Instruction Manual

Instruction Manual Supplement

D103261X012

DVC6000/DVC6200 Digital Valve Controllers

February 2011

Figure 5. Lock‐in‐Last on Loss of Loop Current and/or Supply Pressure for an Assembly with a Single‐Acting Actuator

(Fisher DVC6000 Depicted)

PHOENIX

SWITCH

MCR‐2SP/UI

FISHER 67CFR

FILTER/REGULATOR

AIR

SUPPLY

SOLENOID VALVE

(ENERGIZED)

24 VDC

POWER SUPPLY

FISHER 164A

THREE‐WAY

SWITCHING VALVE

4‐20

OUTPUT

SUPPLY

DIGITAL

VALVE

CONTROLLER

NOTE:

THE ASCO 8320 SERIES SOLENOID VALVE OR EQUIVALENT IS APPROPRIATE FOR THIS ASSEMBLY.

Upon loss of loop current, the relay of the current threshold switch opens. This cuts power to the solenoid valve,

causing the solenoid valve to trip. When the solenoid valve trips, the supply pressure that was holding the switching

valve open is exhausted to atmosphere. This simulates a loss of supply pressure, causing the switching valve to trip.

Note

Use a single power source for both the analog output (AO) card providing loop current to the digital valve controller and the

solenoid valve. This ensures power will be maintained to the solenoid valve so long as power is maintained to the AO card.

Assemblies with Double‐Acting Actuators

The same principle used for assemblies with single‐acting actuators is used for assemblies with double‐acting

actuators. Figure 6 is a schematic of the double‐acting assembly with lock‐in‐last capability shown under normal

operating conditions.