Ultrasonic anemometer

[nico1111]

I am currently embebed in a Project which consists in creating an ultrasonic anemometer, for it, i am using the Texas Instruments TDC1000-C2000 board because i saw that it is possible to create an ultrasonic anemometer with this board. I am using 300 Khz transducers and i am currently working with the Murata MA300D1-1, the PUI UTR-16295K-TP-LWC60 and the Unictron UTR-16295K-TP-LWC60 (i bought them all for tries but i can´t get valid results).

The idea for now is nothing simpler than to measure the signal that i receive from the transducer that sends the signal but i don´t know what it is that we can´t receive a signal. All of the transdcuers are working because i used a signal generator to try if it was a transducer based problem but i gathered this information(excell).

That is when i use the osciloscope and the generator by themselves, but when i use the TDC1000-C2000 with the following configuration i do not obtain any signal received, even at the lowest distance.I changed the 8 Mhz clock for a 10 Mhz clock so the division would be 312,5 khz(that is still the range of my transdcuers) but phiscially it wouldn matter because i should see in the oscilloscope the signal received.  I know there is ringing and i know that the osciloscope (yellow is connected to  TX1 and blue to TX2) is well configured, also i have changed the r3 and r4 200 ohms resistance for 120 ohms resistance and the c4 and c5 capacitors i also changed it for 931 ohms resistance so i would convert it in a resistive circuit, as the texas instruments guide recommend for such application.

I also changed some capacitors and some resistance in the PGA and LNA filters, the first one, i changed the c15 1000pF for a 3.3 nF capacitor and then i changed the c19 and c20 51pF capacitors for 150 pF capacitors and that are all the changes i made. I did the calculations and it would work with these changes but i am having trouble with all the transducers earlier mentioned.

I would like to know why i am failing to capture a real signal when i connect the transducers to the board even if i throw the same voltage with the signal generator and i do receive it perfectly at the same distance anda same voltage. Thank you so much.

[SteveThackery]

It's hard to follow what you are saying. Are you using four transmit transducers, and four receive transducers? Are the transducer pairs facing each other? What voltage is driving the transmit transducers?

[nico1111]

No, i am currently using 2 transducers that both work as tx and rx and yes,m they are facing each other. The voltage is almost 5 V. Thank you for your fast reply.

[tszaboo]

Hi. I tried to use the TDC1000 in similar ways, and it's indeed problematic to measure ultrasound transmitted by air with it.
I'm sure that the IC is made to measure ultrasound in liquids, and the entire internals are setup for that.
What you will find is, that you don't have enough gain to receive signals. And the voltages for the transmitters are too low to drive enough power into the air. Try to measure the voltage on the receivers without it connected to the TDC1000, and see if you can see a signal at all. It should look like a sinx/x signal, with more peaks.

[nico1111]

I already tried with the second transcuer directly connected to the oscilloscope and it isn´t working either, i can´t get a receive signal. Tank you for your fast reply.

[tszaboo]

I already tried with the second transcuer directly connected to the oscilloscope and it isn´t working either, i can´t get a receive signal. Tank you for your fast reply.

Two things. Terminate the receiver with a resistor, so it's not open circuit. If you have an amplifier, like I have a Phillips PM 5171, try placing it between the scope and the receiver.
And drive the transmitter with a signal generator. You might need a lot of voltage to actually drive it, 10-15V easily, maybe more. And it's also possible you need longer signal to excite the transmitter.
Basically try to characterize the physics, the transmitter-receiver and the attenuation in the air before using the TDC1000.
And let us know what you find. I also wanted to build an Anemometer, the first prototype wasn't working well and shelved the project. But I find the entire concept interesting.