CN112051004A - Real-time compensation method for static pressure influence of differential pressure transmitter - Google Patents
Real-time compensation method for static pressure influence of differential pressure transmitter Download PDFInfo
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- CN112051004A CN112051004A CN202010969192.2A CN202010969192A CN112051004A CN 112051004 A CN112051004 A CN 112051004A CN 202010969192 A CN202010969192 A CN 202010969192A CN 112051004 A CN112051004 A CN 112051004A
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
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Abstract
The invention discloses a method for compensating static pressure influence of a differential pressure transmitter in real time. The static pressure value of the differential pressure transmitter measured by the static pressure sensor in real time and the current value output by the differential pressure transmitter measured by the current sensor in real time are input into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, then the static pressure value and the original differential pressure signal are compensated to generate a compensated differential pressure signal and send the compensated differential pressure signal to the current output loop, and the compensated differential pressure signal is converted into a current signal by the current output loop. The invention compensates the error of the differential pressure transmitter caused by the influence of the static pressure in real time through the measured data, the real-time static pressure value and the current of the differential pressure transmitter, greatly weakens the error caused by the static pressure, and greatly improves the measurement accuracy of the differential pressure.
Description
Technical Field
The invention relates to a measuring method in the field of metering measurement, in particular to a real-time compensation method for static pressure influence of a differential pressure transmitter.
Background
When in actual use, the differential pressure transmitter measures the differential pressure of liquid, gas and steam in a static pressure state, converts differential pressure variables into transmittable standardized output signals, and is mainly used for measuring and controlling differential pressure parameters in an industrial process. However, the detection of the differential pressure transmitter is usually performed under the condition that the low-pressure end is communicated with the atmosphere, static process pressure is not applied to the high-pressure end and the low-pressure end of the differential pressure transmitter, namely, the detection is performed in a non-static pressure state, and the detection is inconsistent with the actual use state. It has been reported that uk, norway and france in recent years, 16 samples of differential pressure transmitters taken from 14 major manufacturers were evaluated for static pressure performance, with the following results: the 11 meters fail to meet the manufacturer's specified criteria for static pressure effects, which are much greater than the accuracy requirements of the meters, with 2 meters varying in span by a factor of 4 of their allowable error at the specified static pressure value. It can be seen that static pressure has a significant impact on the technical characteristics of the differential pressure transmitter. For a differential pressure transmitter with poor static pressure performance, the differential pressure transmitter belongs to a qualified product under the detection of a conventional method, but a differential pressure detection result under the static pressure can generate a large error. In actual use, the differential pressure transmitter is often affected by static pressure, and if the differential pressure transmitter is not corrected, the reliability of measured data is greatly reduced.
Disclosure of Invention
In order to solve the requirements and problems in the background art, the invention provides a method for compensating the static pressure influence of a differential pressure transmitter in real time, and measurement errors caused by the static pressure influence of the differential pressure transmitter are eliminated.
The technical scheme of the invention is as follows:
a static pressure influence real-time compensation device of a differential pressure transmitter mainly comprises a static pressure sensor, a current sensor, a static pressure compensation loop and a current output loop; the static pressure compensation loop is respectively connected with the static pressure sensor, the current sensor and the current output loop; the static pressure sensor and the current sensor are respectively connected to a low-voltage end and a current output end of the differential pressure transmitter, the static pressure sensor measures a static pressure value of the differential pressure transmitter in real time and inputs the static pressure value into the static pressure compensation loop, the current sensor measures a current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, then compensates the original differential pressure signal according to the static pressure value and the original differential pressure signal to generate a compensated differential pressure signal and transmits the compensated differential pressure signal to the current output loop, and finally the compensated differential pressure signal is converted into a.
The static pressure compensation loop is connected with an external data source through an RS232 data line, the static pressure compensation loop stores measured data input by the RS232 into the EPROM, and when the static pressure compensation loop is electrified again, the static pressure compensation loop reads the data in the EPROM.
The current signal range output by the current output loop is 4-20 mA.
