I have taken idea "Precision to the Last Micron" posted on http://blog.redpitaya.com/?p=218 and upgraded it by means of extending the distance range. First, i have obtained 40 kHz ultrasonic transducers from Farnell. I have used the same setup than the author in abovemntioned blog, but, instead of using fixed frequency of 40kHz i have created frequency sweep ranging from 39 to 41 kHz. Then i have played the sweep using the pitaya through ultrasonic transducer (tx). I have captured the delayed signal using other transducer (rx).
Then i have detected the time it took for the signal to travel from tx to rx:
I have multiplied tx and rx signals. Since sin(a)*sin(b) = 1/2(cos(a-b)-cos(a+b)) i have got signal which contained 2 spectral lines with frequency difference and frequency sum. From knowing the sweep ramp i was able to calculate the delay and from the delay and speed of sound the distance.
The setup is currently able to measure distance up to 3 m.
Upgrading ultrasonic range finder
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- Posts: 4
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- Location: Ljubljana, Slovenia
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Re: Upgrading ultrasonic range finder
Currently i am describing the solution of ultrasonic range finder in paper which i will submit to IEEE ERK 2014 conference (http://www.ieee.si/erk/).
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Re: Upgrading ultrasonic range finder
Your work is quite interesting.
Do you implement all signal processing operations in the ARM core of the Redpitaya, or on the computer side ? Implementing on the ARM core would be very useful, as we can make stand alone meter with the Redpitaya.
Do you implement all signal processing operations in the ARM core of the Redpitaya, or on the computer side ? Implementing on the ARM core would be very useful, as we can make stand alone meter with the Redpitaya.
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Re: Upgrading ultrasonic range finder
The speed of sound in air is highly dependent on things such as humidity, pressure, temperature and local air vortices,
Altough you will be able to get **resolution** in in terms of measuring the phase of the signal, think a bit about accuracy too.
Unfortunatelly, ultrasonic distance meter cannot be nearly as accurate as a laser distance meter. Unfortunatelly, because it would be so much cheaper!
Altough you will be able to get **resolution** in in terms of measuring the phase of the signal, think a bit about accuracy too.
Unfortunatelly, ultrasonic distance meter cannot be nearly as accurate as a laser distance meter. Unfortunatelly, because it would be so much cheaper!
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