Oscilliscopes

[Djosha]

Re: Oscilliscopes

Hello friends:

Siglent was the Chinese brand that I liked the most, but a failure in the firmware of their arbitrary generators has made me never buy this brand again, since I warned them about it and they never heeded my warnings, but they did about more banal things and without importance.

I usually repair and calibrate a lot of measurement equipment, from multimeters to spectrum analyzers, signal generators and many more related to RF and other measurement fields.

For years I have observed the Owon brand, and honestly they are the ones who never exaggerate in their ads, you buy what you see and do not feel cheated, with a better price than other brands. I prefer them even better than Rigol, who a few years ago manufactured and sold a large number of oscilloscopes with a faulty trigger and never made it public despite claims from only a few of its buyers.

I have quite a few bad experiences with Chinese equipment, if they are junk that you will never have a service manual or spare parts or parts, if there are any on the market, these Chinese brands will never serve you. On the other hand, these Chinese measuring devices do not comply with the regulations of your country, that is why they are sold in small quantities so as not to incur illegalities that can cost them expensive, if these Chinese devices are junk, and cannot be compared with HP / Agilent / Keysight, Tektronix, Lecroy, Rohde & Schwarz etc. Of these brand equipment can be found for quite good prices and fully operational, with a precision superior to Chinese scrap.

This is just my opinion as an electronics professional, which sometimes may not coincide with a member of this great forum, so there will always be different opinions, but any professional in the field will tell you the same as me.

Sorry for my English.

Greetings.

[stj]

Re: Oscilliscopes

if you're in a first world country and when they broke you just throw it to bin and buy another last day's one.

people in "first world countries" are not as well off as you think.
we have thieving governments taxing and stealing everything from us.
thats why we buy everything from china / ali-express.
not to save money, but because we dont have much choice.

western world now is rich criminals in government and peoples growing poorer every month.

[a45lkajertag]

Re: Oscilliscopes

Today any oscilloscope trade is the same if are chinese type one. I mean, it make no sense the tradename, just to be a scope. In the end if you're in a first world country and when they broke you just throw it to bin and buy another last day's one. But if you're not in a first world country it's sad cause all today's oscilloscope (and of course even more if are chinesse type) must been disposable and there's not or even too poor tech support (schematic, spare parts, etc) to get they fixed in a failure event, and considering they must fail in 5 years or less. Best regards.

[EasyGoing1]

Re: Oscilliscopes

the o.s. doesnt surprise me - that's why i use linux.

The only difference there is that you have more granular control over that behavior, as long as you're custom compiling your kernel...

[stj]

Re: Oscilliscopes

the o.s. doesnt surprise me - that's why i use linux.

[EasyGoing1]

Re: Oscilliscopes

hmm...
i cant see why things would be talking unless it's micro$oft upto no good as usual.
maybe some type of service-discovery ping or something.
that or your isp probing your network via TR-069.
which btw is enough reason to NEVER use an isp supplied router/modem!!!

I use a Netgear router with a custom build of OpenWRT.

And I don't even know what to say on your statement of "i cant see why things would be talking" - I don't even know where to begin but trust me ... your ethernet cables have traffic on them CONSTANTLY! Background code running from just about any web page you happen to have loaded, other network based apps chatting to home base in the background ... layer 3 is routing and routing functions are always checking for hop counts, updating routing tables... the list is endless. I use a program for macs called "Little Snitch" and it sits between your IP stack and your apps and you can literally see EVERYTHING that is chatting about on the network and it's phenomenal what you don't realize is going on without your knowledge. Heck, even the operating systems are constantly chatting it up to various places ...

[diif]

Re: Oscilliscopes

hmm...
i cant see why things would be talking unless it's micro$oft upto no good as usual.
maybe some type of service-discovery ping or something.
that or your isp probing your network via TR-069.
which btw is enough reason to NEVER use an isp supplied router/modem!!!

The Macbook uses Bonjour which is multicast.

[stj]

Re: Oscilliscopes

hmm...
i cant see why things would be talking unless it's micro$oft upto no good as usual.
maybe some type of service-discovery ping or something.
that or your isp probing your network via TR-069.
which btw is enough reason to NEVER use an isp supplied router/modem!!!

[EasyGoing1]

Re: Oscilliscopes

the ethernet wouldnt surprise me, it's a low voltage current-drive system.
so it sends short spikes over long wires.

if it is the ethernet then maybe swap that cable for an stp type one.
if it wasnt for the price difference i would use them for everything!

I had not considered Ethernet either. I always make my own cables ... but a solid stp properly terminated wouldn't be a bad idea ... can't cost that much I wouldn't think for like a 15 meter cable. I was thinking maybe even VLAning the scope would reduce the traffic on that wire but then again ... most TCP/IP stacks in any computer is pretty chatty even without any direct traffic happening ... layer three alone is constantly talking back and forth to anything that will listen.

