Author Topic: How much abuse can a function generator on a DSO withstand?  (Read 2378 times)

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Offline Ed.Kloonk

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How much abuse can a function generator on a DSO withstand?
« on: March 18, 2017, 01:34:39 am »
Looking at a scope with built-in function gen.

Wanting to know how fragile the output is, can I expect to blow it up easily or if I'll need a more precise tongue angle technique.

How much self protection do they have if any?
 

Offline tautech

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #1 on: March 18, 2017, 01:43:16 am »
Likely no more than any AWG, short circuit protection only.
Typically you can't just insert their waveform into any part of a circuit. AFAIK all are Gnd referenced just like the BNC shell of the scope inputs.

Brand, model ?
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Offline danadak

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #2 on: March 18, 2017, 11:59:33 am »
You might consider a simple external fast unity gain power buffer
as a protection scheme. A number of vendors have fast OpAmps
configed as unity G and with power stages. Of course this is for
lower frequency applications.

When in doubt interface with some series R and clamps (zeners) to
protect until you become confident in your DUT configuration.

It would be great if vendors of DSO placed power stage on a separate
mini board for replacement in case of blowout.


Regards, Dana.
Love Cypress PSOC, ATTiny, Bit Slice, OpAmps, Oscilloscopes, and Analog Gurus like Pease, Miller, Widlar, Dobkin, obsessed with being an engineer
 
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Offline MrAl

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #3 on: March 18, 2017, 09:36:44 pm »
Hi,

The DSO gen i have has a low pass filter on the back end so it is a little protected already.  Of course you cant go and hook it up to the 120vac line voltage or expect big problems.  So there are limits.

The transistor based gen i have has fairly high output impedance anyway, around 600 ohms, so it is somewhat protected anyway.  Again i would not use it with a high voltage though.

Any of these are really meant for testing other things by connecting it to their inputs (such as an amplifier) or to a passive component such as resistor and cap, resistor and inductor, etc.


 
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Offline tautech

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #4 on: March 18, 2017, 10:33:51 pm »
There's a couple of ways around this:
A DC block or external attenuator like used with spectrum analysers.

Or this power amp for the Siglent range of AWG's:
http://siglentamerica.com/prodcut-fjxx.aspx?fjid=1289&id=1364&tid=16&T=2

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Offline Ed.Kloonk

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #5 on: March 19, 2017, 05:57:43 am »
Thanks for the very sensible replies.
For just audio freq range use only. Entry level scope.
Just for argument's sake.. how would you evaluate the output of the "Signal Sourse"  ;) on the DS1000Z-S?

Tried to copy paste the specs into here. Was messy. Download the PDF, if you are interested...
http://www.emona.com.au/component/phocadownload/category/110-2%20Oscilloscopes?download=1269:DS1000Z



 

Offline tautech

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #6 on: March 19, 2017, 08:06:05 am »
Thanks for the very sensible replies.
For just audio freq range use only. Entry level scope.
Just for argument's sake.. how would you evaluate the output of the "Signal Sourse"  ;) on the DS1000Z-S?

Tried to copy paste the specs into here. Was messy. Download the PDF, if you are interested...
http://www.emona.com.au/component/phocadownload/category/110-2%20Oscilloscopes?download=1269:DS1000Z
Quite novel that it's a 2 channel signal source.
Of course I've had a good play with the inbuilt ARB's of Siglent stuff and they are all single channel. The UI is always a little frustrating compared to a standalone bench ARB but if you are really pushed for bench space they are indeed an option.
Personally if I was seeking 2 channel ARB capability it wouldn't be inbuilt into a DSO of any brand.
Seems like the Rigol has higher output amplitude capability than the SDS1kX+ however the SDS2000X arb is higher again @ 6V.

If it's one of those things you don't have and want the an inbuilt arb is handy, just be prepared to persevere with the UI in order to use them.
You can compare the inbuilt arbs in these datasheets.
http://www.siglentamerica.com/USA_website_2014/Documents/DataSheet/SDS1000X&Xplus_DataSheet_DS010X_E01A.pdf
http://www.siglentamerica.com/USA_website_2014/Documents/DataSheet/SDS2000X_Datasheet_DS0102X-E01B.pdf

I'd recommend you study user manuals and examine the UI of them all to get some idea to which was easiest to use.
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Offline nugglix

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #7 on: March 19, 2017, 08:16:18 am »
Got the DS2000A w/ function gen.
I've to admit that it was wasted money.

The handling is -- bluntly spoken -- crap.
If you adjust it once and let it run for minutes, it might be okay.
But as soon as you start to fiddle, i.e. to experiment, it starts to hurt
(literally for me).

And:
  • you don't get 50 \$\Omega\$ output
  • no sweep
  • only very basic modulation
I don't want you to talk out of it, but be warned: no fun included!

And considering your question: it's a giveaway, like a pen or something.
That's the qualitiy one should expect.

Sorry, but I'd stay away from those built-in f-gens.
 
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Online guenthert

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Re: How much abuse can a function generator on a DSO withstand?
« Reply #8 on: March 20, 2017, 10:30:29 pm »
Well, if it's for audio use, keep in mind the (quite) limited bit depth of the ADC of the scope in mind.  The generator might have 12 or even 14 bit, but the DSO generally has only an 8bit ADC.  To find a fault in a broken system, that will generally be enough, but to test the quality of a hifi system it wont be.  Discrete audio cards for PCs might be a better choice for that.

If on the other hand (self-)education is the primary goal, then there are also choices on the lower end, e.g. the Digilent Audio Discovery (II).  No knobs, but a two channel 14bit ADC and DAC.  Not sure how robust it is, but I have yet to break mine.
« Last Edit: March 20, 2017, 10:33:47 pm by guenthert »
 
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