FeelTech FY3224S 24MHz 2-Channel DDS AW Function Signal Generator

[CustomEngineerer]

Hi stuartmp,

the other day I was playing with an Arduino and wrote a few lines to measure some square waves of the FY3224S in the low frequency region. I was surprised to see that at 1 Hz and below the FY3224S begins to develop a noticeable deviation to the theoretical values.

At 1Hz, the measured period is 1.0053 secs, which is 0.53% too long. In the slowest position of 0.01Hz the period should be 100 secs, I measured 178.95 secs instead, which is 79% (!) too long.
So be aware if you want to use the very slow waves for quantitative measurements.

For anyones convenience I attach the results with other low frequencies.

Greetings from Germany
mcmusic

Curious what makes you so sure those results are due to the generator and not to your code, arduino, or test setup?

[Sredni]

Rounding errors? Accumulating interrupt calls? Maybe.
I would not trust an Arduino Micro in keeping times for more than a few seconds, for example. Perhaps mcmusic would want to share his/her setup and code with us.

At any rate, the 100 vs 170 seconds discrepancy can be verified in less then 3 minutes by hand...watch.

[mcmusic]

Hi Sredni,

you are quite right, you can measure the pulse time for 0.01Hz or 0.02Hz easily with a stopwatch; I came out very close to the Arduino-measured times.

Of course I can share the code, but it is no masterpiece, more a quick hack. I just wrote it for this special purpose. It can not measure more than slow pulses because I used Serial.writes in the ISR. For faster applications one should not do this. Please don't blame me anyone who can write faster code - it just wasn't needed. Below say 20Hz I think this code measures quite well, if you run it on an Atmel 328 with a precise 16 MHz crystal.

I really would like to know if other people's generator are that much off in these very low frequencies.

The setup is quite obvious: connect the 2 GNDs (of generator and Arduino), and connect the generator's hot pin with pin 2 of Arduino. Adjust it to output a square wave between 0V and 4 V.

Greetings,
mcmusic

[Sredni]

I didn't try the AAM (Arduino Automated Measurement), but I fed the signal into my scope (*) to have a look.
While the DDS is not incredibly accurate at the extreme duty cycle and frequency given, I saw no sign of the dire discrepancy you are reporting. Maybe I did not look long enough, but when set to 0.01 Hz with 0.01 duty cycle I get pulses separated by about 100 seconds.

Verified in normal and roll mode several times.

The width of the single pulse appears to be less than 1000 ms, but it's close enough. There is a slight variation from pulse to pulse, but it's hardly noticeable.

As a side note: at 1 kHz the automatic measurements of the Rigol scope (they are based on the pixels shown on screen, not actual memory) are spot on. But this might have more to do with the fact that I had only two pulses on screen and not three, so there were more pixels to make a better assessment.

(*) The overshoot you see in the pulses is due to the fact that I fed the signal into the high impedance input of the scope. The generator behaves better with a 50 ohm termination, of course, but I do not believe this could have affected time measurements in a significant way.

P.S.
I thought I had many more screenshots, but it appears that when my Rigol hit sequential number 43, it decided it was not worth saving them anymore.  Also when I tried to open the last screenshot taken on my PC it made it throw a blue screen of death. Not the first time. Really sudden death, everything but the mobo and cpu stopped, and that includes all fans. And the blue screen message says "windows has stopped to prevent damage to your computer". WTF! 

[nctnico]

On my FS3200S I also get 178s periods when set to 0.01Hz.

[Sredni]

Did you guys try the reset manouver described a few pages back?
Maybe it can be fixed.

[bitseeker]

I was just about to say that. It sure sounds like your calibration needs to be reset.

https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/msg1175563/#msg1175563

[mcmusic]

Hi all,

thanks for your test and pics, Sredni. Interesting that you measure the 100s period time for 0.01Hz exactly.

Also interesting is that nctnico measures exactly "my" value of 178 sec for 0.01Hz.

It seems that Sredni has a different machine compared to nctnico's and mine.
BTW, my SW Rev is 2.0, 2010-2014.

To help clarify, I made also measurements for 0.01 and 0.02 Hz with the scope, see attachments.

The Arduino and the scope measurements are quite similar, 178.949sec (Ardu) against 179.2sec on the scope.

