How Do Sound Waves Measure Water Depth in Physics Coursework?

[Jay_102]

Urgent- Physics coursework on sensing (OCR B)

The coursework is on using sound waves to measure the depth of water in a tank. I emit soundwaves using a sound generator and pick of the reflected wave with a mic. The original wave and the reflected wave are then shown on a osiliscope. I then need to use the speed of sound in air and some how find and combine that with the speed of sound in water? Also I have to measure the different interval time between the reflected wave and original wave?I don't know the speed of sound in water even after research and don't get how to combine them to use S=D/T. I need HELP PLZ!

OCR B

 

[Adrian Baker]

Originally posted by Jay_102
The coursework is on using sound waves to measure the depth of water in a tank. I emit soundwaves using a sound generator and pick of the reflected wave with a mic. The original wave and the reflected wave are then shown on a osiliscope. I then need to use the speed of sound in air and some how find and combine that with the speed of sound in water? Also I have to measure the different interval time between the reflected wave and original wave?I don't know the speed of sound in water even after research and don't get how to combine them to use S=D/T. I need HELP PLZ!

OCR B

Well try this for http://www.npl.co.uk/acoustics/techguides/soundpurewater/

You can read time intervals off the oscilloscope. Try not using a 'sound generator'(?) make one large sharp sound (such as a hammer on a metal plate) and then you can see the original wave and the return wave... but it depends how good your oscilloscope is - can it record and display a trace?

 

[FZ+]

Why would you need the speed of sound in air? Hmm... I suppose you may receive 3 peaks instead of 2 - one for the original, one for the wave reflected from the bottom of the pool, and one for reflection from the bottom.

 

[Nice coder]

T = Timesoundcameback - Timesoundleft
D = S * T
S = 1404.3 + 4.7T - 0.04T^2
speed works from 15-35 degrees C at maximum error of 0.18ms.

use filters and a positive feedback op-amp to detect the pulses.
use an LC filter to detect the apropriate frequency,
use an op-amp with positive feedback and latch-up to detect sound, then measre the difference in time (using clock cycles and a counter) to figure out how much time has elepsed
something like starting the clock (transister bias?) when the pulse leaves, then stoping it see above, when the pulse comes back (using op-amp).
Sorry, i do programming and electronics, but not much else!

 

[Jay_102]

Thankz for all the above its been a real help. Could PLZ on help on one thing. I don't know wot the following are and how they incorperate into my work:
Resolution
response time
systematic bias or drift
sensitivity
random variation