Any reviews or experience with this function generator (MHS-2300A)?

[radupraznaglava]

Can anyone identify the connector at the top of the CPU (see atached picture)?
There seems to be a JTAG.

[jpwaymel]

Hello everybody,

This is my very first post on this forum.

I just discover it (it looks very great !) when searching infos on the MHS-2300A generator.
I receive this piece of equipment to-day without any instruction manual nor pilot S/W.

... And I get all these missing parts reading this post : many many thanks !

Jean-Pierre

[miguelvp]

my google-fu found this pdf manual:

http://blog.pennybuying.com/down/fb/FB170A.pdf

Didn't find the software yet but I only spent 10 seconds searching.

Edit: nevermind, I thought it was a new post

but for what is worth here is a link to the software:

http://mhs2300a-dual-channel-dds-signal-generat.software.informer.com/1.0/

[jpwaymel]

Thanks Miguel !
There are several S/W sources along this post and I add your own source as it may be different.

I've tried this product on stand alone mode and now I'm going to try to connect it to my PC...

[jpwaymel]

I've tried to pilot the MHS-2300A with a qbasic64 program, without success...

Who has tried (with success  ) ?

[usagi]

I highly doubt the 10Mhz and 20Mhz model use updated hardware and it's just software locked.

has anyone determined if we can riglol these to 20mhz? 

[usagi]

anyone know whats up with overshoot/undershoot on the square wave output?

[miguelvp]

anyone know whats up with overshoot/undershoot on the square wave output?

I think that's more a measuring mistake than an over/under shoot.

The FG might output a 50 Ohm impedance signal and the scope is not properly terminated.

Or a probe was used to measure the signal and the ground lead is picking up noise.

Without a picture on the setup on how it was measured I will go to either one of those scenarios. Of course it could be the FG actually over/under shoots, but I think that is very unlikely.

[dadler]

I believe most people are plugging these directly into the front end of their 1meg scope inputs w/o 50 ohm termination.

However, some of the ads for this device show over/undershoot on square wave. I'd hope there vendors would be presenting the unit in its best possible light.

I'll be able to confirm shortly. I just ordered the 5MHz model (hope I can convert it to 20MHz), and I'll run some tests when I get it. Spectral purity, THD, phase noise, etc.

[usagi]

(hope I can convert it to 20MHz)

yes, unlock 20mhz would be fantastic 

[usagi]

the mhs-2300a user manual lists 50 ohm output impedance.

[usagi]

so there seems to be a strange bug, with square wave only. looks like maybe rounding error or 1-off counter bug with duty cycle on square wave.

happens at all frequencies. does not seem to happen with sine output.

[dadler]

I see the same here, only occurs on square wave.

[usagi]

ch1 to 10khz sine, ch2 to 20khz sine. channels should be stable relative to each other but they are not. there seems to be constant phase shift.

channels are only stable when they are both exactly the same frequency.

i suspect programming error somewhere, someone is doing 1-off counter code bug.

[Swemarv]

so there seems to be a strange bug, with square wave only. looks like maybe rounding error or 1-off counter bug with duty cycle on square wave.

happens at all frequencies. does not seem to happen with sine output.

I have the same problem.

[usagi]

bugs:

• jitter with duty cycle, square wave only. possibly rounding error or 1-off counter bug.
• constant phase shift between ch1 and ch2 when frequencies are different (e.g. ch1 10khz, ch2 20khz)

[Mark_O]

Has anyone notified the Seller or Manufacturer of these issues (and gotten any response)?

Or are we just discussing the problems here, while the guilty parties are still in the dark?

[Mark]

Surely the jitter bug is just how the dds works, you'll get the same jitter time at all frequencies which will be 1 period of the master clock freq. 

[usagi]

Surely the jitter bug is just how the dds works, you'll get the same jitter time at all frequencies which will be 1 period of the master clock freq.

no.

it only happens with square wave. not with any other output.

[Mark]

Surely the jitter bug is just how the dds works, you'll get the same jitter time at all frequencies which will be 1 period of the master clock freq.

no.

it only happens with square wave. not with any other output.

The square wave may well be direct from the dds in which case you will see jitter, whereas the others will be through a LUT + filter.

[dadler]

I haven't torn mine down yet--but will soon.

Anyone know if these are implemented with an off-the-shelf DDS chip, or an R2R ladder like some of the other cheaper generators?

[usagi]

Surely the jitter bug is just how the dds works, you'll get the same jitter time at all frequencies which will be 1 period of the master clock freq.

no.

it only happens with square wave. not with any other output.

The square wave may well be direct from the dds in which case you will see jitter, whereas the others will be through a LUT + filter.

jitter would only be expected with non-integer multiples of the main 200mhz clock. so jitter would not be expected at 10khz, 20khz or 5mhz. but we see jitter at all frequencies.

we also see phase shift between channels when frequencies are not exactly the same. ch1 10khz ch2 10khz are perfectly locked, but ch1 10khz ch2 20khz experiences phase shift. this should not happen.

[usagi]

I haven't torn mine down yet--but will soon.

Anyone know if these are implemented with an off-the-shelf DDS chip, or an R2R ladder like some of the other cheaper generators?

per the earlier posts and teardown from this thread, looks like LCMXO2-1200HC-4TG144C FPGA driven by stm32 microcontroller. DAC is resistor ladder.

[dadler]

I haven't torn mine down yet--but will soon.

Anyone know if these are implemented with an off-the-shelf DDS chip, or an R2R ladder like some of the other cheaper generators?

per the earlier posts and teardown from this thread, looks like LCMXO2-1200HC-4TG144C FPGA driven by stm32 microcontroller. DAC is resistor ladder.

Ahh thanks, I somehow missed that post. Thought I was entirely caught up on this thread. Must have skipped a page.

[trberger]

The fy3212 is evaluated and tested by gby in message 17 and 18 of

https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/15/

I can't seem to find a similar test for the mhs2300a in this thread.  Did I miss something?

Why would one choose the mhs2300a over the fy32xx?  I.e. what features add the extra value?

thanks.