Product Overview

Pneumatic Control Manual 717.1
Pressure Section
Product Bulletin P-8000
Issue Date 0580
© 1980 Johnson Controls, Inc.
1
Code No. LIT-7171240
P-8000
Proportional or Two-Position
Pressure Controller
The P-8000 Pressure Controller
is designed for a wide range of
pressure control applications.
The pressure sensing line can
be located where extreme
conditions do not permit
controller mounting or where
operational adjustments to the
controller would be inconvenient.
This instrument is ideally suited
for installations that require the
controller to be mounted on a
local control panel.
Shock and vibration tests have
proven the durability of the
P-8000. The use of flexure
levers reduces hysteresis and
friction. The P-8000 is available
with a low pressure “L” or a high
pressure “H” element assembly.
Action
This controller can be made to
function as a Direct Acting or
Reverse Acting instrument by
Fig. 2: P-8000 Cover Removed
changing the position of the
patented sliding control port. A
Direct Acting controller increases
the output pressure signal on an
increase in the measured
pressure. A Reverse Acting
controller decreases the output
signal on an increase in the
measured pressure.
Repositioning the sliding control
port will also change the
sensitivity on proportional models
and the differential on two-
position models.
Sensitivity is the change in
output pressure per PSI change
in measured pressure.
Differential is the amount of
change in measured pressure
needed to change the output
pressure from maximum to
minimum or vice versa.
Adjustment
Moving the slider upward (Direct
Acting) or downward (Reverse
Acting) from the midpoint on the
rail increases the sensitivity for
proportional action applications
and decreases differential for
two-position applications. The
rail is marked DA (Direct Acting)
and RA (Reverse Acting).
The output pressure is indicated
on an integral 0 to 30 PSIG gage
that is visible through the cover.
The set point dial, which is also
visible through the cover, has
ranges on both sides as listed in
the Specifications table. An
external adjustment knob
assembly is available.
Operation
As the pressure in the sensing
line increases or decreases,
it is measured by the element
diaphragm of the P-8000. The
pressure change at the
diaphragm is transmitted to a
system of flexure levers that
open and close the control port.
This causes the output pressure
of the P-8000 to change
according to the measured
pressure change.
Mounting
The P-8000 is designed for
surface mounting. Use the air
connections on the sides, and
the controlled pressure
connection at the bottom of the
base.
Fig. 1: P-8000
Pressure Controller