JPS62235529A - Automatically calibrating induction type sodium level meter - Google Patents

Abstract

PURPOSE:To perform a calibration without the operation of a worker by providing arithmetic means for calibrating input signals from an A/D converter to prescribed level signals corresponding to a zero point and a span point by an manual input or a level switch detection output. CONSTITUTION:Electric signals corresponding to a sodium level 21 are continuously applied to a signal converter 23 from a level detecting coil unit 20 via a transmission line 22. The electric signals are converted to current level signals by the signal converter 23 and inputted to an A/D converter 24 and converted to digital signals thereby to be inputted to an automatic calibrator 25. The calibrator 25 calibrates sodium level signals from the converter 24 by conducting a prescribed arithmetic operation and a calibrated output is D/A-converted (26) to be level-displayed on a display 27. Thus, by preparing a program so as to determine a zero point and a span point, only raising a liquid level from a lower limit enables a calibration to be performed without the operation of a worker.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a level meter, and particularly to an automatically calibrated induction type sodium level meter in a fast breeder reactor or the like that uses sodium. Of course, the automatic calibration induction type sodium level meter of the present invention can also be used for level measurement in general sodium storage tanks.

[Conventional technology]

Generally, in nuclear reactors such as fast breeder reactors, the sodium level is measured using a level needle.

By the way, in a nuclear reactor, it is necessary to constantly monitor the sodium free liquid level in the reactor vessel, and for this purpose, an induction type sodium level meter as shown in Figure 4 is usually used as a level meter. In the figure 0, 10 is an AC power supply,
11 is a primary coil, 12 is a secondary coil, 13 is a signal converter, and 14 is an output indicator.

This induction type sodium level meter consists of a secondary coil 1 that is electromagnetically coupled to a primary coil 11 that is excited by an AC power source 10.
The sodium level is continuously measured from the output voltage of Since the voltage generated at 12 becomes smaller, the degree to which the coil is immersed in the sodium solution, that is, the sodium level, is measured by measuring the secondary coil output voltage. E, secondary coil 1
The output voltage value of 2 is large when the sodium level is low;
Smaller when sodium levels are high. This secondary coil output voltage is then converted by the signal converter 13 into a standard current level signal of 4 to 20 mA. That is, as shown in the diagram (a) in Figure 5, at the zero point (lower end of the coil), 4.0 mA,
It is converted to 20.0 mA at the span point (upper end of the coil section). Then, the sodium level is displayed on the display device 14 in correspondence with this current value itself.

[Problem that the invention seeks to solve]

However, due to the effects of aging and operating temperature in nuclear coupler facilities, for example, the diagram in Figure 5 (
As shown in b), the output current value at the zero point (lower end of the coil) is 2.
The value may be as low as 0mA, or the span point (upper end of the coil)
However, I could only obtain a low output current value of 18.5mA,
A situation could arise where the display device did not display the correct sodium level.

In this case, an initial calibration was performed prior to actual operation. Initial calibration is done through trials of gradually increasing sodium levels. In other words, when the sodium level is below the zero point (lower end of the coil), the current level signal does not change during that time. ) to know that the following is true. Therefore, the observer operates the signal converter so that the current level signal value at that time is a preset value, for example, the current level value is 4.0 mA at the zero point (lower end of the coil). This performed the initial calibration of the zero point (lower end of the coil). Similarly, when the sodium level is increased and the sodium level exceeds the span point (upper end of the coil section), there is no change in the current level signal value, so the observer can see that the sodium level is at the span point (
Since it can be seen that the current level signal value at that time exceeds the preset value (for example, 20゜OmA at the span point (above the coil part)) The initial calibration of the span point (top of the coil section) was performed by adjusting the transducer.

As seen from the diagrams (a) and (b) in Figure 5, the sodium level and the current level signal are in a nearly linearly proportional relationship, so if the initial calibration is done as described above, during actual use,
The current signal level produced at a level midway between the lower and upper ends of the coil will lie on diagram (a) of FIG. 5 and will indicate the correct sodium level.

