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Rigol Rubbish DG800 - An expensive piece of Junk

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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:

--- Quote from: beatman on May 12, 2024, 07:57:39 am ---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.

--- End quote ---
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:

--- Quote from: eTobey on May 12, 2024, 05:34:31 am ---I would not expect the fuel tank of a car with 160HP to be only like 15 liters  ::)

--- End quote ---
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 outputYou 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:

--- Quote from: Aldo22 on May 12, 2024, 03:02:42 pm ---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?

--- End quote ---

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? 

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