Several problems easy to ignore in the use of ultrasonic flowmeter
是一种使用十分方便的流量仪表，特别是在大口径供水管线上，便携式超声波流量计可以将探头安装在管道外表面，实现不断流、不破坏原有管线测 Ultrasonic flowmeter is a very convenient flow meter, especially on large-diameter water supply pipelines. Portable ultrasonic flowmeters can install the probe on the outer surface of the pipeline to achieve continuous flow without damaging the original pipeline measurement.
Traffic is welcomed by the majority of users.
Ultrasonic flowmeters have advantages unmatched by other flowmeters, and they will definitely become the first choice for people to measure flow in the near future. Here are a few examples of the advantages of ultrasonic flow meters for your reference:
First, the external clip type ultrasonic flowmeter can achieve non-contact flow measurement, even if it is an insert or internal type ultrasonic flowmeter, the pressure loss is almost zero, and the convenience and economy of the flow measurement is the best.
Second, the ultrasonic flowmeter can measure various media such as water, gas and oil, and its application field is very wide.
Third, the manufacturing cost of the ultrasonic flowmeter is almost independent of the caliber, and it has the comprehensive competitive advantage of reasonable price and convenient installation and use in large caliber flowmetering occasions.
Fourth, the portable ultrasonic flowmeter can realize a flowmeter to measure the flow on a variety of pipe diameters and various materials of the pipeline. It is the preferred type of flowmeter for online calibration, comparison or period verification as a standard meter.
Fifth, the ultrasonic flow meter has the convenience of tracing the source based on the two basic physical quantities of length and time. It can be predicted that it will surpass the flow meters of other principles as the carrier of the flow standard or even the flow reference.
Sixth, the ultrasonic flowmeter consumes very little energy to operate, which can easily achieve long-term battery power supply. In addition, the advanced intelligent host can conveniently carry out wireless network communication, and its application prospect is broader.
The development prospect of the ultrasonic flowmeter is so promising, one is the inherent superiority of its flow measurement principle, and the other is the rapid advancement of microelectronic technology.
At present, the most commonly used ultrasonic flowmeters in the water supply industry are mainly liquid portable ultrasonic flowmeters. In actual use, many users fail to grasp the main points of ultrasonic flowmeters and ignore the measurement results.
Think, so have all kinds of doubts about the ultrasonic flowmeter: "Does this flowmeter measure accurately?" Questions such as this have become a hot topic in the industry.
The best platform for evaluating the quality of a flowmeter is the flow standard device. By statistically verifying the conclusions of ultrasonic flowmeters over the years, we have found that the indicators of ultrasonic flowmeters and other speed flowmeters
It is comparable, and its linearity is particularly good when the flow rate is large enough. So why do you feel that the ultrasonic flowmeter is inaccurate in actual use? Through investigation and analysis, we find that users often ignore the
Face a few questions.
I. Incorrect verification or calibration of the ultrasonic flowmeter
Any flowmeter needs to be verified or calibrated before use, and portable ultrasonic flowmeters are especially important here. As you know, there are three sets of probes (large, medium and small) for portable ultrasonic flowmeters, which are applicable respectively.
For different pipe diameter ranges, the combination of each set of probes and the host is a set of independent flow meters in a sense.
If you only use a small probe to verify or calibrate a portable ultrasonic flowmeter on a small-diameter flow standard device, then if you use a large probe to measure the flow of a large pipe, you are using an unchecked flowmeter.
The measurement accuracy of a calibrated or calibrated flowmeter cannot be guaranteed, because the current technical level cannot guarantee the interchangeability of the probes, not to mention the difference between the size probes is a variable that cannot be ignored.
Therefore, the correct method should be: based on the user's own use situation as a reference, as much as possible on the flow standard device with the same or close to the use of the pipeline diameter of the portable ultrasonic flowmeter verification of multiple pipes
Or calibration. At a minimum, ensure that each set of probes configured with the flowmeter is calibrated.
Verification or calibration agencies record the test caliber and probe number on the certificate when issuing a verification or calibration certificate. The purpose is to prevent misunderstanding. Those that equate portable ultrasonic flowmeters with other fixed caliber flows
The understanding of the meter is wrong, which is one reason why some users do not use the portable ultrasonic flowmeter.
