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Rigol Rubbish DG800 - An expensive piece of Junk
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eTobey:
Warning:
Fanboys should not keep reading this!

I got the Rigol DG812, and i am really dissapointed... say furious. It has some nice features, but some dont work at all, and other issues make the work with it rather challenging. It feels like i bought a chines 100$ wavegen. I just had trouble debugging my code, but it wasnt the code, it was the rigol.  :palm:

Here is a list i made, hope some might find it useful (Yes, its only negative feedback):

- Socket protrude on the back, almost set it on the back while unwrapping
- The knob works as good as a button. Turning it faster does not speed it up! It does spin wobbly... Its a disgrace!
- Keypad closes unintentionally while seemingly hitting between the buttons.
- Cursor jumps on different place when reached lower limit on setting up amplitude/Frequency.
- Sometimes putting in numbers in the numberpad will replace old value (as it should behave), and sometimes not.
- Ramp wave only 200kHz? WTF? This thing says 10MHz on the case...
- Menu for choosing modulation wave jumps back up or chooses an item after scrolling down.
- No color guidance on the display. The only color is printed at the sockets.
- Text on top sometimes stays the same (Modulation/Continous)
- Square highlevel 1.5V and lowlevel 0V is a 0-3V level!
- Highlevel limit not working on hamonics -> 4.9V with 3V limit. Negative limit is also exceeded.
- Longer dialog messages can not be read, as they appear only for about 1-2 seconds.
- No option to have signals constantly aligned. You have to hit button align over and over again, after settings are changed.
- Activating the counter, and then the generator again: Settings gone!
- USB on backside
- USB sticks are hardly working.
- Major GUI bugs:  Menu switches when activating DSSC
- Not possible to set up negative or above 360° phase shift. No rollover either.
- Burst and sweep does not work with ext trigger (only FM mod, or other)
- High or low level limit in general settings can not be set, if the current waveform has conflicting settings.
- Changing PWM period causes pulses to be smaller or bigger than set up values from before or after.

Limits were in place, and one would not know were the conflict were:
- Low level limit only to -1.5V not 0

Dont bother asking me about details, its just not worth it, just buy something else.
shabaz:
Hi,

A few of the items on the list sound like they may be related to a 50 ohm setting, specifically the comment about the square wave high level, and the mention about the harmonics limit. I don't own this instrument so I'm making a guess based on experience with other signal generators.

The 200 kHz ramp is mentioned in the datasheet (it is very normal for such waveforms to be spec'd to a far lower frequency for AWGs, so that needs to be examined closely in the datasheet when buying any AWG, even expensive ones).
eTobey:

--- Quote from: shabaz on May 10, 2024, 06:51:27 pm ---A few of the items on the list sound like they may be related to a 50 ohm setting,

The 200 kHz ramp is mentioned in the datasheet...

--- End quote ---
Whatever setting there may be behind: If i set a limit, then it should not be exceeded by setting 50Ohm. Someone else here on the forum fried his 150$ FPGA when it went negative.

200kHz is very poor, no matter what the datasheet says.
Sensorcat:

--- Quote from: eTobey on May 10, 2024, 07:23:30 pm ---200kHz is very poor, no matter what the datasheet says.

--- End quote ---

So you are unhappy with what you got, even if it is in accordance with the data sheet.

You could:

* Do some research on what the reason might be. Hint: There is one.
* Ask someone for the reason.
* Look at data sheets of generators in the same price category, or one higher, to find out that their specs are all 'poor'.These choices would result in a learning effect.

You could also:

* Return the unit and replace it with one with higher spec.
* Use the hardware you already have in a clever way to get a ramp with higher frequencies. Hint: It is possible.
* Build something better on your own, perhaps only for the ramp function.These choices have the potential that your problem gets solved.

Why do you choose an option that is less likely to result in any improvement for you?
alm:

--- Quote from: eTobey on May 10, 2024, 05:40:37 pm ---- Ramp wave only 200kHz? WTF? This thing says 10MHz on the case...

--- End quote ---
Is this the first generator you've used? The bandwidth number on the case is always just for sinusoidal signals. You need to consult the datasheet for anything else. For square waves some generators will have dedicated hardware, but ramps are not so easy and will probably be done using the arbitrary waveform generator which needs a lot of samples per cycle.


--- Quote from: eTobey on May 10, 2024, 05:40:37 pm ---- Square highlevel 1.5V and lowlevel 0V is a 0-3V level!
- Highlevel limit not working on hamonics -> 4.9V with 3V limit. Negative limit is also exceeded.

--- End quote ---
This sounds a lot like having the generator set for a 50 Ohm output but running it with a high-impedance load. The way the output impedance setting works (it's not actually switching a resistor but just doubling the figures) this is bound to happen. Have you used any other generator with a selectable 50 Ohm / hi-Z "output impedance"? Because any other generator you buy will likely have the same issue.
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