Working principle
It operates by generating an ultrasonic wave or pulse and measuring the time it takes for the echo to return. An ultrasonic transmitter receiver along with the necessary signal conversion unit is mounted on top of tank for measurement of level of either solids or liquids as shown in figure. The ultrasonic waves generated by transmitter are directed towards the liquid surface in the tank which is to be measured. These waves get reflected from the surface of the liquid and are received by the receiver. The time take by the wave during its travel is a measure of the distance travelled by the wave. Therefore the time ‘t’ between transmitting and receiving a wave is proportional to the distance ‘d’ between ultrasonic set and surface of the liquid in the tank. As the distance ‘H’ between ultrasonic set and the bottom of the tank is fixed time‘t’ becomes a measure of level ‘l’ ie, t α d α (H-l).
Principle : It operates by generating on ultrasonic pulse and measuring the time it takes for the echo to return. In below diagram ultrasonic pulse source which is acts as transmitter. It will generate pulse which will pass through liquid and reflect back after certain time depend on level of liquid and base which will capture by receiver. Time will be measure between generation pulse and echo which then calibrated in term of distance.
Working Principle: ultrasonic level detector works on the principle of SONAR. It consists of a ultrasonic transmitter-receiver set mounted on the top of the tank. The beam is projected downward by the transmitter and is reflected back by the surface of the material inside the tank. The time ‘t’ taken between the transmitting and receiving a pressure pulse is proportional to the distance between the ultrasonic set and the surface of the content inside the tank.
where, l - level inside the tank. H - height of tank d - distance from the top of the tank upto the surface of content inside the tank.
Advantages: 1) They have no moving parts. 2) Used for both solid and liquid level measurement. 3) It is a non-disturbance technique.
Disadvantages: 1) Complicated design 2) Temperature compensation is required 3) The dirt affects the accuracy of the measurement.