Measurement Dropped During Lightening

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Anonymous Poster #1	Measurement Dropped During Lightening 10/30/2012 4:09 PM
	on a refinery plant during the lightening the analog signal(4~20ma)drop to 50% for a less than 1 second.while all groundings on transmitter body,signal cable one end,junction box body are perfectly grounded.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Measurement Dropped During Lightening 10/31/2012 4:21 AM
	Slug the input. "In a process plant, if it happens in less than a second, it isn't real." - Simon McCandlish, Control Systems Lecturer. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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jack of all trades Guru Join Date: Sep 2006 Location: Auckland, New Zealand Posts: 8777 Good Answers: 376	#2 Re: Measurement Dropped During Lightening 10/31/2012 3:39 PM
	Sounds like the lightning caused the output to change momentarily, possibly due to the ground potential rising relative to the signal causing the momentary shift in perceived measured value (or something). Good grounding cannot protect against a ground potential change, but like a ship riding a wave the ship is generally OK as long as all of it rides the wave at the same time (eg- no potential voltage difference, no damage). __________________ jack of all trades
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