Rigol Rubbish DG800 - An expensive piece of Junk

[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. 

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]

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...

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]

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

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]

- Ramp wave only 200kHz? WTF? This thing says 10MHz on the case...

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.

- 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.

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.

[Martin72]

Look at data sheets of generators in the same price category, or one higher, to find out that their specs are all 'poor'.

Plus take a look at the specs before buying, instead of complaining about it afterwards in the now familiar way.

[thm_w]

Ah yes, super "expensive" at the princely sum of $300... DG800 is a low end generator, I'd say its fine for what you pay, and fine for average student or hobbyist working on basic designs. And with a few minutes of hacking you can unlock 100MHz.

The DG800 Pro can be had for the same price and resolves *some* of your complaints (like USB on the front). Has other issues like loud fan, etc. Still, if I had a choice I'd pick the dg800 pro for the larger UI.

Previous threads:
https://www.eevblog.com/forum/testgear/rigol-dg800-combining-arbitrary-waveform/
https://www.eevblog.com/forum/testgear/new-rigol-16-bit-function-generators-dg800900-series/msg5268007/#new

I feel really bad for any retailer that has to deal with people like OP.

[xrunner]

- Socket protrude on the back, almost set it on the back while unwrapping
...
- USB on backside

Both of these are clearly seen in pictures you could have easily known about before buying. 

[DaneLaw]

Warning:
Fanboys should not keep reading this!

You sound like the pedicle of a fanboy.
You see a well-known brand "Rigol" and expect the moon while purchasing the cheapest from this specific brand, without any incentive to do basic due diligence' and then you hurry on the internet and generalize the whole DG800 series as "rubbish & junk" primarily from your own lack of knowledge.

- Ramp wave only 200kHz? WTF? This thing says 10MHz on the case...

- if you wanted a DG800 unit that could do more than 200kHz ramp, then why not purchase a DG800 with higher ramp tolerances.
Did you even look in the datasheet before purchasing your new Rigol waveform generator.?

[eTobey]

"could have looked at the datasheet / pictures" 
I would not expect the fuel tank of a car with 160HP to be only like 15 liters 
I couldnt care less about your input, as this information is only intented to help others decide. 

[beatman]

All manufactures have different series and platforms start with basic model with optional upgrade packages or locked futures.In most of times the hardware stay the same except the inputs outputs.

[tautech]

All manufactures have different series and platforms start with basic model with optional upgrade packages or locked futures.In most of times the hardware stay the same except the inputs outputs.

Despite this quite valid fact, it is a valuable skill to be able to read and properly understand datasheets.

[Aldo22]

What leaves me somewhat perplexed about signal generators are the different "specialties" in the specifications.
I think that better in one discipline does not automatically mean better in other/all disciplines.

For example, my AWG built into the $130 Hanktek scope has a 1MHz ramp.
It can also do 25MHz AWF. A 50MHz square wave is possible with an AWF.
But then the vertical resolution is probably only 12bit and the maximum amplitude is 7Volt.
Cheap FY3234s has a sampling rate of 250MSa/s etc.
Accuracy and noise etc. would have to be compared separately.

What I want to say: At least in the lower price range, there is no simple "better" or "worse", but you always have to compare the individual features.
Is that correct? What is most important?

[Sensorcat]

I would not expect the fuel tank of a car with 160HP to be only like 15 liters 

It's just that you did not buy a car with 160 hp, the DG800 is the equivalent of a chinese scooter designed with little more than budget in mind. The 15 litres tank you got is huge for this class of vehicle.

Let's take a look at two serious AWGs for comparison, both roughly 10 times the price of the DG800, both primarily designed to solve problems, not to match pocket money:

• Keysight 33500B Series, max. ramp frequency 200kHz, non-upgradable, Non-linearity (typ) < 0.05% from 5% to 95% of the signal amplitude
• Tektronix AFG31021, max. ramp frequency 500kHz, higher limits available in series, Linearity, typical (1 kHz, 1 Vpp, 100% symmetry) ≤ 0.1% of peak output

You have (from DaneLaw's post above): 200kHz, Linearity, typical (1 kHz, 1 Vpp, 100% symmetry) ≤ 1% of peak output. Which means that the frequency limit has been pushed in order to impress people who do not look careful, to the point where the non-linearity rises to frightening levels.

The frequency limit, especially for the ramp function, is not a hard barrier defining what the system is capable to provide, it's a decision to set a limit at a point where the signal otherwise becomes useless. In general, linearity degrades with increasing frequency. Since linearity is the number one criteria for a ramp, naturally the decisions vary depending on the intended customer type. Rigol plays the game here of showing heavy limitations only in the datasheet, while the shorter fact sheets will be quiet about 1% linearity, typical, at 1 (!) kHz. Tek uses the same set of lame conditions, but offers 10 times better linearity, and resists the temptation to push to the point where their hardware reaches 1%. Keysight delivers 0.05% for an extreme wide range of conditions, but restricts the frequency instead.

Does that mean you can't get ramps with frequencies above the respective limit? Of course not, the only thing you cannot get is a ramp function above the respective limit with a specified linearity. If you need something ramp-ish with higher frequency, just use your AWG as an AWG: Enter a ramp as an arb function and check how far you can get. The Keysight 33522B, for example, has no problem to create a 10MHz unspecified ramp-ish function that way.

[2N3055]

What leaves me somewhat perplexed about signal generators are the different "specialties" in the specifications.
I think that better in one discipline does not automatically mean better in other/all disciplines.

