Products > Test Equipment
Best Brand Name for an Oscilloscope?
nctnico:
--- Quote from: mwb1100 on December 01, 2022, 07:06:27 pm ---I can't believe all the posts I see where people say they can do 0402 work without magnification - those things are not much larger than a grain of sand!
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Soldering is definitely doable if you have good eyesight but for a final check of the solder joints, you'll need to use a magnifier. Also having really good lighting is a must. I have about 400 Lux >95% CRI at my workbench surface level.
MrAl:
--- Quote from: BillyO on December 01, 2022, 02:12:07 pm ---
--- Quote from: MrAl on December 01, 2022, 12:50:51 pm ---Oh ok that sounds good, but i wonder if that 18 inches of coax is affecting the readings. As long as it is good coax i guess you're ok there.
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Properly terminated coax is a much better bet than any passive probe. That 18" bit of coax will out perform my 500MHz Tek 6139 probes.
--- Quote from: MrAl on December 01, 2022, 12:50:51 pm ---Interesting little gadget though. What main chip is that based on? That really tells all.
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It's a 74AC14. It should be able to get sub 2ns Tr, but just. Maybe 1.7ns. That's what I'm after.
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That looks reasonable then. I was thinking of the FAST version or FASTr version of TTL.
MrAl:
--- Quote from: rsjsouza on December 01, 2022, 01:42:11 pm ---
--- Quote from: MrAl on December 01, 2022, 12:57:37 pm ---
--- Quote from: rsjsouza on November 30, 2022, 07:17:32 pm ---I would only put Owon's VDS1022/VDS1022I on the category of good price/performance ratio. Others reported several issues with their offers, including some videos from Dave himself.
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Hi,
Would you happen to have a link to one of Dave's reviews?
I searched but didnt find one yet, except with other members reviews.
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Duckduckgo'ing for "eevblog owon oscilloscope" yields:
https://www.eevblog.com/forum/testgear/are-owon-oscilloscopes-worth-it/
And the Owon VDS1022/VDS1022I megathread, including even a much improved version of the software modified by the community:
https://www.eevblog.com/forum/testgear/owon-vds1022i-quick-teardown-(versus-the-hantek-6022be)/
--- End quote ---
Those look interesting too, i was hoping for reviews on the 200 series which i think are the 240, 270, etc. These are 40MHz and 70MHz rated units. Not sure which ones are newer, the 200 series or the ones you show here i guess that is the 1000 series.
MrAl:
--- Quote from: nctnico on December 01, 2022, 01:28:11 pm ---
--- Quote from: MrAl on December 01, 2022, 12:56:05 pm ---
--- Quote from: nctnico on November 30, 2022, 10:56:43 pm ---
--- Quote from: BillyO on November 30, 2022, 09:05:07 pm ---
--- Quote from: tautech on November 30, 2022, 08:25:25 pm ---Are you making these Billy ?
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I may, once I have them where I want them and there is enough demand for them. Otherwise I can just make the files available.
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Before you get all wound up about risetime, be aware that risetime tells you nothing about the bandwidth on an oscilloscope. When using risetime the assumption is that the 0.35 number is constant for all oscilloscopes. Unfortunately it isn't. The only proper way to measure the bandwidth of an oscilloscope is to sweep the input using a levelled RF generator.
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There is a way to compensate for the rise time of the input wave if that is what you are talking about.
Also, when they quote the 0.35 constant what levels are they touting the rise time is measured at?
Is it the 10 percent to 90 percent thresholds, or something else?
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No, this is not the threshold but it is a factor that says how steep the signal amplitude drops with increasing frequency. The number 0.35 only applies when an oscilloscope has a 1st order (RC) roll-off. However, in order to maximise bandwidth and minimise aliasing, a lot of DSOs have much steeper (higher order) filters for which the number 0.35 no longer applies. Since this number is typically not specified (although Keysight does for some of their oscilloscopes IIRC), you can't use a steep edge to determine bandwidth accurately. To make matters worse, the bandwidth can also depend on the V/div setting. For low V/div settings the signal needs to be amplified first instead of attenuated and the amplifier may have a different bandwidth than the attenuator. You see some claiming bandwidths that far exceed what the oscilloscope specifies but it can be completely different at low V/div settings. In the end the manufacturer should specify what the oscilloscope is capable off at all V/div settings. Again, testing with a function / frequency generator at various levels gives you a far more detailed picture of what is going on.
This is what I measured on my GW Instek GDS-2204E:
--- Quote ---There is also the settling time which is rarely mentioned, which i see affects some digital scopes.
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You mean overload recovery time?
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Oh so i guess we see some differences AGAIN between CRT and DSO scopes, that's a pain in the neck.
The settling time is the time to settle to within 99 percent of maximum, and that is an important spec of any ADC. I think the percentage used can be different though, such as 95 percent or something. So if you shoot a 1v high square wave into the front end and the scope display starts to rise, it's the time it takes to get to 99 percent of the full max which in this case would be 0.99 volts. This could be a lot longer than the rise time. This was a big concern for me when i was designing a 100MS/s scope way back in the early 1990's.
gf:
A suitable ADC driver can charge the S&H capacitor to settling within the sample interval.
At the end, the settling time of the overall system is still predominantly determined by the impulse/step response of the analog frontent.
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