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LNMP Finishing touches - wiring the battery pack and enclosing - Page 5

post #61 of 66
Thread Starter 

Ha, I was going to cheat and do that anyway, since I had my voltage divider set up last night and I was sooo close.

 

This morning, I can't get it to work. I thought I could build a divider circuit. Is my math off? Here's my setup:

 

signal in - 1M resistor - meter probe red - meter - meter probe black - 1K resistor - signal ground (out)

 

I'm getting ... holy cats, is it the laptop not running on battery that is causing me to get inconsistent readings?

post #62 of 66

You must have missed my recommendation that the total resistance of the divider be around 1K.

 

And yes, you probably should be running the laptop on battery here, if only as a matter of principle. It removes a potential source of problems, so you don't have to even ask the question of whether it's a risk.


Edited by tangent - 2/20/13 at 10:13am
post #63 of 66
Thread Starter 

Oops. Bad math. Always the factors of ten, they are getting me. Well I have the divider correct (if ugly), and the input signal is just right:

 

 

Measuring at the output with SW1 jumped and unjumped, I get a difference that is a factor of ten.

 

So far, so good. This is what scares me from the assembly guide:

 

"The procedure to trim the amp’s gain is conceptually simple"

 

I'm going to re-(nth) read the next section... any hints?

Thanks, Tangent!

-Sara

post #64 of 66
Thread Starter 

What scares me is that this is what I get out of the output:

post #65 of 66
Thread Starter 

Final PICS!!!

I have a feeling I'll be searching for or starting a new thread on.... how to use it!

 

 

post #66 of 66

So you pushed on through the calibration and found out what was giving the odd reading, and corrected it?

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