DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
© 1998-2003 DH Instruments, Inc .
Page 208
Jog Adjust flow slightly at a flow point prior to taking DUT and reference readings at the
point. Jog is most often used when testing visual output devices such as rotameters to
set the flow so that the DUT indication is on the nominal flow point prior to taking data
at the point.
COMPASS Test Definitions allows “jog before dwell” to be included in the
test procedure.
K Factor
A factor representing the relationship between the process gas and a surrogate gas for
a DUT. Also called gas conversion factor. See the molbox Operation and Maintenance
Manual,
[K] Section, for additional information.
Leak Check A process in which a pressure is set in the test system and then allowed to evolve
freely for 60 seconds. The decay rate of the pressure over time is used as an
indication of the leak present in the system.
COMPASS Test Definitions can include a
leak test at the start of the test. See the molbox Operation and Maintenance Manual,
Leak Test Section.
Manual Flow
Control Indicates, in a Test Definition, that the flow will not be controlled in response to remote
commands sent by COMPASS. When running a test, COMPASS will therefore prompt
the user to set the flow at each point.
Mass Flow Flow measured in terms of quantity of gas per quantity of time. Nearly all flow
measurements, including volumetrically based flow units such as “sccm”, are mass
flow measurements. See also “volume flow” and “actual flow”. See the molbox
Operation and Maintenance Manual,
[Unit] Section, for an extensive discussion of flow
units of measure.
Microrange An optional molbox RFM feature which improves flow measurement resolution and
accuracy under 10 % of FS of the molbloc. Includes a low differential RPT and valve to
put the RPT into and out of service.
Normal DUT
Operating
Conditions; Normal
Operating Pressure
and Temperature The gas pressure and temperature conditions under which a DUT is normally operated.
The conditions for which it is calibrated. Normal Operating Conditions must be
specified in DUT Definitions that include a gas density correction.
Perfect Mass Flow
Units Volumetrically based mass flow units of measure that assume ideal gas behavior for all
gases (compressibility factor of 1). See the molbox Operation and Maintenance
Manual,
[Unit] Section, for an extensive discussion of flow units of measure.
Process Gas The gas for which a device under test is to be characterized or calibrated. The gas that
will actually flow in the device under test when it is used in a process.
Purge A procedure used to assure that the “old” gas species has been completed removed
from the test system when a “new” gas species is being flowed. Purge can be included
in
COMPASS test definitions at the start of a test and/or when a molbloc has been
changed. See the molbox Operation and Maintenance Manual, Purge Section.
Ready/Not Ready Indication from a molbox of when flow is stable within the stability limit and below the
flow Reynolds number limit. A Ready condition is required in a test sequence for the
test to continue and readings to be taken. See also
Stability Limit . See the molbox
Operation and Maintenance Manual, Ready/Not Ready Section.
Reference, Flow The device that will be used by COMPASS as the source of reference flow values
when running a test; the flow standard in the test, the value of flow measured by the
reference flow device.
Return to Start Execute the flow point sequence in reverse order.
RPT Reference Pressure Transducer. The pressure transducers used in molbox1 and
molbox RFM are referred to as RPTs.
Span
The difference between the minimum and the maximum DUT input or output.
Often referred to as full scale but more meaningful than full scale for DUTs whose
minimum flow or output is not zero.
Stability Rate of change of flow in flow unit/second.