JPS6113167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inductive liquid level gauge that detects the level of a conductive liquid. Inductive liquid level gauges, which are easy to maintain and have a simple structure, are used to detect the level of conductive liquids, particularly liquid sodium, which is a coolant used in fast breeder reactors. However, the liquid level gauge is
Changes in the temperature of the conductive liquid cause the output voltage to fluctuate and cause errors. Therefore, various temperature-compensated inductive liquid level gauges have been devised that are configured to detect the temperature of the conductive liquid and use the detected signal to perform temperature correction on the measured liquid level signal. As an example, an inductive liquid level gauge shown in FIG. 1 will be described. In the figure, a stainless steel sheath 1 indicated by a broken line is a conductive liquid, such as liquid sodium 2.
It is immersed inside. An excitation coil 4 and a first detection coil 5 are wound around a bobbin 3 disposed within the sheath 1, and a second detection coil 6 is further wound below the surface of the conductive liquid. . The excitation coil 4 is excited by an AC power source 7 that supplies current. Here, the output voltage of the second detection coil 6
By correcting the output voltage V ₁ (liquid level detection signal) of the first detection coil 5 using V ₂ (temperature detection signal of the conductive liquid), a signal corresponding to the liquid level l can be obtained. That is, the temperature T of the inductive level gauge configured in this way
The output voltage V ₁ of the first detection coil 5 with respect to V 1 has the relationship shown in FIG. 2, and is expressed by the following equation.

V ₁ = A(T)・l+B(T) (1) Therefore, A, which is the relationship between the temperature of the conductive liquid,
(T) and B(T) are determined from the temperature of the conductive liquid, and by substituting the values into equation (2), the liquid level l can be determined.

l=1/A(T)・[V ₁ −B(T)] (2) Since the temperature T of the conductive liquid is a function of the output voltage V ₂ of the second detection coil 6, A(T) =A{T
(V ₂ )}, B(T)=B{T(V ₂ )}.
Therefore, the relationship between the output voltage V ₁ of the first detection coil 5 and the output voltage V ₂ of the second detection coil 6 and the liquid level l is as follows: l=1/A{T(V ₂ )}・[V ₁ −B{T(V ₂ ). Also, a=1/A{T(V ₂ )}, b=B{T(V ₂ )}/A
If we set {T(V ₂ )}, then l=aV ₁ −b (4). Since a and b can be determined by calculation or experiment once the structure, material, and dimensions are determined,
The temperature-corrected liquid level l can be determined from V ₁ and V ₂ .

However, in the case of this inductive liquid level gauge, the output voltage V ₂ of the second detection coil 6 that detects the temperature of the conductive liquid is determined by the SIGNAL/BIAS ratio (ratio of change in output voltage to change in temperature of the conductive liquid). ) is very small, and there is a problem that temperature compensation cannot be performed sufficiently.

The present invention has been made in view of the above circumstances, and its purpose is to provide an inductive liquid level gauge that significantly improves the SIGNAL/BIAS ratio of the output voltage of the second detection coil used for temperature compensation. It is.

The present invention will be explained below with reference to an embodiment shown in FIG. A stainless steel sheath 1, shown in broken lines in the figure, is immersed in a conductive liquid, for example liquid sodium 2. A first excitation coil 8 and a first detection coil 9 are wound around a bobbin 3 disposed within the sheath 1 in multiple layers. A second excitation coil 10 and a second detection coil 11 are arranged below the first excitation coil 8 and detection coil 9. Moreover, the first excitation coil 8 and the first detection coil 9 are connected to liquid sodium 2, which is a conductive liquid.
It is located surrounded by. The first and second excitation coils 8, 10 are connected to the first and second AC power supplies 31, 32.
It is excited by The output voltages V ₁ and V ₂ obtained from the first and second detection coils 9 and 11 are passed through first and second amplifiers 12 and 13, respectively, to first and second rectifier circuits having wave circuits. 14,1
It is rectified by 5. The rectified voltage V ₄ obtained from the second rectifier circuit 15 is the rectified voltage V 4 obtained from the second rectifier circuit 15.
and sent to the second function generators 16, 17, where the functions a=a{T(V ₄ )} and b=b{T
(V ₄ )} is generated. That is, the first and second function generators 16 and 17 calculate the relationship between the liquid level l of the liquid sodium 2 and the output voltage V3 of the first detection coil ₉ as follows: l= _aV3 -b (4') Constants a and b are temperature corrected. Output signal a of the first function generator 16 and the first rectifier circuit 14
The output voltage V ₃ of is sent to the multiplier 21, where aV ₃ is calculated. Then, the output signal a·V ₃ of the multiplier 21 is subtracted by the output signal b of the second function generator 17 in the subtracter 22, so that aV ₃ −
b=l is found. The signal thus obtained from the subtractor 21, that is, the output signal of the arithmetic circuit 20, is sent to the display circuit 23, where the liquid level l is displayed.

