Design And Principle Of Operation - Samson 611 Mounting And Operating Instructions

Design and principle of operation

3 Design and principle of oper-
ation
The Type 6116 i/p Converter is used to con-
vert a direct current input signal into a pneu-
matic output signal for measuring and con-
trol tasks. The i/p converter consists of an
Type 6109 or Type 6112 i/p Converter
Module and a downstream volume booster.
The input is a load-independent direct cur-
rent of 4 to 20 mA or 0 or 20 mA. The out-
put is a pneumatic signal of 0.2 to 1 bar or
other signal ranges up to max. 8 bar.
Principle of operation (see Fig. 4)
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 p , which is produced on the
K
flapper (6) by the air jet leaving the nozzle
Type 3241-1
Fig. 3: Application
12
TROVIS 6493
Supply
air
e
p
Type 6116
(7). The supply air (9) flows to the bottom
chamber of the volume booster (8) and a
certain amount of air determined by the dia-
phragm position flows past the sleeve (8.5)
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 backpressure pushes the dia-
phragm (10) and the plug sleeve (9) down-
wards. As a result, the supply air causes the
output pressure p
A
state of equilibrium is reached in the dia-
phragm chambers.
When the backpressure p
phragm moves upward, releasing the plug
sleeve and thus allowing the output pressure
p to escape through the venting (EXHAUST)
A
until the forces are equal again.
Switch-off electronics
Devices with an input range from 4 to
20 mA have a slide switch which activates
the switch-off electronics (see Fig. 5). This
function allows the input signal to be set to
0 mA when the signal falls below the switch-
ing point of 4.08 mA. This causes the pneu-
matic output to be vented to approximately
100 mbar. This guarantees, for example the
tight shut-off function of a valve. This func-
tion requires a characteristic which passes
through the zero point, for example at an
output signal of 0.2 to 1 bar.
to increase until a new
drops, the dia-
K
EB 6116 EN