This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.
On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.
I'm pretty sure the scope isn't a limiting factor here. We're talking about square waves of 25MHz and below and 3GHz (120 times the frequency of the 1st harmonic) is more than enough bandwidth to capture all relevant frequency components. The scope has also been calibrated pretty recently.
The cable has been tested a while ago up to 600MHz. I also did a quick comparison with a brand new 1m RG-58 cable and the results are the same (both cables are high quality cables and not some cheap chop suey stuff).
QuoteWhen I see top and bottom ringing, what are the possible origins of that error?
Difficult to say but I'm sure it's from the AWG. Maybe there's a mis-match with the internal termination (I'll see if I can check with external termination tomorrow).
I also noticed that at higher frequencies the DG1062z shows some slight jitter.
Home made ARB I built for a home project back in the 80s. It can record and playback. No DSO at home back then.... 6800 based, used some 3055s for the
Home made ARB I built for a home project back in the 80s. It can record and playback. No DSO at home back then.... 6800 based, used some 3055s for the
That's gotta be the best-looking home made anything from the 80s I've ever seen.
Home made ARB I built for a home project back in the 80s. It can record and playback. No DSO at home back then.... 6800 based, used some 3055s for the
That's gotta be the best-looking home made anything from the 80s I've ever seen.
Thanks! Back then I had to build a lot of my equipment. Here are a few pictures of it...
Next to my Hitachi analog scope.
Some of the main board.
Top of the main controller board.
You want square waves... I'll give you square waves!!!!
Sorry. I just wanted to be a part of this killer thread and I don't have any really nice square wave equipment.
I've done some experiments using an ON Semiconductor NBSG11 and some kind of oscillator: That's what I got (sorry for the crappy image, I've only had my mobile phone with me and this thing only saves to floppy disk...):
Scope is an 20GHz Sampler in some old HP 'Digital Communication Analyzer'.
See this thread: http://www.mikrocontroller.net/topic/295617#3335040 (German) for more infos and pics.
I've done an improved version where I mounted the NBGS11 dead-bug-style and directly connected it to SMA connector, didn't come out much better, but was a royal pain to assemble. I'll have to see were I got pictures of that one...
Tek R7103, S4 with sampling head extender connected straight to Tek 284 pulse generator.
This is a surprisingly interesting thread. A square wave being both hard to generate and measure at high dv/dt and frequency.
On the generator side - what do you have to spend to get a high-quality square wave. There are a million Fluke, HP, Agilent, etc on eBay. I am about to buy a 1Ghz scope and need an AWG and just a plain Function Gen (for general purpose uses like injecting noise into a circuit). Trying to learn how to understand the sources of the errors to make full use of the new scope. I have spent too much time chasing my tail on a design only to learn that my measurement was the problem, not the circuit.
Nice to see something old enough to be in KC. I bet the lamp holder is actual glass. Any idea on the age? 50s? I can just see someone driving their high tech relay logic with this back in the day!
Here is an historic one from a Levell TG150D that I've just been given and hope to restore (it is very noisy at present).
The maximum it can do is 2.5V and 160kHz (nominal 150kHz but the dial goes a bit higher).
EDIT:
I realise that I had the attenuated set for 20dB so I've added a shot with it off below.
Nice to see something old enough to be in KC. I bet the lamp holder is actual glass. Any idea on the age? 50s? I can just see someone driving their high tech relay logic with this back in the day!
That's actually contradictory: you can't have RG-58 that's not "chop suey". The original spec for the stuff is terrible.
This discussion with images has gone a ways to show how proper instrumentation should be done and all the things that can go so very wrong. A single mis-step in the instrumentation set up and the results will easily mis-lead resulting in a very wrong conclusion of circuit or instrument behavior.
Stuff that can go wrong and it becomes increasingly difficult as the rise times shrink and transmission distances grow.
*Poor coax performance. Common RG58 is pretty poor for any serious RF work. This why semi-rigid coax, Gore, Huber-Suhner and similar coax cables with known specifications should be used for nanosecond-picosecond pulse work. Beyond losses as frequency goes up, coax cables often have dispersion which compounds the problems.
*Impedance match for all component in the system. Deviations cause ripples and reflections in the response.
*Don't trust the scope image alone, know what to expect before setting up the instrumentation and if those results do not appear figure out why.
*No matter how much automation, quality-state of the art instrumentation or what not understand every tiny aspect of the test set up. As frequencies goes up, levels goes down and related are pushed to extremes all it takes is one tiny item wrong and BIG errors happen.
*Keep in mind what one is trying to achieve with the measurement as over kill is not always needed to get the desired result. There is a balance here. One does not need a picosecond pulser with matching instrumentation to test an audio amplifier.
*Then there are probes.. which are an entire universe of good and bad, some times REALLY BAD.
Bernice