EDS E-Flow, Руководство пользователя, Страница: 4 / 24

1.2.2 Principle Depth Of Flow Measurement
The E-Flow radar level sensor uses highly accurate pulse coherent radar (PCR) technology. The micro-strip
planar antenna emits very narrow microwave pulses (unlike typical ultrasonic sensors that have a large
measuring angle). The E-Flow PCR level sensor reflects the signal off the water surface measuring the time
interval for the signal to travel. The time interval between the transmitted pulse and the received pulse is
proportional to the distance between the sensor and the surface of the water.
Due to the extremely high propagation speed of electromagnetic waves from the E-Flow, the time interval
between the transmitted pulse and the received pulse is very small. Compared with the traditional ultrasonic
level sensors. The E-Flow further improves the accuracy of depth by using developed modulation and
demodulation technology. Through the pulse coherence method, the E-Flow accurately identifies the time
interval and phase difference between the transmitted pulse and the received pulse, greatly measurement
accuracy and repeatability. The E-Flow firmware the uses the onboard wave cancellation algorithm to carry
out a final check of accuracy and repeatability of the recorded depth.
1.2.3 Flow Measurement Principle
The velocity and level measurements recorded by the E-Flow sensor is used to calculate the flow rate. Flow
rate (also known as Q, as the flow, or as throughput) is the amount of fluid moving through a channel or pipe
in a period of time. For example, if 100 litres of water move past the sensor in one minute, the flow rate is
100 litres per minute (LPM).
To calculate the flow rate, two things are needed:
The cross-sectional area of the wetted channel (A) and the average velocity (V).
Cross-sectional area is determined using the dimensions of channel and the measured level.
Average velocity is determined using the surface velocity (measured by the sensor) and empirical
equations.
Flow rate
is calculated by using the Continuity Equation: Flow Rate = Average Velocity x Area
E-Flow Radar Flow Meter Manual V1.24 3