General electronics question...

[joecool234]

Ok, enough already...this is retarded.

Yeah, electrons flow from - to +, but everyone is leaving out a crucial fact. Electrons are negatively charged. If a negative charge is flowing to the left, a positive flow to the right is analogous.

Why is the gravitational constant always given a positive value? Gravity always points down, so it should be negative, right? Well, it all depends on the frame of reference.

If every engineer/university/data sheet uses a + to - convention, than that frame of reference should be considered a standard. And for extensive purposes, it is. And it should be taught this way as well. End of story.

 

[Sirje31337]

This thread has gotten rediculously out of hand, lol. The question was. Can/how do you test a capacitor.

 

[joecool234]

This thread has gotten rediculously out of hand, lol. The question was. Can/how do you test a capacitor.

Eh, whatever...I think the OP deserted us a long time ago. This should be made a sticky titled "How to divert on the longest tangent possible."

 

[Whatsisname]

bad example

Why is the gravitational constant always given a positive value? Gravity always flows down, so it should be negative, right? Well, it all depends on the frame of reference.

 

[Kerri Ann]

Eh, whatever...I think the OP deserted us a long time ago. This should be made a sticky titled "How to divert on the longest tangent possible."

lol, amen!

 

[aL Mac]

bad example

If you are going to say that someone's example is bad, you should give reason as to why. Argument and counter-argument are how we go about debating things.. by just stating "bad example" you could have just instead said "I think you're stupid" or "idiot" However, by resorting to name calling, you leave out factual and logical reasoning... perhaps for good reason (that is you have none).

I'm not trying to insult, I'm just saying I'd like an explanation before you say someone is wrong.

 

[joecool234]

This should be made a sticky titled "How to divert on the longest tangent possible.

good example:

If you are going to say that someone's example is bad, you should give reason as to why. Argument and counter-argument are how we go about debating things.. by just stating "bad example" you could have just instead said "I think you're stupid" or "idiot" However, by resorting to name calling, you leave out factual and logical reasoning... perhaps for good reason (that is you have none).

I'm not trying to insult, I'm just saying I'd like an explanation before you say someone is wrong.

 

[rockr001]

personally...I would remove the part and use a quality DMM(that has a setting to test capacitance) like a fluke DMM for instance and then check the cap that way...if it has a reading that is within a 1-2% tolerance then it should be fine for a while...just replace it in the circiut and look for the problem elsewhere...that is the easiest way to "TEST/CHECK" a cap....however...if you see the cap discolored or bulging anywhere then I would replace it instead of even bothering testing it as these are signs of a failing component anyway....you can also check the resistance of it to get a "general" idea as to the status of the component....

I know I will probably get flamed for trying to stay on topic and telling everyone else(those that strayed anyway) to stfu and take the debate elsewhere...this was never about what theory is correct...and for whoever mentioned NY schools..I grew up there and went to school for electronics and they did teach it "backwards" to what conventional thinking was/is...so it was taught to me the "Correct" way.....flowing from - to +....but thats just me...btw I went to Bryant $ Stratton for my electronics degree

 

[joecool234]

personally...I would remove the part and use a quality DMM(that has a setting to test capacitance) like a fluke DMM for instance and then check the cap that way...if it has a reading that is within a 1-2% tolerance then it should be fine for a while...just replace it in the circiut and look for the problem elsewhere...that is the easiest way to "TEST/CHECK" a cap....however...if you see the cap discolored or bulging anywhere then I would replace it instead of even bothering testing it as these are signs of a failing component anyway....you can also check the resistance of it to get a "general" idea as to the status of the component....

I know I will probably get flamed for trying to stay on topic and telling everyone else(those that strayed anyway) to stfu and take the debate elsewhere...this was never about what theory is correct...and for whoever mentioned NY schools..I grew up there and went to school for electronics and they did teach it "backwards" to what conventional thinking was/is...so it was taught to me the "Correct" way.....flowing from - to +....but thats just me...btw I went to Bryant $ Stratton for my electronics degree

Uh, a cap that is 1-2% of target spec would probablly be the most expensive cap on earth. Most caps have tolerances to +/-20%. Good ones have +/-10%. I think a few are spec'd for +/-5%.

