RCTIME Question?

MichelB

Hi all, in BASIC Stamp Manual and in Help of BASIC Stamp Editor v2.4.2 we can see:
time = -tau x (ln(Vfinal / Vinitial))
Time = -1 x 10E-3 x (ln(5.0v / 1.4v)) = 1.273 x 10E-3, Where the sign "-" gone?

Tracy Allen

ln(.) should have the smaller final value in the numerator and the larger final value in the denominator, and the ln(.) of a ratio less than one is a negative number, times the negative tau, is a positive result.

Vfinal=1.4
Vinitial=5
ln(1.4/5) = ln(0.28) = -1.272965675813

and
-1E-3 * -1.272965675813 = +1.272965675813 E-3

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Tracy Allen
www.emesystems.com

MichelB

You are right dear Mr Allen, but the following line in the Help of BASIC Stamp Editor v2.4.2·"Time= ... (ln(5.0v / 1.4v))..." is wrong and must be "... (ln(1.4v / 5.0v))...". By the way I'll begin Applied Sensors and I want to know what lines from your App-notes must I add to have more precision with DS1620. Thank you and best regards.

Tracy Allen

Good catch on the mistake in the help file.

I have an article on the high resolution mode of the DS1620 posted at www.emesys.com/OL2d1620.htm#DS1620-HR. Dallas Semi revised the DS1620 so that the counts per degree is now fixed at 16, rather than a higher but variable number. The code still works, with either the old or the new version of the chip.

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Tracy Allen
www.emesystems.com

MichelB

Thank you sir and best regards.

Steph Lindsay

Thank you for reporting the error in the Help file, and good timing since I am working on an update for it. Sorry the error caused you trouble!

-Stephanie Lindsay
Editor, Parallax Inc.

MichelB

Your welcome Steph.

Best regards.