What is doppler flow meter?
Doppler circulate meter is a type of ultrasonic circulate meter. These devices use the scientific principle of the Doppler effect to measure the volumetric flow via a pipe. This is finished in such a means that the Doppler flow meter is clamped to the outside of the pipe, so it doesn’t disturb the circulate as different kinds of move meters require.
เกจวัดแรงดัน use the frequency of the ultrasonic beam to determine the flow fee of a liquid. This measurement is feasible as a end result of Doppler impact discovered by Austrian scientist Christian Johann Doppler within the early 1800s. Essentially, the Doppler impact means that the frequency of a sound wave is determined by the motion of the sound receiver, or the source of the sound relative to the medium through which the sound travels. In this case, the medium in which the sound wave propagates is the liquid flowing through the pipe.
In order for a Doppler flowmeter to work properly, the liquid should comprise particles or bubbles, so it works well for soiled liquids, however not so well for clear water. The move meter emits an ultrasonic signal, which is mirrored by particles and bubbles, resulting in a shift in sign frequency. This frequency shift is measured by the flowmeter.
How does doppler flowmeter work?
The Doppler flowmeter converts the measured frequency shift into a volumetric circulate rate. The velocity of move in the pipe is calculated using the frequency shift, the original frequency of the ultrasonic signal, the velocity of the sound via the emitter materials, and the sine of the angle of the sign into the liquid. Once the speed is known, the volumetric circulate fee could be simply calculated by multiplying the speed by the world of the pipe.
In calculating the move price, the meter detects the rate on the discontinuity, not the speed of the fluid. The velocity of flow (V) can be decided by the following equation.
V = (f 0 – f 1 )Ct / 2f 0 cos(a)
where Ct is the velocity of sound inside the transducer, f0 is the transmission frequency, f1 is the reflection frequency, and a is the angle of the transmitter and receiver crystals with respect to the tube axis. Since C t / 2f zero cos(a) is a continuing (K), the connection may be simplified to
V = (f 0 – f 1 )K
Thus, the flow rate V (ft/sec) is proportional to the change in frequency. The move price (Q in gpm) in a pipe with a specific internal diameter (ID in.) can be obtained by the following equation
Q = 2.45V(ID) 2 = 2.45f zero -f 1 )K 2
The presence of acoustic discontinuities is crucial to the correct operation of a Doppler flow meter. The typically accepted rule of thumb is that for correct sign reflection, a minimum of 80-100 mg/l of strong particles are +200 mesh (+75 microns) in measurement. In the case of bubbles, a diameter of 100-200 mg/l between +75 and +150 microns is good. If the size or concentration of the discontinuity changes, the amplitude of the reflected signal will be shifted, introducing errors.
Doppler flowmeters may have one or two sensors. Both types comprise a transmitter and a receiver, but in a single sensor Doppler flow meter they are contained in a single sensor. Reflected particles in the liquid reflect the transmitted signal back to the receiver. In a dual sensor circulate meter, the transmitter and receiver are sandwiched on opposite sides of the pipe.
Doppler circulate meters can be a good monitoring possibility because they don’t intrude with circulate and require little upkeep. In addition, they can present fast and correct circulate measurements for a wide range of liquids under a wide range of temperature and circulate conditions. On the opposite hand, liquids must contain air bubbles or particles for the meter to work properly, and lined or stainless-steel piping can intervene with the transmitter sign and cut back measurement accuracy.
Advantages of Doppler ultrasonic circulate meters
Doppler flow meters can be used where different meters do not work. This may be liquid slurries, aerated liquids or liquids containing small or massive quantities of suspended solids. The advantages could be summarized as follows.
Less obstruction to circulate
Can be installed outdoors the pipe
Pressure drop equal to the equivalent length of a straight pipe1
Low circulate cut-off
Corrosion resistance
Relatively low power consumption
Extended studying:
Ultrasonic circulate meter working principle
Select the best water move meter
Mass flow fee vs volumetric flow price
Relation between flow and straine
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What is doppler circulate meter?
