Best equipment to identify line noise issues - Page 1
Forum section: electronics / testgear

author: fcharron
author_rank: Newbie
timestamp: January 02, 2016, 11:07:52 pm
content: Hi,I am currently using powerline network adapters at home (Homeplug). 99% of the time, it is functioning properly. I tested the bandwidth between the two terminals over a day and it seemed pretty stable.However, once in awhile (once or twice every evening), I experience a full network disconnection.I suspect line noise to be responsible, and am unsure of what would be the best way to verify my theory, and if it is accurate, locate the noise source.Here is what I am currently weighing on using:Using a DMM with data logging featuresUsing an oscilloscopeMy budget is quite limited. I would not like to spend more than 100$-150$ on a multimeter, but reading this forum, I saw that most models in that price range have input protection issues and I would prefer keeping all my fingers intact and not burn my house down. I don't know how much that is a problem for the usage I intend on doing with it (measuring voltage over time on 110V mains). Aside from that very specific problem I have right now, and maybe some vacuum tubes testing (I built a Bottlehead Crack amplifier, and might want to upgrade it later on), I mostly plan on using the meter for light digital use (Raspberry Pi, Arduino, etc...).As for an oscilloscope, while I guess it would help me visualize the issue, my budget would only allow me to buy either a used one or a cheapo solid-state kind (SEEED DSO Nano and such), or a PC-based one (not sure I am too keen on making a connection between my computer and the mains, though). Aside from debugging my immediate issue, I would not have much use for an oscilloscope, so I would rather put my money on a DMM.If it wasn't for the input protection issue, I would probably go for a UT61E, based on the readings I made on this forum.Can anyone tell me:Would a logging DMM help me verifying my hypothesis and locate the noise source?Is the input protection an issue for the usage I intend on doing?Is there another method to identify the line noise I am not thinking about?Please note that while my questions are somewhat of the 'newbie' kind, I have an EE degree, although I did not work in that field for a decade, which is why I refer to this forum for advice. I can understand EE talk though, so don't be shy on detailsThanks in advance

author: radhaz
author_rank: Regular Contributor
timestamp: January 03, 2016, 04:08:11 am
content: I'm pretty sure you want to use a scope:

author: billfernandez
author_rank: Regular Contributor
timestamp: January 03, 2016, 06:45:18 am
content: My guess is that the problem probably stems from some form of high frequency noise. I can't imagine that any datalogging DMM would be able to make any kind of measurement that would show such transient high frequency phenomena.You're right to be cautious about a chain of connection from the powerline to the measurement inputs on a measurement device connected via USB to a PC.

author: SeanB
author_rank: Super Contributor
timestamp: January 03, 2016, 07:11:31 am
content: I would hazard the disconnection occurs when either you or a neighbour turns on a microwave oven, or a water heater. Both can inject high levels of noise on the power lines. Microwave from the RF current and the water heater from arcing contacts in the thermostat.

author: Shock
author_rank: Super Contributor
timestamp: January 03, 2016, 09:24:35 am
content: Quote from: SeanB on January 03, 2016, 07:11:31 amI agree, I was working this weekend where someone had an ethernet over power network, as soon as the microwave was started it killed the network dead.I know it doesn't help but people who know better would not use that system unless it was totally unavoidable. The fact that techs are installing it with home internet connections for various reasons is pretty sad. I've seen it being used to get to the other side of a room when wireless is perfectly reasonable solution latency wise and already setup and working.

author: fcharron
author_rank: Newbie
timestamp: January 03, 2016, 06:54:04 pm
content: I'm living in a fully detached bungalow: can a neighbor's microwave oven still affect my mains? If so, is there any way I can shield my house from this? (Some kind of filter on the mains maybe?)I am using a powerline network because I was having huge reliability issues with wireless. I tried G, N, 2.5Ghz, 5Ghz, I still had dead zones in my house, and I had complete signal drop when my microwave was running. As for running an Ethernet cable through he walls, my house configuration would make this very difficult.

author: SeanB
author_rank: Super Contributor
timestamp: January 03, 2016, 07:45:20 pm
content: Microawaves are attenuated a little by walls, but power line impulse noise can travel pretty far, as it has a very poor transmission line to convey it. If you and your neighbours share a pole pig then it will be conducted to your house for sure. Even the transformer can pass high levels of RF noise through the primary secondary capacitance.

author: billfernandez
author_rank: Regular Contributor
timestamp: January 03, 2016, 08:05:19 pm
content: Quote from: fcharron on January 03, 2016, 06:54:04 pmTypically in America high voltage power lines are run through a neighborhood then step-down transformers are placed so that each transformer can feed four houses. The transformer will act as a low-pass filter between the high voltage power line and the lower voltage transformer output, but the four houses sharing that output are attached in parallel, and thus not filtered from each other.There are filters that can be placed by an electrician (or advanced hobbyist) in the main breaker panel, but I don't remember offhand any to recommend.As I recall,http://www.smallnetbuilder.comhas lots of articles on dealing with WiFi issues. You might also checkhttp://thewirecutter.comreviews of WiFi routers.