Instrument calibration factors are given on the portable ultrasonic flowmeter verification or calibration certificate. Various flowmeters will give an instrument factor during calibration due to principles, manufacturing, etc., but the names and expressions are different
Nothing more. The portable ultrasonic flowmeter is equipped with multiple sets of probes, which may have several instrument correction factors for different calibers. When using a flowmeter to measure the flow, make sure to use the meter correction factor correctly, and don't forget
It is necessary to be careful not to mix them during use. It is good practice to make sure that the instrument correction coefficient set in the host is correct before the formal measurement.
2. Ignoring the requirements for the use conditions and environment of the flowmeter
Any velocity type flowmeter has certain requirements for the flow field of the fluid in the pipeline being measured, and the ultrasonic flowmeter is no exception. When the installation position of the flow meter cannot guarantee the length requirements of the straight pipe sections before and after, the flow field is unstable
The measurement error caused by the calibration cannot be ignored. Many users are restricted by instrumentation wells to measure at locations that cannot meet the installation requirements, which increases the measurement error.
The time difference ultrasonic flowmeter is particularly sensitive to air bubbles mixed in the water. The accompanying air bubbles will cause the flowmeter to show instability. If the accumulated gas coincides with the installation position of the probe, the flowmeter will not work.
Make. Therefore, the installation of the ultrasonic flowmeter should avoid as far as possible the locations that are easily affected by gas such as the pump outlet and the highest point of the pipeline. The installation point of the probe should also avoid the upper and bottom of the pipe as far as possible, within a range of 45 ° from the horizontal diameter.
During installation, also pay attention to avoid pipeline defects such as welds.
的安装使用环境应注意避开强电磁干扰和振动，在使用中我们发现，高压线下方，车辆密集的马路边，主机附近使用手机或对讲机都会对测量产生或多 The installation and use environment of the ultrasonic flowmeter should pay attention to avoid strong electromagnetic interference and vibration. In use, we found that under the high-voltage line, vehicles are densely on the side of the road, and the use of mobile phones or walkie-talkies near the host will cause more or less measurement.
Or less impact.
Third, the inaccurate measurement caused by the inaccurate pipeline parameters
The portable ultrasonic flowmeter probe is installed outside the pipe. It directly measures the flow velocity of the fluid in the pipe. The flow rate is the product of the velocity and the area of the pipe. The pipe area and channel length are manually performed by the host.
The input pipeline parameters are calculated. The accuracy of these parameters directly affects the measurement results. In other words: even if the flowmeter measures the flow rate very accurately, if you enter a set of inaccurate pipe parameters, the measurement result is
Pipeline parameters are best obtained by actual measurement methods. Errors may occur in the way of checking design drawings and inquiring people who are familiar with the situation, because the actual construction situation often differs from the design parameters.
The manufacturing deviation is sometimes not negligible, and parameters such as the wall thickness of the pipe that has been used for a period of time will also change over time.
The actual measurement of pipeline parameters should also pay attention to the rationality of the method, and the measuring gauges and instruments used for measurement must be calibrated. When measuring the outer diameter of the pipe, pay attention to the possible influence of the rust and dirt on the outer protective layer and outer layer of the pipe on the measurement.
When using a portable ultrasonic flowmeter for flow measurement on a small pipe diameter, the error caused by the inaccurate input of the pipe inner diameter cannot be ignored. For example: the absolute error of the inner diameter measurement is also 1 millimeter, so for DN1000
The relative error of the inner diameter of the pipeline is 0.1%; the relative error of the inner diameter of the DN100 pipeline is 1.0%. The flow rate is proportional to the square of the inner diameter (the area of the inner diameter of the pipe). It is also the measurement error of the inner diameter of 1 mm.
使用管线口径越大测量越容易准确， The flow measurement error caused by the DN1000 pipeline is only about 0.3%, while the flow measurement error caused by the DN100 pipeline is about 3%. It can be seen that the larger the pipeline diameter of the portable ultrasonic flowmeter, the easier and more accurate the measurement.
The smaller the pipe diameter, the harder it is to measure. Therefore, some people recommend that portable ultrasonic flowmeters are best used in pipelines above DN300 for some reason.
The installation distance of the probe is an important measurement parameter that must be accurately guaranteed. In order to ensure that the best signal strength is found, some users use the method of moving a probe to find the signal. Often, the signal has the wrong installation distance of the probe.
This loses one another. The correct method is: move the two probes in parallel, find the best installation point on the premise of ensuring that the installation distance of the probe meets the requirements, and after the signal is found, you must use the actual measurement method to confirm that the installation distance of the probe is accurate.
