IBM 1627 Manual page 8

Carriage
Single Step
Drum
Single Step
Carriage
Fast Run
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Power
On/Off
Drum
Fast Run
Power
Power On
Indicator
Figure 1-3. IBM 1627 Plotter Model 1
per second. The switch is used in the same manner
as the carriage fast run control to move the pen to
any desired area of the graph, or for operational
checkout of the drum control circuits and the drum
step motor.
extreme humidity conditions. In order to maintain the
desired high accuracy of the plotter, when plotting on
chart paper with a printed grid, a scale factor adjust-
ment mechanism is provided on the carriage axis for
increasing or reducing the size of each step of the
carriage a small amount to match the grid.
This is accomplished by providing a variable size
loop in the carriage drive cable between the step
motor and the carriage, A control mechanism allows
the loop to be made larger or smaller at a variable
rate proportional to the carriage travel. The rate at
which the size of the loop is changed is determined by
means of the control knob projecting through the top
of the cabinet near the left-hand side. When this
scale factor adjustment control knob is set to zero,
the loop is maintained at a size that will give abso-
lute. 010" steps, or 29.000" of carriage travel for
2900 input pulses. For each division plus or minus
on the knob, the total carriage travel of 29" will be
changed plus or minus. 010", i. e., plus one incre-
ment will give a total carriage travel of 29.010" for
2900 input pulses and minus one increment will give
28.990". A maximum of ±30 divisions on the knob
provides limits of carriage travel from 28. 700" to
29. 300" for 2900 input pulses.
Drum Single Step
The Drum Single Step switch allows the drum to be
moved in single step (1/100") increments either up
or down. This control, in combination with the car-
riage single step control, permits the operator to
accurately align the pen on a point or fixed co-
ordinate on the graph.
Carriage Scale Factor Adjustment (Model 2 Only)
A carriage travel scale factor adjustment is provided
for the purpose of varying the carriage travel to
compensate for stretch or shrinkage in the graph
paper (Figure 1-5). The graph paper is printed at
50%relative humidity to a high degree of accuracy,
but is subject to either stretching or shrinking at
1.3