Hi All
also got a FeelTech FY6600
regarding CD: I don't even know if I can read it. I do have an old PC with CD collecting dust somewhere, but I don't feel like digging it out. So if anyone does get a link...
I played around a bit with the FY6600, and it seems to work OK. Sine is exactly the same as generated by the one build into my DS1074Z-S. (I compared with A-B math function) Square has a slightly better rise time (about 8ms instead of the 12ns of the build in.) And control is a *lot* easier. That is the biggest problem with the DS1074Z-S build in: really bad controls. Frequency wise, on a 15Mhz signal, they differ about 100Hz, drifting back and forth a bit. So about 6ppm. I suspect that is pretty OK for cheap equipment like these two.
Signal wise, I found only one problem: all vertical edges (square, step, sawtooth) have a 5ns variance in timing. Regardless of the frequency, you always get runt edges 5ns apart. I suspect the max resolution of some internal CPU or DAC frequency is showing here. It of course is only important for higher frequencies, shown is 15Mhz. The Blue one is the DS1074S-Z internal signal, its fuzzy because I am triggering on the yellow FY6600. As you can see, apart from the 5ns variance, the FY6600 has a better rise time and a better shape.
Control wise, it works a *lot* better then the DS1074Z-S internal signal gen. Pretty intuitive too.
A few minor control annoyances:
- You cannot stop the modulation. You can select other modulation parameters, but you cannot stop. The only way I found is to set it to use Channel 2 as mod source (that is default anyway) and then stop channel 2. That will go back to normal signal gen mode. Unlike Sweep, which you can start, and stop at will. Just press CH1...Doh.
- The "Wave" button does not only highlight the waveform menu option, so the rotary button can be used on that menu, but immediately advances the value selection as well. Iow, selects the next waveform. This is different than all the other buttons (like Freq, Ampl, Offs, Duty, Phas) which all select the menu on the first press, and only the second press advances the value (or you can use the rotary button). Not very important, but a bit annoying.
- 00'010.000'000'000KHz is a pretty weird way of writing 10 Khz. I had to stare at that for a while. I think there are better ways to indicate the frequency.
Edit: And now it is displaying 00'002'000'000'000uHz to show 2KHz. 2 billion microHerz
Must be a setting somewhere.... OK, not important. The value is technically correct.
So since FeelTech seems to be reading this topic, please take note.
Thanks
Edit: to get these square waves without overshoot, I had to properly terminate with 50 Ohm.
Edit2: This is a FY6600-60M version 3.1 English
More edit: SYNCI also played with the SYNC function. It has external SYNC in and out, and supposedly you can link multiple devices together, as well as sync CH1 anc CH2.
Some problems with both:
While I do not have two devices, when I put mine in master mode, all it outputs is a 1V square wave that matches CH1 (0V~1V 50 Ohm). No fancy protocol. So you'd think I can also link any other signal source if I match that. No avail, whatever I try, I am not getting it to follow another signal source. Some disclosure by FeelTech would be nice.
SYNC between CH1 and CH2 it works better. It all works nicely at lower frequencies, lets say < 5MHz, but at higher frequencies, the phase starts to go wrong.
The problem seems to be that CH1 and CH2, when "in phase" are still 4ns apart. Again this 4ns (I now believe the 5ns above is also 4ns)
This is of course due to the 250MSa/s specification for the device: 250MSa/s means 1 sample every 4 ns
That means that if you specify 0 degree phase difference, at <5 MHz frequencies, they are pretty much in sync (4ns = 7 degrees).
But at 60MHz they are pretty much in quadrature (4ns = 86 degrees)
So if you specify 86 degrees offset, they are actually in-phase.
So, at 5Mhz, in-phase is indeed in-phase (roughly). But then if you dial up to 60MHz, you visibly see it shift out of phase.
Now here is the weird thing: You can still then correct the 60MHz to in=phase, by setting it to 86 degrees.
And even weirder, somehow you can also set it to all phases in-between with a pretty good resolution.
I think its because the Sine at this point is filtered rather then sampled, but I was still surprised by it.
It does mean FeelTech could fix this, they could "correct" the phase automatically with software, just like I can manually.
And indeed, the DS1074Z-S internal generator does not have these problems, even though its only using a 200MSa/s DAC.
Use equal length cables dummy!
Yet more edit: SWEEPIt works. But I suddenly realize I miss a sweep/trace/scan output. Not sure what the name is. But a sawtooth that shows how far the sweep is, and that I can feed into my scope as X trigger.
One could naturally have this if CH2 could be used as driver for the sweep in stead of VCO, but that is not an option: only fixed time window and VCO are allowable sources.
So I took CH2, looped it into the VCO and that works but it is a bit unclean. In fact, I found it better to simply put a sawtooth on CH2 and do FM modulation, that also causes a frequency sweep. AM for amplitude sweep. For PWM, still have to use the CH2-VCO loop.
Request/suggestion to Feeltech: allow CH2 as source for Sweep, using the default 5Vpp as normal rather then the 0-5V from VCO. Or alternatively, output the set sweep time values as sawtooth on CH2.
Still good. I wanted a device that is easier to control then the DS1074Z-S internal one, and that can do SWEEP.
I don't think I will be often running at high frequencies. And the sweep is 'workable'. So I am happy with the device. For now.
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