Doppler circulate meter is a kind of ultrasonic circulate meter. These gadgets use the scientific principle of the Doppler impact to measure the volumetric move by way of a pipe. This is finished in such a means that the Doppler flow meter is clamped to the surface of the pipe, so it doesn’t disturb the flow as other types of move meters require.
Doppler circulate meters use the frequency of the ultrasonic beam to discover out the circulate fee of a liquid. This measurement is feasible due to the Doppler effect discovered by Austrian scientist Christian Johann Doppler in the early 1800s. Essentially, the Doppler effect means that the frequency of a sound wave is determined by the motion of the sound receiver, or the supply of the sound relative to the medium by way of which the sound travels. In this case, the medium in which the sound wave propagates is the liquid flowing via the pipe.
In order for a Doppler flowmeter to work correctly, the liquid should include particles or bubbles, so it actually works well for dirty liquids, but not so properly for clean water. The flow meter emits an ultrasonic sign, which is mirrored by particles and bubbles, resulting in a shift in sign frequency. This frequency shift is measured by the flowmeter.
How does doppler flowmeter work?
The Doppler flowmeter converts the measured frequency shift right into a volumetric flow fee. The velocity of move in the pipe is calculated using the frequency shift, the original frequency of the ultrasonic sign, the rate of the sound through the emitter material, and the sine of the angle of the signal into the liquid. Once the velocity is known, the volumetric move price may be easily calculated by multiplying the velocity by the area of the pipe.
In calculating the circulate rate, the meter detects the velocity on the discontinuity, not the velocity of the fluid. The velocity of flow (V) could be decided by the next equation.
V = (f zero – f 1 )Ct / 2f 0 cos(a)
where Ct is the velocity of sound contained in the transducer, f0 is the transmission frequency, f1 is the reflection frequency, and a is the angle of the transmitter and receiver crystals with respect to the tube axis. Since C t / 2f zero cos(a) is a constant (K), the relationship can be simplified to
V = (f 0 – f 1 )K
Thus, the flow rate V (ft/sec) is proportional to the change in frequency. The move rate (Q in gpm) in a pipe with a selected inner diameter (ID in.) can be obtained by the next equation
Q = 2.45V(ID) 2 = 2.45f 0 -f 1 )K 2
The presence of acoustic discontinuities is important to the correct operation of a Doppler flow meter. The usually accepted rule of thumb is that for correct sign reflection, a minimum of 80-100 mg/l of stable particles are +200 mesh (+75 microns) in size. In the case of bubbles, a diameter of 100-200 mg/l between +75 and +150 microns is right. If ไดอะแฟรม or concentration of the discontinuity modifications, the amplitude of the reflected sign shall be shifted, introducing errors.
Doppler flowmeters might have one or two sensors. Both varieties comprise a transmitter and a receiver, however in a single sensor Doppler circulate meter they’re contained in a single sensor. Reflected particles in the liquid replicate the transmitted signal back to the receiver. In a dual sensor flow meter, the transmitter and receiver are sandwiched on reverse sides of the pipe.
Doppler flow meters could be a good monitoring option as a end result of they don’t interfere with flow and require little maintenance. In addition, they’ll present fast and accurate circulate measurements for a extensive range of liquids beneath a big selection of temperature and flow situations. On the other hand, liquids should include air bubbles or particles for the meter to work properly, and lined or stainless steel piping can interfere with the transmitter signal and scale back measurement accuracy.
Advantages of Doppler ultrasonic flow meters
Doppler flow meters can be utilized the place other meters don’t work. This may be liquid slurries, aerated liquids or liquids containing small or large quantities of suspended solids. The advantages may be summarized as follows.
Less obstruction to move
Can be installed outdoors the pipe
Pressure drop equal to the equal length of a straight pipe1
Low move cut-off
Corrosion resistance
Relatively low power consumption
Extended reading:
Ultrasonic flow meter working principle
Select the proper water flow meter
Mass flow fee vs volumetric circulate price
Relation between move and stresse