sandy47@.ucsc.edu (Larry McElhiney) (02/28/91)
Article posted for a fellow engineer (Larry Hoppis).
Larry
-------
The following HP48 program which finds parallel resistance elements
will be useful for both electronics technicians and hobbyists.
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).
%%HP: T(3)A(D)F(.);
@ PARAL - Large Version L. Hoppis 2/25/91 DONE Rev 1.1
DIR
RPAR
\<< DUP .976300098965 / LN 2.39852613838E-2 / CEIL \-> r x
\<< PICT { # 0d # 0d } BLNK REPL { # 0d # 0d } PVIEW
x 'INDX' STO 0 'y' STO
DO INDX 2.39852613838E-2 * EXP .976300098965 * DUP
MANT 2 RND SWAP XPON ALOG * DUP
r OVER * SWAP r - /
.976300098965 / LN 2.39852613838E-2 /
IF DUP FP .5 <
THEN FLOOR
ELSE CEIL
END
2.39852613838E-2 * EXP .976300098965 * DUP
MANT 2 RND SWAP XPON ALOG * DUP2 DUP2
* ROT ROT + / r %CH
IF ABS DUP ACCU <
THEN 2 RND \->STR " % -- " + ROT DSP " || " +
ROT DSP + + PICT SWAP 1 \->GROB # 16d y # 7d
* # 2d + 2 \->LIST SWAP GOR
ELSE 3 DROPN
END 'y' 1 STO+ 'INDX' 1 STO+
IF y 8 >
THEN 0 'y' STO TONE 0 WAIT
CASE DUP 15.1 ==
THEN
IF x 9 + INDX <
THEN 'INDX' 18 STO-
END
END
END PICT { # 0d # 0d } BLNK REPL
ELSE 0
END
UNTIL 16.1 ==
END 'y' PURGE r
\>>
\>>
DSP
\<< DUP MANT SWAP XPON
CASE
DUP 6 \>=
THEN 6 - "M\GW"
END
DUP 3 \>=
THEN 3 - "k\GW"
END " \GW"
END SWAP ALOG ROT * \->STR
CASE
DUP SIZE 2 <
THEN ".00" +
END
DUP SIZE 3 <
THEN ".0" +
END
DUP SIZE 4 <
THEN
IF DUP "." POS
THEN "0" +
END
END
END SWAP +
\>>
TONE
\<< 5000 .02 BEEP 3000 .01 BEEP \>>
ACCU .5
BLNK
GROB 131 64 FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF701000000000000000000000000000
00004010000000000000000000000000000000401000000000000000000000
00000000004010000000000000000000000000000000401000000000000000
00000000000000004010000000000000000000000000000000401000000000
000000000000000000000E4010000000000000000000000000000002401000
000000000000000000000000000E4010000000000000000000000000000002
401000000000000000000000000000000E4010000000000000000000000000
00000040100000000000000000000000000000024010000000000000000000
00000000000240100000000000000000000000000000024010000000000000
000000000000000002401000000000000000000000000000000E4010000000
00000000000000000000000040100000000000000000000000000000024010
00000000000000000000000000000240100000000000000000000000000000
02401000000000000000000000000000000240100000000000000000000000
00000002401000000000000000000000000000000040100000000000000000
00000000000002501000000000000000000000000000000650100000000000
0000000000000000000E501000000000000000000000000000000A50100000
00000000000000000000000002501000000000000000000000000000000040
1000000000000000000000000000000E401000000000000000000000000000
0002401000000000000000000000000000000E401000000000000000000000
0000000002401000000000000000000000000000000E401000000000000000
00000000000000004010000000000000000000000000000002401000000000
00000000000000000000024010000000000000000000000000000002401000
0000000000000000000000000002401000000000000000000000000000000E
40100000000000000000000000000000004010000000000000000000000000
00000040100000000000000000000000000000004010000000000000000000
00000000000040100000000000000000000000000000004010000000000000
00000000000000000040100000000000000000000000000000004010000000
00000000000000000000000C40100000000000000000000000000000024010
00000000000000000000000000000240100000000000000000000000000000
02401000000000000000000000000000000C40100000000000000000000000
00000000401000000000000000000000000000000040100000000000000000
00000000000000401000000000000000000000000000000040100000000000
00000000000000000000401000000000000000000000000000000040100000
00000000000000000000000000401000000000000000000000000000000040
1000000000000000000000000000000040FFFFFFFFFFFFFFFFFFFFFFFFFFFF
FFFF70
INDX 299
CST { { "PARAL" { RPAR } } { "ACCUR" {\<< ACCU \>> \<< 'ACCU'STO \>> } }
{ "" { } } { "NEXT" { } } { "PREV" { } } { "QUIT" { } } }
PPAR { (-6.5,-3.1) (6.5,3.2) X 0 (0,0) FUNCTION Y }
END
--
Larry L. Hoppis PO Box 472, Mt. Hermon, CA 95041 USA
quality!hoppis@ucscc.UCSC.edu
(408) 336-3651