Instruments that measure fluid flow are collectively referred to as flow meters or flow meters. The flowmeter is one of the important instruments in industrial measurement. With the development of industrial production, the accuracy and range of flow measurement requirements are getting higher and higher, and the flow measurement technology is changing with each passing day. Various types of flow meters have been introduced to suit various applications. More than 100 flow meters have been put into use. From different perspectives, flow meters have different classification methods. There are two commonly used classification methods. One is to classify according to the measurement principle adopted by the flowmeter: the second is to classify according to the structural principle of the flowmeter.
Sort by measurement principle
a. Mechanical principle:
Instruments belonging to such principles have differential pressure type, rotor type using Bernoulli's theorem;
Impulse type using the momentum theorem, movable tube type;
Direct mass equation using Newton's second law;
a target using the principle of fluid momentum;
Turbine using the angular momentum theorem;
Vortex type using vortex principle of fluid oscillation;
Use the total static pressure difference of the pitot tube type as well as volumetric and sputum, trough and so on.
b. Electrical principle:
Electromagnetic,
Differential capacitor type,
Inductive,
Strain resistance type, etc.
c. Acoustic principle:
Ultrasonic.
d. Thermal principles:
Thermal type,
Direct calorimetry,
Indirect calorimetry and so on.
The main technical parameters of ultrasonic external clamp flowmeter:
Measurement accuracy: better than 1%
Repeatability: better than 0.2%
Measurement period: 500ms (2 times per second, 128 sets of data collected per cycle)
Working power: 220VAC/8~36VDC
Maximum flow rate: 64m / s (flow rate resolution 0.001m / s)
Display: 2 × 10 Chinese characters backlit LCD can display instantaneous flow and positive, negative, net cumulative flow, flow rate, etc.
Operation: 4×4 touch keyboard (F4 main unit magnetic 4 button) operation
Signal input: 3 channels of 4-20mA analog input, accuracy 0.1%, can input pressure, liquid level, temperature and other signals
2-way three-wire PT100 platinum resistor
Signal output: 1 isolated RS485 output
1 way 4-20mA or 0-20mA output
1 channel isolated OCT (programmable between pulse width 6~1000ms, default 200ms)
1 relay output (pulse width 200ms)
Data storage: Optional built-in data storage (SD card) can store time, instantaneous flow, accumulated flow, signal status, etc., through special software, can import data into computer for statistical and management
Communication protocol: MODBUS protocol, M-BUS protocol, FUJI extension protocol, and compatible with communication protocols of similar products of other domestic manufacturers
Other functions: automatic memory before 512 days, the first 128 months, the first 10 years of positive / negative / net cumulative flow
Automatically remember the first 30 times of power-on and power-off time and flow rate, and can realize automatic or manual addition of traffic, which can be read by MODBUS protocol.
Programmable batch (quantitative) controller, fault self-diagnosis function
Software upgrade via code file transmitted via E-mail
Protection level: sensor IP68, F4 host IP68, remaining host IP65
Explosion-proof grade: EXdIIBT4 (JN-100F2 type)
According to different output signals, these products can be divided into LWGY-□N type and LWGY-□A type.
LWGY-□N type sensor: 12～24VDC power supply, three-wire pulse output, high level ≥8V, low level ≤0.8V; signal transmission distance ≤1000m;
LWGY-□A type transmitter: 24VDC power supply, 2-wire 4-20mA output, signal transmission distance ≤1000.
This type of turbine flow products are divided into basic type and explosion-proof type (ExdIIBT6).
2, intelligent integrated turbine flowmeter
Intelligent integrated turbine flowmeter adopts advanced ultra-low-power single-chip microcomputer technology to develop a new intelligent instrument integrating turbine flow sensor and display integration. It adopts double-row liquid crystal field display, with compact structure, intuitive reading and reliability. High, free from external power interference, lightning strike, low cost and other obvious advantages. The instrument has three-point correction of the meter coefficient, the intelligent compensation meter coefficient is nonlinear, and field correction can be performed. The high-definition LCD displays both instantaneous flow (4 significant digits) and cumulative flow (8 significant digits with clear function). All valid data is not lost after 10 years of power failure. These turbine flowmeters are explosion-proof products with an explosion-proof rating of ExdIIBT6.