JP2615532B2 - Zero compensation method for high-precision differential pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-precision differential pressure measuring apparatus used for measuring the level of a fluid in a tank, measuring the density of a fluid, measuring the flow rate and flow velocity of a fluid, and measuring the atmospheric pressure. The present invention relates to an improvement in a method for correcting a zero point.

[0002]

2. Description of the Related Art In measuring the level, quantity and density of a liquid contained in a tank, air is blown into the liquid using a thin tube whose tip is located in the liquid to reduce the back pressure. The air purge method for measuring is widely used. An example of the air purge method will be described with reference to FIG. FIG. 1 illustrates an example of a differential pressure measuring device for measuring a liquid level of a liquid nuclear fuel material 2 contained in a tank 1, and includes two air purge thin tubes 3 in a tank. 4 has been inserted. The tip of the thin tube 3 is arranged at a predetermined depth in the liquid, and the back pressure is applied to the high pressure side of the differential pressure transducer 6 via the high pressure side pipe 5 having the valve V1. On the other hand, the tip of the thin tube 4 is located above the liquid level, and the back pressure is applied to the low pressure side of the differential pressure transformer 6 via the low pressure side pipe 7 having the valve V3. The high-pressure pipe 5 and the low-pressure pipe 7 are connected by a short-circuit pipe 8 on the downstream side of the valves V1 and V3.
Are arranged. When measuring the differential pressure, the valves V1 and V3
Is opened, and the back pressure difference between the thin tubes 3 and 4 can be measured by the differential pressure converter with the valve V2 closed.

[0003] Since the tank containing the nuclear fuel material is relatively small, the pressure difference is as small as several hundred mm to several thousand mm of water. In addition, the amount of nuclear fuel material must be measured accurately,
Therefore, when measuring the base differential pressure, high accuracy of about ± 0.2 mm water column is required. However, the differential pressure transducer used in the differential pressure measuring device is one when the ambient temperature changes.
The zero point moves by about ± 0.2 mm water column per degree Celsius, and the change is added to the measured value to cause an error. Therefore, it is necessary to correct the zero point of the differential pressure converter.

The correction of the zero point of the differential pressure converter in the differential pressure measuring apparatus shown in FIG. 1 has conventionally been performed by the following steps.
FIG. 3 shows the relationship between the pressure change in the differential pressure changer and the open / closed state of the valve.

[0005] 1) In the differential pressure measurement state, the valve V1 is opened and the valve V2 is opened.
With the valve closed and the valve V3 open, the high-pressure side pressure and the low-pressure side pressure are respectively applied to the high-pressure side and the low-pressure side of the differential pressure converter 6, and the differential pressure is measured. If the measurement is performed in this state, the zero point moves due to a temperature change, and the change is added to the measured value to cause an error.

2) Then, zero point correction is started. That is, when the three valves are simultaneously opened and closed, the valve V1 is closed, the valve V2 is opened, and the valve V3 is closed, both ends of the differential pressure transducer 6 are short-circuited, and the zero-point output VD moved due to the temperature change.
Which is input to the digital memory 9.

3) When a zero point correction command is given to the digital memory 9, the sign of VD is inverted to -VD,
By adding this value to VD by the adder 10, a correction output 0 (= VD-VD) is obtained.

4) After correcting the zero point in this way,
Return the three valves to the open / closed state in 1) and return to the differential pressure measurement state.

[0009]

According to the above-described conventional zero point correction method, it is possible to effectively correct the zero point movement of the differential pressure converter due to a temperature change. However, the zero point of the differential pressure converter does not move only due to the temperature change, but also moves due to the pressure applied to both ends of the high pressure side and the low pressure side of the differential pressure converter. Full scale is 10,
2,0 mm using a quartz vibration type differential pressure transducer with a water column of 000 mm.
Taking the case of measuring the differential pressure of a water column of 00 mm as an example, the zero point moves about ± 0.2 mm water column per 1 ° C. of the temperature change of the differential pressure transducer, and the pressure 1, which is applied to both ends of the differential pressure transducer,
The zero point moves about 0.1 to 2.5 mm water column per 000 mm water column. In the above-mentioned conventional zero point correction method in which both ends of the differential pressure converter are short-circuited to make the differential pressure zero, in the state of 3),
A high pressure side (for example, 2,000 mm
An intermediate pressure (for example, 1,000 mm water column) between the water column) and the low-pressure side (for example, 0 mm water column) remains in common. Therefore, the zero point is also moved by the residual pressure applied to both ends of the differential pressure converter, and the conventional zero point correction method that only corrects the zero point movement due to the temperature change cannot perform highly accurate and accurate zero point correction. Was.

Therefore, the present invention provides not only a zero point shift due to a temperature change but also a differential pressure converter at both ends of a high-precision differential pressure measuring apparatus as shown in FIG. It is an object of the present invention to provide an improved zero point correction method capable of effectively correcting a zero point movement caused by a common pressure.

[0011]

That is, the present invention provides a differential pressure transducer, a high pressure side pipe having a valve V1 connected to the high pressure side of the differential pressure transducer, and a low pressure side connected to the differential pressure transducer. Correction of the zero point of a high-precision differential pressure measuring device comprising a low-pressure pipe having a closed valve V3 and a short-circuit pipe having a valve V2 connecting the high-pressure pipe and the low-pressure pipe downstream of the valves V1 and V3. When correcting the zero point from the differential pressure measurement state with the valve V1 of the high-pressure pipe and the valve V3 of the low-pressure pipe opened and the valve V2 of the short-circuit pipe closed, After closing the valve V1 of the high-pressure side pipe while keeping the valve V3 open, the valve V2 of the short-circuiting pipe is opened to release the pressure remaining on the high-pressure side of the differential pressure transducer to the low-pressure side, Next, the valve V3 of the low pressure side pipe is closed to perform zero point correction of the differential pressure transducer. It is an feature.

