Object: Parallel Resistor Calculator (Rev 1.2)
From: sandy47@.ucsc.edu (Larry McElhiney)
Date: 28 Feb 91 21:30:47 GMT
Sender: usenet@darkstar.ucsc.edu
Organization: University of California, Santa Cruz Open Access Computing
Lines: 180


Don't you just hate it when you post a program (groan) and find a bug
in it two hours later??? Well at least I'm in good company lately *:-).

Please reload the new version 1.2 of PARAL, and happy computing!

Apologies to the Bandwidth watchers.

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The following HP48 program which finds parallel resistance elements
will be useful for both electronics technicians and hobbyests.

USE:  Put the value of the resistance you want on the stack and press
PARAL (softkey 'A' in the 'CST' menu). PARAL presents a list of values
(standard 1%) which when paralleled will yield the desired value. The
accuracy of each combination is also displayed. The required accuracy
is specified by the variable ACCU.  The soft key ACCUR ('B') stores
and retrieves this accuracy variable.

Pressing any key while PARAL is running will advance the display to
the next 'page' of values. The previous 'page' may be displayed by
pressing the soft key PREV ('E'). The program may be exited by
pressing softkey QUIT ('F'). Note that the soft key functions will not
be visible during the execution of the program but will continue to
function normally.

THEORY:  PARAL uses an equation derived with the HP48 from a list of
valid 1% values.  This list was created using the formula

            INV(96)
    X = X*10        for all values between 1 ohm and 1 G ohm

                                0.0239852613838*X
The HP48 found  0.976300098965*e

This equation and its inverse form the basis of PARAL. When X is any
integer a unique one percent value will be found. The values created
with this equation must then be rounded to 3 digits in order to
represent the standard one percent value set. The inverse of this
equation creates n 'bins' which, when integer, represent the nth one
percent value.

PARAL is accurate to at least 4 decimal places for all values
from 1 ohm to 9.76E499 ohms (now that's a big resistor *:-)).

SPECIAL LOADING INSTRUCTIONS:

The GROB element must be edited and turned into a single line
before it can be loaded into the calculator.  If you are loading
this program by hand :( get a cable! (or create a blank GROB and
store in in BLNK -> #130d #63d BLANK 'BLNK' STO).


--
Larry L. Hoppis         PO Box 472, Mt. Hermon, CA  95041  USA
quality!hoppis@ucscc.UCSC.edu

(408) 336-3651