The method comprises the steps that a static pressure sensor measures a static pressure value of a differential pressure transmitter in real time and inputs the static pressure value into a static pressure compensation loop, a current sensor measures a current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, the original differential pressure signal is compensated according to the static pressure value and the current value after being analyzed and processed by an established differential pressure transmitter compensation model to generate a compensated differential pressure signal and the compensated differential pressure signal is sent to a current output loop, and finally the compensated differential pressure signal is converted into a 4-20mA current signal by the current output loop.
The differential pressure signal curve after the compensation of the differential pressure transmitter compensation model is as follows:
Z＝z+z'
wherein z' represents a compensation correction curve, and z represents a differential pressure signal curve before compensation.
The invention has the main innovation that the static pressure value measured by the static pressure sensor in real time and the current value measured by the current sensor in real time are used for compensating the differential pressure signal of the differential pressure transmitter so as to convert the differential pressure signal into new current for output, thereby realizing accurate real-time compensation.
The invention has the beneficial effects that:
the invention compensates the error of the differential pressure transmitter caused by the influence of the static pressure in real time through the measured data, the real-time static pressure value and the current of the differential pressure transmitter, greatly weakens the error caused by the static pressure, greatly improves the measurement accuracy of the differential pressure, converts the compensated differential pressure value into a (4-20) mA current signal and outputs the current signal for the user.
Drawings
FIG. 1 is an installation diagram of a differential pressure transmitter and compensation arrangement employed in the present invention.
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 1, the compensation device mainly includes a static pressure sensor, a current sensor, a static pressure compensation loop and a current output loop; the static pressure compensation loop is respectively connected with the static pressure sensor, the current sensor and the current output loop; the static pressure sensor and the current sensor are respectively connected to a low-voltage end and a current output end of the differential pressure transmitter, the static pressure sensor measures a static pressure value of the differential pressure transmitter in real time and inputs the static pressure value into the static pressure compensation loop, the current sensor measures a current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, the original differential pressure signal is compensated after being analyzed and processed according to the static pressure value and the current value to generate a compensated differential pressure signal and transmits the compensated differential pressure signal to the current output loop, and finally the compensated differential pressure signal is converted into a 4-.
The invention is especially suitable for differential pressure transmitter which is obviously influenced by static pressure but actually works under high static pressure, the static pressure is also called rated pressure or working pressure, and the maximum pressure can reach 50MPa according to the design of the differential pressure transmitter.
The static pressure compensation circuit is connected with an external data source through an RS232 data line, the static pressure compensation circuit stores measured data input by the RS232 into a memorizer EPROM, and when the static pressure compensation circuit is electrified again, the static pressure compensation circuit reads the data in the EPROM.
The static pressure influence real-time compensation method of the differential pressure transmitter of the compensation device comprises the steps that a static pressure sensor measures a static pressure value of the differential pressure transmitter in real time and inputs the static pressure value into a static pressure compensation loop, a current sensor measures a current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, the original differential pressure signal is compensated according to the static pressure value and the current value by utilizing an established differential pressure transmitter compensation model for analysis and processing, a compensated differential pressure signal is generated and sent to a current output loop, and finally the compensated differential pressure signal is converted into a 4-20mA current signal.
The differential pressure signal curve after the compensation of the differential pressure transmitter compensation model is as follows:
Z＝z+z'
wherein z' represents a compensation correction curve, and z represents a differential pressure signal curve before compensation.
Examples
The method comprises the steps of testing a differential pressure transmitter by using a high static pressure differential pressure standard piston type pressure gauge under different static pressures, wherein an output signal value I and a corresponding pressure value P have a corresponding relation at the moment
For the convenience of understanding and calculation, the test results are converted into pressure values as follows:
let x be the standard differential pressure value, znLinear fitting is carried out by utilizing a least square method for the actual output differential pressure value of the differential pressure transmitter, and linear equations of output signals of the differential pressure transmitter before compensation under the static pressure actions of 0kPa,1000kPa, 2000kPa, 3000kPa, 4000kPa, 5000kPa and 6400kPa are respectively obtained as follows:
the derivatives obtained by differentiating the straight lines in the above formula group respectively under different static pressures (0kPa,1000kPa, 2000kPa, 3000kPa, 4000kPa, 5000kPa, 6400kPa) are 1.000042, 1.000589, 1.001246, 1.001989, 1.002661, 1.003289 and 1.004323.
