Oscilloscope questions?

C

Corey Esson

New Member

• May 7, 2015

• #21

Hi pfelectronicstechnician. Did you ever get an answer on this? Not even sure you are still on this forum or not? I'm stumped here as well.

Thanks!
Corey

 

JimB

Super Moderator

Most Helpful Member

• May 7, 2015

• #22

Hello Corey Esson, welcome to the forum.
pfelectronicstechnician has not visited this site sinec February 2013.

What is stumping you?
Do tell, maybe we can help.

JimB

 

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Corey Esson

New Member

• May 7, 2015

• #23

Hi JimB, well just the fact that I dont understand what the waveform would do?
I also think that its D in the answer as well?

Thanks in advance for any and all responses

Corey

 

JoeJester

Active Member

• May 7, 2015

• #24

If D is the answer, can you post a screen shot of the question and all the answers?

 

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Corey Esson

New Member

• May 7, 2015

• #25

Well, I can try. Wouldn't be for s couple hours till I get home. Not sure how to do this though?

 

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Corey Esson

New Member

• May 7, 2015

• #26

Oh I see, up load file. K. I'll try this in a couple hours. Thanks!

 

Tony Stewart

Well-Known Member

Most Helpful Member

• May 7, 2015

• #27

If you slow down the sweep to 5ms/div and touch the probe dont be alarmed if thus looks huge as 60Vpp is collected by your body as antenna. When touch any ground at the same time, it is suppressed . Since this likely a 10:1 voltage divider probe, it will be 10M Ohms and thus it is only microamps which is harmless.

When sweeping fast like 10us/div and triggered off thus input using -ve edge trigger from from centre, it may appear like a DC floating offset. But the signal is just stretched flat.

I prefer Irfanview for windows to crop, copy and paste to this forum.

But any glue works....

 

Tony Stewart

Well-Known Member

Most Helpful Member

• May 7, 2015

• #28

pfelectronicstechnician said:

The oscillator generates a sine
wave with a small DC component. The waveform produced by the oscillator is shown on the oscilloscope.
The thermistor in the circuit has a positive temperature coefficient. What will happen to the waveform of this
circuit if the temperature rises?
A. The amplitude of the waveform will decrease.
B. The waveform will drift upward on the oscilloscope screen.
C. The waveform will drift downward on the oscilloscope screen.
D. The amplitude of the waveform will increase.

I think its D, correct or not enough info?

Click to expand...

B since it is DC biased PTC means if polarity is correct, the voltage will drift up as there is no waveform. Correct polarity means if a constant current is provided from constant V to an equalt or midscale thermistor value R then to thermistor, if R of thermistor increases with temp, so will voltage. Normally thermistors are rated at 25C for R, which is the fixed value you would choose in series from V+ if you were interested in measuring around room temp, +\- x deg C

 

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Corey Esson

New Member

• May 7, 2015

• #29

Here hopefully is a screenshot. Question number 4.

See if I'm right but now also looking into Tony Stewart's post.

Corey

 

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Tony Stewart

Well-Known Member

Most Helpful Member

• May 7, 2015

• #30

Ah sine wave source and PTC on top side so inverted response.

D you are correct.

Either implementation works. Depending what you want,

 

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Corey Esson

New Member

• May 7, 2015

• #31

THANK YOU VERY MUCH TONY!!
At the risk of sounding totally stupid.....what does PTC stand for?

At work I need to just get an O scope out and play with it for a while, we use them sometimes but not a lot.

Again, many thanks?
Corey

 

Tony Stewart

Well-Known Member

Most Helpful Member

• May 7, 2015

• #32

No problem.. Try google PTC temperature and also check google "images"

 

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Corey Esson

New Member

• May 7, 2015

• #33

I'll do that.

Corey

 

atferrari

Well-Known Member

Most Helpful Member

• May 7, 2015

• #34

Mr Esson (aka Corey)

I suggest you to get REALLY used to google whatever (as PTC on your case), like this:

"PTC acronym"

It works; you will get, in no time, a long list of sites, showing long lists of acronyms. Almost a pun...

Be prepared to get many acronyms but usually one or two are related, in this case, to electronics. Your intelligence should do the rest.

Buena suerte.

 

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Corey Esson

New Member

• May 7, 2015

• #35

Atferrari, thank you soooo much. I'm learning that Google is my friend. Google is how I stumbled across this web site/forums. I'm glad I did it. I did look up PTC Temperature and then found NTC Temperature as well. All very educational and informative to help me in my career in electronics.

Thank you very much and it is all very appreciated from everyone that has helped me today.

Corey Esson
"When its upside down and burning, you've gone too fast"