Specifications

3. OPERATION
Page 61 © 1998-2007 DH Instruments, a Fluke Company
3.4.6 [DISPLAY]
 PURPOSE
To select, from a variety of choices, the information that is displayed in the molbox RFM main
run display.
 PRINCIPLE
molbox RFM supports a variety of ADVANCED FLOW MEASUREMENT functions that are
generally displayed on the second (bottom) line of the molbox RFM display. In summary, the
available DISPLAY functions included are:
RATE: Calculates and displays the current rate of change of flow in current flow
units/second (see Section
3.4.6.1). This function is a useful indication of
the
stability of the flow being measured. It is often used as a “go/no go” criterion
for when to take data when comparing molbox RFM and a DUT (e.g., in a
calibration).
AVERAGE: Calculates the average flow measurement over a user specified period of time
and displays the average, the standard deviation about the mean and a
countdown in seconds to the next average (see Section
3.4.6.2). This function
is often used to filter out flow noise in an unstable system or to gather a
corresponding sample when comparing molbloc/molbox
measurements to
another device with a long integration time (e.g., a volumetric flow standard).
The magnitude of the noise is quantified by the standard deviation about the
mean. A second screen allows the instantaneous flow values to be viewed
during an averaging cycle.
HI/LO: Records and displays the maximum and minimum flows measured since HI/LO
reset (see Section
3.4.6.3). This function is used to keep track of the minimum
and maximum
flow observed over a period of time or to monitor whether a flow
min/max limit has been exceeded.
TOTAL: Totalizes the mass or volume flowed over a period of time (see Section
3.4.6.4). Used to measure total mass or volume over
a period of time. Can be
useful in calibrating or verifying a totalizing flow device, when comparing
molbloc/molbox to a gravimetric standard or to add or remove a specific
quantity of mass or volume to/from a system.
UNIT: Displays the measurement of flow through the molbloc simultaneously in a
second flow unit (see Section
3.4.6.5). This function is convenient when
working with an unfamiliar flow unit of measure
to simultaneously display a
familiar unit or any time a real time flow unit conversion is desired.
DEVIATION: Continuously calculates and displays the deviation, in % of reading, between
the current flow measured by molbox RFM and a target flow defined by the
user (see Section
3.4.6.6). This function is useful in quickly calculating
the
error of a DUT’s measurement or control, or the evolution of flow around and/or
away from a desired set point.
FREEZE: Captures and displays the instantaneous flow value measured by molbox RFM
when the [ENTER] key is pressed (see Section 3.4.6.7). This function is useful
to record the flow present at the time of an operator observed trigger event.
CLEAN: Blanks out the second line of the display (see Section 3.4.6.8). This function is
used when a simple display of
flow measured by the molbox RFM, without
additional information, is desired.