Consider the following statements regarding ultrasonic flowmeters : 1. There are no moving parts. 2. They cannot measure flow quantities in reverse flow. 3. There is no direct contact with the fluid, there is no danger of corrosion or clogging. Which of the above statements are correct ?
- A1 and 2 only
- B1 and 3 onlyCorrect
- C2 and 3 only
- D1, 2 and 3
Solution
Concept
Features of ultrasonic flowmeters
Step-by-step solution
1. They have no moving parts (true). 2. They can measure flow in both directions, including reverse flow (false). 3. Clamp-on transducers do not touch the fluid, so there is no corrosion or clogging (true).
Explanation
The transit-time difference of the ultrasonic signal gives the velocity with its sign, so reverse flow is measured too.
Why the other options are wrong
Statement 2 is wrong, so options containing it are wrong.
Shortcut
Ultrasonic: no moving parts, non-intrusive, bi-directional.
Common mistake
Accepting statement 2.
Correct answer: B) 1 and 3 only