has anybody posted the before and after results of a transient response test? I have been watching for this but never found it.
Yes, many times. It's buried somewhere in the massive DS1054Z threads. Measured bandwidth on these scopes is about 140MHz.
Like I said, I specifically watched for this and never saw any results posted. I just did another search and found nothing except for a depressing number of posts by me on the subject.
A time domain test would be redundant to the frequency sweeps that have been made. These scopes have no fancy DSP, so the time domain response can be inferred from the frequency domain response, which is known to be a smooth rolloff.
Did you use the forum search? It's bad.
I will go through the discussion thread you linked ... again ... but I don't remember finding anything definitive.
What about the video on the first page?
What about the video on the first page?
Unfortunately the test conditions in the video are not ideal. He has to use an external feedthrough termination on the Rigol but does *not* check it against the internal terminations on the other oscilloscopes so we do not know what effect it had.
The hacked Rigol's settling time seems reasonable but that 5ns ramp after the edge indicates a problem and doubly so since the ETS DSOs he used indicate that the pulse has real overshoot. That is exactly the sort of thing I would expect on a DSO hacked for extra bandwidth because the transient response would look better at lower bandwidth. Most users would never notice it however, it does *not* meet the specifications of a good 100 MHz oscilloscope.
"has anybody posted the before and after results of a transient response test?"
That may be true but your question was this:"has anybody posted the before and after results of a transient response test?"
We know how the 'scope works internally so we know there's no physical difference between a DS1054Z and a DS1104Z.
The video shows a rise time on a hacked DS1054Z that indicates 150MHz bandwidth.
What more do you want? It's a $400 'scope...
An oscilloscope is a time domain instrument so I want the transient response to be as good as possible; if I saw the result shown in the video and it was accurate, then I would assume that the oscilloscope is broken or in need of calibration.
Maybe I should have been more specific. Has anybody posted any rigorous transient response test results?
We know how the 'scope works internally so we know there's no physical difference between a DS1054Z and a DS1104Z.
The designs and production may be identical but Rigol could be grading them after production for the ones which will support 100 MHz with good transient response and the ones which will not. As I recall, the design includes no adjustments so alternatively maybe they do board rework which takes time adding to the cost.
QuoteThe video shows a rise time on a hacked DS1054Z that indicates 150MHz bandwidth.
What more do you want? It's a $400 'scope...
It *is* a great deal but if the results shown in the video are accurate, then the hacked model may not be a 100 (or 150 MHz) oscilloscope in the same sense that that the genuine model is which is what everybody is claiming. An oscilloscope is a time domain instrument so I want the transient response to be as good as possible; if I saw the result shown in the video and it was accurate, then I would assume that the oscilloscope is broken or in need of calibration.
If I wanted just bandwidth, then I could tweak the high frequency compensation of on oscilloscope and get it at the expense of transient response. Tektronix actually did this as an option on their old 7704A which came in 200 and 250 MHz versions.
There is a guy on Ebay who takes 150 MHz Tektronix 2445Bs, bypasses the fixed bandwidth limiting filter between the delay line and vertical CRT amplifier, reconfigures them, and sells them as 400 MHz 2465Bs. Do they actually perform like real 2465Bs? They do unless the user looks closely and most users lack a 50ps reference level pulse generator which would reveal what is going on and they would not notice when using standard passive probes with their high circuit loading except under very controlled conditions. These hacked "2465Bs" have lower bandwidth and poorer transient response than real ones and can never be adjusted to meet the 2465B specifications.
QuoteWe know how the 'scope works internally so we know there's no physical difference between a DS1054Z and a DS1104Z.
The designs and production may be identical but Rigol could be grading them after production for the ones which will support 100 MHz with good transient response and the ones which will not. As I recall, the design includes no adjustments so alternatively maybe they do board rework which takes time adding to the cost.
After recalibration the 500µV also worked fine. Without recal the 500µV where horizontal moved.
An oscilloscope is a time domain instrument so I want the transient response to be as good as possible; if I saw the result shown in the video and it was accurate, then I would assume that the oscilloscope is broken or in need of calibration.
