Answer / mohammed abbas

The difference between pneumatic positioner and electro
pnematic is that.
Pneumatic positioner will get the control signal in the
form of pneumatic (air) from the controller that is (3 to
15 psig)as a input to the pneuamtic positioner and it will
compute and give the pnematic output to air operating
devices or final contol element.it is pneumatic to
pneumatic converter and works totally on pnematic air
only.it will work on the priciple of force balance
mechanism.
Electro pneumatic positioner will recive the control signal
in the form of electrical signal that is (4 - 20ma)and this
elcetrical siganl through positioner it is given to i/p
converter wihch is inbuilt within a positioner body and the
elcetrical sigal will induce magnetic energy aronud the
coil and it will move the fallper away or close from the
nozzle and the nozzle pneumatic back pressure will insrese
and decrese depending upon the eletrical signal .it will
convert electrical signal to pneumatic.it will work on the
priciple of faradays law of electromagnitism.

Answer / jeetu chaudhary

The only difference between Pneumatic Positioner
and Electropneumatic Positioner is the
electropneumatic (i/p) converter unit in the
electropneumatic
positioner to convert the electric signal from the
controller into a
proportional pneumatic signal.
These positioners use a flapper-nozzle system, which
operates
according to the force-balance principle. They can be
applied
for both normal and split-range operation.

Answer / mallu byali

it will work as a trnsducer from 0 to 15 psi which is
convert by 4 to 20 ma ele signal. it has flaper mechanisum
no any role apply on this.

Please send me the sample question of Instrumentation of hpcl/iocl exam. my mail id hihi_kiholo@rediffmail.com

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