Sensors & Transducers: Flow Sensor Unit 2 Part 5

Que2.17. How ultrasonic inflow detector work? 

Answer  1. Ultrasonic inflow detectors use sound  swells to determine the  haste of a  fluid flowing in a pipe.  2. At no inflow conditions, the  frequentness of an ultrasonic  surge transmitted  into a pipe and its reflections from the fluid are the same.  3. Under flowing conditions, the  frequence of the reflected  surge is different  due to the Doppler Effect.  4. When the fluid moves  briskly, the  frequence shift increases linearly. The  transmitter processes signals from the transmitted  surge and its  reflections to determine the inflow rate. 2.17.1.  Detectors  Water inflow  5. Conveyance time ultrasonic inflow detectors  shoot and admit ultrasonic  swells  between transducers in both the upstream and downstream directions  in the pipe.  6. At no inflow conditions, it takes the same time to travel upstream and  downstream between the transducers.  7. Under flowing conditions, the upstream  surge will travel slower and  take  further time than the(  briskly) downstream  surge.  8. When the fluid moves  briskly, the difference between the upstream and  downstream times increases.  9. The transmitter processes upstream and downstream times to determine  the inflow rate.   

Que2.18. What are the advantages, disadvantages and   operations of ultrasonic inflow detectors? 


Advantages  1. It doesn’t block the path of liquid inflow. 

2. The affair of this  cadence is different for  viscosity,  density and temperature  of the liquid. 

3. The inflow of liquid is bidirectional. 

4. The dynamic response of this  cadence is good. 

5. The affair of this  cadence is in analog form. 

6. Versatility is good. 

7. There’s no contact to liquid. 

8. There’s no leakage  threat. 

9. There are no moving  corridor, pressure loss. 

10. High  delicacy. 


1. It’s  precious as compared with other mechanical inflow  measures. 

2. Design of this  cadence is complex. 

3. audile  corridor of this  cadence are  precious. 

4. These  measures are complicated as compared with other  measures. 

5. It can not measure cement or concrete pipes bonethey rusted. 

6. It does n’t work once the pipe contains holes or bubbles in it. 


1. These  measures are used in wastewater and dirty liquid  operations. 

2. These  measures are used wherever chemical  comity,  lower   conservation, and low- pressure drop are  needed. 

3. These  measures are used to measure the  haste of a liquid through  ultrasound to  dissect volume inflow. 

4. These  measures measure the  difference between the conveyance time of ultrasonic   beats which transmits with the direction of liquid inflow. 

5. This is one kind of device for volumetric inflow  dimension for liquids  as well as  feasts.  

Que2.19. bandy the working of ray( or  optic) inflow detector. 

Answer  1. Ray( or  optic) inflow detector work on the principle of optics i.e., they  measure the inflow rate using light. 

2. generally, they employ a set- up  conforming of a ray ray and photodetectors. 

3. Then, the  patches of the gas flowing through the pipe scatter the ray  ray to produce  beats which are picked- up by the receiver as shown in 2.19.1. 

4. also, the time between these signals is determined as one would know  the distance by which the  print- sensors would be separated, which in  turn leads to the  dimension of the speed of gas. 

5. As these  measures measure the  factual speed of the  patches constituting  the  feasts, they remain  innocent by the thermal conditions and the  variations in gas inflow. 

6. Hence, they’re able of  furnishing  largely accurate inflow data indeed  when the  terrain is most unfavourable. 

Que2.20. How ultrasonic  position detectors work? 

Answer  1. Ultrasonic  position detectors work by the “ time of flight ” principle using the  speed of sound. 

2. The detector emits a high-  frequence  palpitation, generally in the 20 kHz to  kHz range, and  also listens for the echo. Ultrasonic/  position detectors  measure distance by using ultrasonic  swells. 

3. The detector head emits an ultrasonic  surge and receives the  surge reflected  back from the target. 

4. Ultrasonic/  position detectors measure the distance to the target by measuring  the time between the emigration and  event. 

5. principally, the transmitter divides the time between the  palpitation and its  echo by two, and that’s the distance to the  face of the material. 

6. The transmitter is designed to  hear to the loftiest  breadth return   palpitation( the echo) and mask out all the other ultrasonic signals in the  vessel. 

7. The distance can be calculated with the following formula, . The value is multiplied by1/2 because T is the time for go- and- return  distance.  

Que2.21. What are the advantages and disadvantages of  ultrasonic  position detectors? 

Answer  Advantages  1. Non-contact with product. 

2. Suitable for wide range of liquids and bulk products like maquillages and  grains. 

3. Reliable performance in  delicate service. 

4. No moving  corridor. 

5. dimension without physical contact. 

6. delicacy of0.25 with temperature compensation and  tone- estimation. 


1. Not suitable for advanced pressures or in a vacuum. 

2. The temperature is limited to 170 °C.  

Que2.22. bandy the working principle of capacitive  position  detectors. 

Answer  Working principle  1. The principle of capacitive  position  dimension is grounded on change of  capacitance. 

2. An insulated electrode acts as one plate of capacitor and the tank wall  or reference electrode in anon-metallic vessel) acts as the other plate.  The capacitance depends on the fluid  position. 

3. An empty tank has a lower capacitance while a filled tank has a advanced  capacitance. 

4. A simple capacitor consists of two electrode plate separated by a small  consistence of an insulator  similar as solid, liquid, gas, or vacuum. This  insulator is also called as dielectric. 

5. Value of C depends on dielectric used, area of the plate and also distance  between the plates.  A =  Effective area of the operators  d =  Distance between the operators. 

6. This change in capacitance can be measured using AC Bridge. 


1. dimension is made by applying a Radio frequence( RF) signal  between the conductive  inquiry and the vessel wall. 

2. The RF signal results in a  veritably low current inflow through the dielectric  process material in the tank from the  inquiry to the vessel wall. 

3. When the  position in the tank drops, the dielectric constant drops causing  a drop in the capacitance reading and a  nanosecond drop in current inflow. 

4. This change is detected by the  position switch’s internal circuitry and   restated into a change in the relay state of the  position switch in case of  point  position discovery. 

5. In the case of  nonstop  position sensors, the affair isn’t a relay state,  but a gauged  analog signal. 

Que2.23. Give the advantages, disadvantages and  operations of  capacitive  position detectors. 

Answer :


1. fairly affordable 

2. protean 

3. Bear  minimum  conservation 

4. Reliable 

5. Contains no moving  corridor 

6. Easy to clean 

7. Rugged 

8. Simple to use. 


1. This system can not work with accoutrements  having varying dielectric  accoutrements . 

2. Indeed acids and caustics that do n’t appear to  cover the  seeing element  are so conductive that the thin film they leave can beget serious  crimes  in  dimension. 


1. To measures  situations of  Liquids  ii. Powered and  grainy solids  iii. Liquid essence at  veritably high temperature  iv. thawed  feasts at  veritably low temperature  sharp accoutrements  like hydrofluoric acid 

2. veritably high pressure artificial processes.

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