-free state. However, the present invention is not limited to this. In the winding structure of the present invention, it is only necessary that the platinum wire 3 is wound around the winding frame 2 in a non-inductive manner in a coil-like manner in a strain-free state. You may wind by a heavy coil system etc.

1 ... Standard platinum resistance thermometer (standard thermometer)
2 ... reel (2a ... upright piece, 2b ... fitting groove, 2c ... through hole, 2d ... through hole)
3 ... Platinum wire (3a ... Terminal)
4 ... temperature sensing part 5 ... external lead wire (5a ... tip)
6: Connection between the end of the platinum wire and the tip of the external lead wire

Claims (2)

A platinum wire that is non-inductively wound in a coil shape in a strain-free state with respect to the winding frame;
An external lead wire that is connected to the platinum wire and outputs the electrical resistance value of the platinum wire that changes during temperature measurement;
In the winding structure in the temperature sensing part of a standard platinum resistance thermometer equipped with
The standard is characterized in that a part of the external lead wire is wound around the winding frame in the same direction as the winding direction of the platinum wire from the connecting portion connected to the terminal portion of the platinum wire. Winding structure in the temperature sensing part of a platinum resistance thermometer for use. In a standard platinum resistance thermometer equipped with a temperature sensing unit that detects temperature,
The temperature sensing part is
A platinum wire that is non-inductively wound in a coil shape in a strain-free state with respect to the winding frame;
An external lead wire connected to the platinum wire and outputting the electrical resistance value of the platinum wire that changes during temperature measurement to the outside;
The standard is characterized in that a part of the external lead wire is wound around the winding frame in the same direction as the winding direction of the platinum wire from the connecting portion connected to the terminal portion of the platinum wire. Platinum resistance thermometer.

Images