abbey road d enfer

Big disappointment with DSO
« on: February 23, 2019, 05:08:12 AM »
I was lured by an ad for a Hantek DS4102C, that combines a DSO and a DDS. I thought it would be handy for quick basic work like frequency response eval.
The DDS performance seemed adequate, with 0.1% midrange THD.
I asked them, before buying, if it was capable of producing a Bode plot, to which they answered positively.

It turns out it is impossible to change the generator frequency while the DSO is operating.
In order to change frequency, one has to exit the Measure mode, enter the DDS mode and change the frequency. I talked with their service guy, he told me that it is just not possible to do what I wanted!
He finally suggested I use a separate generator (!), adding that the DSO was capable of displaying the incoming frequency (!!).

Of course, there is no way to produce a Bode plot, which seemed to me like an easy addition since the hardware is already there and it should take only an additional software piece.

What are these people thinking?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


ruffrecords

Re: Big disappointment with DSO
« Reply #1 on: February 23, 2019, 07:03:13 AM »
My experience with DSO has also been frustrating. I got a basic Rigol 20MHz. The triggering on this thing has a mind of its own. Also, when hunting down a low level high frequency signal I got more showing on the display from the probe's pick up of the noise spewing out the front of the LCD display.

So I bought an old single channel 10MHz analogue scope off eBay for £30. It instantly locked onto the signal I was hunting. I now have the DSO sitting on top of the analogue scope. I mainly use the DSO just to measure pp amplitude and frequency.

Cheers

ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Gus

Re: Big disappointment with DSO
« Reply #2 on: February 23, 2019, 08:53:50 AM »
When I was looking for a DSO for home I got frustrated with all the lower price models issues(lower price than a Keysight >$4,000 etc.)
I stayed away from hantek and some other brands and selected a GDS-2004E and I only noticed something that I assumed would work did not. I ended up thinking I should have bought a used tek or used keysight instead.

I found the EEV blog videos and forum to be helpful when looking for lower priced test gear.

Does this Hantek have the weird voltage scaling?

The DSO4204C prices I found are low https://www.circuitspecialists.com/hantek_dso4204c_200mhz_4ch_digital_oscilloscope_with_1ch_arbitary_waveform_generator.html

If I was to buy another scope etc I now would want to have a hands on test without looking at the manual.

Rant. DSO scopes are a pain at times, different brands have different look a feel, I often need to think before finding the correct button to push to get to the measurement I want to use if I use a scope brand I have not used before.

A good link about probes
https://www.youtube.com/watch?v=JMMlkBLxwos

Re: Big disappointment with DSO
« Reply #3 on: February 23, 2019, 09:22:42 AM »
Ive been in two minds for years about a modern scope ,I never had luck with valve ones .
I do hear from some that at times and old analog scope beats the modern dso in some ways .
The computer can handle a lot of the work now in terms of fft and math functions ,distortion analysis voltage measurement etc ,
Theres a lot to be said for the old familiar analog scope interface , you get up the waveforms you want with a minimum of twiddling ,and no menus .

Theres a buddy of mine, many many years in electronics , he has of course a modern TEK dso ,but it still  sits in second position to the old cro scope on the work bench . And he mentioned sometimes the cheaper modern scopes dont trigger properly

The older TEK scopes look nice but their invariably huge and parts could be an issue by now , The whole thing about a scope is small amounts of distortion arent visible on it anyway ,so is a program like REW (dedicated to audio)  far better for that purpose  , and live with a simple scope .

