DH Instruments COMPASS FOR MOLBOX, Руководство пользователя

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COMPASS

for molbox™ User’s Manual
© 1998-2003 DH Instruments, Inc .
Page 22
5.1.4.4 RUN THE TEST
Now that the COMPASS System Configuration includes the hardware necessary
to run the test, use [Run] , [Run Test] to start a test sequence. COMPASS calculates
two (2) flow data fields that are associated with the rotameter test. The field that
contains the flow that is generated using the measured gas pressure and temperature
and the Square Root Density Correction is called “Ref Q DUT Cond”. This is the
flow rate that is in the DUT’s units and corrected to what the Reference flow would be
at the DUT’s normal operating conditions. The other flow value that
COMPASS
calculates is the “Ref Q”. This is the Reference flow displayed in the DUT’s flow units,
without any type of gas density correction. “Ref Q DUT Cond” should always be
used as the actual flow through the DUT and in evaluating its performance.
The data field “DUT Q” is the calculated value of flow derived by scaling the
DUT Output Range to the DUT Flow Range. It is calculated at each point
assuming a linear output. This is the value that is used to calculate percent
errors, either as a percent full-scale or of reading.
5.1.5 EXAMPLE #5
“How do I set up to calibrate a DUT that outputs volume or actual flow units such as
ccm, cfh, or accm, acfh?
Volume or actual flow units of measure are NOT mass flow units. Very few flow
measurements are made in these units even though the unit used may refer to volume
(there are important differences between volume or actual units and volumetrically based
mass flow units such as sccm). Before using volume or actual flow units, be absolutely
sure that this is, in fact, what you want. See the [Unit] Section of the molbox Operation
and Maintenance Manual for complete information on different flow unit types.
COMPASS “axxxx” units correspond to volume or actual flow units in molbox.
Measuring actual or volume flow requires the actual pressure and temperature of the gas at the
DUT to be known when a test is run. Current gas pressure and temperature data is indispensable
to the determination of flow in volumetric or “actual” flow units.
COMPASS supports different ways
of acquiring gas pressure and temperature data including automatic data acquisition and manual entry.
5.1.5.1 DUT DEFINITION SETUP
Select the [Setup], [DUT], [Header] tab, and specify the DUT’s process gas
(see Section 8.5.2).
Select the [Setup], [DUT], [Range] tab, and select or create the DUT’s Flow Range
units (these will be in units of flow such as accm, or acfh) and enter its Flow Range
(see Section 8.5.4). Enter the DUT’s Output Range units, and enter its Output Range.