Design And Principle Of Operation - Samson 6111 Mounting And Operating Instructions

Design and principle of operation

3 Design and principle of oper-
ation
The Type 6111 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 Module and a
downstream volume booster.
The i/p converter is available as a
rail-mounting unit or field unit (see sec-
tion 3.1).
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. 6)
When operated, the supplied direct current i
flows through the plunger coil (2) located in
the field of a permanent magnet (3). At the
Fig. 4: Rail-mounting unit
12
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
(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).
The output signal p
the nozzle (7). The offset spring (8.2) ensures
that the output signal is at least 100 mbar
even at an input signal of 0 mA. 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
p upstream of the restriction (8.4) to rise.
K
The cascade pressure increases until it corre-
sponds with the input current.
Fig. 5: Field unit with stainless steel housing
is used also to supply
A
EB 6111 EN