[0012]

[Operation] At the stage of starting the zero point correction, the valve V of the low pressure side pipe is set.
After the valve V1 of the high-pressure pipe is closed with the valve 3 open, the valve V2 of the short-circuit pipe is opened, whereby the pressure remaining on the high-pressure side of the differential pressure converter is released to the low-pressure side. No pressure remains between the pressure transducers. In this state,
By closing the valve V3 of the pipe, both the valve V3 and the valve V1 are closed.
In this state, zero point correction is performed. Thus, by giving a time difference to the operation of the valve, not only the zero point movement caused by the temperature change but also the zero point movement caused by the pressure applied to both ends of the differential pressure converter can be effectively corrected. Furthermore, the valve V1 of the high pressure side pipe and the low pressure side pipe
Zero correction can be performed with both valves V3 closed.
For example, it can occur in the upper space in the tank 1 of FIG.
Eliminate the effect of short-period pressure fluctuations on zero correction
Can be.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the differential pressure measuring device shown in FIG. 1, description will be given in order so as to be compared with the above-mentioned conventional zero point correction method. FIG. 2 illustrates the relationship between the pressure change of the differential pressure changer and the open / closed state of the valve in the method of the present invention, and corresponds to FIG. 3 of the conventional method.

1) In the differential pressure measuring state, the valve V1 is opened and the valve V2 is opened.
With the valve closed and the valve V3 open, the high-pressure side pressure and the low-pressure side pressure are respectively applied to the high-pressure side and the low-pressure side of the differential pressure converter 6, and the differential pressure is measured. If the measurement is performed in this state, the zero point moves due to a temperature change, and the change is added to the measured value to cause an error.

2) Then, zero point correction is started. That is, the valve V1 is first closed, and then the valve V2 is opened.
At this stage, the valve V3 remains open, the pressure remaining on the high pressure side of the differential pressure transducer 6 is released to the low pressure side, and no pressure remains between both ends of the differential pressure transducer. After sufficiently releasing the pressure remaining on the high pressure side to the low pressure side, the valve V3 is closed. At this point, both ends of the differential pressure transducer 6 are short-circuited,
The zero point output VD shifted by the temperature change and the pressure applied to both ends of the differential pressure converter is obtained, and is input to the digital memory 9.

3) When a zero point correction command is given to the digital memory 9, the sign of VD is inverted to -VD,
By adding this value to VD by the adder 10, a correction output 0 (= VD-VD) is obtained.

4) After correcting the zero point in this way,
The three valves are returned to the open / closed state of 1) in the reverse order of the above-mentioned open / close order, and returned to the differential pressure measurement state.

In the above-described measurement example in which a full-scale quartz-crystal vibrating type differential pressure transducer having a water column of 10,000 mm is used to measure the differential pressure of a water column of 2,000 mm, the pressure applied to both ends of the differential pressure converter is 1, 0.1-2.5 per 000 mm water column
Although the movement of the zero point on the order of mm water column occurs, according to the zero point correction method of the present invention, the movement of the zero point caused by the pressure applied to both ends of the differential pressure transducer can also be corrected.

When operating each valve with a time difference, the operation of each valve can be simply and reliably controlled with a predetermined time difference by using a timer.

[0020]

As can be understood from the above description, according to the present invention, when correcting the zero point of the differential pressure converter, not only the zero point movement caused by the temperature change, The zero point movement caused by the pressure applied to both ends of the differential pressure transducer can also be effectively corrected. Furthermore, both the high-pressure piping valve and the low-pressure piping valve
The zero point correction can be performed with the
The effect of pressure fluctuation on zero compensation can be eliminated.
You. As a result, a more accurate differential pressure measurement can be performed as compared with the conventional zero point correction method that only corrects the zero point movement caused by the temperature change.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a differential pressure measuring device using an air purge method.

FIG. 2 is an explanatory diagram showing a relationship between a pressure change of a differential pressure changer and an open / closed state of a valve in the zero point correction method of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a pressure change of a differential pressure changer and a valve opening / closing state in a conventional zero point correction method. 5: High pressure side pipe, 6: Differential pressure transducer, 7: Low pressure side pipe, 8: Short circuit pipe, V1, V2, V3: Valve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-158328 (JP, A) JP-A-62-38336 (JP, A) JP-A-62-207924 (JP, A)

Claims (2)

(57) [Claims] 1. A differential pressure transducer, a high pressure side pipe having a valve V1 connected to a high pressure side of the differential pressure transducer, and a low pressure side pipe having a valve V3 connected to a low pressure side of the differential pressure transducer. , Valve V1
And a short-circuit pipe having a valve V2 connecting the high-pressure pipe and the low-pressure pipe downstream of the valve V3. When correcting the zero point from the differential pressure measurement state in which the valve V3 of the side pipe is opened and the valve V2 of the short-circuit pipe is closed, the valve V1 of the high-pressure pipe is kept open while the valve V3 of the low-pressure pipe is opened. Is closed, the valve remaining on the high pressure side of the differential pressure converter is opened to the low pressure side by opening the valve V2 of the short-circuit pipe, and then the zero point correction is performed by closing the valve V3 of the low pressure side pipe. A method for correcting a zero point in a high-precision differential pressure measuring device, characterized in that: 2. The method according to claim 1, wherein the opening and closing operation of each of the valves V1, V2, V3 is controlled by a timer.