This is where engineering degrees aren't worth shit in my book (I'm not biased...I have one too). Unless you take many many labs, no course that I know of teaches real-life considerations. I had no idea what "tolerance" was until I actually started prototyping at work. University courseload tends to over-emphasize mathematical equations, when these equations NEVER fully carry over to the real world. The equations should be used as a guideline.

P.S. I will reiterate the fact that negative current flows from - to +. If you want to think of current as a negative number, be my guest.

 

[plot]

Uh, a cap that is 1-2% of target spec would probablly be the most expensive cap on earth. Most caps have tolerances to +/-20%. Good ones have +/-10%. I think a few are spec'd for +/-5%.

This is where engineering degrees aren't worth shit in my book (I'm not biased...I have one too). Unless you take many many labs, no course that I know of teaches real-life considerations. I had no idea what "tolerance" was until I actually started prototyping at work. University courseload tends to over-emphasize mathematical equations, when these equations NEVER fully carry over to the real world. The equations should be used as a guideline.

P.S. I will reiterate the fact that negative current flows from - to +. If you want to think of current as a negative number, be my guest.

in my electronics engineering technologist course, we have a lab with every eet class. (the degree is geared towards "design engineering")

 

[gee]

This is where engineering degrees aren't worth shit in my book (I'm not biased...I have one too). Unless you take many many labs, no course that I know of teaches real-life considerations. I had no idea what "tolerance" was until I actually started prototyping at work. University courseload tends to over-emphasize mathematical equations, when these equations NEVER fully carry over to the real world. The equations should be used as a guideline.

Never a truer word spoken.

I'm proud to be an electrical engineer that gets his hands dirty in the lab... I've easily learned 10x what i've learned in EE through experience.

But you can't dismiss theory; you need predictable results, and when things aren't as predicted, you need explanation (which often comes back to theory - you forgot a stray inductance or something)

 

[Teancum]

Ok, I'm driving this even more off-topic, but in response to the previous post....

AMEN

I was a Teaching Assistant in a EE Lab last semester. Most of the labs dealt with these chips we have from AMI that contain a couple dozen MOSFETs in various configurations (current mirrors, single transistors, etc). Each of the labs consisted of three parts: calculate what parts you need and how the circuit should behave, simulate it on PSpice, and build/test/debug the circuit.

The last few labs focussed on building a kind of op-amp using this IC. And EVERYONE had problems. Some chips were burnt out (from abuse, intentional or no). But mostly, they all needed tweaking in some way. And we made the students figure it out. Such was a typical conversation:

Student: My circuit doesn't work.
Me: In what way
Student: I'm not getting any signal out.
Me: Are you putting a signal in?
Student (I'll give them the benefit of the doubt): Yeah.
Me: Where does the signal disappear?
Student: Huh?
Me: You have a 3-stage amp. at which stage does the signal get squashed?
Student: I don't know.
Me: Go find out, and then figure out what's wrong with that stage.

Not only did it make the students (many of whom are in some of my classes this semester) learn how to build circuits better, it made my job a whole lot easier.

 

[fat-tony]

We had a fair bit of homework regarding tolerance and sensitivity to go with our "Electronic Instrumentation and Analog Circuits" course. This is for an EE degree (not EET or anything like that). Through our program, we have 3 practical labs covering various topics (analog, digital, power systems), and 2 design lab courses where you design and build a system throughout the semester. Adding to this is that some of the courses, while not having official lab times scheduled do require a fair bit of lab time (ie the Verilog class you have to actually burn and test an FPGA).

Officially, the scheduled labs take 3 hours / week, but that's generally a huge underestimate, and with all the work involved typically take up 6 or 7 (5 hours in the lab, 1 or 2 doing the writeups)