RADAR TYPE LEVEL MEASUREMENT : (TIME OF FLIGHT)


Radar type level transmitter is used for measuring the closed tank level of the special liquid, especially radioactivity liquid. The radar instrument consists of a smart transmitter a radioactivity ray emitting sensor, and an antenna. The sensor emitting the radar rays when proper electrical supply given to the transmitter. The sensor hides of the antenna. The radar rays fill into the tank. The two technologies on the market are frequency modulated continuous wave (FMCW) and pulsed wave time of flight.


In pulsed wave time of flight radar pulses which are produced piezo-electrically applying voltage are emitted by a sender, reflected by the product surface and again detected by a receiver. From the Time of Flight (TOF) of the pulse the distance between the sender and the surface is determined using the known velocity of propagation. The level can be calculated from the below equation,

D= c t/2

where,


c = speed of light 300,000 km/s

d= distance between transmitter/receiver and surface of liquid.


FMCW systems, however, continuously emit a swept frequency signal and distance is inferred from the difference in frequency between transmit and receive signals at any point in time. This non-contact technology produces highly accurate level measurement in storage tanks and some process vessels. Radar is an excellent, but fairly expensive technology for continuous level measurements. They are various influences such as powders, heavy vapors, surface turbulence, foam and even ambient noise can affect the returning signal. The primary disadvantage is cost. The pressure ratings on radar antenna are limited and the device cannot measure interfaces.


Radar level measurement come in two different type out of them one is guided wave radar (GWR) and non guided wave radar. in guided wave radar pulse is guided through rod and carry return signal through same rod by calculating time level can easily

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