Hantek 6254BC USB Oscilloscope 250MHz

[5282]

are this is really 250mhz good oscilloscope
it's 1gsa/s per channel or 250msa/s per channel ?

[ataradov]

Memory Depth: 64K. It is mostly a useless toy.

[gf]

are this is really 250mhz good oscilloscope
it's 1gsa/s per channel or 250msa/s per channel ?

I recently bought the "small brother" 6074BD with 70MHz analog bandwidth and built-in signal generator for 138€. Is it a good scope? Well, it does display waveforms - what more can I expect for this price? The advertised features seem to be more or less available, the GUI is rather simple, and there seem to be a couple of bugs in the GUI logic. It is very nasty that the driver is not signed, making it necessary to press F8 while booting and start Windows with driver signature checking disabled. I'm also encountering Windows bluescreens (crash in the Hantek driver). Generally I find it somewhat noisy (at least w/o averaging), but when I look at video reviews for other DSOs, they seem to be noisy as well - maybe I need to lower my expectations.

The sampling rate is 1Gsamples/s when only one channel is enabled, 500Msamples with two channels enabled, and 250Msamples with 3 or 4 channels enabled. This is basically dictated by the HMCAD1511. If you look at the datasheet http://www.analog.com/media/en/technical-documentation/data-sheets/hmcad1511.pdf you'll see the capabilities of this ADC chip.

[ This chip seems to be used in several lower-priced scopes as well, IIRC also in the Rigol DS1000Z series and the Siglent SDS1000X-E series, but IIRC, the Siglent was said to include two if them, enabling 500Msamples when all 4 channels are enabled - please correct me somebody if I am wrong. ]

64k memory depth is IMO ok for real time waveform display (still enabling averaging up to 128 captured frames), but there certainly do exist use cases where even 1M is by far not enough. I find it even more nasty that the FFT is limited further (IIRC just 1k points from the center of a captured frame), yielding only low wavelength resolution. I did not find any ram chips on the board, so I guess that the 64k likely reside directly in the Spartan FPGA.

The signal generator seems to work basically, but I did not get some of its features like sweep or FM working, likely software bugs as well. I'm not sure, but my feeling is that the DDS seems to be clocked with a fixed frequency (100MHz?), leading to noticeable frequency jitter when generating signals with higher frequencies which are not integral fractions of 100MHz (particularly visible of course when generating square wave signals). I did not find a dedicated DDS chip on board, but only a DAC902, so I guess that the DDS itself is implemented in the Spartan FGPA.

EDIT: My expectations were obvioulsy misguided by the fact that the technical data don't use the term "DDS" at all, but "Arbitrary Waveform Generator" and specify "DAC: 2K~200MHz adjustable". On the other hand, the feature overview does indeed say "200MSa/s DDS, 12bits of vertical resolution" and does not claim anything beyond that. However, 200MSa/s would be beyond the specification of the DAC902, which is a 165MSa/s DAC. I'm still not sure whether it's really 200 - as specified, or just 100?

gf