JPH039221A - Superconducting liquid level gage - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a superconducting liquid level gauge, and particularly to a superconducting liquid level gauge for measuring the liquid level of a refrigerant used in a superconducting magnet of a magnetic resonance diagnostic apparatus (MRI). This relates to superconducting liquid level gauges.

[Prior Art] Fig. 5 and Fig. 6 show a conventional superconducting liquid level gauge. a heat shield (2) that reduces the amount of radiant heat entering the inner container (1); a vacuum container (3) that encloses the outer surface of the heat shield (2) and provides vacuum insulation by keeping the inside vacuum; It consists of a liquid level sensor (5) for detecting the level of liquid helium (4) in the container (1), a current and voltage lead wire (6), a measuring device (7) consisting of a constant current power source and a voltmeter, etc. The liquid level sensor (5) is the sixth
As shown in the figure, superconducting wire (8) for detecting the liquid level
, a protection tube (9) that supports and protects this superconducting wire (8), an insulator (10) provided on the inner surface of this protection tube (9), and liquid helium flowing into the protection tube (9). an opening (11) provided for ease of use; current leads (12a) for current supply drawn out from both ends of the superconducting wire (8);
(12b), and voltage leads (13a) and (13b) similarly drawn out from both ends of the superconducting wire (8).

With the above configuration, when the liquid level sensor (5) is inserted into the inner container (1), liquid helium (4) is released from the opening (11).
enters the protective tube (9) and is filled to the liquid level. In this state, when a constant current is supplied from the current leads (12a) (12b), the portion of the superconducting wire (8) in the gas is not cooled properly, so its superconductivity is destroyed, and it becomes a resistor. On the other hand, the part of the superconducting wire (8) that exists during the night is well cooled, so it remains in a superconducting state. Therefore the voltage lead (1
When the voltage is measured from 3a) and (13b), it becomes possible to detect the voltage corresponding to the resistance of the superconducting wire portion in the gas, and the liquid level can be measured.

[Problem to be solved by the invention] Since the conventional superconducting liquid level gauge is configured as described above, when measuring the amount of liquid helium in a cylindrical container, it is necessary to convert it from the output voltage of the liquid level sensor and the shape of the container. There was a need.

This invention was made to solve the above-mentioned problems, and its object is to obtain a superconducting liquid level gauge that can obtain an output voltage that is approximately proportional to the amount of liquid.

[Means for Solving the Problem] In the superconducting liquid level gauge according to the present invention, the mounting angle is set so that the output voltage of each of the plurality of liquid level sensors has the same proportionality coefficient with respect to the liquid amount. There is.

[Function] In this invention, since the output voltages of the plurality of liquid level sensors are proportional to the liquid amount, either the liquid amount or the output voltage can be directly read.

[Example] Figures 1 and 2 show an example of the present invention, and Figure 1 shows a double cylindrical cryogenic container with a horizontal axis and a hole in the center. In the figure, the outer cylinder (1
a) and inner 1i (lb), outer cylinder (2a) and inner cylinder (2b) of heat shield, outer cylinder (3a) and inner cylinder (3b) of vacuum container,
Further, the surfaces of the heat shields (2a) and (2b) facing the vacuum vessel side are covered with an insulation layer (14) consisting of a reflective material and a spacer. Inner and outer cylinders (la),
Three liquid level sensors (5a), (5b), and (5c) are provided at a constant angle relationship inside the inner container configured by (lb).

The connections of the liquid level sensors (5a), (5b), and (5c) are as shown in Fig. 2. Each sensor (5a) to (5c) is installed at a fixed angle with an upper and lower one. The center one is mounted vertically, and these liquid level sensors are connected to the heater (15a), superconducting wire (8a), and connection lead (
L6a), heater (15b), superconducting wire (8b), connection lead (16b), heater (15c), superconducting wire (8c)
) are connected in series in order, and a constant current power supply (17a) and a voltmeter (
18a) are connected in parallel.

With the above configuration, since the cryogenic container is a double cylinder with its axis horizontal, the amount of liquid per unit depth changes depending on the height of the cylinder. Therefore, the central liquid level sensor (5b) is installed vertically, and when the rate of change in voltage of the output of this liquid level sensor (5b) is a/liter/volt, the other liquid level sensors (5b)
Install a) and (5c) at an angle so that the output voltage is about a liter/volt. Therefore, the output voltage of the liquid level sensors (5a), (5b), (5c) is i
The value is approximately proportional to &ffi.

Therefore, it is possible to know the liquid m from the output voltage without providing a special nearer in the totalizer (7).

In the above embodiment, the liquid level sensor was connected as shown in Fig. 2, but as shown in Fig. 3, the circuit of the heater (15d) (15e) (15f), which causes the superconducting breakdown of the superconducting wire, is If it is provided independently and energized by another constant current power supply (19), the error output voltage caused by the heater can be removed.
Accuracy is improved.

Also, as shown in Figure 4, heaters (15g) (15h) (
15i) circuit using superconducting wire (8g) (8h) (8i)
By connecting the heaters in series and measuring the voltage from both ends of the superconducting wire (8g) and (81), error output voltage due to the heater can be eliminated, and the constant current power supply (17c) can also be connected in series. It becomes possible to conduct electricity.

Here, in the conventional device shown in Fig. 5, the liquid level sensor is inserted into the low temperature part rather than the room temperature part, so the superconducting wire (8
) has a normally conducting part, and when it was energized by a constant current power supply, the superconducting breakdown progressed smoothly up to the liquid helium surface, but as shown in Figure 1, when the liquid level sensor and all the liquid level sensors are at low temperatures, the rated current value There were times when superconductor destruction did not proceed smoothly. In this invention, since a heater is attached to the top of the sensor, superconductor breakdown proceeds smoothly with a low constant current, making it possible to stably measure the liquid.

[Effects of the Invention] As described above, according to the present invention, a heater is attached to the upper part of the liquid level sensor, and the mounting angle is adjusted so that the output voltage per unit liquid volume of each liquid level sensor is the same. Therefore, there is an effect that an output approximately proportional to the liquid amount can be stably obtained over almost the entire area of the inner container.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of essential parts of an embodiment of the present invention, FIG. 2 is a wiring diagram of the one shown in FIG. 1, FIGS. 3 and 4 are wiring diagrams of other embodiments, and FIG. FIG. 6 is a front sectional view of the conventional superconducting liquid level gauge in use, and FIG. 6 is a longitudinal sectional view of the liquid level sensor in FIG. 5. (5a) (5b) (5c)...Liquid level sensor, (8a)~
(81)...Superconducting wire, (15a) to (151)...Heater, (17a) to (+7c), (19)...Constant current power supply, (18a) to (18c)...Voltmeter. In each figure, the same reference numerals refer to the same or corresponding parts.

Claims (1)

[Scope of Claims] A liquid level sensor consisting of a superconducting wire, a heater attached to the superconducting wire and causing the superconductor to break down, and a support for supporting the superconductor and the heater; A superconducting liquid level meter comprising a constant current power supply that supplies current, and a voltmeter that measures the output voltage of the liquid level sensor, wherein the heater connects the liquid level sensor to the upper end of the superconducting wire. Multiple units can be installed in the depth direction of the liquid, and
A superconducting liquid level gauge, characterized in that each of the liquid level sensors is arranged at an angle such that an output voltage per unit liquid volume is a substantially constant value.