OWON Oscilloscopes

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 Post subject: Re: Some tests with new SDS7102V (Versions 2.6 and 2.8.2)
PostPosted: Thu Dec 27, 2012 11:12 pm 
Site Admin

Joined: Wed May 16, 2012 7:54 am
Posts: 187
Here some tests with new SDS7102V version 2.8.2.

Note: before I have made risetime test with Tektronix generator. In specs it have <1.3ns risetime but I have measured it... it is far more fast (perhaps under 1ns). It is clearly faster than this now used HP. So, this affect some amount and so these results are not directly comparable (exept if you think what itr affect... also pulse shape is littlebit different)

Risetime tests made using HP8161 pulse generator around 1.3ns specified risetime and measured around 1ns. 2meter coaxial cable and Tektronix 50 0hm feed thru terminator in scope input. (this method is not best possible but comparable to my other tests. Note that with thois method there is not 50ohm impedance becouse oscilloscope input is not "ideal")
All images, exept last one only CH1 in use.

Sweep tests and sinewaves are from Agilent 8644B signal generatorwhat have very good flatness and extremely good signal purity in this frequency area.
Same notes and connection as risetime test exept cable is around 1m.

Note: Voltage bands are I: 2mV to 100mV, II:200mV to 1V, III: 2V to 10V

V/div 50mV (band I), sweep start green line and in end it go back to starting freq. Sweep is linear and sweep time is 100s. Oscilloscope 10s/div. One div is 25MHz. Oscilloscope is in peak mode.
-3dB point is around 175MHz related to 1MHz signal level.

V/div 500mV (Band II), sweep start green line and in end it go back to starting freq. Sweep is linear and sweep time is 100s. Oscilloscope 10s/div. One div is 25MHz. Oscilloscope is in peak mode.
-3dB point is over 200MHz (225MHz) related to 1MHz signal level. (note shape... perhaps if better impedance matching there is less "waves" in shape and it is possible then -3dB point may move down (or up))

Same settings and source level, sinewave 300MHz and infinite persistence for looking if some trig instability and/or vertical wobbler.

Same but reasonable level with 200mV/div for better wobbler visibility.

Note, scope freq counter stops around 320MHz. Signal can trig up to around 400-450MHz and after then totally "game over"
(using single channel. With 2 channel of course Nyquist "wall" is 250MHz and near this point and all over this... just impossible in practice and theory.)

Risetime Voltage band I. Signal shape is very good. Risetime (frequency response) is clearly better than specified. (<= 3.5ns)

Risetime Voltage band II. Signal shape is good. Risetime (frequency response) is clearly much better than specified. (<= 3.5ns) around 2.2ns in this test system. (better test system and maybe still better result)

Same as before but now infinite persistence for collect corner wobbling better visible in still image (this is one aliasing effect).

With Voltage band I it is not so interesting becouse there is less high frequencies to ADC and so less alising (corner wobbling in square wave) So I take this next more clear image.


Same with 2 channels on (2x500MSa/s) (CH2 out from window)
This is natural result. There now can see markable amount of aliasing (corner wobbling in this case)

This is natural becouse there is signal what include lot of high frequency components far over Nyquist "wall" (250MHz (500MSa/s)) going to ADC input.
(signal is: 1ms period, around 20ns pulses and true risetime is around 1 - 1.3ns and this risetime mean it have lot of components over this Nyquist limit. )

If I drop input signal risetime example to 2.5ns - 3ns it reduce dramatically this wobbling... of course - also in theory.

This is natural becouse ADC can see these high frequency components what are far over Nyquist. This is "problem" in all this kind of oscilloscopes. More wide freq band in analog front end before ADC without also higher sampling speed give naturally this result.

With digital oscilloscopes it is very important to understand all many faces of aliasing and also some methods for avoid mistakes in measurements. Extremely careful need be with FFT as long as you look signal what is "unknown".

 Post subject: Re: Some tests with new SDS7102V Version 2.6 and 2.8.2
PostPosted: Tue Jan 01, 2013 6:09 pm 
Site Admin

Joined: Wed May 16, 2012 7:54 am
Posts: 187
Becouse last time I have made tests with littlebit bad signal source now here is some new tests pictures about risetime. Test signal itself risetime is (checked) 1ns. (less or equal). It is measured in system where impedance is real 50ohm.

Here it is connected then to Owon using same cable but Tektronix 011-0049-01 "better than nothing" quality feed thru terminator connected to Owon input. (note that this is also source for error.. this do not give real 50 ohm impedance due to oscilloscope input reactive components) But in this freq area and with this needs of accuracy this do not mean so much in practice - imho.

Images where persistence is set on, they are for show trigger instabilities and possible aliasing in signal corners.

200mV and 100mV uses different voltage band in oscilloscope. (Whole V area is divided to three bands. (2)5mV - 100mV|200mV-1V|2V-10V / div ) lowest band have littlebit slower risetime.
Calculating freq -3dB point is not at all accurate if use old "thumb rule" 350/risetime ns. It depends BW shape etc.

Here new images (from Owon random individual V2.8.2 what I have in stock now. (and manufacturing lot 1246).
(1V rising (or falling) edge is highest level what I can drive out from Tek cal generator so this is explanation for used.)

03RT-Ow-CH1-200mV.png [ 17.26 KiB | Viewed 2202 times ]
04RT-Ow-CH1-100mV.png [ 17.27 KiB | Viewed 2202 times ]
08RT-Ow-CH1-100mV-persist.png [ 17.97 KiB | Viewed 2202 times ]
09RT-Ow-CH1-5mV-persist.png [ 18.56 KiB | Viewed 2202 times ]
10RT-Ow-CH2-200mV.png [ 17.84 KiB | Viewed 2202 times ]
11RT-Ow-CH2-100mV.png [ 17.98 KiB | Viewed 2202 times ]
 Post subject: Re: Some tests with new SDS7102V Version 2.6 and 2.8.2
PostPosted: Sat Jan 12, 2013 4:50 pm 
Site Admin

Joined: Wed May 16, 2012 7:54 am
Posts: 187
Tested USB speed.

I have not before tested it, only looked that "acceptable".

Many times peoples want take 1:1 screen image from oscilloscope to PC.
Of course there can also take wave data but it is other case, it is bin data and it need first convert to other format before it can handle in other softwares. (conversion can make example using Owon Oscilloscope software)

But many times want just screen image. This is very frustrating if it takes long time, example even tens of seconds.

If you save image directly to USB stick, it is slow. I have not tested different USB memories and it may affect some but still it is slow. For just some 2 or three images it is acceptable but very frustrating if need take lot of images sequentially.

If need fast transfer I recommend to use PC.

From oscilloscope there can take one image or there can also take contiuously images as long as you stop this process.
Image transfer time is around 1,25 second per one image.
I have tested it using 60 second time window and look how many images was stored to PC.
Result was 48. It may vary dependent of computer. In my case test PC was IBM T42 1,7GHz + 2G memory and winXP SP3.
Owon image size is 800x600
File size is: 1.37 MB (1,440,054 bytes)
File size on the disk: 1.37 MB (1,441,792 bytes)
In Owon Oscilloscope software you can adjust delay between images if need more slow.

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