1. Brief Introduction
Ultrasonic technology flow meter is comprised of calculator and ultrasonic sensor. Paired ultrasonic sensors include non invasive sensor, insertion sensor and the sensor that is attached to inner pipewall or the bottom of channel .
Clamp on transit time ultrasonic transducers need to be mounted on the external wall of the measured pipe by V methods, Z method and W method . Dual-channel ultrasonic flow meter is similar to single channel’s . The difference that single channel ultrasonic flow meter needs one pair of sensor to install, but double-channel ultrasonic flow meter needs two pairs of sensors to install. The sensors are clamped to the outside and get flow readings directly through pipe wall. The accuracy is 0.5% and 1%. Transit time type ultrasound sensor is just ok to measure clean and little dirty liquids .
Clamp on doppler ultrasonic transducers need to be mounted on the outer pipe directly opposite each other and it is just ok to measure dirty liquids, there must be some particles large enough to cause longitudinal reflection, the particles need to be at least 100 microns (0.004 in.) in diameter of 40mm-4000mm, If the liquid is very clear, this type flow meter won’t work well .
Area velocity sensor usually is attached to inner pipe wall or installed at the bottom of channel. For our area velocity sensor, the lowest liquid level is required to be higher than 20mm or above the sensor’ height, the sensor height is 22mm, to ensure the good accuracy, the min. liquid level needs to be from 40mm to 50mm.
To ensure the good accuracy, both type meters need enough straight pipe, normally, it asked the upstream 10D and downstream 5D at least, where D is pipe diameter . Elbows, valves, and other devices that disturb laminar flow can drastically reduce accuracy.
2. How to work for transit time ultrasonic flow meter
For full filled pipe transit time ultrasonic flowmeter, they transmit signals to each other, and the fluid movement in the pipe causes a measurable difference in the sound transit time as it moves with and against the flow. Depending on the pipe diameter, the signal may go directly between the transducers, or it may bounce from wall to wall. Like Doppler technology, the transducer measures stream velocity, which translates to flow.
Area velocity type flow meter, Water Velocity in the vicinity of the DOF6000 Transducer is measured acoustically by recording the Doppler shift from particles and microscopic air bubbles carried in the water. Water Depth above the DOF6000 Transducer is measured by a pressure Transducer recording the hydrostatic pressure of water above the instrument. Temperature is measured to refine the acoustic recordings. These are related to the speed of sound in water, which is significantly affected by temperature. Flow rate and total flow values are computed by flow calculator from user defined channel dimension information.
3. Types of ultrasonic flow meter
Transit time technology : TF1100-EC wall mounted or mounted permanently, TF1100-EI insertion type, TF1100-CH handheld type and TF1100-EP portable type;
SC7/ WM9100/Ultrawater inline type ultrasonic water flow meter including thread connection and flange connection .
TF1100-DC wall-mounted clamp on two channels ultrasonic flowmeter, TF1100-DI insertion type two channels ultrasonic flow meter and TF1100-DP portable type battery operated two channels ultrasonic flow meter.
Doppler time technology: DF6100-EC wall mounted or permanent mounted, DF6100-EI insertion type and DF6100-EP portable type.
Area velocity method: DOF6000-W fixed or stationary type and DOF6000-P portable type;
4. Common characteristics
1. Ultrasonic technology
2. Normally, transit time ultrasonic flow meter is more precise than doppler type flow meter .
3. Can’t measure above 200℃ liquid .
5. Common limitations
1. For Transit time and doppler full pipe ultrasonic flow meter, the pipe must be full of liquid with no air bubbles .
2. For clamp on ultrasonic flow meters, pipes must be homogenous materials capable of transmitting sound. Materials like concrete, FRP, plastic lined metal pipe, and other composites interfere with sound wave propagation.
3. For non contact ultrasonic flow meter, the pipe usually should have no internal deposits and the outer surface must be clean where the transducer mounts. Sound transmission can be aided by putting grease or similar material on the interface with the pipe wall.
4. For non invasive ultrasonic flow meter, it’s best to mount the transducers on the sides of the pipe at the 3:00 and 9:00 positions, rather than the top and bottom. This avoids any sediment on the pipe bottom.
Post time: Dec-19-2022