For example, my AWG built into the $130 Hanktek scope has a 1MHz ramp.
It can also do 25MHz AWF. A 50MHz square wave is possible with an AWF.
But then the vertical resolution is probably only 12bit and the maximum amplitude is 7Volt.
Cheap FY3234s has a sampling rate of 250MSa/s etc.
Accuracy and noise etc. would have to be compared separately.

What I want to say: At least in the lower price range, there is no simple "better" or "worse", but you always have to compare the individual features.
Is that correct? What is most important?

You always have to read specifications carefully and decide if they are useful to you.
For high end expensive equipment even more so because stakes are higher.

There are many details to pay attention to.
For instance that Hantek 1MHz ramp, does it specify linearity error?
Triangle wave is hard to do linear at high frequencies.

At highest square wave frequency, what are rise/fall times of edges? Are they so slow that it is trapezoidal wave instead? Are rise/fall times guaranteed at highest output amplitude? 

[Aldo22]

You always have to read specifications carefully and decide if they are useful to you.
For high end expensive equipment even more so because stakes are higher.

There are many details to pay attention to.
For instance that Hantek 1MHz ramp, does it specify linearity error?
Triangle wave is hard to do linear at high frequencies.

At highest square wave frequency, what are rise/fall times of edges? Are they so slow that it is trapezoidal wave instead? Are rise/fall times guaranteed at highest output amplitude?

Don't get me wrong, I'm not trying to talk up my cheap Hantek. It's just an example that I know.

I just find it very difficult to orientate myself with the specifications of a signal generator because they vary so much.
It would be easy if the specifications went in the same direction.
e.g. 16bit vert. res., 300Msa/s, square rise time 3ns etc.
But it's not like that.
It's 12bit, 250MSa/s, 3ns RT OR 16bit, 125MSa/s, 16ns RT etc.
A beginner doesn't know which spec is more important.
I think this is also eTobey's problem. He thought he had a "good" signal generator. But apparently he is not happy with some of the specs.

Apparently "good" and "better" is not so easy to determine here.

P.S. Attached is a 50MHz Hantek square wave (AWF 2*square, 50Ohm load 2V->1V), clearly at the limits of the scope and the signal generator,  but quite stable and no sine wave.
And a 1MHz ramp @7Vpp.

[Martin72]

Rigol Rubbish DG800 - An expensive piece of Junk

It is about time that this title was changed, even if it would ultimately serve the purpose of self-protection.

[KungFuJosh]

Rigol Rubbish DG800 - An expensive piece of Junk

It is about time that this title was changed, even if it would ultimately serve the purpose of self-protection.

Yeah, it's redundant anyway. 😉😉

[jonpaul]

Just usual junk from China, suggest for the $300, get a  used 1980s or 1990s HP FG AWG

j

[ebastler]

get a  used 1980s or 1990s HP FG AWG

What would be your recommendation for a dual-channel HP AWG in that price range? The HP 33120A looks plausible but is single-channel only. Did they make a comparable model with two channels?

[Aldo22]

What would be your recommendation for a dual-channel HP AWG in that price range? The HP 33120A looks plausible but is single-channel only. Did they make a comparable model with two channels?

Could you explain to me what is better about the 33120A than a modern AWG?
That's an honest, naive question. I would like to understand it.
When I look at the specs, I don't see much that sounds particularly great.

Amplitude resolution 12 bits
Sample rate 40 MSa/s
Sine 100 μHz - 15 MHz
Square 100 μHz - 15 MHz
Triangle 100 μHz - 100 kHz
Ramp 100 μHz - 100 kHz
Rise/Fall time < 20 ns
etc.

So how do I know that this device is good/better, other than by hearsay?

[ebastler]

I don't think I claimed that it is better. 

Some specs are a tad better than the low-end Rigol discussed in this thread (e.g. total sine distortion in the audio range), others are a tad worse. Overall, both punch in a similar class, I'd say. The modern devices have more features, e.g. dual-tone and harmonic generation, a touch screen, and USB instead of RS-232 & GPIB. They might also have a few unexpected software bugs, which are less likely in mature HP and comparable gear. A comprehensive service manual is available for the 33120A, but not for the Rigol to my knowledge.

I think it's largely a matter of preference whether one likes "solid feel and established brand" or "made in China, more features". In the specific case at hand, I am not aware of a (roughly) comparable HP dual-channel generator in this class, so the vintage route might not offer a real alternative.

[Aldo22]

I don't think I claimed that it is better. 

That's right, you didn't say that, but Jean-Paul did.
I was referring to your post because you mentioned a specific model.

My question to @jonpaul remains: Why is a 40 year old HP FG AWG better than "junk from China" when the "junk from China" is better in almost every specification?
How can I tell?

I mean, I know that some people say that a Mercedes-Benz /8 is the best car ever.
But would you really buy one today? 

[Berni]

The OP should try one of the cheap Hantek signal generators, those are a buggy mess of a cheap chinese product.

Not saying the Rigol DG800 series is perfect, but it is a damn good deal for the price. It is very feature packed for its price class and it does work reliably without any major UI problems (even if the UI is not the best out there).

Feel free to purchase a more expensive signal generator if you have more advanced needs. But in this price range you will be hard pressed to find something better.

[Aldo22]

The OP should try one of the cheap Hantek signal generators, those are a buggy mess of a cheap chinese product.

To which specific model does your statement refer?

HDG3000B Series
HDG3000C Series
HDG6000B Series

Can you share your experience with us?
Information on these is relatively scarce.