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Rob Spiegel
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Blogger
Re: The human senslors
Rob Spiegel   6/7/2013 12:11:54 AM
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Yes, I agree, Chuck. But I would give the old timers a tad more credit. The seat-of-the-pants is actually decades worth of feel and experience. The old guys think that the numbers are less reliable than real-world experience. But, like Moneyball, you can't count the numbers out -- so to speak.

MartyHoyodeman
User Rank
Iron
Re: Human touch, or other temperature sensing methods.
MartyHoyodeman   5/20/2013 6:58:20 PM
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A very long time ago I was working on a Tape Control Unit that had a 750 watt linear 5VDC supply (among others) and was having intemittent issues. First thing was to check the supply voltage which was just fine. I then threw a scope on the supply and saw some noise that was a bit above spec and it would come and go. I opened it up and smelled hot metal. The recitifcation was done with 2 diodes that were mounted on a couple of large aluminum plates used as heat sinks (CT xformer). The cables were bolted to the plates as the diodes were also bolted to them as connections. One of the bolts was no longer shiny and I touched it to see if it was loose.... it was..... it was also about 300 or 400 degrees. I left my finger print permanently in the now dull finish of the bolt head. I know it was warmer than the boiling point of water as I put a dab of spit on the bolt just to see how hot it was and it vaporized instantly. After cooling things down, cleaning things up and replacing the bolt/nut/washers and correctly tightening it, everything worked as expected. The point I am making here is when you are dealing with 100's of watts of power, the touch/feel test is quite useable as I found many times after that first incident, however, I tend to be much more careful and to not touch the connection points directly anymore. Infrared thermometers are cheap now and work very well as a bit of insurance. BTW - My finger prints did reappear on my finger some weeks later. LOL

William K.
User Rank
Platinum
Human touch, or other temperature sensing methods.
William K.   5/18/2013 1:59:08 PM
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this is a good example indeed. I have seen a similar situation associated with motor starters used with three-phase electric motors. I was asked to investigate one which kept tripping the overload switch, which is a thermal switch designed to trip from smaller overloads. But I was not able to touch the terminals, they were live on the 480 volt circuit. But touching the wire insulation next to the termianl gave an adequate clue that it was warmer than it should be. So tightening the connections solved the problem. 

For the safety people who are freaking out that somebody would open an enclosure with the power on, understand that I had great insight into exactly which places were safe to touch, and that I was and still am able to do that kind of test safely. BUT, of course, it should not be attempted by just any person who thinks that they are qualified because they once read how to do it. That attitude is so very ISO9000!

Charles Murray
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Blogger
Re: The human senslors
Charles Murray   5/17/2013 6:53:12 PM
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Oddly enough, Rob, that sounds like the same diviide that was going on in the book (and movie), "Money Ball." The younger executives tended to trust the numbers, while the older scouts seemed to take more of a seat-of-the-pants approach. While the two areas -- engineering and baseball -- would seem on the surface to be unconnected, I do believe the phenomenon you're describing is age-related, across the board.  

Cabe Atwell
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Blogger
Re: The human senslors
Cabe Atwell   5/10/2013 4:10:46 PM
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I just has a screw down terminal issue early this week. I was troubleshooting a speed sensor problem interfacing with a stepper motor control board. I was stripping wires, testing continuity, etc. Then it dawned on me... check the screw down terminal at the stepper driver. Loose.

Problem solved.

C

bobjengr
User Rank
Platinum
HUMAN TOUCH
bobjengr   5/7/2013 6:08:08 PM
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As a recent high school graduate I decided that university study could wait so I applied for and got a job as a die setter.  I really wanted to save up for college.  Back in those days student loans were definitely not that available and graduating with debt was frowned upon.  My job was basically loading dies onto OBI press equipment, running trials, and then turning that press over to the operator.  There was one guy, Richard, who could tell just by hearing the die operate as to whether or not the set was installed properly, had and the correct alignment.  All of this was accomplished by hearing the operation.  Richard was an amazing example of the fact that our senses are great assets when used for jobs described by David.  Excellent post.

Rob Spiegel
User Rank
Blogger
Re: The human senslors
Rob Spiegel   5/6/2013 6:15:46 PM
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One thing that is interesting, Chuck, is the divide between sensing things and using data. I'm hearing that young engineers at plants trust the data, while the older engineers trust their senses. In this divide, those who trust the data may have the advantage.

Rob Spiegel
User Rank
Blogger
Re: The human senslors
Rob Spiegel   5/6/2013 11:07:02 AM
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Good point, Cabe. As for using senses to troubleshoot, apparently vision is not such a good indicator, as you suggested in not being able to see the grounding problem with the screws.

tekochip
User Rank
Platinum
Re: You Gotta Love Your Work
tekochip   5/6/2013 9:07:07 AM
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You're right, of course.  If 100mA is good, 2A is better!

Battar
User Rank
Platinum
Re: You Gotta Love Your Work
Battar   5/6/2013 8:59:33 AM
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Tekochip, that sounds like a wimpy attitude. We had the same problems with x86 cards which could have over 50 100nF dcoupling caps, and sometimes one of them would go short circuit. Which one? We current - limited to 2 amps, the one that caused a blister needed replacing. It didn't take long to find the culprit. 100mA wouldn't do it for us.

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