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Model EA91A＆EA90A
CAUTION
5.3.2 Model EA90A Electro-pneumatic Valve Positioner (Intrinsically Safe Explosion-protected Construction)
■Wiring Procedure
The Model EA90A Electro-pneumatic Valve Positioner is designed to ensure intrinsically safe. However,
electric or magnetic energy from other electric apparatuses and wires may cause adverse affections on
the intrinsic safety system. To avoid these affections, perform external wiring in accordance with the
instructions described below. For details, refer to"New Recommended Practice for Explosion-protected
Electrical Installations".
⑴ Identify intrinsically safe circuits and un-instrinsically safe circuits, and separate intrinsically safe
circuits from other electric circuits.
⑵ Take appropriate measures to prevent influences such as electrostatic induction and electromagnetic
induction.
⑶ Minimize inductance and capacitance of the wires as much as possible, and always make them lower
than maximum value if operating condition is specified.
⑷ Protect the wires against external damages.
⑸ Be sure to ground uncharged open metallic parts.
⑴ Connect wires in accordance with the wiring diagram shown in Item 5.1.2.
⑵ The parallel pipe female thread G1/2 (PF1/2) female screw is used for conduit connection.
⑶ Condition for External Wiring of Intrinsically Safe Circuit :
Set the parameter of intrinsically safe circuit and the parameter of safety barrier so that the conditions
described below are satisfied.
Lw ≦ Lo
Cw ≦ Co
Lw : Inductance of External Wiring of Intrinsically Safe Circuit
Lo : Permissible Inductance of Intrinsically Safe Circuit
Cw : Capacitance of External Wiring of Intrinsically Safe Circuit
Co : Permissible Capacitance of Intrinsically Safe Circuit
Effective internal inductance and effective internal capacitance of EA90A Electro-pneumatic Valve
Positioner are negligibly small.
⑷ Use insulated wires or cables for Intrinsically Safe Explosion-protected Construction. Use metal tubes,
metal conduits, or metal protective tubes as needed to mechanically protect external wiring and prevent
induction.
⑸ Place the Model EA90A Electro-pneumatic Valve Positioner away from other electric apparatus as
far as possible, and separate its wiring from the others.
