8Head - Fluke MOLBOX RFM Operation And Maintenance Manual

molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
OPERATION
To access the MANUAL MICRORANGE function, press [SPECIAL] and select <7micro>.
The display is:
If the manual microrange option is not installed, this menu will not appear. An <Option
not installed> message appears in its place.
Select <1off> or <2on>. Operation returns to the run screen with the manual microrange in
the condition specified.
Turning the microrange option OFF may reduce the accuracy of flow measurements under
10 % of the flow measurement range and may lead to unexpected results.
Manual microrange option ON is indicated by <d> (option ON, using microrange
differential RPT) or <a> flashing (option ON, not currently using microrange differential
RPT) in the microrange option designator character of the main run screen (top line,
th
6 character from the right). Manual microrange option OFF is indicated by a blank
designator or the <m> that indicates automatic microrange ON.
Turning ON or OFF manual microrange by pressing [SPECIAL] and selecting <7micro>
overrides the current setting of automatic microrange (see Section 3.4.7).
3.6.8 <8HEAD>
PURPOSE
To cause a pressure fluid head correction to be added or subtracted to the pressure
measured by the molbox RFM reference pressure transducers in order to predict the
pressure at height the height of the molbloc when the molbloc is at a level other than the
molbox RFM's reference level.
PRINCIPLE
molbox RFM measures absolute and differential pressure in molbloc flow elements. The
molbox RFM reference pressure transducers (RPTs) are calibrated with the height of the rear
panel pressure quick connectors as the pressure reference level.
performing a calibration or test, the molbloc is at a different height than the molbox RFM's
pressure reference level. This difference in height, frequently called head, can cause a
significant difference between the pressure measured by the molbox RFM at its reference
level and the pressure actually present at the molbloc at a different height. In this case, it is
useful to make a head correction to the pressure measured by the molbox RFM in order to
predict the pressure actually applied at a different height.
molbox RFM can calculate head pressures for all the gases it supports (see Section 3.4.2),
over its working pressure range. The HEAD function allows the difference in height between
the molbox RFM and the molbloc to be specified and causes the resulting head pressure to
be added to the pressure measured at the molbox RFM rear panel quick connectors.
[SPECIAL], <8head>, is used to specify the height difference between the molbox RFM rear
panel quick connectors and another height. Entering a height of zero turns the function off.
© 1998-2007 DH Instruments, a Fluke Company
Manual microrange:
1off 2on
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