What is doppler move meter?
Doppler flow meter is a type of ultrasonic move meter. These gadgets use the scientific precept of the Doppler impact to measure the volumetric move through a pipe. This is completed in such a means that the Doppler move meter is clamped to the outside of the pipe, so it doesn’t disturb the move as other kinds of circulate meters require.
Doppler move meters use the frequency of the ultrasonic beam to discover out the flow fee of a liquid. This measurement is possible as a outcome of Doppler impact discovered by Austrian scientist Christian Johann Doppler within the early 1800s. Essentially, the Doppler effect suggests that the frequency of a sound wave is dependent upon the motion of the sound receiver, or the source of the sound relative to the medium via which the sound travels. In this case, the medium during which the sound wave propagates is the liquid flowing by way of the pipe.
In order for a Doppler flowmeter to work correctly, the liquid must comprise particles or bubbles, so it actually works nicely for soiled liquids, however not so well for clean water. The circulate meter emits an ultrasonic signal, which is reflected 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 fee. The velocity of move in the pipe is calculated using the frequency shift, the original frequency of the ultrasonic sign, the speed of the sound via the emitter materials, and the sine of the angle of the sign into the liquid. Once the rate is thought, the volumetric move fee may be simply calculated by multiplying the velocity by the world of the pipe.
In calculating the flow rate, the meter detects the velocity at the discontinuity, not the velocity of the fluid. The velocity of circulate (V) may be determined by the following equation.
V = (f zero – f 1 )Ct / 2f 0 cos(a)
where Ct is the speed 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 connection may be simplified to
V = (f zero – 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.) may be obtained by the next equation
Q = 2.45V(ID) 2 = 2.45f zero -f 1 )K 2
The presence of acoustic discontinuities is critical to the correct operation of a Doppler flow meter. The generally accepted rule of thumb is that for correct sign reflection, at least 80-100 mg/l of strong particles are +200 mesh (+75 microns) in dimension. In the case of bubbles, a diameter of 100-200 mg/l between +75 and +150 microns is ideal. If the size or concentration of the discontinuity changes, the amplitude of the mirrored sign will be shifted, introducing errors.
Doppler flowmeters may have one or two sensors. Both types include a transmitter and a receiver, but in a single sensor Doppler flow meter they’re contained in one sensor. Reflected particles in the liquid mirror the transmitted sign again to the receiver. In a twin sensor flow meter, the transmitter and receiver are sandwiched on reverse sides of the pipe.
Doppler move meters could be a good monitoring choice as a end result of they do not intervene with circulate and require little maintenance. In addition, they will provide quick and accurate flow measurements for a wide range of liquids underneath a selection of temperature and flow conditions. On the opposite hand, liquids should include air bubbles or particles for the meter to work correctly, and lined or stainless-steel piping can intrude with the transmitter signal and scale back measurement accuracy.
Advantages of Doppler ultrasonic move meters
Doppler move meters can be utilized the place different meters don’t work. This may be liquid slurries, aerated liquids or liquids containing small or large quantities of suspended solids. The advantages can be summarized as follows.
เกจวัดแรงดันลม10bar to circulate
Can be installed outside the pipe
Pressure drop equal to the equivalent length of a straight pipe1
Low circulate cut-off
Corrosion resistance
Relatively low energy consumption
Extended studying:
Ultrasonic flow meter working precept
Select the right water circulate meter
Mass circulate rate vs volumetric move price
Relation between flow and stresse
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What is doppler move meter?
Doppler circulate meter is a type of ultrasonic circulate meter. These devices use the scientific principle of the Doppler impact to measure the volumetric move via a pipe. This is finished in such a means that the Doppler move meter is clamped to the outside of the pipe, so it does not disturb the flow as other types of flow meters require.
Doppler move meters use the frequency of the ultrasonic beam to determine the move fee of a liquid. This measurement is possible as a end result of Doppler effect found by Austrian scientist Christian Johann Doppler in the early 1800s. Essentially, the Doppler effect suggests that the frequency of a sound wave is decided by the movement of the sound receiver, or the source of the sound relative to the medium by way of which the sound travels. In this case, the medium during which the sound wave propagates is the liquid flowing by way of the pipe.
In order for a Doppler flowmeter to work properly, the liquid must comprise particles or bubbles, so it really works nicely for dirty liquids, but not so well for clear water. The flow meter emits an ultrasonic sign, which is reflected by particles and bubbles, resulting in a shift in signal 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 price. The velocity of flow within the pipe is calculated using the frequency shift, the original frequency of the ultrasonic sign, the velocity of the sound through the emitter material, and the sine of the angle of the sign into the liquid. Once the speed is known, the volumetric move price can be simply calculated by multiplying the velocity by the world of the pipe.
In calculating the circulate rate, the meter detects the speed on the discontinuity, not the velocity of the fluid. The velocity of flow (V) can be determined by the following equation.
V = (f zero – f 1 )Ct / 2f 0 cos(a)
the place 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 constant (K), the relationship could be simplified to
V = (f 0 – f 1 )K
Thus, the circulate rate V (ft/sec) is proportional to the change in frequency. The circulate rate (Q in gpm) in a pipe with a particular internal diameter (ID in.) could be obtained by the next equation
Q = 2.45V(ID) 2 = 2.45f zero -f 1 )K 2
The presence of acoustic discontinuities is important to the correct operation of a Doppler flow meter. The typically accepted rule of thumb is that for correct signal reflection, at least 80-100 mg/l of stable particles are +200 mesh (+75 microns) in dimension. In the case of bubbles, a diameter of 100-200 mg/l between +75 and +150 microns is right. If the size or focus of the discontinuity modifications, the amplitude of the reflected sign will be shifted, introducing errors.
Doppler flowmeters might have one or two sensors. Both types contain a transmitter and a receiver, but in a single sensor Doppler flow meter they are contained in one sensor. Reflected particles within the liquid replicate the transmitted sign back to the receiver. In a dual sensor circulate meter, the transmitter and receiver are sandwiched on opposite sides of the pipe.
Doppler move meters can be a good monitoring option as a end result of they don’t intervene with move and require little upkeep. In addition, they will present quick and accurate move measurements for a variety of liquids under quite so much of temperature and move situations. On the opposite hand, liquids must comprise air bubbles or particles for the meter to work properly, and lined or chrome steel piping can intrude with the transmitter signal and cut back measurement accuracy.
Advantages of Doppler ultrasonic move meters
Doppler move meters can be utilized the place other meters do not work. This could additionally 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 circulate
Can be put in outside the pipe
Pressure drop equal to the equivalent length of a straight pipe1
Low flow cut-off
Corrosion resistance
Relatively low energy consumption
Extended reading:
Ultrasonic flow meter working principle
Select the best water circulate meter
Mass move price vs volumetric flow fee
Relation between circulate and pressuree