Long time no post!
After a period of about 3-4 months which was spent on the bubble forcing idea, it was decided that it wasn’t going anywhere and it was cancelled. This meant that I had lost a great deal of time and needed to make it up. So, whats been going on recently:
Euronoise paper on [...]
Update on what I have been doing over the Christmas period, including impact detection, more anechoic testing and more 25m drop testing!
I have bought the final tank! Another milestone passed!
I now have two tanks, the small box that was used for the stairway experiments and the new 0.8m diameter circular tank, on the roof collecting data. The small box is still lined in the anechoic, but the large is not. Because of this, we get lots [...]
I have just computed the absorption coefficients for the drop impacts, instead of a pulse generation.
To do this, I imported the raw drop data into Matlab and manually set all of the areas that had any bubble noise to zero. Then I went back to my software and averaged the pulses like before. Back in [...]
I have now completed the anechoic lining tests and reached an acceptable combination of materials.
To recap, over the last couple of weeks I have used an audio frequency amplifier to increase the transmit power of the pulsed tx signal. I expected this to provide poor results since the pulse was 6.6 uS long, hence providing [...]
For about 2 weeks now I have been struggling to find a test that I could perform to ascertain the absorption coefficient in a small tank. The problem is that this tank is only 0.5 m x 1.5 m x 0.3 m and most tests are producing spurious reflections that are masking the reflection that [...]
The Final Preamplifier for the acousic disdrometer has been designed and built and is working well. Below are a few pictures. The only thing that I would do differently next time is make the whole thing single supply rather than dual supply. Becuase I have used a rail splitter and connected the ground from that [...]
I have come to the conclusion that voltage amplifiers are better than charge amplifiers. Equations state that the gain should be the capacitance of the hydrophone divided by the capacitance of the integrating capacitor. When creating two circuits with (about) the same gain, the voltage amplifier always outperforms the charge amplifier.
This could be because of [...]
I have implemented a new microcontroller that has simultaneous sampling and a slightly higher sampling rate. I could then interpolate the data with pretty good results using a simple padding + band pass filtering technique. The higher the SNR the better it worked.
However, I have hit a great big wall. It all [...]
I’ve had a very serious problem recently regarding the long term stability of the NI-4462.
Problem:
Everything works fine for about 20-inf secs but then all of a suddent the DAQmxReadAnalogF64 function returns a 1 rather than a 0.
Solution:
The errors were buffer overrun errors (annoying that the 4462 almost always returns 1 as an error. [...]