DH Instruments FPG8601, Руководство по эксплуатации и обслуживанию

Страница: 75 / 166

6. FPG TOOLS
Page 63 © 2007 DH Instruments, a Fluke Company
ICON DESCRIPTION
[Internal
Calibration]
Activates the internal calibration process that is used to correct the slope of the FPG by
comparing the current output of the load cell with the output of a known mass. The
relative error between the readings is used to determine a new calibration factor for the
FPG. Refer to Section 5.3 for details on the internal calibration process.
The results of the internal calibration display with the option to: activate the new
calibration, log the calibration information to the calibration log file print the calibration or
simply to cancel.
An internal calibration must be executed every time the pressure measurement mode is
changed. Failure to do so will result in an FPG span error.
The internal calibration process can automatically be performed with each system zero
if the <Auto run internal calibration > option is selected (see Section 6.6.2.1 ).
[Purge System]
Activates the purge sequence to hasten the process of obtaining stable conditions within
the lubricating volume. Purging is frequently required when changing measurement mode
and after initial FPG startup. The FPG lubricating volume is cycled in pressure a number
of times until the change in relative humidity inside the load cell reduces to a value within
the factory limit.
[Read ATM]
Press this button to force an atmospheric measurement. Internal valves are actuated to
expose the internal pressure transducer to atmosphere until a stable value is obtained.
The valves are then actuated to expose the transducer to the lubricating volume pressure
for normal operation. Error associated to typical changes in atmosphere are not
significant while error associated to changes in lubrication pressure can be significant (see
Section 2.7).
During normal operation, atmosphere is refreshed when gauge mode is set and at
intervals based on the <ATM/Lube Switch Delay> (see Section 6.6.4.1), which is typically
set to about 15 minutes. As a result, the display of atmosphere on the
<Diagnostics
Display>
is not a real time update. If a faulty reading is ever made, the error would
persist for several minutes. Use this function to update the value.
[Open Bypass
Valve]
Opens the FPG bypass valve. This function effectively, isolates the high and low ports of
the FPG. Before a manual pressure can be set, this feature must be used to allow a
differential pressure on the FPG piston-cylinder.
The icon on the toolbar does not represent the current state of the bypass valve.
Instead, the icon represents the action the function will carry out.
[Close the
Bypass Valve]
Closes the FPG bypass valve. Use this icon to manually return to a zero condition. In
absolute mode, the leak of lubrication pressure through the bypass to the reference port
induces a differential pressure. To view 0 differential pressure in absolute mode the
vacuum reference must also be shut off by deactivating valve 9 (see Section 5.2.1).
[Open Control
Reference]
Activates the FPG control reference valve 11 (see Figure 13). When the VLPC is
activated, this feature is disabled and control of the valve is based on the active VLPC
range. When zeroing the FPG, the valve is automatically closed for the duration of the
zero and opened if the valve was activated at the beginning of the zero.
[Close Control
Reference]
Deactivates the FPG control reference valve 11. When the VLPC is activated, this feature
is disabled and control of the valve is based on the active VLPC range.
[Raise Internal
Calibration Mass]
Removes the internal calibration mass from the measuring mechanism of the load cell.
The process takes approximately 10s. During this time, the FPG pressure is not valid.
This function is available in advanced user level only (see Section 6.10).