HP42S / DM42 program: Parallel Impedance calculator

Start a new program with: GTO . . PRGM

key commands                            display
                                        { 13-Byte Prgm }
  PGM.FCN LBL    ALPHA PARA           LBL "PARA" 
1/x                                     1/X
X<>Y                                    X<>Y
1/x                                     1/X
+                                       +
1/x                                     1/X
                                        END

This program is executed with XEQ PARA

Using the program

What is the total impedance of the two impedances Z₁=1-j12 and Z₂=3+j10 in parallel? (j is the symbol for the imaginary part of a complex number. Often i is used for this).

(1-j12) // (3 +j10)

1, Enter, -12, COMPLEX
3, Enter, 10, COMPLEX
XEQ PARA

result: 27.2+j7.1

Algorithm

For two parallel impedances (complex number resistors):
      
              1          Z1 * Z2
Z_total = ------------- = ---------
         1/Z1 + 1/Z2     Z1 + Z2

Written by Guido Socher