Principle Of Operation - Samson 6000 Series Mounting And Operating Instructions

2.3 Principle of operation

See Fig. 2 on page 6.
The device consists of an i/p converter mod-
ule and a downstream volume booster.
When operated, the supplied direct current i
flows through the plunger coil (2) located in
the field of a permanent magnet (3). At the
balance beam (1), the force of the plunger
coil, which is in proportion to the current, is
balanced against the force of the dynamic
backpressure. The backpressure is produced
on the flapper plate (6) by the air jet leaving
the nozzle (7).
The supply air (SUPPLY 8) flows to the bot-
tom chamber of the volume booster (8) and
a certain amount of air determined by the
diaphragm position flows past the sleeve (9)
and leaves through the output (OUTPUT 36).
As the input current and the forces acting on
the plunger coil increase, the flapper (6)
moves closer to the nozzle (7). This causes
the backpressure and the cascade pressure
p upstream of the restriction (8.2) to in-
K
crease until the cascade pressure corre-
sponds with the input current.
The increasing cascade pressure pushes the
diaphragm (10) and the plug sleeve (9)
downwards. As a result, the supply air caus-
es the output pressure p
new state of equilibrium is reached in the di-
aphragm chambers.
When the cascade pressure drops, the dia-
phragm moves upwards, releasing the plug
sleeve and thus allowing the output pressure
p to escape through the venting (EXHAUST)
A
until the forces are equal again.
EB 6116 EN
to increase until a
A
General safety instructions
Switch-off electronics (see Fig. 3)
Devices with an input range from 4 to
20 mA have a slide switch which activates
the switch-off electronics. This function allows
the input signal to be set to 0 mA when the
signal falls below the switching point of
4.08 ± tolerance. This causes the pneumatic
output to be vented to approximately
100 mbar. This guarantees, for example, the
tight shut-off function of a valve.
This function requires a characteristic which
passes through the zero point, for example,
for the version with 4 to 20 mA/0.2 to 1 bar.
If the characteristic line does not pass
through zero, for example, for an allocated
output signal from 0.8 to 2.7 bar, then the
pneumatic output is vented to a remaining
pressure of approx. 0.3 bar when the
switch-off electronics are activated.
bar
1.0
0.8
0.6
0.4
0.2
4 8 12 16 20
bar
3
2.7
2
1
0.8
0.3
4 8 12 16 20
Fig. 3: Switch-off electronics and remaining
pressure
Output 0.2 to 1 bar
Remaining pressure
approx. 0.1 bar
mA
Output 0.8 to 2.7 bar
Remaining pressure
approx. 0.3 bar
mA
7