DH Instruments FPG8601, Руководство по эксплуатации и обслуживанию

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5. SYSTEM OPERATION
Page 37 © 2007 DH Instruments, a Fluke Company
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5.1 OVERVIEW
This section describes general operation of the FPG after the system is properly set up. This includes:
all necessary pneumatic supply connections to the VLPC and FPG, control connections between the FPG
and VLPC, the connection of any DUT that may be used with the system, all instruments are powered on
and FPG Tools is in
[Run Monitor]
run mode (see Section 6.5.2). Refer to Sections 7, 8 and 10 for
information on maintenance and troubleshooting the FPG.
Always start FPG Tools with the [Run], [Run Monitor] menu option (see Section 6.5.2). This puts the
software in a mode that is very similar to a standalone instrument. The outputs of the FPG and any
connected DUT are automatically polled by the software and all toolbar functions are active. From this
state all basic operations of the FPG can be performed.
5.2 ZEROING THE FPG
The FPG should be zeroed frequently to avoid errors associated with changes in conditions and zero drift.
More specifically, always zero the FPG when: first powered on, after changing measurement mode and
warming up (see Section 6.9.2), before making a comparison with another instrument and when tare
conditions have changed beyond the factory limits (see Section 6.6.4). Because of the importance of this
function, a pneumatic bypass valve is built into the FPG to allow fully automated zeroing. To zero the
FPG, press the
[Zero System]
toolbar option (see Section 6.6.4). FPG Tools will first set a zero condition
in the FPG, wait for stability, then activate the new zero data. The active zero results are available on the
<Tare Values>
display window (see Section 6.3.3).
5.2.1 ZERO CONDITION
In gauge mode, the zero condition is reached when the bypass valve is open and all pressure
control connections to other instruments are isolated. Basically, the FPG should have the
high and low ports directly connected together with no other pressure influences. FPG Tools
automatically makes the valve adjustments as necessary when possible and vents any
controlled pressure in the VLPC.
The absolute mode zero condition is the same as the gauge condition with the addition of
deactivating the reference port vacuum isolation valve (V9). The reference port vacuum must
be isolated to prevent a bias associated with the natural differential pressure caused by flow
from the upper port through the bypass to the vacuum. The pump does not have to be turned
off while zeroing.
While zeroing the FPG in absolute mode, the FPG line pressure will increase due to the
lubricating flow. If left in this state for a prolonged amount of time, the FPG line
pressure will exceed the lubrication pressure causing a reverse pressure situation. Using
the automatic zeroing function of FPG Tools will avoid this by imposing a timeout on the
zero process. If proper zero conditions are not met, the zero process is aborted and an
error message is displayed on the status bar.