HP SCOPEZoom zoom ZOOOOOM !!!
OK so as planned, today I RTFM a bit and explored Megazoom land.
Pulled my Metrix MX554 bench DMM to put it on the bench next to the scope, so I could fiddle with its rear end, hum, DB25 serial port connector, that is.
It's the perfect candidate for this demonstration... a short burst of digital content when you press "Print" on the front panel to send out the current reading, low speed, as well as a real world example. Just perfect example.
See piccies below. First I adjusted the sweep speed to fit the burst completely on the screen, and that's 10ms / DIV.
Then measured its length with the cursors. It's about 66ms.
According to the DMM manual, the baud rate on this thing is fixed, it's 2400Baud. So that's a bit time of about, almost, 417us.
So that means we have about 160 bits in that burst.
So then I started to zoom in on the signal, to see when it would start to look degraded/segmented... but I zoomed and zoomed and it would still look like a nice square signal.
So I kept zooming to see if I could zoom enough to display a single bit across the screen and measure / verify the bit time.
Well see pic, sure enough you can ! Not only that, but far from running out of steam, it even has the audacity of showing you details like the rising and falling edges, look !!!
You can start to distinguish the edges, it's starting to look like an analog signal now. So I used the cursors again, to measure the bit time. I placed the cursors about half way into the edges, and bingo... 417us, spot on what we calculated !
So... can we zoom even more, and make the rising edge span the entire screen ? See pic again... yes we can !!
Not only that, but look, it still looks like an analog waveform, not a bunch of straight lines ! But Vince, you say, are you foolish, gullible enough to believe that the scope actually has enough samples to draw such a nice smooth / realistic edge ? It's just the (sin x)/x interpolation ! That thing would show you a nice smooth/curvy/ analoguy waveform even if had only 3 samples to work with !
To which I reply : NO !
As it turns out, this scope somehow does NOT even offer Sine interpolation ?!
Only vectors / linear. Which means that as soon as you are getting low on samples, you immediately notice it of course, it just can't hide... PLUS you can turn off the interpolation altogether to display only individual dots representing each sample / data point. So I did that and yes, indeed there are plenty enough samples to zoom even more !
So then once I had the rising edge on the screen, I tried to do an automatic rise time measurement on it, see if that would work, manual said it should... and it does. Look, 4us...
So the burst was initially acquired at 10ms/DIV, then we zoomed to a single bit out of 160 and that was at 50us/DIV, so x200 zoom factor.
Then we zoomed even more to see the rising edge of that single bit, and that was at 2us... x 5000 zoom factor, and still looked nice / detailed !
So it's all truly incredible and fantastic. I just can't do that with my Tek TDS 544A despite it being much higher end and much faster and much higher sampling rate.
The TDS has only 50K memory, and even then it should be less, but there was a 50K "deep memory" option and my scope had it, phew.
If I capture a burst like this, and then try to zoom on it by modifying the speed sweep... it destroys the data, gone !
And once captured, I can't do automatic measurements on the waveform, from what I remember, so not very useful anyway.
So the best you can do is single shot the burst from the get go with the fast sweep, the "zoomed in" factor, then navigate it.. but that's it. You can't have an overview of the signal, and then zoom on it, or start zoomed in and then zoom out... as soon as you touch the time base knob it clears the screen
So the Megazoom is incredible... it does simple useful things but things that you can not do with another scope, or even another HP non Megazoom, I guess.
The simple fact that once the burst / data is acquired, that you can be sure it won't get deleted, that it's there to stay, that you can zoom in and out on it, that you can make manual and automatic measurements on the acquired data, do all the "post processing" that you want on the data.... it's just heaven.
I am sold, I want the same with 32MB of memory and 10GS/s sampling !
Everyone should have a Megazoom in his lab, it brings only joy and happiness at the bench.
I hope you liked this little experiment, I sure did !
I will post it on my YT channel : " EEVFrog ". Somehow " EEVBlog " was already taken, some Aussy bloke I gather, whatever
OK I will try to go to bed before 3AM this time.... 01H46 now as, I will be strong, have decided I won't do anything anymore at the bench this evening...