*Just found someone locally with a pair of Tek 475's ,one working one not , 200mhz I think ,  reasonably priced , I think Im going to arrange  a viewing this afternoon .
« Last Edit: February 23, 2019, 09:48:57 AM by Tubetec »

abbey road d enfer

Re: Big disappointment with DSO
« Reply #4 on: February 23, 2019, 09:58:33 AM »
Once one has got accustomed to DSO's idiosyncracies, it's quite usable.
The main incentive for me was the combined scope+gen and the smaller format.
It turns out only the latter is pertinent. Since I don't have a permanent bench at home and lugging my CRO has become a growing pain, I'll use the DSO, whatever its limitations. But I want to have a lightweight gen.
 I've found PC with a soundcard takes too much space on my temporary bench.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Big disappointment with DSO
« Reply #5 on: February 23, 2019, 11:30:50 AM »
Just contacted the guy , he's only a mile or two away , someone else has first refusal on the pair of 475's ,
He's having a massive clear out of a lifetimes accumlated stuff from the repair trade , I'll go down next week check it out .

The neatness of the new DSO's is remarkable , bench space saved huge ,miles of realestate .

Ive used the Feeltech fy 6800 arb gen a while now , its a fine lightweight generator ,with external attenuation its great for audio , not up with the best by any means but adequate even for distortion measurement and the price tag is keen .Interface and software have their own quirks ,but its intuitive enough that your going right out of the box . there is some cheap skating in the psu and output stage especially ,which hampers opperation at the high frequencies or higher amplitude output signals  ,but for most applications in audio this wont matter much .

EEV blog has 70 odd pages on the unit and its predecessor the fy6600.

Gold

Re: Big disappointment with DSO
« Reply #6 on: February 23, 2019, 01:02:49 PM »
The main incentive for me was the combined scope+gen and the smaller format.


This looks cool in theory but I’m having a hard time evaluating its performance from the information provided. Specifically the noise floor of the hardware.  I usually judge by the minimum vertical division  on a scope but that isnt in the specs.
https://www.redpitaya.com/

Audio1Man

Re: Big disappointment with DSO
« Reply #7 on: February 23, 2019, 04:58:50 PM »
I use many tools and each has their own unique specialties. As an Analog engineer I want to see the million plus points between OFF & ON and signal levels as they change.

I have several scopes and each has its own great uses. My bench has 2 ea. Tek 2465B, one for the AP the other general use. The Tek 2430 has now been retired and replaced by a Hantek DSO5102P. The DSO square wave tests had noise on the tops & bottoms of the signal as the convertors are 8 Bit. This is a problem when looking for great detail as you don’t know if there is some oscillation or other instability. The Analog scope is needed to verify all is well. The Hantek is a great tool as it measures voltage, frequency and many other things that are needed. It SAVES DATA onto a USB stick and this makes documentation easy.
I have seen several newer DSO for >$$ and they still can’t replace a true analog scope in many places.
Duke.

abbey road d enfer

Re: Big disappointment with DSO
« Reply #8 on: February 24, 2019, 02:23:02 AM »

This looks cool in theory but I’m having a hard time evaluating its performance from the information provided. Specifically the noise floor of the hardware.  I usually judge by the minimum vertical division  on a scope but that isnt in the specs.

Never use a 'scope for noise evaluation; their bandwidth is way too large. A 20MHz scope sees a 200 ohm resistor as a noise voltage of -100 dBu. 30 dB more than an audio meter.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Big disappointment with DSO
« Reply #9 on: February 26, 2019, 05:03:32 PM »
I had a look at the Tek 475's today , one works sort of ,the other powers up by no display .
I have the option to buy both for around 170 euros , but I really dont want to land myself with something that only half works .
I brought my arb gen with me to test the unit , displayed smaller voltage waveforms well enough ,but anything above a few volts and either top or bottom of the sine wave was flattened , so I suspect all isnt well in the working unit . I see lovely examples on EbayUS around the same money ,but much better condition ,shipping would be a killer though .
Not sure what to do .
.


abbey road d enfer

Re: Big disappointment with DSO
« Reply #10 on: February 26, 2019, 05:18:39 PM »

Not sure what to do .
.
AFAIK, UK has the highest density of second-hand test equipment brokers.
I googled "second hand oscilloscope" and there are a number of 465's with a price of about 150£ with free p&p.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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