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Topic: Ultrasonic Anemometer (Read 32 times) previous topic - next topic

carl47

On a rocking sail boat it should be as accurate as an eggcup type. I have used the same response time constant.

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why the ZCD  has a pot R 22 ?

We want to detect above the noise level and I want it to occur before the envelope detector. An improvement would be for the ZCD to be fixed and the envelope to be adjustable.

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D1 , on the envelope detector.

This is not a rectifier but an Amplitude modulation detector. A precision rectifier would bring the detection level down but I dont know if it is really necessary.

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On the 4052, why we need -5 V?

This may be a bit of overkill as the negative voltage on the analog input is very small(it can cope with -5v).
You should try to leave it out and see if it works for you.

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What I mean if we send pulse 1 , the corresponding reversed pulsed will be after 300 other pulses

Yes but remember we are getting an average over time.
Also I found that you need a couple of pulses before the circuit becomes stable(I drop the first couple of measurements).

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It looks like if the diff is less than 200 (ie half period), then you add a pulse.

I need some more information to answer that.

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about transducers behavior and define Northerror[20] .

Now this was just trial and error and I chose 20 as a reasonable figure. This is an area were there could be much improvement.

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Even you mentioned that we do not have individual Tof, I think we do have it, since envelope measures that

Yes we do not have an accurate figure for tof to use in that equation.

Keep me informed on your progress.
I am going to revisit this design  as my next project but I will be busy on another project for some months.

Cheers.

zenonmb

Carl,

I was expecting the ZCD to detect zero volts crossing, but you are right, noise might impose a threshold above 0 V.
I also thought that ZCD will allways happen before envelope .
On step # 3 , you are mentioning that the meaasurement might not be in the appropiate pulse, so you get the diff and if it is less than 200 (half pulse), then you add another pulse (400) . if diff is more than half pulse (200), then you remove one.
My question to you is how do you know that this is needed? and what nakes you think that if diff>200 then substract one pulse.
Regards,

zenon

PS : Will let you know my progress . So far , just on the analog side . I have two oamp LM358 for first stage (instead of your transistors), then a precision recitifer (because the diode 1N4148 was not working) , ZCD and envelope detector .
One of my problems is that the tranducer cables, pick the signal from the sending end.So, when I receive the signal, I have a strong one (picked by the cable) and the real signal , very weak.


carl47

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My question to you is how do you know that this is needed?

What we get is the difference  "diffav" now this value will vary as shown by the wind function.
Using this function we can determine what is needed for a given value.

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pick the signal from the sending end

I used twin shielded microphone cable to feed the transducers. Earth the shield only at the circuit board.

I hope the opamps work.  It will simplify the circuit layout.


tom125

hello;
1-i construct the circuit correctly but when i download program to my arduino(arduino uno) it gave me unreal and constant values.I just download operation part and i dont have lcd so i wanna use pc for monitor how can i do this is it possible?
2-Another problem is with transducers(tr-40-16b)  my transducer has two pin one is short and another one is long how can i connect transducer to circuit?we have to use just microphone cable? so how can i connect these transducer with microphone cable?
Thanks...

carl47

#14
Jun 03, 2012, 06:51 am Last Edit: Jun 03, 2012, 06:53 am by carl47 Reason: 1
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it gave me unreal and constant values


I can't follow this. What exactly gives you these values? Is it the Arduino IDE ?

Please provide exact details on what you have connected.

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two pin one is short and another one is long


The drive signal is a balanced pair one wire for each pin(long or short). You should use shielded cable which
has a third connection - the shield.
Earth the shield at the circuit board end and leave the end at the transducer unconnected.

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