Hello all,
I am new to this forum and this is my first post. I have been looking at purchasing a Owon SDS7102V scope and ready to order it but then I paused after reading about the "video trigger jitter" and "ground noise problem" in this scope.
I contacted my local dealer (Saelig) with the following question and received the following answer along with waveform captures.
It looks to me like the GND noise problem is resolved. What is your opinion? I am new to DSOs so I am unsure if my conclusion is justified by the screenshots provided by the dealer.
**** Begin question to dealer ****
I want to purchase the Owon SDS7102V oscilloscope but I am concerned about the following two manufacturing defects. Have these been fixed? If I get a scope tomorrow will it continue to have the same problems?
Video trigger jitter
http://owon.forumup.com/about153-0-asc-15-owon.htmlNoisy GND problem
http://owon.freeforums.org/under-work-about-gnd-noise-t21.html**** End question to dealer ****
**** Begin reply from dealer ****
I took a look at both of the links concerning the jitter associated with video trigger. I also set up an inexpensive camera having an NTSC output for a test.
What I found as that there is jitter on the order of about 1us with the source I used. This is what I used – the MV401TV-N unit, which sells for about $60.
http://www.saelig.com/product/VI024.htm The next question I would ask is about the jitter associated with the source. I don’t have a high-quality reference with which to compare. However, the signal itself is sufficiently stable to work with, and, if a critical measurement must be made, all one has to do is depress the Run/Stop key and freeze the image.
On the other hand, perhaps this is an opportunity for improvement for Owon, and I’ll pass the issue along to my factory contact.
While we’re discussing jitter, you should know that the timebase jitter and inter-channel skew for the Owon is very low. I’ve attached three screen captures of a 10MHz squarewave, where the trigger is on the falling edge. Channel 1 trace (in red) is shown with infinite persistence turned on – each minor division is 400ps. Similarly, the inter-channel skew is <200ps. Incidentally, the Tabor generator is specified at <2ps.
The frequency control on the Owon SDS scopes is quite good, even considering the cost, so that makes me suspect my video source.
The second question is about baseline noise. There is discussion on the web about noise spikes being found on the ground connection for the square wave ‘compensation’ signal on the front panel. This may be leakage from the SMPS, but I have not confirmed this. At any rate, this does not affect one’s measurements, even at maximum sensitivity.
By paying attention to proper cable routing, the use of high-quality cables and connectors, good grounding techniques, etc. much, if not all, of the ambient noise can be sufficiently reduced to acceptable levels. I’ve also attached a few photos and screen captures of an SDS7102V scope to show you what can be done at millivolt levels.
The “Baseline noise – normal” is what you will se if the inputs are left open. The -50dBm pictures are using good-quality cabling and correct impedance-matching (the -40dBm and -50dBm are the same setup, just different settings). The -40dBm photo shows a 5mVp-p signal.
**** End reply from dealer ****