If you look at the 4 subsequent Arduino measurements, you see that they are quite stable (aside from a very little thermal drift after switch-on in the last position). This speaks for stable conditions both of the FY3224S and the Arduino. Yes, I do trust these Ardu results, particularly because they can be checked with a stopwatch so well and easily.

Some wrote that I should make a calibration reset. I am pretty sure that this is not the cause, because between 10Hz and 23 MHZ I have a really great accuracy in the respective period times.

I made a reset anyway, but I dont't think it worked right. I followed this post
https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/msg1135001/#msg1135001
and never got into a "calibration menu" and I did not get a value to write down. When I follow the reset procedure all I get is a - sign (minus sign, top left) after about half a second, no matter when I release the 2 buttons after 2 secs or more.

Greetings,
mcmusic

[nctnico]

I have software revision 2.0 2010-2014 as well.

[Sredni]

I'm on 3.5. Bought last December. (Last version seems to be 3.6)
So maybe that's one of the things that were fixed.

Sorry, guys, I'm not aware of any means to update the firmware of this thing.

[Mickster]

Good day all,
has anyone managed to positively ID the op amps in these sig gens, because I need to replace one which is buggered.
Somewhere back in this thread, there is a link to a TI datasheet for a "THS3002", but during my searching I also came across this:
https://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/p/502262/1819948
You would think that TI would know their own devices and it is not uncommon for manufacturers in certain countries to re-mark IC's in an attempt to obfuscate any ID attempt.
Any hint of another suitable, drop-in replacement would also be greatly appreciated.

BTW, I have confirmed the op-amp itself is knackered, as I swapped the one from CH1 which wasn't working, with CH2 which was, and the previously-working CH2 is now dead. I have all the functions on CH1 again now, so I'm not too bothered about leaving it as-is for a while and getting back to it at a later date.

Regards.

[garymck]

anyone seen one of these yet:
https://www.banggood.com/RD-JDS6600-DDS-Signal-Source-Dual-Channel-Arbitrary-Wave-Function-Generator-Frequency-Count-p-1148682.html?rmmds=search

3 models up to 40mhz

Looks like a viable alternative to the FY3224S, also looks to be powered by a wall wart,,,

Google search brought up only a couple of pages of hits, all ads...nothing on Youtube yet either...
cheers
Gary

[ebclr]

Here a more detailed view

https://world.taobao.com/item/549827466535.htm?spm=a312a.7700714.0.0.CyQUZQ#detail

[stuartmp]

Hi All,

I am just wondering if its possible to generate a Square wave using the FY3224S that is slower that 0.01hz ie. 100 Seconds

I am trying to check the charge time of a large capacitor on my oscilloscope and I would like a longer time period.

Any advise on this would be very much appreciated.

Cheers.

Stuart

[coromonadalix]

you could build clock dividers with ttl logic chips ?? divide by 10 by 100 by 1000   it depends how many dividers you want, there's divide by N  chips

[derosoft]

Hi every one!  I've been reading it seems all of the post here and I still have a question?  What is a DC Wave???  How would you use that?
Thanks,

Curious

[nctnico]

Hi every one!  I've been reading it seems all of the post here and I still have a question?  What is a DC Wave???  How would you use that?

In general:
That is intended to output a DC value. I'm hesitating to write that it is somewhat accurate but depending on the function generator it may be more accurate than a generic power supply. Also the output of a frequency generator has a 50 Ohm resistor in series so it is less likely you break something.

[Lighthammer]

Hello,
I got my FY3224S 24MHz from Banggood (with discount and priority direct mail under 55 Eur).

Firmware 4.0 2010-2017

Calibration is good: +40Hz at 10MHz (measured with calibrated PM6624)
Calibration stays after you use sweep (and power cycle).
Manual trigger mode ok, no issues. Ref.: https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-function-signal-generator-manual-trigger-has-bugs/
All waveforms can be set up to 24MHz (with the usual distortion on waveforms other than sine above 6MHz)
If you change any parameter there is still an interruption of signal generation of 1.36ms.

I will to the power supply mod with https://www.banggood.com/DIY-USB-Boost-Single-Turn-Dual-Power-Module-Linear-Regulators-Multiple-Output-Power-Kit-p-1022517.html and power it from a heavy wall wart with transformer.