The influence of pipeline lining on the measurement is also very large. Some old pipelines use cement mortar lining for anticorrosion. If it is ignored during the measurement, a great error will occur, because the thickness of the cement mortar lining is generally not the same.
Negligible numbers, coupled with its rough surface and easy to adhere to sand, and easy to fall off into pieces, may have a great impact on the measurement. During the measurement, if no lining parameters are input, the signal should not be found in normal operation.
Consider that the pipes may be lined. Ultrasonic flowmeter is an excellent flow meter. The convenience and economy of flow measurement that it brings us are unmatched by other flowmeters. Let ’s not misunderstand because of our carelessness.
测量流量时出现的绝大多数问题都是由人为因素造成的，超声波流量计已经为我们承担了很多责任，它是我们值得信赖的好朋友 It has been proved in practice that most of the problems that occur when using ultrasonic flowmeters to measure flow are caused by human factors. Ultrasonic flowmeters have already taken on many responsibilities for us. It is our trusted friend
Characteristics and types of ultrasonic flowmeter
The ultrasonic flowmeter uses the time difference method as the principle to measure the liquid flow in a circular tube. The flow velocity of the fluid is proportional to the time difference between the forward and countercurrent propagation of the ultrasonic wave. In addition, phase difference method, frequency difference method and the like can also be used. It has stable type,
Small zero drift, high measurement accuracy, wide range ratio (velocity range: 0.01-12m / s), strong anti-interference ability, etc.
1. Ceramic sensor, metal alloy adhesive. High strength, wear resistance, corrosion resistance, not easy to scale. It is especially suitable for the measurement of high temperature and highly corrosive liquids. Using metal adhesive, the bonding is more firm, the use temperature can reach 160 ℃,
It is especially suitable for acoustic sensors, which greatly improves the engineering practicability of the sensors.
2. Micro power consumption and digital design. The overall use of micro-power hardware-level software design, digital transmission, digital reception and digital analysis of ultrasonic signals, to achieve a comprehensive digital design, the whole power consumption is less than 0.3W. Battery supply
The power consumption of the electric machine is only 0.2mW.
3. Excellent measurement and management functions. Adopt advanced analysis and calculation technology in software design to ensure accurate measurement function. In addition, advanced management functions are designed. This series of instruments can be viewed at any time during the previous ten years.
Waiting instrument operation data.
4. Flexible maintenance performance. Using the commutation adaptive technology, this series of instruments can automatically eliminate the zero point error in the measurement process, and can freely change the converter and sensor during the maintenance process without affecting the measurement accuracy.
5. Chinese characterization technology. The meter's data input and measurement process display all Chinese characters, so that the operator can operate without using the manual.
★ Plug-in ultrasonic flowmeter: Non-stop installation can be performed by using our special drilling device. Generally, it is mono measurement. To improve the measurement accuracy, three channels can be selected.
★ Pipeline ultrasonic flowmeter: need to cut open the pipeline to install, but the future maintenance can not stop production. Choice of mono or tri-channel sensors.
★ External clip type ultrasonic flowmeter: can perform fixed and mobile measurement. Use a special coupling agent (cured at room temperature, silicone rubber or high-temperature long-chain polymer grease) for installation without damaging the pipeline.
：便携使用，内置可充电锂电池，适合移动测量，配接磁性传感器。 ★ Portable ultrasonic flowmeter : portable use, built-in rechargeable lithium battery, suitable for mobile measurement, with magnetic sensor.
：体积小，重量轻，内置可充电锂电池，手持使用，配接磁性传感器。 ★ Hand-held ultrasonic flowmeter : small size, light weight, built-in rechargeable lithium battery, handheld use, with magnetic sensor.
：用于爆炸性环境液体流量测量，为防爆兼本安型。 ★ Explosion-proof ultrasonic flowmeter : It is used for the measurement of liquid flow in explosive environments. It is explosion-proof and intrinsically safe. That is, the converter is explosion-proof and the sensor is intrinsically safe.
★ Flow measurement system: It consists of multiple ultrasonic flow meters and system master station. Suitable for centralized measurement of excess pipes.
★ Ultrasonic Calorimeter: Used for heat measurement of heating system.
★ Battery-powered ultrasonic flowmeter: An integrated ultrasonic flowmeter powered by a lithium battery. It is suitable for measurement occasions without commercial power supply. A battery can be used for ten years and has a variety of measurement functions.