HP 181A Operating And Service Manual page 10

Section II
Paragraphs 3-38 to 3-43
to describe the operation of the Model 181A/AR. The
. definitions ofthese words and phrases which apply to
_the Model 181A/AR are as follows:
a. WRITE-To transform an input signal into a
visible display on the CRT screen.
b. PERSISTENCE-The iength of time a single
Sweep written display remains visible on the CRT
Screen (INTENSITY and sweep time constant).
c. STORE-To retain, at reducedintensity, a dis-
piay which has been written on the CRT.
d. VIEW-To redisplay onthe CRT screen, at nor-
mal intensity, a stored display.
e. ERASE- To remove all displays, and blooms
which have been stored, or written with persistence
on the CRT.
f. INTENSITY-The brightness of a display as it
is written on the CRT sereen ( PERSISTENCE and
Sweep Time Constant).
g. BLOOM-A visible, non-symmetrical expan-
sion of a display written on the CRT screen.
LIB EAT A I 2 ]
Figure 3-2. Fade Positive and BackgroundIllumination.
3-4
Model 181A/AR
h. FADE POSITIVE-Display obscured by slow
blooming, see Figure 3-2A.
i BACKGROUND ILLUMINATION-A green cloud
of illumination visible on the CRT screen, see Figure
3-2B.
j SWEEP TIME-The time (inseconds, millisec-
onds, or microseconds) required for the beam to move
horizontally one unit of distance across the CRT screen,
when writing a display.
3.38. CONTROL FUNCTIONS.
3-39. PERSISTENCE ANDINTENSITY. These controls
contribute to the duration of afterglow ofadisplay. The
PERSISTENCE control sets the rate at which a display
is erased; INTENSITY sets the brightness of the trace
as it is written. With a given PERSISTENCE setting,
the actual duration of trace afterglow may be increased
by increasing the INTENSITY. Since the PERSISTENCE
control sets the rate of erasing a written display, it
follows that a brighter trace will require more time
to be erased. Conversely, a display of low intensity
. wil disappear more rapidly. The same principle
applies to a stored display of high and low intensity.
The storage mesh of the CRT is not
easily damaged, however, a high-
intensity repetitive trace or spot, writ-
ten on the screen for an extended time,
may not erase completely. To prevent
CRT damage, use minimum INTENSITY
which will give the desired display for a
given PERSISTENCE setting.
3-40. PRESENTATION SELECTION, Push button
controls select the mode in.which the CRT functions,
With ERASE push button depressed, the other three
functions are disconnectedandall stored and persist-
ing displays are removed from the CRT. The WRITE
and MAX W. modes are the only conditions in which
a display may be written on the CRT screen. The
STORE mode disconnects the WRITE and ERASE func-
tions and retains written displays (at reduced intens-
ity) on the CRT. INTENSITY, PERSISTENCE, and
ERASE do not function in the STORE mode. The
VIEW mode intensifies the stored dispiay to a set
brightness and again, INTENSITY, PERSISTENCE,
and ERASE do not affect the display.
3-41. MAX WRITE. When MAX W. push buttonis de-
pressedandthen the ERASE push button is depressed
and released, the storage surface is erased and then
primed (or pre-fogged) to allow much faster writing
on the storage surface. The display, however, has
reduced contrast and fades positive more rapidly. The
contrast and storage time are also reduced in this
mode.
3-42. OPERATING TIPS.
3-43. This information is provided toaidthe operator
in becoming familiar with the Model 181A/AR controls
andtheir functions, andtoserveas a guide for obtain-
ing the desired CRT display.
a. For normal persistence operation, depress
WRITE push button and turn PERSISTENCE control
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