Products > Test Equipment

MHS-5200A function generator teardown / review / reverse engineering

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usagi:
wonder if the MHS-5200A shares the same issues as we found in the MHS-2300A (which seems to share very similar design and components).

SaabFAN:

--- Quote from: commie on August 13, 2015, 09:03:43 pm ---
--- Quote from: SaabFAN on August 13, 2015, 08:17:50 pm ---Because it is almost 200€ cheaper than anything similar from Rigol, Siglent, Hantek, etc.

--- End quote ---

But there are two options you can take, one is to buy a old skool (XR2206 based) function generator like the GFG-8215A dc-3MHz, alternatively save your money until you can afford AWG like the Rigol DG1022.

The MHS-5200A is simply badly designed  :-//

--- End quote ---

I already have an XR2206, although only capable to do a little over 100kHz, and the DG1022 was among the devices I was considering (the others were a SDG1000-Series and a comparable unit from Hantek), but they both were priced almost 200€ higher. With this unit I spared me the trouble to figure out all the software-stuff and if I need an accurate amplitude-control, I can still build the amplifier and AGC-circuits I have already drawn up for my own signal-gen.
The digital stuff can probably hold its ground pretty well against the units from the other manufacturers. The problem is the final analog output, which we hopefully can modify enough so it does its job properly.
Besides: With only about 15€ I can make this thing portable (LiPo-Cell, Boost-Converter, Charger + some wires and an additional switch). I doubt this is possible with a DG1022. :D

In hindsight, the FY32XX would probably have been better: 12bit, 50Msps more, twice the waveform-length, more amplitude.

Comparison with the MHS-2300 would be interesting indeed: The analog part seems to be a lot more complicated and incorporates even a few adjustable components.

devttys0:
SaabFAN: The overshoot/ringing on the square wave output is probably due to the elliptic low pass filter they use on the output of the DAC, but I haven't verified that yet.

commie: I didn't expect it to really be any good. Like I pointed out in the video, there's nothing worse than buying test gear you can't trust. But it is fun to take cheap stuff apart and hack at it, which is mostly why I got one.  :)

And yes, the CFA is definitely slew rate limited:

SaabFAN:
Why did they use an inverting configuration in the first place? Is there any benefit to it? Easier to design, issues with DC-Bias, etc.?

devttys0:
Not sure exactly, perhaps they did it to more easily set the input impedance to the amp, especially for terminating the DAC filter. Seems uncommon for CFAs.

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