Improper use of an oscilloscope - Page 1
Forum section: electronics / general

author: edy
author_rank: Super Contributor
timestamp: February 01, 2015, 11:15:47 pm
content: I watched this episode on Discovery TV called "Humanology: Electric Human" and my bull$#!t meter went up. Has anyone seen this show? There is a lady who claims that electrical appliances and lights go haywire around her. So a local university came up with a "test" where they had her hold an oscilloscope probe in each hand and the researcher held another pair. They showed her movies that would get her emotionally excited and while initially her "trace" was at the same level as the researcher, when she saw certain scenes her trace moved up to 3x the level of the researcher (i.e. normal).So what exactly was the oscilloscope showing? They were unclear as to whether she was being probed compared to ground or whether she was holding 2 ungrounded probe tips. The show made it sound like her level of electricity was higher. Sounded like such crap. The video preview is here, I couldn't find the whole show on YouTube:Then there is a guy from Puerto Rico who gets zapped and does tricks lighting paper on fire with his fingers, touches mains and shorts high voltages through his body without any apparent affect. They do all sorts of tests on him and their conclusion is he does pass current through himself but is somehow immune to the pain from it, and his muscles don't seem as sensitive. At first they say he has greater resistance but he is passing current so it must be his skin has reduced resistance along itself but the underparts of his skin must have more resistance so the current passes superficially and does not enter the nerves and blood vessels which would cause internal damage. As if his skin was like aluminum foil or acting as a Faraday cage.Anyone seen this show?

author: helius
author_rank: Super Contributor
timestamp: February 01, 2015, 11:27:37 pm
content: Sadly, today's purportedly "educational" television is just rating-driven nonsense. History Channel is nothing but nazis and aliens, nazi aliens, etc, and The Learning Channel is almost as bad. Fakirism like in your second example was even featured on PBS' Nova, to put the problem in perspective.It is not a secret to anyone that resistance of the skin changes in response to emotions, this is used to detect lying in the polygraph machine. The likelihood that an accurate and honest description of electrical phenomena is going to come from your television is near zero—the days of top-notch programming like "Eureka!" and "The Mechanical Universe" are behind us, alas.The perception that you are "causing streetlights to go out" is actually not that uncommon. It's a result of an insidious confirmation bias, because under normal circumstances you do not pay any attention to streetlights at all. I've noticed it myself and I am not some X-Factor electrical human.I saw your second video was short and took a look at it. One thing that struck me is that passing high voltage, high currents over the surface of the body is not really that unlikely. If you had low concern for your personal safety you could first use a barrier cream and then paint something like silver nitrate over your skin. That would be invisible but highly conductive.

author: edy
author_rank: Super Contributor
timestamp: February 02, 2015, 02:04:58 am
content: You are right about these channels. I thought my kids could learn something useful but they are more and more pseudoscientific sensationalist garbage and lacking any scientific methodology or any science fact. My biggest concern is that they come across as being science. For example, in that show I watched they had physics department experts and some lab researchers studying the people... One used an oscilloscope which looked great for TV but based on how it was used seemed completely wrong. The other guy who would conduct and spark out his fingers could have been tested in a controlled way with appropriately measured AC/DC, high voltage and low, amp measures through parts of his body and checking to see what levels of current are there. The conclusion was human skin can normally handle shock and current of that level but he must have had formed a "resistance" to it... didn't know whether they meant resistance in the electrical sense or tolerance. And since the guy had been zapping himself from age 13, he probably fried all the pain receptors associated with feeling electrical shock yet they concluded he could still feel pain because one of the scientists pinched him and he said he felt it.

author: briselec
author_rank: Regular Contributor
timestamp: February 02, 2015, 02:07:58 am
content: So can he attract the silverware too?

author: timb
author_rank: Super Contributor
timestamp: February 04, 2015, 05:32:05 pm
content: Damn, that kid must have ate the fridge magnets as well as all the food inside!Sent from my Smartphone