Scaling Without Using The Sc Instruction - HP 7470A Interfacing And Programming Manual

Scaling Without Using the SC Instruction
The 7470plotter movements are in terms of plotter units where a plotter
unit = 0.025 mm. While the plotter can be scaled into user units using
the SC command, it may be convenient for you to write programs
where numbers to be plotted are in some units other than plotter units.
These "user units" can be converted into plotter units by the computer
using the following equations:
P2 — P1 P2 —P1
Xscaled= L': Ax'+' Plx" Ulx—"L';(
U2x _ Ulx U2x _ Ulx
P2)/'Ply P2y_P1y
Yscaled : T-— Ay 'i' P ly— Uly-A
U2y _ Uly U2y _ Uly
where: Ax is the X—coordinate of the desired point in user units,
Ay is the Y—coordinate of the desired point in user units,
Plx is the X-coordinate of P1 in plotter units,
Ply is the Y—coordinate of P1 in plotter units,
P2X is the X—coordinateof P2 in plotter units,
P2y is the Y—coordinateof P2 in plotter units,
Ulx is the X—coordinate of P1 in user units,
Uly is the Y-coordinate of P1 in user units,
U2};is the X—coordinateof P2 in user units, and
U2y is the Y—coordinateof P2 in user units.
To demonstrate the use of the scaling equations, let's go through an
example.
Example 1:
Problem
Scale the platen area (P1 = 250,279 and P2 = 10 250,7479) into
user units where P1 = 0,0 and P2 = 25 000,18 000. At the center
point (X= 12 500, Y = 9000), draw a circle with radius 2500 as
follows:
C-2 REFERENCE MATERIAL