[HoracioDos]

Hello
Does anybody know if firmware can be updated or if it can be cloned with an IC programmer?
Thanks!!

[bitseeker]

I haven't yet seen anyone upgrade the firmware in theirs. Even the manual on FeelTech's download page is for firmware version 1.4.

[drehspulinstrument]

Hi,
i received my FY3200S yesterday. I changed the USB serial converter to a FTDI, but cannot get it to communicate from PuTTy terminal. Connections are as with the CH340 module, RX of mainboard to TX of the USB adapter and vice versa, Gnd to Gnd and VCC floating (it seems floating on the CH340 board because it is powered from the usb port. 5V are provided from the mainboard but not used by the USB bridge.) The FTDI module is set to 5V. I had checked before on the oscilloscope that the original board outputs TTL level.
 The motivation for the modification is that on my office computer the CH340 driver won't install.
What are the communication settings, i read somewhere 9600, 8N1, and tried both this and 57.6 kbps.
I also put the FTDI board in loopback configuration (RX and TX tied together) to exclude that this is the problem, but it works, i see the echo of my typing on the terminal.
Is there any sequence to initialize external control or a combination of buttons to press on the function generator to enable remote mode?
I regret i had not tried at home to communicate over the original module from PuTTy.
The bluetooth to serial module mentioned earlier in this thread is also a nice feature!
Thanks for any hints

[Muxr]

Good day all,
has anyone managed to positively ID the op amps in these sig gens, because I need to replace one which is buggered.

Devttys0 goes over the default amplifier op amps used and even suggests a better slew rate replacement, as well as some other improvements, worth a watch.

[Kleinstein]

The better amplifier is definitely an improvement.
Changing the filter is a 2 side thing: it makes the square wave sharper, but it will also add image frequencies to the sine output.

The square wave still have a big problem with jitter at other than a few special frequencies. So get a really nice square one would need to add a sine to square wave converter circuit (e.g. comparator and maybe optional divider). In this case the original filter would be better.

There is also the rather poor DNL of the ADC when the highes bit changes. It might be worth to adjust at least the highest bit.

[ruiseixas]

I just modded my FY3224S with a proper 3-wire grounded power cord... and managed to blow up the power supply board, (in spectacular fashion I might add), in the process of making this thing "safer".    I won't go too deep into my faux-pas, but suffice it to say that you are supposed to connect the SECONDARY-side-gound (low voltage DC ground) to mains-earth-ground.  Do NOT, under any circumstances, connect the PRIMARY-side "ground" (from the bridge rectifier) to mains-earth-ground.   That isn't a meant to be earth-ground.  It's the ground "reference" of the primary.

I've noticed that FeelTech is using whatever power supply they can get their hands on, as mine looked nothing like the ones posted by med6753 & tombddiver.  My unit came with a very nice SICO-650 power supply.  (Well, it WAS nice 'till I fried it).  I put in a "Universal DVD Replacement Power Supply" I managed to find on Amazon. It took some searching to find one with the required +5v & +/-12v  outputs.

My mod included a toggle switch in the grounding path, in case I ever have the need to "float" the BNC outputs, the way the unit is shipped from FeelTech.  Otherwise that switch stays in the safe/gounded position.

One more note;  The sticker on the bottom of the unit is printed on an ink-jet printer.  If it gets wet, it will bleed and smear.

My Feeltech also has the SICO-650 switching power supply. If it's as good as you say what is the point to mod this Signal Generator nowadays? 

[gwu]

Hi,

Does anyone have the version with a PSU that has 2x 5V and +18V -18V outputs? The measured values for 5V are around 5.5V, whilst the +18V is around 17.8V, and -18V is around -16.3V (from memory).

I measured the voltage at the BNC outputs and it seems that there is about 3.3V AC.  I was going to modify the PSU as per https://sdgelectronics.co.uk/feeltech-fy3200s/ but now I am wondering if its worth it especially with now more commonly available transformers becoming 24V and no centre taped ones. The model on the board is SCL021 V1.5 .

Also, the USB input board has an IC with some resistors one it, and a capacitor.  Also an improvement?