If y is the static pressure value, linear fitting is carried out on different static pressures and derivatives through a least square method to obtain a slope fitting curve
The differential pressure signal curve before compensation of the differential pressure transmitter obtained by integrating the above formula can be expressed as follows:
z＝6.74×10-7xy+0.99996x+C
for different static pressure values (0kPa,1000kPa, 2000kPa, 3000kPa, 4000kPa, 5000kPa, 6400kPa), the intercepts in the above formula group are respectively equal to-0.022190, -0.019214, -0.009286, -0.005262, -0.015952, -0.005095, -0.001476, and after the intercepts are subjected to three-time curve fitting by a least square method, an intercept fitting curve C can be obtained:
C＝1.49×10-14y3-8.6×10-10y2+8.2×10-6y-2.35×10-2
finally, the differential pressure signal curve before differential pressure transmitter compensation can be expressed as:
z＝6.74×10-7xy+0.99996x+1.49×10-14y3-8.6×10-10y2+8.2×10-6y-2.35×10-2
correcting the influence part of the static pressure y, and correcting a zero system error, wherein a compensation correction curve is as follows:
z’＝-6.74×10-7xy-1.49×10-14y3+8.6×10-10y2-8.2×10-6y+0.025
the compensated differential pressure output curve is:
Z＝z+z'
Z＝z-6.74×10-7xy-1.49×10-14y3+8.6×10-10y2-8.2×10-6y+0.025
after compensation and correction, the test results are converted into pressure values as follows:
the post-compensation error change compared to the pre-compensation pressure measurement is as follows:
and the error comparison of the differential pressure transducer under each static pressure before and after compensation shows that the output error influenced by the static pressure is effectively compensated. The maximum error of the differential pressure transmitter before compensation reaches 0.5 percent once under the influence of static pressure, the error of the differential pressure transmitter after compensation is controlled within 0.1 percent, and the compensation effect is obvious.
Claims (5)
1. A real-time compensation method for static pressure influence of a differential pressure transmitter is characterized by comprising the following steps: the static pressure sensor measures the static pressure value of the differential pressure transmitter in real time and inputs the static pressure value into the static pressure compensation loop, the current sensor measures the current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, then the original differential pressure signal is compensated according to the static pressure value and the current value after being analyzed and processed by an established differential pressure transmitter compensation model to generate a compensated differential pressure signal and the compensated differential pressure signal is sent to the current output loop, and finally the compensated differential pressure signal is converted into a current signal by the current output.
2. The differential pressure transmitter static pressure effect real-time compensation method of claim 1, characterized in that: the differential pressure signal curve after the compensation of the differential pressure transmitter compensation model is as follows:
Z＝z+z'
wherein z' represents a compensation correction curve, and z represents a differential pressure signal curve before compensation.
3. The differential pressure transmitter static pressure effect real-time compensation method of claim 1, characterized in that: the method adopts the following compensation device which mainly comprises a static pressure sensor, a current sensor, a static pressure compensation loop and a current output loop; the static pressure compensation loop is respectively connected with the static pressure sensor, the current sensor and the current output loop; the static pressure sensor and the current sensor are respectively connected to a low-voltage end and a current output end of the differential pressure transmitter, the static pressure sensor measures a static pressure value of the differential pressure transmitter in real time and inputs the static pressure value into the static pressure compensation loop, the current sensor measures a current value output by the differential pressure transmitter in real time and inputs the current value into the static pressure compensation loop, the static pressure compensation loop converts the current value into an original differential pressure signal according to the measuring range of the differential pressure transmitter, then compensates the original differential pressure signal according to the static pressure value and the original differential pressure signal to generate a compensated differential pressure signal and transmits the compensated differential pressure signal to the current output loop, and finally the compensated differential pressure signal is converted into a.
4. The differential pressure transmitter static pressure effect real-time compensation method of claim 3, wherein: the static pressure compensation loop is connected with an external data source through an RS232 data line, the static pressure compensation loop stores measured data input by the RS232 into the EPROM, and when the static pressure compensation loop is electrified again, the static pressure compensation loop reads the data in the EPROM.
5. The differential pressure transmitter static pressure effect real-time compensation method of claim 3, wherein: the current signal range output by the current output loop is 4-20 mA.
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Application publication date: 20201208 |