Rigol DS1052E stray RF? - Page 1
Forum section: electronics / general

author: MikeK
author_rank: Super Contributor
timestamp: January 29, 2012, 02:29:31 am
content: I've just noticed recently that I can't have the TV on while my scope is on, because the scope causes interference (TV antenna, no cable). It also interferes with my ham radio. I haven't had the Rigol apart, but I've seen teardown pics and I thought I remembered seeing a metal box around the internals.What gives?Mike

author: amspire
author_rank: Super Contributor
timestamp: January 29, 2012, 04:01:50 am
content: I haven't had interference from my Rigol.If you hold an oscilloscope probe near the Rigol power cable, do you get a strong HF pickup? The noise is probably on the power cables, and perhaps the TV is on the same circuit, rather then a different circuit back to your switchboard.Anyway, probably a good idea to get some clip on ferrite filters for the power cords of the Rigol, the TV and the HAM gear.Something like this:http://www.ebay.com/itm/120844241649.http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-454I think you can get them from Mouser, etcRichard

author: vtl
author_rank: Regular Contributor
timestamp: January 29, 2012, 04:15:18 am
content: Would those filters do anything? I've taken apart my Rigol and it already has line filters in its power supply

author: amspire
author_rank: Super Contributor
timestamp: January 29, 2012, 04:55:19 am
content: If the Rigol with line filters and a shielded case is causing interference, then either the shielding or the line filter is not eliminating all the noise.If the noise is in the mains cable, the ferrite filters will attenuate the signal, particularly above 100MHz.Richard

author: MikeK
author_rank: Super Contributor
timestamp: January 31, 2012, 01:30:28 am
content: I'll try the ferrite bead, but putting the probe near the power cable doesn't show much interference...I get way more interference by grabbing the plastic probe end with my bare hand.

author: IanB
author_rank: Super Contributor
timestamp: January 31, 2012, 01:45:08 am
content: I'm puzzled. If you grab the scope probe with your hand it causes the scope to radiate interference to your TV and radio? That's odd, since the scope probe is an input. It shouldn't have any signals on it to radiate. Sounds like something might be horribly wrong.

author: MikeK
author_rank: Super Contributor
timestamp: January 31, 2012, 03:21:37 am
content: Sorry. I meant that the noise showing up on the scope is greater when I grab the probe than when I put the probe near the power cable.

author: IanB
author_rank: Super Contributor
timestamp: January 31, 2012, 04:02:10 am
content: Quote from: MikeK on January 31, 2012, 03:21:37 amOh, I see.

author: IanB
author_rank: Super Contributor
timestamp: January 31, 2012, 04:52:44 am
content: I investigated what happens with my DS1102E.With the probe next to the power cord, I pick up mains frequency with some "spikes" near the zero crossing points:On closer examination the spikes are a ringing at about 640 kHz:There wasn't much signal strength next to the power cord though. However, when I touched the probe tip with my finger, I got a signal about 100x stronger:I expect my house to be full of 60 Hz LF radiation, but it's not obvious where the ringing is coming from. It could be from the scope, but I'd have to turn the scope off to confirm, and then I'd have no way of checking whether the signal went away. Ah, but then I remembered all the lights in my house are on dimmer switches. I turned off all the lights and the ringing spikes went away. I was left with nothing on the scope except 60 Hz. So as well as I can tell, my Rigol is not radiating any RF noise that is easy to pick up with the probe.

author: MikeK
author_rank: Super Contributor
timestamp: January 31, 2012, 02:45:37 pm
content: Thanks for that, Ian. I'm excited to get home from work to check mine.

author: flolic
author_rank: Frequent Contributor
timestamp: January 31, 2012, 04:17:16 pm
content: My work lamp has CFL in it. It emit terrible amount of noise in 50kHz range, and my DS1102E can pick up that noise with ease.In fact, I must turn damn lamp off every time I'm about to measure low level signals.

author: Fraser
author_rank: Super Contributor
timestamp: January 31, 2012, 07:36:23 pm
content: Interestingly, the Rigol DSO LCD display used to use a CCFL, with associated HT inverter to power it. The newer models moved to LED backlighting which I would expect to be RF quiet. Discharge tubes of any type can be a source of RFI so I am glad my DS1052 is the LED version.

author: MikeK
author_rank: Super Contributor
timestamp: January 31, 2012, 11:30:41 pm
content: Quote from: IanB on January 31, 2012, 04:52:44 amI got similar results, but my zoom in was much more frenzied:http://s176.photobucket.com/albums/w174/upand_at_them/?action=view&current=MVI_0416.mp4