Intrinsic Safe Barrier Assembly - Wayne Dresser Vista 1 Series Service Manual

3.5. FAULT REPORTING, continued
3.6.

INTRINSIC SAFE BARRIER ASSEMBLY

The Intrinsic Safe Barrier (ISB) assembly is located in the electronic head of the dispenser.
Its function is to ensure that the amount of electrical energy introduced into the hydraulics
cabinet is within acceptable limits. This barrier uses resistors, fuses, transistors and zener
diodes to limit energy out of the barrier. In the dispensing cycle, when the operating lever
is lifted, the nozzle switch moves to the closed position. This causes the nozzle signal on
the computer base to go from a +5 VDC potential to zero or ground potential, which alerts
the microprocessor to begin a new sale if the dispenser has been authorized and the push-
to-start, cash/credit or grade select switch has been pressed. In addition to the nozzle switch
circuits, the pulser selects are also protected by the ISB assembly.
The ISB circuit board
limiting redundant (2 in parallel) zener diodes which will limit voltage potential to approx-
imately 6.2 VDC. This energy limiting circuit eliminates the possibility of arcs in the
hydraulic area of the dispenser.
The ISB assembly is a sealed assembly and must be repaired at the factory. The ISB circuit
board in the assembly is not replaceable in the field. The complete assembly shown in
Figure 3-6. must be replaced if the ISB board becomes inoperative. See Section 7 for
replacement procedures.
22
Part No. 920160 Rev A
NNNNN.S Sale Money
PF.20.BB Sale Volume
NNNNN: Transaction Counter
S: Side 1 or 2
P: Product Source (0-7)
F: Fault Source (0-7, "H" or "L")
20: Fault Code 20 (Jitter pulse logging error)
BB: Maximum jitter count allowed
see Figure 3-6. contains current limiting resistors and voltage
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February 1997