Small signal removal of flow meter Field practical operation plan

Abstract: Small signal removal of flow meters The information on the actual operation plan on site is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. What is small signal ablation? What Causes Small Signal Resection? What is the effect of small signal cutoff on metrology data? What is the method of small signal removal? Signals such as flow (such as differential pressure signals) often produce a series of very small values ​​corresponding to actual values. For more flow meter manufacturers to select models and price quotations, you are welcome to inquire. What is small signal ablation? What Causes Small Signal Resection? What is the effect of small signal cutoff on metrology data? What is the method of small signal removal? Signals such as flow (such as differential pressure signal) often correspond to actual values ​​and will generate a series of very small values ​​(this is often due to interference or false signals caused by sensors and transmitters with high accuracy). Only by removing this part of the signal can we get more meaningful value. This part of the work of removing the signal is called small signal removal. What Causes Small Signal Resection? Take the differential pressure flowmeter as an example; in the actual situation of our on-site measurement, the energy medium users of large production units can basically meet the requirements of the standard whether it is instantaneous value or cumulative flow; Range (10%-90%), the actual operating range of the differential pressure is within 10% of the differential pressure range of the instrument, although there has been a small signal cut (usually 0.2%) in data processing, it will still cause flow measurement. greater impact. When the differential pressure is running at the bottom limit, the theoretical error between the error and the flow measurement can reach 100%. Since the flow rate is relatively small when the differential pressure is running at the bottom limit, it may have little effect on the total amount of the whole day, but if it is at the bottom limit for a long time In the case of operation, it has a great impact on the accuracy of measurement and the validity of energy medium data. For example, in a steelmaking unit (4 converters), oxygen blowing in steelmaking is not a continuous process, generally lasting 15 minutes. In the time period when oxygen is not used, the influence of small signals on the flow is huge. The oxygen consumption of steelmaking is basically about 20,000m3/h, and about 30% of the time per hour is in the small signal state. The flow deviation can reach about 9%, and the actual deviation is basically close to 1% after running all day. Although it can meet the requirements of three-level metering, in order to more accurately calculate the energy consumption and the statistical balance of related data, the small signal is removed. Still very necessary. According to on-site maintenance experience and experiments, the main reasons for the small signal are as follows: 1) The differential pressure transmitter is inaccurate during calibration. When the calibration personnel adjust the differential pressure transmitter, they only adjust the output signal to If the accuracy of the differential pressure transmitter is within the required range, without understanding the actual situation of the on-site differential pressure, it may cause the output of the transmitter to increase or decrease; 2) The differential pressure transmitter may have zero drift during use. . The zero point output of the differential pressure transmitter will change with time, it may drift positively, or it may drift negatively from time to time, but from the actual situation on site, the positive drift is still the majority; 3) The signal goes through a series of transmissions After the path is converted into a digital signal through the conversion unit, distortion may be caused. When the differential pressure transmitter transmits an analog signal, the PLC processes a digital signal, and certain errors may occur during the conversion process. There is no differential pressure signal in the throttling device, but a non-zero signal displayed by the computer is a small signal; 4) In the process of material belt transportation in winter, the material will often adhere to the belt, resulting in repeated measurement of the belt scale. Although this part does not belong to the category of the flow throttling device discussed above, it is also a small signal to the measurement data. Influence; how to cut out small signal? Small signals cannot be blindly removed, and must be treated differently according to the actual situation of the on-site process and the different energy media that need to be measured. If they are all handled uniformly, it is not very rigorous. For example, the metering system of a certain steel is mainly divided into two types, one is the 893 system in the late 1990s, which is mainly distributed in the old area of ​​a certain steel, and the other is the currently used metering ring network with PLC system. Both systems can cut off small signals in the flow calculation formula of the host computer. Because when there is no differential pressure signal, the flow measurement system will display the small signal value, as long as the signal is set as a parameter, it can be subtracted when the flow is calculated.

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