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We are developing an ultrasonic fluid/water level indicator, and are encountering some of the following problems.
At the recieving end, The comparator output becomes unexpectedly high as the module accepts any signal (including static) as its input.
We assume it might be due to the improper filtering of the input.
The Current setup consists of the transmitter generating 40KHz from a PIC16F877A and the revciever end is made up of the 3 OP-Amps (2 for amplifcation, 1 for comparator)
Could someone please explain as to how to filter the input waves to the required level (40 KHz ideal) ?
When you say unexpectedly high - do you mean in relation
to the input or by some means you didn't expect? (Maybe a bad
component in the op amp circuit is what I'm thinking)
If it is an input issue you could use some form of level clamping
but presumably you designed with that in mind in the first place
If you need frequency filtering a bandpass can be designed with
a few resistors/caps - I think this is what you are asking for?
Isn't the comparator in the PIC suitable for this (just curious why you need
the op amp for that)
I've only used ultrasonics once (short range motion detector to switch on a light) but didn't encounter any background or other issues. If I remember rightly my TX was also my RX though.
I'm guessing you should be ok with an RC bandpass filter.
any one of you worked on Doppler's shift in ultrasonics.
I am working on a project in which i have to analyse the frequency distortion of an ultrasonic wave when passed through different gemstones it is beneficial in testing the quality of those stones
You will not get the frequency change, but you can measure velocity change. But I would assume, that this will be not large and you will need the device, that can measure it with high precision.
If you want, I can help. I find the idea could be interesting, but only in the case, if you will measure the sound speed with sufficient precision.
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