EEVblog #386 - Glass Delay Lines Part 2

Part 2 on Piezo-electric acoustic glass delay lines.
Some measurements and playing around.

Delay line info:
(chapter 6.9)

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[liambradymusic]

Hi Dave, that delay line blog triggered a memory from my colour television service time back in the '70's, a figure of 63.943uS comes to mind which is a half cycle short of 4.43361875MHz and was used to separate the R-Y ande B-Y colour difference signals for demodulation, it's all a bit vague now but that's what I remember, thanks for all your blogs Cheers Liam

[movaxh]

Around 28:53 interesting things happen, you will see a bump on input transciver at 2*delay_time. These is back reflection captured back by input transciver. Cool. Leter you see bump at 3*delay_time at output transciver. Makes perfect sense.

[Dibblah]

It is usable - Look at SAW touchscreens. Very cool in kiosk applications where you need them to be vandal proof. There is a significant amount of post-processing of the signal as well as wave guides laser cut in the glass. Cool video again!

[Falcrist]

This is an amazing video for gaining an understanding of glass delay lines. It's clear, you're enthusiastic, and it seems to me to require some concentration from the viewer. These are all hallmarks of excellent educational content!
Thumbs up, Dave.

[FrozenHaxor]

Excellent! I love how Dave is mastering the scope, making everything so easy in just a blink of an eye!

[EEVblog]

Yes, it works like a circular access memory just like any other delay line type.

[gamccoy]

I did watch Mike's video and it was excellent. I loved this one, too. I also watch the "signal path" blog. I feel like a kid in a candy store with so many opportunities to get good information about EE. Keep 'em coming !!!

[yasirnoori]

That's amazing Dave, thanks a lot. I do similar stuff with photonic wavelengths. We call them slow light delay lines.

[Pieh]

I was hoping to see some hard core silly-scope action from the delay lines, I was not disappointed.

[EEVblog]

I had a try but could not get any internal reflection. Would likely have to coat the external edges with a mirror.

[mkubiak]

I love watching your videos there vary good... I remember taking one of them apart in our old JC Penny VCR from 86~87 that was when I was 15 years old. I didn’t know what they where till i stumbled on to your Video now thanks!

P.S. Watching your videos have stared me getting all my electronics stuff out of the dust and started looking for new equipment.

[TunioMir]

Hey that last part, when Dave is squeezing the glass, is that how force gauge work?

[EEVblog]

That's the beauty of engineering. One product like that camcorder would be enough to spawn dozens or even hundreds of videos on various aspects of things!

[flubba]

Do you think it would be possible to turn the squeezing-dampening effect into a pressure sensor of sorts? The attenuation of the amplitude looks very linear to your squeeze force.

[Jenny_Digital]

Intriguing... I fancy making a circuit that recycles some data though it to see how many times it'll go through before being mullered. I know it wasn't made for it but my obsession with vintage computing makes this into a good project for me. Keep uo the good vids Dave!

[StephenOwensTV]

I just wanted to say, your videos are a fantastic source of entertainment to me. On this channel and my others, you really do a great job ;)

Steve

[bulwinkle]

Surely at each reflection there's going to be a change of phase and a differential one to boot as each wave hits the reflective surface at an angle so that each wave hits the reflective surface progressively across each wavelength.

[EEVblog]

No, this has nothing to do with circular access memory. I didn't have any time in the last video to do any measurements on the thing.

[ottoodell_dell]

The LC groups are adding a little correction to the del.time +a bandpass filter of course, extremelly important with the NTSC color systems, and not quite so strict in the PAL (phase alternating lines)color encoding mode.

[WhitentonMike]

Interesting, at 29:00 in the video we are seeing an echo in the source where the output reflected the signal backward through the delay line put a little blip on the input.