[flcs2020]

Re: Oscilliscopes

MASTECH is a good brand from China, you can think about it

[Per Hansson]

Re: Oscilliscopes

Also, good to know - if I'm reading what you said correctly - that the ground lead can act as an antenna for nearby noise ... so it's better - in many cases I assume - to simply leave it disconnected when taking a reading?

Well you need a ground (or to use two probes instead of the ground).
What I was saying is that the long ground wire acts like a loop antenna:
It is better to use the short spring clip that you can put on the probe tip instead.

[stj]

Re: Oscilliscopes

the ethernet wouldnt surprise me, it's a low voltage current-drive system.
so it sends short spikes over long wires.

if it is the ethernet then maybe swap that cable for an stp type one.
if it wasnt for the price difference i would use them for everything!

[EasyGoing1]

Re: Oscilliscopes

do you get the spikes without any probes?

btw, try to find the cause - it will effect other stuff like radio.
i suspect it's a low current psu - like an led lamp.

With no probes connected, NO, there is no noise on the screen that I can detect anyway. When I was getting the noise, the scope had right next to it ... just centimeters away, a USB-C port replicator. And it does all kinds of stuff like HDMI on three channels, Gigabit Ethernet, Audio in and out and of course there are lots of digital clocks in that thing and no idea if or how it's shielded or even if it needs to be given how everything it's doing is all digital signaling. No RF of any kind (no Wifi etc.).

Then about half a meter from the scope is my new MacBook Pro. Then about a full meter from the scope is an Xbox One which is technically always on with a low-power kinda thing and a 55" flat screen TV which was also powered off but plugged in. The laptop and the TV would be the only source of RF noise in the WiFi hardware. I have WiFi disabled on the Xbox. Next to the TV which would be about 1.2 meters away from the scope is a Cisco brand Cable TV DVR ... bout 8 years old I would say give or take. It is always on.

OH, also about ¼ meter behind the scope is a Logitech - powered subwoofer connected to two speakers. That unit is always on, but I did not have any sound playing through the speakers when I was taking those readings.

But besides those things, there were no powered electronics within 10 meters of the scope.

My guess is that it was the USB-C port replicator.

[EasyGoing1]

Re: Oscilliscopes

This looks normal to me, but one important thing you did not mention yet:
stj asked if you had removed the ground clip when taking these measurements?
It is important to understand that the ground clip acts like an antenna:
That is why they include that little spring you can use instead of the long ground wire.
I.e. if you are going to perform high frequency measurements you can't use the ground wire!
(And if you are using the scopes built in probe compensation signal then it is not needed anyway since it is anyway already referenced to the scopes (mains) ground).

I had a lengthy conversation with the Siglent rep over on EEVBlogs, and determined that yup it is indeed normal. Also, good to know - if I'm reading what you said correctly - that the ground lead can act as an antenna for nearby noise ... so it's better - in many cases I assume - to simply leave it disconnected when taking a reading?

Also, as I pointed out earlier, the noise goes away completely when I moved the scope to the other room where no nearby electronics were powered on. I haven't tried it yet without the ground lead connected, but I will as soon as I have the opportunity.

[Per Hansson]

Re: Oscilliscopes

Now if this thing is behaving NORMALLY, I'll leave it alone and keep it, but if you think it might even be slightly defective, I got Amazon Prime ... they'll send me a new one, and come pick this one up at no cost to me with no questions asked.

What would you do?

This looks normal to me, but one important thing you did not mention yet:
stj asked if you had removed the ground clip when taking these measurements?
It is important to understand that the ground clip acts like an antenna:
That is why they include that little spring you can use instead of the long ground wire.
I.e. if you are going to perform high frequency measurements you can't use the ground wire!
(And if you are using the scopes built in probe compensation signal then it is not needed anyway since it is anyway already referenced to the scopes (mains) ground).

[stj]

Re: Oscilliscopes

do you get the spikes without any probes?

btw, try to find the cause - it will effect other stuff like radio.
i suspect it's a low current psu - like an led lamp.

[diif]

Re: Oscilliscopes

OK, I just created an account on eevblog ... how do I find this "tautech" character?

Click the members tab at the top of the forum page.

[EasyGoing1]

Re: Oscilliscopes

well if you think it's a problem, go ask tautech i think he's called, on eevblog.
he's a siglent rep

OK, I just created an account on eevblog ... how do I find this "tautech" character?

[EasyGoing1]

Re: Oscilliscopes

well if you think it's a problem, go ask tautech i think he's called, on eevblog.
he's a siglent rep

This is my first real oscilloscope. I have no idea if they are normally susceptible to RF noise like that. It does seem to me to be a bit much, but, if this is normal for scopes, then I will simply be aware of it and act accordingly moving forward. But if this is not something that is standard with scopes, then I should get it replaced.

My question is, what would YOU do if it were your scope?

[stj]

Re: Oscilliscopes

well if you think it's a problem, go ask tautech i think he's called, on eevblog.
he's a siglent rep