DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
Page 27
© 1998-2003 DH Instruments, Inc .
these are the temperature and absolute pressure of the gas that will flow through
the DUT when it is used in the field (this is NOT measured the gas temperature
and pressure during the calibration). If you know the normal operating conditions
that were used for the DUT’s previous calibration, these conditions should be
entered for this calibration to be compared to the previous calibration. If you don’t
know or if you want to change the DUT’s normal operating conditions, enter the
desired normal operating conditions for the DUT and the new calibration will be
valid for the DUT when used under those conditions.
5.1.8.2 TEST DEFINITION SETUP
Generally, when running this type of DUT, the DUT output is adjusted to the DUT
cardinal point at each flow increment. When using an
<Other Controller> as the
flow control method, use the <Jog Before Dwell> feature on the Test Definition
[Control] tab to allow this (see Section 9.5.6).
There is nothing out of the ordinary about setting up a test for this example (see Section 9).
5.1.8.3 TEST HARDWARE SETUP
The flow meter installation should be made following the manufacturer’s recommendations.
The gas pressure and temperature should be measured as close to the DUT as possible.
To correct for the effects of changes in gas density at different flow conditions, the gas
temperature and pressure at the DUT must be known during the test. This information
must be manually entered into
COMPASS if it can’t be obtained electronically.
The setup of manual entry of pressure and temperature is a two part process.
The
[Setup], [System], [Pressure Measurement] and [Temperature Measurement]
should both read <Manual> when manual entry is to be used (see Section 10.2).
Use the [Tools] , [Options] , [Run Test] tab to specify whether temperature and
pressure will be entered at the “first point”, “each point” or by “use default value”
(see Section 11.6).
To set up automatic pressure and temperature measurement first create the
Hardware Definitions of the measuring devices using the
[Setup], [Hardware],
[Temperature] and/or [Pressure] tabs (see Section 10.3.4). Next they must be
selected for use by COMPASS using the [Setup], [System], [Temperature]
and/or [Pressure] pull-down menus (see Section 10.2).
5.1.8.4 SET UP DATA GRID
To display appropriate data in the Data Grid during the test, use the [Tools], [Options],
[Grid] tab (see Section 6.7.5) and select the appropriate column headings. For tests
using gas density corrections, the proper reference flow value to use is “Ref Q DUT Cond”
(reference flow at DUT conditions). It is the adjusted reference flow value after
making corrections for the effect of density changes on the DUT. This is the value
of the flow that would be going through the DUT if it were currently at its normal
operating conditions. In other words, this is the flow value that would produce the
current DUT output, if the DUT were at its normal operating conditions.