testing question

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langjahr@comcast.net said:
You should know
-Some meters respond to average values but display a calculated RMS value, while others respond to RMS and display it.
-That a waveform with high voltage spikes on it may be ruining your meter even though the meter shows a value well within range.
-A meter doesn't care what it's looking at, it will display a value. If it's looking at a sine wave, that value has a lot of meaning. Otherwise, . . .?
-The instrument that does the least interpretation for the user (a scope) may also be the hardest to use.
-Instruments have limited bandwidths, so if you looking for the short-duration spike that's causing your problem, you may not always see it.
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i dont use averging meters just true RMS. im thinking of getting a simpson multimeter soon. used one in trade school and really enjoyed using one.
 
langjahr@comcast.net said:
You should know
-Some meters respond to average values but display a calculated RMS value, while others respond to RMS and display it.
-That a waveform with high voltage spikes on it may be ruining your meter even though the meter shows a value well within range.
-A meter doesn't care what it's looking at, it will display a value. If it's looking at a sine wave, that value has a lot of meaning. Otherwise, . . .?
-The instrument that does the least interpretation for the user (a scope) may also be the hardest to use.
-Instruments have limited bandwidths, so if you looking for the short-duration spike that's causing your problem, you may not always see it.
Click to expand...


So what now about a useless scope? Have you ever worked in industrial maitenance with lots of electronics?

You mean a scope isn't really worth it doing construction work, right?
 
76nemo said:
So what now about a useless scope? Have you ever worked in industrial maitenance with lots of electronics?

You mean a scope isn't really worth it doing construction work, right?
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last time i used a scope was trade school in the electrical lab. we just plugged it into the DC voltage so the teacher could show us about the different kinds of sine waves
 
electricalperson said:
last time i used a scope was trade school in the electrical lab. we just plugged it into the DC voltage so the teacher could show us about the different kinds of sine waves
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You mean ACV?
 
electricalperson said:
he plugged it into AC so we can see the sine wave then he put it into DC (alot of the stuff we worked with we used DC for some reason) so we can see what that wave looked like
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There is no wave in straight DC unless it's AC coupled. I know you know that, we lost each other. I am a magnet for doing that alot.

See the signature,..."Certified Dummy":D ?

Now you know where it comes from;)
 
76nemo said:
There is no wave in straight DC unless it's AC coupled. I know you know that, we lost each other. I am a magnet for doing that alot.

See the signature,..."Certified Dummy":D ?

Now you know where it comes from;)
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yea instead of seeing the sine wave from ac voltage we would see a straight line. not sure what the DC waveform is called
 
Heart of the problems

Heart of the problems

You had asked earlier about more detailed troubleshooting, what else did you learn from a scope and power quality?
 
76nemo said:
You had asked earlier about more detailed troubleshooting, what else did you learn from a scope and power quality?
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i didnt learn anything about power quality in school we were just talking about what the different power sources look like and nothing more. i wish we talked more about it but a lot of kids in class didnt care so the teacher didnt care either and some of us that wanted to learn suffered because of it
 
I think scopes

I think scopes

. . .are good when you are getting results that don't make sense with instruments that do the interpretion for you.

There's not many things more basic than a voltage vs. time display. And from what I'm hearing from you guys, pure sine waves are becoming pretty rare.

And, nowadays, these expensive little buggers are handheld, battery operated (so you don't have to worry about isolating them from the line) and versatile. And sometimes, I guess for factory maintenance stuff, you need statistical functions, and they have them.

Even car mechanics are forced to use these things. No more breaker points or carburetors.

But, I mostly worked in electronics, so I may be biased.
 
76nemo said:
Did your trade school get into motor drives, PLC's, ...any electronics?

Did you ever discuss distortion and THD?
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we had a PLC that i played around with. i was able to program it to push a black disk off the conveyor and stamp the white disks. but thats all i done and it was pretty simple. i believe it was a training device by allen bradley or something like that. it wasnt a real PLC found in a factory. never had training in electronics
 
Electrical Person: There are testing companies all over the country. Some of their tech's are EE's - but not all of them. If you can get in the door you could work your way up wtih experience to more technical testing. They do lots of testing that does not require great engineering skills. And if it does you can learn it on the job.

I traveled all over the country as a start up engineer doing start up at new power plants, and we tested everything before it could be energized. The only thing construction was allowed to energize was the lighting system!

At one point I went to a Multi-Amp (now AVO) school in Texas for a couple weeks to attend classes on Protective Relay testing. This was right after a major hurricane had made a mess of Florida. Everyone of us in the class was offered a job by Multi-Amp in Florida, to help get the the Florida electrical grid repaired. I think we had 10 guys in the class, 2 were alread Multi-Amp employees who were sent to this school for additional training, as they had never tested protective relays.

Two guys of that group of 10 were engineers. The other 8 were electricians with a heavy background in industrial trouble shooting.
I guess what I am really trying to say is you need to work in an environment where you will be doing maintenance and trouble shooting. You won't get that in commercial or residential. Trouble shooting electrical systems for a home or store just is not the same.

Something in your favor...A lot of the testing we used to do is now being contracted out to these testing companies. In the past we would rent the major test equipment we needed from GE Rents. So those testing companies have had to grow, and required more employees.

Good luck.... It was the greatest job in the world. I truly did love my job.
 
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