DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
Page 25
© 1998-2003 DH Instruments, Inc .
5.1.6.3 RUN THE TEST
Use [Run] , [Run Test] to start the test sequence (see Section 7.2).
5.1.6.4 PLOT THE DATA
Once the test is complete, you can use the Plot options to product a plot of either
Reference flow or DUT output versus point number (see Section 12.4).
5.1.7 EXAMPLE #7
“How do I set up to use COMPASS to compare molbox/molbloc flow to that of a piston
prover or bell prover?”
The flow output of the molbloc can be connected to the input of a piston prover or bell prover and then
their flow indications can be compared. This example assumes that the prover’s flow indication
is in mass flow units (such as kg/sec), or volumetrically based mass flow units (such as sccm).
This implies that the prover accessories include density correction hardware and software.
Volume or actual flow units (such as accm or cf are NIT mass flow units. When running this type
of test take extra care to assure that the plumbing used for interconnection is leak-free, and that
the inlet pressure to the molbloc is within its calibration limits.
5.1.7.1 DUT DEFINITION SETUP
Select the [Setup], [DUT], [Header] tab, and select the DUT’s process gas (see Section 8.5.2).
In this type of comparison the calibration gas should be the same as the process gas.
Piston provers and/or bell provers do not usually have gas conversion or “K” factors.
Select the [Setup], [DUT], [Correction] tab, and ensure that “None” has been
selected for the Gas Density Correction Type (see Section 8.5.3).
Select the [Setup], [DUT], [Range] tab, and select or create the DUT’s Flow Range
and Output Range units (these will be in units of mass flow such as sccm, slm,
kg/sec, etc.). Enter the DUT’s Flow Range and Output Range (see Section 8.5.4).
Select the [Setup], [DUT], [Test] tab, and select the calibration gas (see Section 8.5.6).
5.1.7.2 TEST DEFINITION SETUP
Select [Setup], [Test], [Sequence] tab, and enter the test sequence parameters.
Set the Stability time and Dwell time to 0 seconds, and Averaging Time to manual,
this will allow you to control and ensure that the prover is within its test stroke
while the molbox is reading and averaging data (see Section 9.5.4).
Figure 12. Example 7, Test Setup