Note that the functions a(T) and b(T) generated by the first and second function generators 16 and 17 are the same as those of the sheath 1 and the first and second excitation coils 8 and 10 that constitute the liquid level gauge. , first and second detection coils 9, 11,
Once the structural material and dimensions are determined, they can be set arbitrarily by calculation. Also functions a(T) and b
(T) can also be determined experimentally.

As shown in FIG. 3, the detector section for detecting the liquid level or temperature is constructed as follows. That is, the excitation coil and detection coil in the sheath 1 are
A first excitation coil 8 and a first detection coil 9 for detecting the liquid level, and a second excitation coil 10 and a second detection coil 11 for detecting the temperature of liquid sodium are arranged separately from each other. are doing.

As shown in FIG. 1, the structure of a conventional detector part includes an excitation coil 4, first and second detection coils 5,
6 or wrapped in Bifilar. Therefore, the magnetic flux generated from the excitation coil 4 is
Since all of them are directly interlinked with the second detection coil 6, the SIGNAL/BIAS ratio of the second detection coil 6 is extremely small. On the other hand, as shown in Figure 3,
If the structure is such that the second excitation coil 10 and the second detection coil 11 are provided coaxially apart from each other on the bobbin 3, the magnetic flux generated from the second excitation coil 10 can be directly directed to the second detection coil 11. The induced voltage caused by the linkage is reduced. Therefore,
Second detection coil 1 that detects the temperature of the conductive liquid
The SIGNAL/BIAS ratio of 1 can be significantly improved.

Note that the second excitation coil 10 and the second excitation coil shown in FIG.
It is not preferable that the separation distance between the detection coil 11 and the detection coil 11 is too short or too long, and it is desirable to set the separation distance to an optimum distance. Also, as a second AC power supply 32 outputs,
Select the frequency at which the SIGNAL/BIAS ratio of the temperature detection signal is the largest, and apply this frequency to the second excitation coil 11.
It is desirable to have the water flow to

According to the present invention described in detail above, the liquid level of the conductive liquid can be accurately detected even if the temperature of the conductive liquid changes. Also, inside the sheath constituting the main body of the liquid level gauge are first and second excitation coils and a first
Since it is only necessary to house the second detection coil, the structure is simple, robust, and easy to maintain.

[Brief explanation of the drawing]

Figure 1 is a layout diagram showing an example of the structure of a conventional temperature-compensated inductive level gauge, and Figure 2 is the liquid level l and detection when the temperature of liquid sodium is taken as a parameter in the inductive level gauge. A characteristic diagram showing the relationship between the induced voltage _V1 of the coil and FIG. 3 is a circuit diagram showing an embodiment of the inductive liquid level gauge according to the present invention. 1...sheath, 2...liquid sodium, 3...
Bobbin, 8, 10...first and second excitation coils, 9,11...first and second detection coils, 1
6, 17...first and second function generators, 20...
... Arithmetic circuit, 22 ... Subtractor, 23 ... Display circuit, 31, 32 ... First and second AC power supplies.

Claims (1)

[Claims] 1. A sheath immersed in a conductive liquid, a first excitation coil and a first detection coil housed within the sheath and located at positions surrounded by the conductive liquid, and a second excitation coil and a second detection coil housed in the conductive liquid and arranged below the surface of the conductive liquid; and first and second detection coils that supply current to the first and second excitation coils. AC power supply and
and an arithmetic circuit having a first function generator and a second function generator for temperature-correcting the liquid level of the conductive liquid based on the output voltage of the second detection coil. , a proportionality constant a and a constant b in the relational expression l= _aV3 -b between the output voltage _V3 of the first detection coil and the liquid level l of the conductive liquid in the first and second function generators, respectively. An inductive liquid level gauge that is characterized by temperature compensation.