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| Why do you think there aren't more "good" USB oscilloscopes? |
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| PlainName:
--- Quote ---Should an USB scope always provide the sample sequences, or would it be better if it sometimes returned the combined acquisition buffer instead? --- End quote --- It would be nice if one had the choice :) Much of the time, a snapshot of the acquisition buffer every display update would be fine - we often want a real-time display as we're poking at things and setting up. But sometimes you want a looong capture you can scroll through at your leisure, and the USB scope scores there because it has the entire PC storage resource to play with. |
| jasonRF:
--- Quote from: JPortici on February 16, 2023, 12:20:55 pm --- --- Quote from: TomKatt on February 16, 2023, 11:18:08 am ---So why do you think there aren't more USB scopes on the market? --- End quote --- current offerings satisfy demand --- End quote --- This. Most professional users want a bench scope (I have never seen a USB scope at work), and when a USB scope is in order there are already enough 'good' options available. There is a pretty big barrier to entry in this market: need to have good hardware, good software, and to chip business away from Picotech need to have either a significantly lower price or some better specs or additional features that people care about. There are companies that are trying to do this, for example TiePie https://www.tiepie.com/en/usb-oscilloscope/handyscope-hs6 but if you are going to spend that much, do you go with the 'unknown' brand or just go with Pico? Keysight offers a couple of models but they have weird limitations (eg the 1250 point FFT size). They also fit into Keysight card-cages alongside other instruments to make self-contained systems, and I suspect that is what they are really designed for. For the hobby market --- Quote from: EEVblog on February 16, 2023, 12:19:33 pm ---- snip - people expect cheap, which is what the chinese ones deliver. But cheap means you don't have any money left for a decent software development team. Look at the Digilent Analog Discovery 2 for example, there is basically nothing in the hardware yet it's US$400, the same price as a great and vastly more capable in many respects 4CH USB bench scope. Why? Because the software and support is awesome and you pay a premium for that. - snip - --- End quote --- is exactly right. Some of the 'cheap' scopes have good-enough hardware. But the software keeps them far away from being a 'good' scope. The Owon vds6102a multi-resolution scope is a prime example. Some of the cheap scopes are a mediocre mixed-bag for hardware and software - the DreamSourceLab scopes are examples: only 10 mV/div sensitivity, fast updates on USB3 models, software that actually works well but has almost no features beyond the basics. Some scopes might have okay software, but have some weird hardware issues. Virtins comes to mind, and while I have never used their Multi-Instrument software, it looks feature-rich. The issue is the hardware. Sample-rates are only 2.5 times the bandwidth with a single channel running, so with 2 channels running you only have 1.25x sampling. Likewise, only 40 kSample memory. But they have some nice-looking signal generators built-in that can also stream, which could be interesting for lower-frequency work. If I saw one for a good price on ebay I would probably pick it up for funsies just for the streaming waveform generator. When I was looking to get a 'nice' USB scope for hobby use last year I quickly realized that Pico was the only game in town. Since I did not have that large of a budget I just patiently waited for a good deal on ebay and got lucky on a used 5244B. This approach only worked because I did not need more than 2 channels; it is very rare to see large discounts on 4-channel scopes. jason |
| 2N3055:
--- Quote from: jasonRF on February 17, 2023, 01:42:03 pm --- --- Quote from: JPortici on February 16, 2023, 12:20:55 pm --- --- Quote from: TomKatt on February 16, 2023, 11:18:08 am ---So why do you think there aren't more USB scopes on the market? --- End quote --- current offerings satisfy demand --- End quote --- This. Most professional users want a bench scope (I have never seen a USB scope at work), and when a USB scope is in order there are already enough 'good' options available. There is a pretty big barrier to entry in this market: need to have good hardware, good software, and to chip business away from Picotech need to have either a significantly lower price or some better specs or additional features that people care about. There are companies that are trying to do this, for example TiePie https://www.tiepie.com/en/usb-oscilloscope/handyscope-hs6 but if you are going to spend that much, do you go with the 'unknown' brand or just go with Pico? Keysight offers a couple of models but they have weird limitations (eg the 1250 point FFT size). They also fit into Keysight card-cages alongside other instruments to make self-contained systems, and I suspect that is what they are really designed for. For the hobby market --- Quote from: EEVblog on February 16, 2023, 12:19:33 pm ---- snip - people expect cheap, which is what the chinese ones deliver. But cheap means you don't have any money left for a decent software development team. Look at the Digilent Analog Discovery 2 for example, there is basically nothing in the hardware yet it's US$400, the same price as a great and vastly more capable in many respects 4CH USB bench scope. Why? Because the software and support is awesome and you pay a premium for that. - snip - --- End quote --- is exactly right. Some of the 'cheap' scopes have good-enough hardware. But the software keeps them far away from being a 'good' scope. The Owon vds6102a multi-resolution scope is a prime example. Some of the cheap scopes are a mediocre mixed-bag for hardware and software - the DreamSourceLab scopes are examples: only 10 mV/div sensitivity, fast updates on USB3 models, software that actually works well but has almost no features beyond the basics. Some scopes might have okay software, but have some weird hardware issues. Virtins comes to mind, and while I have never used their Multi-Instrument software, it looks feature-rich. The issue is the hardware. Sample-rates are only 2.5 times the bandwidth with a single channel running, so with 2 channels running you only have 1.25x sampling. Likewise, only 40 kSample memory. But they have some nice-looking signal generators built-in that can also stream, which could be interesting for lower-frequency work. If I saw one for a good price on ebay I would probably pick it up for funsies just for the streaming waveform generator. When I was looking to get a 'nice' USB scope for hobby use last year I quickly realized that Pico was the only game in town. Since I did not have that large of a budget I just patiently waited for a good deal on ebay and got lucky on a used 5244B. This approach only worked because I did not need more than 2 channels; it is very rare to see large discounts on 4-channel scopes. jason --- End quote --- I assure you predominant number of Picoscopes is sold to companies... |
| jasonRF:
--- Quote from: 2N3055 on February 17, 2023, 01:48:41 pm --- I assure you predominant number of Picoscopes is sold to companies... --- End quote --- I believe it. And I would be shocked if they did not dominate that market. My writing can be meandering, but in the first part of my post I was trying to say that we probably don’t have a lot more ‘good’ usb scopes because Pico has cornered the market for the most part. It would take a lot of up-front investment for another company to challenge them. The big players like Tek/Keysight/etc must believe that there just in’t enough money to be made in that market. Jason |
| hans:
I personally think the reason an USB scopes are not very popular, is similar to how many other TE doesn't use GUI's that only operate on PCs. Most people want buttons and don't mess around with desktop software. You boot it up and it always is up in 1min, anyone can use it, etc. I don't think it's the problem that laptops are going out of fashion. In university we sometimes have people showing up with iPad Pro's to C programming classes in 1st year CS/EE. "Because it's a capable piece of kit right?"... yes the iPad Pro with M1 is very fast.. but it runs a crippled OS and is not made for power users. As staff we have to inform them politely they didn't got the right equipment. There is a reason many universities give 'strong recommendations' or even 'requirements' for which laptops to use. In my old school from 2008 era we still had school machines, but they went out of fashion and nobody used them. I don't see these anymore, except for in the library, I think... As @EEVBlog suggested, HDMI outputs can help with the small displays, But for reasons I state before, the PC connectivity can be very important. Namely; a scope has quite a neat seat of hardware under FPGA control (ADCs, DACs) which could also be used in 'rolling' timebase more (a ADC/DAC stream). People pay tons of money to have A/D and D/A boxes for radio equipment. In essence an USB scope doesn't have to be simpler than a desktop scope. But it seems to be a common design goal, I agree. The main challenge is to transmit waveform data over a cable. The FPGA in the scope can do all the triggering, acquisition, segmenting, etc. Then on a desktop screen, it could be rendered and analyzed with far more processing power.. For automation, which I'm all for in a modern lab, this can be a bliss. If you just want to probe around, give me knobs. But let's say a scope is trying to reach 1M wfm/s at 120pts per waveform. Then that's 120MS/s to transmit over USB, with some framing associated. Even if those samples are >8-bit (e.g. hi-res ADC or hi-res oversampling etc.), then that's about 240MB/s of data to transfer. Modern USB standards can easily cope with this. You could even higher waveform pts to accommodate larger displays or sampling fidelity. Problem is that this kind of custom protocol and implementation is not simple.. and the PC needs to have some grunt as well to do the phosphor drawing outside of FPGA/ASIC fabric. |
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