Modern industrial automation control field for the application of the flowmeter
is becoming more and more in large petrochemical, pharmaceutical and other site we can often see based on all kinds of measuring principle, to adapt to all kinds of different measurement conditions and requirements of the flowmeter, level gauge, it is the use of these monitoring instrumentation and related equipment, to make our industrial automation control, be normal operation, to improve the level of the whole national economy and production benefit of enterprise has played a huge role.
Flow meter, there are many types of each flow meter
has its uniqueness, different from other products when we are in the selection and installation attention should be paid to adapt various working condition of the instrument work.
For flow meter products on the basis of their own unique one must satisfy the basic conditions, including the following aspects: a, reliability requirements & ndash;
This is one of the basic requirements for any flowmeter, flow meter should have high reliability, continuous process of modern industrial devices tend to be large, instrument faults easily lead to instability of the process, for installation in the line of flow meters in the event of failure, and impossible to repair specially to stop the process, so the instrument manufacturing and system design are * consider reliability, including the reliability of the thermal resistance for temperature compensation.
Compared with some instrument makers are prone to fault the inconvenience of maintenance parts of double.
There are some manufacturers design the replacement under the condition of continuous flow sensor methods.
Some electromagnetic flow meter manufacturer provides a continuous flow replaced electrode methods and tools, all of these improve reliability created good conditions.
Second, the stable performance & ndash;
Flow measuring output should have good stability, if there is a noise flow signal itself, should be through the damping adjustment in the table, make stable to value for easy reading.
With the regulator of regulating system, should make the controller output has no obvious oscillation.
Three, strong anti-jamming capability (1) vibration interference resistance.
Most of flow sensor installed on the pipeline, the environment condition is bad, the vibration is a big interference, so the flow sensor, converter, etc should have strong ability of anti-interference.
Some of the vortex street flowmeter and the coriolis mass flowmeter is not ideal because the ability to resist vibration interference, at the scene with bad, appear & other;
Out of thin air & throughout;
And & other
High value & throughout;
Wait for a phenomenon.
(2) the ability to resist radio frequency interference.
At the scene of the industrial installation flowmeter has a variety of interference sources, such as the workshop of driving past, or someone nearby interphone, forklift truck drove will cause certain flow meter said value increases, this is because the driving the radio frequency electromagnetic waves emitted by appliances, forklift truck, spark plugs, walkie-talkie radio frequency electromagnetic wave from the antenna by some ways into the instrument, interfere with its work.
Especially intelligent electromagnetic flowmeter for the external environment of particularly sensitive to the influence of electromagnetic waves, sound waves outside the influence of ultrasonic flowmeter measurement is larger, in recent years, people began to attach importance to influence on radio frequency interference.
Measuring instrument add radio frequency interference effect index, and take many measures to improve the anti-interference ability.
Fourth, the diversity of the output signal.
The commonly used signal output types are: analog output AO: namely 0/4 ~ 20 madc, such signals are commonly used for ordinary;
Also the output voltage can be used, but the transmission distance is limited by the larger.
Switch output DO: how high or low the level of the output signal can be custom or instrument factory default set to on or off;
Switch time is according to the characteristics of the signal or application in signal will have different duration;
PO: pulse signal the signal with a pulse represents a fixed amount of measurements are, aux output for flow meter, as the basis of integral count;
Mixed signal: analog signal is the superposition of digital signals.
Common is HART communication through the analog signal circuit, also similar BRAIN communication protocol, etc. ;
Digital signal output: it can be subdivided into serial communication and the bus communication, serial communication is commonly RSC32C or RSA22, RS485, industry in the majority with MODBUS protocol;
Bus communication has many kinds of types in the industry, a typical representative of FFBUS, ProfiBus, CAN, etc. , these signals are according to different application requirements and configuration in the instrument, front several about such as thermocouple or heat resistance temperature signal, CAN't call the output signal, CAN only be called temperature component measurement mode or output mode, of course, now many DCS or PLC card input ports CAN be directly to this way of measuring the output signal.
Five, the flowmeter influence short time & ndash;
There are a lot of flow measuring up and regulator in regulating system, requirements of flow measuring response time within 1 s.
Constant value control system in traffic, the flow measurement link if the total time constant is greater than 1 s, could significantly influence on control quality, serious causes the system oscillation, unable to work.
In this paper by embellish instrument technology co. , LTD. Arrange release.
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