Time calculation problem

Hi,

Yes! Use radians NOT degrees.

Cheers - Joe

Thanks for your reply Joe. Isn't [2 * 3.14 * 50] the number of radians in 1 second at 50 Hz.?

Brian

Hi again,

Yes, but the arccos of a number gives you radians and the

2*pi*f bit gives you radians per second. Dividing one by the other, the radians cancel and you're left with seconds.

Cheers - Joe

Isn't that what I want -- charging time in seconds? That's what this formula is suppose to give me. Am I missing something here?

Brian

Grab my equation tool at:

and extract out the file EQ.EXE that's inside.

At a DOS prompt, type in: EQ acos(359/361)/2/pi/50

It will print out the figure you are getting from the PDF file.

The others have pointed out that your ARCCOS() function is probably returning something other than radians -- in particular, degrees. For example, if you use my equation tool and enter this: EQ deg(acos(359/361))/2/pi/50

you will then get your 0.0192 out.

This whole thing is called "operator error." ;)

Jon

Brian,

As I said at the beginning, switch (your calculator) to radians and you will get the answer they do.

ACOS (359/391) = 0.105 rads

2*pi*50 = 314.159 rads/sec

So Tc = 0.105/314.159 ~= 0.335 sec (allowing for rounding)

It is simply rads over rads per second.

Cheers - Joe

Thanks Joe, that is what I was missing (switching the calculator to radians). Sometimes, the simplest things, are the hardest to figure out where you went wrong. Thank you for your patience.

Brian

Thanks for your offer Jon. Since Joe told me what I was doing wrong, I won't need your offer.

Thanks,

Brian