Samson 611 - 3 Design and Principle of Operation

12 EB 6116 EN
Design and principle of operation
TROVIS6493
Type3241-1
Type6116
Supply
air
p
e
Fig.3: Application
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
owsthroughtheplungercoil(2)locatedin
theeld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
K
, which is produced on the
apper(6)bytheairjetleavingthenozzle
(7).Thesupplyair(9)owstothebottom
chamber of the volume booster (8) and a
certain amount of air determined by the dia-
phragmpositionows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apper(6)
moves closer to the nozzle (7). This causes
the backpressure and the cascade pressure
p
K
upstream of the restriction (8.2) to in-
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
to increase until a new
state of equilibrium is reached in the dia-
phragm chambers.
When the backpressure p
K
drops, the dia-
phragm moves upward, releasing the plug
sleeve and thus allowing the output pressure
p
A
toescapethroughtheventing(EXHAUST)
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.