In addition, special level detection switch means are separately provided at a level position slightly above the bottom end of the level detection coil and a level position slightly below the top end of the level detection coil section, and the observer can detect when these level switches are activated. Some devices let you know when the sodium level has reached a certain point. In this case, for convenience, the level where the lower level switch is installed is the zero point (lower switch position),
For convenience, the position where the upper level switch is provided is called the span point (upper switch position). If such a level detection switch means is provided, the current level signal value at each specific level is set in advance, and the signal converter is adjusted as before so that the current level signal value is set in advance. I did an initial proofreading.

In this specification, when zero point is simply written without the parentheses, it means that the handling is the same for both zero point (lower end of coil) and zero point (lower switch position) regarding calibration. do. Also, simply writing the term "span point" without the parentheses () means that the handling is the same for both the span point (upper end of the coil section) and the span point (upper switch position) regarding calibration.

However, adjusting the signal converter for initial calibration
A skilled technician uses an adjustment screwdriver to delicately adjust the output adjustment trimmer in the signal converter. This work takes time even for an experienced technician, and beginners may find it difficult to achieve the desired accuracy. It was extremely difficult to adjust.

The present invention is intended to solve the above-mentioned problems, and aims to enable anyone to easily adjust level meters, which conventionally could only be done by skilled engineers, and to eliminate individual differences in adjustment. shall be.

[Means for solving problems]

For this purpose, the automatic calibration induction type sodium level meter of the present invention has a level detection means, an A/D converter into which the detected level signal is input, and an input from the A/D converter by manual input or level switch detection output. The present invention is characterized by comprising calculation means for calibrating the signal to a predetermined level signal corresponding to the zero point and the span point, and display means for displaying the calibrated output.

[Effect]

The automatic calibration induction type sodium level meter of the present invention has two types of adjustment: manual mode and automatic mode. In manual mode, the adjuster presses the key to set the zero point when the sodium level falls below the lower measurement limit. For the span point, enter the output value corresponding to the span point from the keyboard when the sodium liquid level rises to the span point,
When the set span button is pressed, the span point is adjusted by the automatic calibration device.0 In automatic mode, the sodium level is increased from below the measurement lower limit, and the point where the liquid level signal appears is the zero point. The span point is detected by the level switch attached to the detector, and the level switch detection output is used as an external input to raise the sodium level from below the measurement lower limit, automatically setting the zero point and span without any keyboard operations. The points are set.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of an automatic calibration inductive sodium level meter according to the present invention, and FIG. 2 is a block diagram of the automatic calibration device shown in FIG. Coil part, 21 is sodium level, 22
is a signal transmission line, 23 is a signal converter, 24 is an A/D converter, 25 is an automatic calibration device, 26 is a D/A converter, 27
is the liquid level indicator, 2nd is the tank, 30 is the microprocessor unit (MPU), 31 is the RAM, 32 is the ROM
, 33.34 is a peripheral device interface adapter (
PIA), 35 is the keyboard, 36 is the indicator, 3
7 is a data bus.

First, the level detection coil unit 20 continuously outputs a voltage signal corresponding to the sodium level 21, and this output signal is applied to the signal converter 23 through the transmission line 22 to generate a voltage of several mA to 20-odd mA. converted into a current level signal. This current level signal is converted into a digital computer input signal 1e by the A/D converter 24 and input to the automatic calibration device 25.

In this automatic calibration device, the following calculations are performed and a computer output signal 1e'' is output.
When the zero point (lower end of the coil) is set at a current level of 4.0 mA, the following calculation formula is applied.

re '-((Is-Z)-4)XSk+4...
・(1)! e゛2 Computer output signal Ie: Computer input signal Z: Correction amount Sk for zero point calibration Coefficient for Nispan calibration In the above equation (1), correction 11Z and coefficient Sk are calculated in advance for calibration prior to actual sodium level measurement. This is the value determined through trials. The correction 1z and coefficient Sk determination process will be described below.

Now, if the sodium level is below the zero point (lower end of the coil), it is clear that the Ie value remains constant during that time, and the value thus observed is T e l*arol
(lower end of the coil).

It is also clear that when the sodium level is above the span (upper end of the coil), the Ie value remains constant during that time, and the value thus observed is ('' (lpa+t
1 (upper end of the coil part).

The purpose of this trial was that at the zero point (lower end of the coil) Ie'
The purpose is to determine the correction NZ1 coefficient Sk that calibrates so that le' becomes 4 and 20 at the span point (upper end of the coil), so at the zero point (lower end of the coil) elssro) Z) 4) X
20 at Sk+4 span point (upper end of coil part) = ((111+5paal Z) 4)
XSk+4 needs to hold true.

