Author Topic: FY6800 - DDS signal generator questions  (Read 1223 times)

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Online Andreas

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FY6800 - DDS signal generator questions
« on: June 22, 2019, 07:29:07 pm »
Hello,

I am trying to use the USB connection of the FY6800 since I plan to write a software to automate some measurements.

There are 2 things that I have found which are annoying:
(At least with the "delivered" documentation which is also not complete).

I want to do 80% AM modulation (e.g. 1kHz) on a variable frequency (sweep) and amplitude.

1) every time that I change the frequency with the WMF command e.g. with a terminal program then the AM modulation gets switched off.  I will have to re-switch on with the undocumented "WPM4" command.
Which a) cost time (~400ms) and b) gives together with issue 2) glitches on the output power.

2) When doing AM I would expect that when I switch on the modulation that the average amplitude remains the same and changes between 20% and 180% with 80% modulation against the 100% unmodulated signal.
Not so the FY6800: the modulated signal changes between 20% and previous 100%.
This way the 80% AM modulation turns out to be only m = (1.03-0.217) / (1.03 + 0.217) = 65% instead of 80%.

Are there any (undocumented) commands which solve my issues?

with best regards

Andreas
 

Offline windsmurf

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Re: FY6800 - DDS signal generator questions
« Reply #1 on: June 22, 2019, 11:19:35 pm »
...
2) When doing AM I would expect that when I switch on the modulation that the average amplitude remains the same and changes between 20% and 180% with 80% modulation against the 100% unmodulated signal.
Not so the FY6800: the modulated signal changes between 20% and previous 100%.
This way the 80% AM modulation turns out to be only m = (1.03-0.217) / (1.03 + 0.217) = 65% instead of 80%.
...

Maybe just make the 100% level your desired 180%?
1.03v x 1.8 = 1.854v

For the desired 80% modulation (20% level), set it to : 1 - (1.03v x 0.2) / (1.03v x 1.8 ) = 88.3%

 
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Online Andreas

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Re: FY6800 - DDS signal generator questions
« Reply #2 on: June 25, 2019, 04:13:04 am »
Hello,

most probably this will be the way to go.

on the other side: when I change the frequency manually by using the rotary switch: the AM modulation is not switched off.
So there should be also a way to change the frequency from the USB interface without switching off the AM.

with best regards

Andreas
 

Offline ed512

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Re: FY6800 - DDS signal generator questions
« Reply #3 on: August 21, 2019, 09:03:25 pm »
My FY6900 seems to have a USB interface but the supplied DDS Signal PC Software does not connect or seem to be able to connect.  The user's manual does not say anything clear about the interface.  I have noticed in this forum that some users have been able to connect their PC to the FY6900.  What am I doing wrong?
 

Online Andreas

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Re: FY6800 - DDS signal generator questions
« Reply #4 on: August 21, 2019, 09:27:49 pm »
Hello,

assuming that the FY6900 is not different to the FY6800 in this regard:
- You need a CH340/341 driver for the USB interface.
- when attaching the USB-connection you should get a new virtual COM-Port in the Device Manager.
- You should be able to communicate with a terminal-Program "WMF100000000" should set the frequency to 100 Hz.
- Some programs do not work with COM-Ports above COM-Port 9 -> eventually re arrange the COM-Port numbers
- I have tried the FY6800 Software together with my FY6800
  -> it works on a Windows XP machine which I have used together with "portmon" to log the commands.
  The main functions should not be different between the models. (so perhaps the FY6800 Software is worth a try).

Can you check if my 2 problems regarding remote control are still there with the FY6900? (either with a terminal program or with the delivered software)

with best regards

Andreas
« Last Edit: August 21, 2019, 09:30:22 pm by Andreas »
 

Offline ed512

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Re: FY6800 - DDS signal generator Frequency Units
« Reply #5 on: August 21, 2019, 09:40:19 pm »
MY FY6900 user manual states: "Under setting frequency status, press ADJ Knob to change frequency units among MHz, KHz, Hz, mHz, μHz."

 I want to change the units from kHz to Hz.  How do I access the 'setting frequency status' screen?  Also, my adjust knob does not have a 'press' function; it only rotates.
 

Offline ed512

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Re: FY6800 - DDS signal generator questions
« Reply #6 on: August 21, 2019, 09:43:30 pm »
What is a CH340/341 driver?  I am using a Win7 machine.
 

Offline bdunham7

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Re: FY6800 - DDS signal generator Frequency Units
« Reply #7 on: August 22, 2019, 03:37:39 am »
MY FY6900 user manual states: "Under setting frequency status, press ADJ Knob to change frequency units among MHz, KHz, Hz, mHz, μHz."

 I want to change the units from kHz to Hz.  How do I access the 'setting frequency status' screen?  Also, my adjust knob does not have a 'press' function; it only rotates.

Press the "FREQ" button, then use the 'OK' button to change the units.  I guess they forgot to rewrite that part...
 

Offline ed512

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Re: FY6800 - DDS signal generator questions
« Reply #8 on: August 22, 2019, 03:20:09 pm »
Yes, I think there is a lot they forgot to write.  I am not very good at guessing how to use something; I usually need specific instructions.  Anyway, your frequency units instructions worked.  Thanks.
Do you know anything about the USB interface?  From another post response I learned that the interface is not like every other USB interface on the planet.  Apparently I need to do some hacking to make their user interface chat with the generator.
 


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