11 hours ago •
The objective of this experiment is to check :
- If class-oriented library works
- The TGC functionning, and its calibration
- Have fun introducing new class functions
Type of signal
Curve of the gain
Impact of gain on noise
FFT - content of such a line
- 05/23/2018 at 21:10 • 0 comments
04/17/2018 at 20:35 •
One can also see that the level of noise has improved by a factor of 4.. or more.
But I'd need to be more rigourous to get precise numbers =)
Log as usual is available.
04/08/2018 at 21:35 •
Ultrasounds, traveling in the medium they image, are attenuated by the very same medium and the further they progress, the faintest the echo comes back.
In order to compensate for this attenuation, the echoes are usually amplified by by a variable gain which renormalize these echoes.
The plots below represent in blue, unsimplified signals, and, in green, the amplified signal, with a gain shifting from 0% to 100% in 200us. It seems that makes the echoes great again =)
More in the log.
03/18/2018 at 20:57 •
I just got an interesting mechanical probe, a Bard Site Rite - piezo at 7.5MHz. The plug is quite simple, and digging into the cable yields 2 pairs of cable, one coax, a bigger cable with two "big" cables. I've made sure it's a mechanical probe. The aim is to try and see if I can connect it to my board and get an image.
Good point for this probe is that it unscrews nicely.
and even better, it has changeable heads!
I assume two pairs of cables are for motors / actuators, coax is for the signal coming back (hence the bead). But how can I see that on the pins above?
Going to search for the reference manual and other resources. I'd rather not unscrew the head yet!
02/27/2018 at 22:07 •
Some good news again =)
I got to better control pulses (I need to really read more carefully datasheets), got acquisitions at 64Msps, really looking good, and got some (badly formed at the moment) images!
Acquisitions - going to specs at 64Msps. Thanks David =)
Pulser: getting 200ns wide 75V pulses (blue is the pulse with a piezo on, in yellow is the 'damping' control signal.
Getting some images from a "damaged" probe
More on the log!
02/24/2018 at 19:43 •
That's moving forward! I'm getting some results with the following setup - using a piezo with a fixed distance, and a pulser at 25V.
Getting nice echoes (x-label in us)
The gain control works as well =)
and the FFT looks relatively clean!
02/11/2018 at 22:47 •
I needed to replace some elements, some stuff is erratic, but hey, I've been able to set up all registers, run the analog part, and control the DAC gain. I (just) need to run the ADC now, the fpga still thinks s.he's not working ;)
Some pulse control works, and pulses too! With a 10x probe, on a 25V pulse
Next step.. digitalization. More on the log.
01/26/2018 at 20:23 •
The clock had to be removed!
Investigation showed no connection through USB.. a ftdi issue. Powers were OK.. but still nothing.
So what? Clock!!
I unfortunately destroyed the 12MHz clock.. well that's it =) I'll be waiting for the new one from digikey.
The clock has to be rotated by 90°
More on the next session !
01/26/2018 at 20:16 •
This has reached a couple of days ago =)
Looks good - ice40 and ram look good. The high-level pulser footprint seems reversed. The 3.3V is on, 5V level looks good, seems good!