Here, Z" 113+--rol 4
(2) Determined as Ielspmnl-4.

In this way, the correction 112 in the calibration equation (1),
Sk is determined in advance through trials.

Specifically, there are two types of initial calibration for determining Z and Sk: manual mode and automatic mode.

In manual mode, when the sodium level is below the lower measurement limit and you press the Set Zero button, the zero point will automatically be adjusted to the lowest output of 4mA, and the span point will be adjusted automatically when the sodium level rises to that span point. When the output value corresponding to the span point is entered from the keyboard and the cent span button is pressed, Z and Sk are automatically determined. In automatic mode, a separate level is attached to the level measurement coil in advance. When the sodium level is below the lower limit, press the start button and let the liquid level rise using the switch, the point where the detection signal of the lower level switch is output will be the zero point (lower level switch position), and The point where the upper level switch is activated is set as the span point (upper level switch position), and the Z and Sk values are automatically determined by the microcomputer program without any input from the keyboard.

Then, at the zero point (lower switch position), the computer output signal I
The calculation formula and calculation program for zero calibration are displayed on the indicator 36, such as how much the s' value is set and how much the computer output signal is set at the span point (upper switch position). A/
The sodium level signal from the D converter 24 is sent to the MPU 3.
Calibrate using the calibration formula at 0, and use the PIA to output the calibrated output.
In addition to the D/A converter 26 through the D/A converter 33, the level is displayed on the display 27.

In other words, for linear objects where the output is uniquely determined by the input, the input and output can be calibrated by determining the zero point and span point, that is, the slope of the input/output characteristic.
Even if the detector signal deviates, the calibration according to the present invention makes it possible to obtain an output commensurate with the original input.

The above calibration procedure will be explained with reference to the automatic calibration flowchart shown in FIG. 3. First, the detection signal from the level meter is A/D converted in step (2), and then the zero point is set in step (2). Step ■
In the manual mode, setting is performed by manual input using a keyboard or the like, and in the automatic mode, setting is performed by a level switch output when a liquid level signal is detected. Next, the span is set in step ■. In step (2), similarly to step (2), settings are made using the keyboard or level switch output, etc. for manual mode and automatic mode, respectively. The zero point and span point adjusted signals are subjected to D/A conversion in step (2) and outputted as a 4-4-2O calibrated signal.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the zero point and span point adjustment of the sodium level meter can be performed by simply pressing a button on the keyboard, and the zero point can be adjusted when the sodium level is below 0%. When the setting button is pressed, the output signal is automatically set to 4mA. In addition, when a known span point is manually set as a percentage and the sodium level rises to the relevant span point, pressing the button to set the span point will result in the span value set by the automatic calibration device even if there is an error in the converter output. The output is calibrated.

That is, by programming to determine the zero point and span point, calibration can be performed without operator intervention simply by raising the liquid level from the lower limit.

Therefore, even if the detector signal deviates, it can be easily adjusted using the present invention, and this method can be applied to any linear type where the input and output signals are uniquely determined. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an automatic calibration induction type sodium level meter according to the present invention, FIG. , a block diagram of a conventional inductive sodium level needle, and FIG. 5 is an explanatory graph showing the relationship between sodium level and current level signal. 20... Coil part of inductive sodium level meter, 21
...Sodium level, 22...Signal transmission line,
23... Signal converter, 24... A/D converter, 25
...Automatic calibration device, 26...D/A converter, 27.
...Liquid level indicator, 28...Tank, 30...Microprocessor unit (MPU), 31...RAM
, 32... ROM, 33. 34... Peripheral device interface adapter (PIA), 35... Keyboard, 36... Indicator, 37... Data bus applicant Power Reactor and Nuclear Fuel Development Corporation Representative Patent Attorney Masanobu Hirukawa (2 others) 4-20mA dh Hb

Claims (1)

[Claims] Level detection means, A to which the detected level signal is input
calculation means for calibrating the input signal from the A/D converter to a predetermined level signal corresponding to the zero point and the span point using the trigger input from the A/D converter, manual input, or level switch;
Self-calibrating inductive sodium level meter with display means to display the calibrated output.