David, what about the trace makes you assume that? The trace looks very similar on the following Tek 2467B with a little more than 1/3 the rise time. The following Tek and Agilent show overshoot. What should the trace actually look like?
Maybe I should have been more specific. Has anybody posted any rigorous transient response test results?
Apparently not, at least in terms you are willing to accept
QuoteQuoteWe know how the 'scope works internally so we know there's no physical difference between a DS1054Z and a DS1104Z.
The designs and production may be identical but Rigol could be grading them after production for the ones which will support 100 MHz with good transient response and the ones which will not. As I recall, the design includes no adjustments so alternatively maybe they do board rework which takes time adding to the cost.
Then how could I call up and get a secret squirrel code to implement the higher bandwidth? All of the upgrades are just a matter of firmware passcodes. Under your scenario, we could get an upgrade code but the scope wouldn't actually perform any better than the 50 MHz variant. This is patently false. It has been shown that the frequency domain bandwidth is in excess of 150 MHz and for all practical purposes, that is adequate.
QuoteQuoteThe video shows a rise time on a hacked DS1054Z that indicates 150MHz bandwidth.
What more do you want? It's a $400 'scope...
It *is* a great deal but if the results shown in the video are accurate, then the hacked model may not be a 100 (or 150 MHz) oscilloscope in the same sense that that the genuine model is which is what everybody is claiming. An oscilloscope is a time domain instrument so I want the transient response to be as good as possible; if I saw the result shown in the video and it was accurate, then I would assume that the oscilloscope is broken or in need of calibration.
If I wanted just bandwidth, then I could tweak the high frequency compensation of on oscilloscope and get it at the expense of transient response. Tektronix actually did this as an option on their old 7704A which came in 200 and 250 MHz versions.
There is a guy on Ebay who takes 150 MHz Tektronix 2445Bs, bypasses the fixed bandwidth limiting filter between the delay line and vertical CRT amplifier, reconfigures them, and sells them as 400 MHz 2465Bs. Do they actually perform like real 2465Bs? They do unless the user looks closely and most users lack a 50ps reference level pulse generator which would reveal what is going on and they would not notice when using standard passive probes with their high circuit loading except under very controlled conditions. These hacked "2465Bs" have lower bandwidth and poorer transient response than real ones and can never be adjusted to meet the 2465B specifications.
I suspect you are going to have to do your own tests although I am not certain of the end game. It's just a simple 100 MHz scope. If anybody wants serious bandwidth, this isn't where they'll start.
The passcodes adjust what restriction are imposed on the analog bandwidth filters and we even have schematics to show how they are implemented courtesy of Dave. The test in the video shows higher bandwidth at the expense of transient response. Are you suggesting that the passcodes should fix the transient response? That is possible but the video does not show it.
Thanks, David. Are you suggesting that the passcodes break the transient response, so an unhacked scope is preferable in this regard, or that the entire line is broken?
The pulse generator I have handy is not fast enough.
I was just playing around with my scope. What does this mean? Does it say anything about the transient response?
How about LiPo battery (perhaps with a cap in parallel) and a mercury switch, short leads, to 50 ohm pass through?
I may be naive, but so far I am rather pleased with my measurement. You said it (presumably the transient response of the scope) was not very good. I understand that we (I) cannot verify the actual signal response, and my test was not highly repeatable (usually would completely fail to capture an edge and I'd get flat or diagonal trace), but I did get several very similar signals ranging from 1.9 to 2.1 ns.
I'm going to keep looking for a more reliable signal. I do not like the avalanche diode as I want a longer pulse width. I do have some microwave stuff around. Maybe I'll find something with an SRD or tunnel diode, and I also read that there is some kind of driver in HDD's. I do want to know how my scope actually performs.
I was just playing around with my scope. What does this mean?
I may be naive, but so far I am rather pleased with my measurement.
I'm going to keep looking for a more reliable signal. I do not like the avalanche diode as I want a longer pulse width.
I'm going to keep looking for a more reliable signal. I do not like the avalanche diode as I want a longer pulse width.
A very simple, but well tested circuit for sharp edges: