| Products > Test Equipment |
| New toy(?) scope, DSO154pro, 1ch, claimed 40MS/s |
| << < (14/19) > >> |
| tatel:
--- Quote from: Dave_g8 on March 07, 2024, 07:24:24 pm ---Hi, I agree that the DSO154Pro is excellent for the price, but you do need to be aware of its limitations. --- End quote --- Of course, however I see more bang for the buck in it than in most other "toyscopes". AFAIK, none of these two-channel low cost models appearing in the last times is able to do a differential measurement. Even if some offer "FFT". If you can't do differential measurements on a low BW 2-channels o'scope, is there much of an advantage in having two channels? At double DSO154Pro's price? Should they have differential measurement, I would think otherwise. So, as next step in the ladder after DSO154Pro, I would rather get an old Hameg 20 MHz than, say, Zeeweii's DSO2512G. About the same bandwidth, but traces are much more stable after you get over half the device's bandwidth, and they do differential measurements. At first it seemed impossible to get one of these under 100€ in Europe, but now I have a couple of them (I still need to decide which one will remain here). One can get 50 MHz bandwidth for a little bit more (another couple Hameg 604-605 was found). Needed to go on the hunt for about six months however. Personally I rather prefer these old boat anchors than one of the new, low-bandwith 2-channel o'scopes appearing now. Unless you really need the portability, of course. But when speaking about portability, DSO154Pro is enough for me. With a separated DMM. YMMV. Don't really know about those Zoyis, etc, but for what they seem to be, I'd stick to my DSO154Pro, I think. Perhaps the Owons, I don't know. They seem to be quite good and portable. I miss differential measurement on them, tho, and have seen complaints about they getting hot, then becoming somewhat unstable. Others will know better I guess. But they look to me as probably the better of the low cost 2 channel oscilloscope-DMM combos, so I do see some value on them. Just not my choice. Newbies on a really tight budget, looking for a cheap o'scope to begin learning, will find more value on DSO154Pro than in most other low-cost offerings. It will remain useful as a portable thing after they outgrow it, just for peanuts. On the next price step, old CRO's will also remain useful after outgrowing them. To, say, look at PSUs without risking to blow up any brand new 4-channel benchscope. For little more. Just my thoughts. |
| BillyO:
In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz. No where near -3dB. |
| Dave_g8:
--- Quote from: BillyO on March 26, 2024, 02:12:42 am ---In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz. No where near -3dB. --- End quote --- Hi, Yes, the analogue bandwidth of the front end is greater than 18MHz. Because the sampling rate of the ADC is only 40MSa/s, this means that the resultant displayed waveform after sin(x)/x interpolation for a square wave input signal will have ripple before and after the transitions which is not present on the actual signal. So although you will see reasonable results for high frequency sine wave inputs, for square waves the result is not so good. If you have sine waves greater than twice the sampling frequency the results will be invalid due to aliasing. For example, a 21MHz sine wave input will be displayed as 19MHz, 22MHz as 18MHz etc.. This behaviour will be the same for all sampling oscilloscopes, but when sampling at say 2GSa/s, the analogue front-end bandwidth will be apparent and interpolation effects will be much less noticeable. |
| BillyO:
--- Quote from: Dave_g8 on March 26, 2024, 01:50:56 pm ---Hi, Yes, the analogue bandwidth of the front end is greater than 18MHz. Because the sampling rate of the ADC is only 40MSa/s, this means that the resultant displayed waveform after sin(x)/x interpolation for a square wave input signal will have ripple before and after the transitions which is not present on the actual signal. So although you will see reasonable results for high frequency sine wave inputs, for square waves the result is not so good. If you have sine waves greater than twice the sampling frequency the results will be invalid due to aliasing. For example, a 21MHz sine wave input will be displayed as 19MHz, 22MHz as 18MHz etc.. This behaviour will be the same for all sampling oscilloscopes, but when sampling at say 2GSa/s, the analogue front-end bandwidth will be apparent and interpolation effects will be much less noticeable. --- End quote --- Right, this will be the same for ANY scope, even an analog scope. Put a 100MHz square wave into a 100MHz analog scope and the result will be far more sinusoidal than square as the front end acts like a low-pass filter removing most of the harmonics above 100MHz. However, I see everyone rating this scope at 15MHz or even less. That's just wrong. It has an honest 18MHz bandwidth. Bandwidth is always specified for a sine wave. To display a decent square wave you need to de-rate the BW by a factor of about 10. So a 18MHz scope will do a fair job of showing a sub 1.8MHz square wave. This is true of any scope at any price. Even then you will have considerable "ripple" on both the top and bottom of the waveform due to the harmonics that make it through the effective filtering of the front end. This is expected behavior. Of course you can expect a $3000 scope to deal with that better than a $30 scope but to even make the comparison is ridiculous. So, I stand by my assertion that his is an 18MHz scope and I'll also add that it's insanely good for the $30 it costs. It completely blows away the 5MHz scope I got in 1978 (which I had to build myself) that cost me the equivalent of $1000 in today's money. On top of that it is arguably the best $30 scope you can currently get. That's the way I see it anyway. |
| Dave_g8:
Hi Bill, As I stated in earlier posts, the DSO154Pro provides excellent functionality and performance compared to other devices in the price bracket. However, I do not agree that an analogue oscilloscope would show the same ripple or wrong frequency, since this is purely an effect of the sampling and interpolation used. |
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