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measuring rise time percentages 10%-90%

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So really all i do is get the 100% voltage and time period of the rise time
or time constant and use my calulator to get the voltage and time percentages.

like if the 100% voltage was 5volts

Whats 10% of 5 volts=
whats 20% of 5 volts=
whats 30% of 5 volts=

i just use my calulator to get these percentages after i measured the
100% voltage
 
walters said:
So really all i do is get the 100% voltage and time period of the rise time
or time constant and use my calulator to get the voltage and time percentages.

like if the 100% voltage was 5volts

Whats 10% of 5 volts=
whats 20% of 5 volts=
whats 30% of 5 volts=

i just use my calulator to get these percentages after i measured the
100% voltage

NO!!!!!
you really are missing the point

if you were asked to get the rise-time it is natural to assume the time it takes for a signal to go from 10% of its maximum to 90% of it maximum.

IF you want to work out some capacitance somewhere via watching its charge-curve then the time taken needs to be between 0% of the voltage and 67% of the voltage.

Both are measures of rise-time just between difference voltages.
What if someone asked to find the risetime for a 20%-80% curve?


The reason why the voltages are expressed as percentages is because soo many different voltage rails are used.
IF everything ran off 10V, then risetime would be defined as the time it take for the signal to change from 1V to 9V.

But since signals can be 1.5,3.3,5.10,12,15 and all denomination between it is easier just to define a standard definition for risetime as 10%-90%

Remeber
rise time is in time. the 10%,20%... are voltages

You need to calculate the time between the two voltage levels[/b]
 
Styx, remember the old saying:
"I like to bang my head against the wall because it feels so good when I quit!"
Just think how good you'll feel when this is over!
 
I hate to mention this, because I've done it before, but this fellow "Walters" who started this string is a lost cause, and he shouldn't be going near a 9v battery, let alone AC line voltage. Do a search on all of his previous posts, and you'll catch my drift. I think we went through 30+ replies about impedance vs. resistance and he was just as clueless at the end as he was at the beginning. I have to admit, I am surprised he hasn't given up yet.
 
heathtech said:
I hate to mention this, because I've done it before, but this fellow "Walters" who started this string is a lost cause, and he shouldn't be going near a 9v battery, let alone AC line voltage. Do a search on all of his previous posts, and you'll catch my drift. I think we went through 30+ replies about impedance vs. resistance and he was just as clueless at the end as he was at the beginning. I have to admit, I am surprised he hasn't given up yet.
I learned electronics by studying it in school. OK, I had done some hobby stuff, but I was still pretty much clueless.
When you learn in a structured environment, the material is presented in an order that makes sense. New stuff builds upon the old.
When you try to learn it on your own, you look stuff up on the Internet, you ask questions in forums, you read books, etc. A lot of the stuff you encounter is out of sequence. If this is what Walters is doing, I can sorta symphasize with him. He need to take some classes, paying attention to prerequisites. If he is going to school, then like I already said, he should probably find another field of endeavor.
Yeah, I know that self-teaching works for some of you guys. It might have worked for me too, although there is a lot of stuff I know I would still not understand (e.g., Laplace transforms). For some people, I don't think it works so well.
 
heathtech said:
I hate to mention this, because I've done it before, but this fellow "Walters" who started this string is a lost cause, and he shouldn't be going near a 9v battery, let alone AC line voltage. Do a search on all of his previous posts, and you'll catch my drift. I think we went through 30+ replies about impedance vs. resistance and he was just as clueless at the end as he was at the beginning. I have to admit, I am surprised he hasn't given up yet.
I think he's just a troll. His posts are just to string you along and I can only assume he gets some perverted elation at getting people annoyed. Either that, or he wants to get quickly from novice to master expert by the number of postings he has made. If you don't reply he may go away!

He has posted this same initial question on another forum (ignoring the replies he has already received from here).
 
rise time is in time. the 10%,20%... are voltages

So percentages are only expressed as voltages not in time?

So if the rise time 100% was 50ms to get the percentages

whats 10% of 50ms
whats 20% of 50ms
whats 30% of 50ms

and i just use a calculator to get theses percentages ?
 
ok thsi walters bloke is a prick

seems he is just stringing us all along. We have tried to help and he is just taking the piss
 
Styx said:
...We have tried to help and he is just taking the piss

walters said:
Is this the way to do it ?

pretty much :wink:

Sorry I couldn't resist.

I was going to help, but those with greater patience than I have made such efforts, seemingly in vain, I really don't know what to add.....
 
Thanks alot guys for helping me out im not playing games i just don't know how to do this stuff but if this is the real way to do this then i know
how do to it then
 
walters said:
Thanks alot guys for helping me out im not playing games i just don't know how to do this stuff but if this is the real way to do this then i know
how do to it then
Walters, if you are really not pulling our collective chain, then perhaps you can tell us your age, your educational background, why you need or want to know this information, etc.
 
Just trying to get to electronics more, how to use the oscilloscope more ,
and to learn how to do measurements , testing, checking i lack this knowledge sorry
 
walters said:
Just trying to get to electronics more, how to use the oscilloscope more ,
and to learn how to do measurements , testing, checking i lack this knowledge sorry

Walters, I can understand your desire to learn, but please expand on the question Ron H. asked. Tell us your age and educational background and what you plan on doing with the newfound knowledge if you ever grasp it. Sometimes people get impatient, but we all mean well and we don't want to see someone get injured playing with something they don't understand. Let me tell you, I have been hit by 110 and 220 volts AC more than once, and it really teaches you to respect it. In my younger days I pulled security wire in old attics, sweating on hot summer days, and believe you me, 110 volts feels like 1000 when you are sopping wet! Not everyone can be mechanical or electronically adept, so don't feel stupid if you don't get it. I have absolutely no idea how to build a Dam, but I won't loose one minute of sleep knowing that some people do, and because those people do, I don't have to. Get it?
 
I have already suggested that the only way to get him to understand is to ask him questions, and stop giving him the answers. If he would stop ignoring the questions, this thread can still flow.

Now, assuming the initial voltage is -1V, then it rises to 6V. At what voltage is it when the voltage has risen 20%? At what voltage is it when the voltage has risen 80%?
 
walters said:
Whats 20% of 6 volts?
whats 80% of 6 volts?
Maybe you can stop asking questions and try attempting to answer what I have asked. I'm asking the simplest of maths questions in simple english. Or do you have problems understanding what percentages are? It doesnt matter if you give the wrong answer, just tell us how you arrive at the answer.
 
Whats 20% of 6 volts? 1.2volts
whats 80% of 6 volts? 4.8 volts

i did 6 divided by 20% = 1.2v
i did 6 divided by 80% is 4.8v

is this right or wrong sorry
 
To get a electronics Test tech. job i need to know this stuff

OK, you want to be an electronics test technician. Great, wonderfull! Here is the skill you need to have first and foremost: logical troubleshooting. Here is an easy example:
If I come to you with an electronic device, say a VCR, and I tell you that it doesn't turn on when I plug it in, what would be the first thing you would check? There is no right or wrong answer here, because there are several possible causes. Just give me a possible answer and I will tell you if it makes sense.
 
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