6. FPG TOOLS
Page 79
© 2007 DH Instruments, a Fluke Company
Figure 36. <Internal Limits> <Humidity>
Table 23. <Internal Limits> <Humidity>
Options
LABEL
DESCRIPTION
Display a
warning if the
%RH changes by
(numeric entry field)
The maximum change in load cell humidity since the last system tare.
Large changes in humidity can be caused by the lack of water in the
bubbling system.
Minimum %RH
value
(numeric entry field)
The minimum operating humidity. Using the FPG when the load cell
environment has a humidity less than this value can lead to invalid
measurements. The effect of humidity on the load cell dramatically
increases when humidity is small, < 40 %. In this condition, a small change
in humidity will have a large change on the load cell output.
If the minimum humidity cannot be obtained, make sure the bubbling system
contains water and that all pressure connections are secure and correct.
Maximum %RH
value
(numeric entry field)
The maximum operating humidity. Using the FPG under high humidity
conditions can lead to unnecessary wear on internal system valves.
Typically, purging reduces the humidity within the necessary limits.
6.6.4.5
<MASS>
All limits related to the load cell output are defined on this tab. Specifically, the
stability criterion and limits on the internal calibration process. Since the internal
calibration process affects the actual slope of the FPG (see Section 5.3), take
special care when adjusting these parameters. When an internal calibration is
run manually, any limit related failure generates an error message specific to
the problem.
Internal calibrations run during automatic test sequences are not activated
when any of the internal calibration limits are exceeded. Make sure the limits
entered are reasonable for the test conditions.
