9. APPENDIX
© 2007 DH Instruments, a Fluke Company
Page 187
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9.1
GLOSSARY
Absolute
As in absolute pressure. Pressure expressed relative to vacuum.
Accumulation
A single GFS flow measurement that is accomplished by measuring the change in mass and time at
one flow rate.
GFS Tools
PC-based software program used as the interface to the GFS2102 system.
Sample
A Depending upon the flow rate and a setting that requires a fixed amount of mass to change to get
meaningful data, of all the measurements read from the balance and time stamped by the LCM during
and accumulation, less frequent updates or
samples
of these measurements of mass and time are
selected for use by GFS Tools.
Average Flow
A simple average of discrete flow values at the defined sample interval since the beginning of an
accumulation.
Best Fit Flow
The best fit flow as determined by calculating a real time best fit at the defined sample rate since the
beginning of an accumulation, with the fit forced through zero.
AMH (AMH-GFS2102)
Automated mass handler; specialized platform for vertical actuation of the reference gas cylinder and
reference mass on and off the balance mass tray, especially for AutoZero function.
DUT
Device under test; the item being tested or calibrated by GFS, often a molbloc.
FS (Full Scale)
The full scale value is the maximum value or the span of a measurement range. Limits and
specifications are often expressed as % FS.
Condensation
Drops of water that form on a surface (like the reference gas cylinder while flowing) when the surface
temperature drops below the dew point of the surrounding air.
Gauge
As in gauge pressure. Pressure expressed relative to atmospheric pressure.
Dew point
The temperature at which air cannot hold all of the moisture in it and condensation begins to form.
Reference Mass
The nominally 2.0 kg calibrated mass ring supported by a plate of the AMH-GFS2102 that is used for
the AutoZero and balance span functions.
LCM
Laboratory conditions monitor. LCM is a stand-alone device that is the central data collection
component of GFS2102.
MFC-CB
MFC control box. MFC-CB is a GFS system component used for sending analog flow set point
signals to mass flow controllers, and possibly for reading DUT analog output.
MFC
Mass flow controller. Used for setting stable flows in the GFS system.
Gravimetric
Relating to or using the measurement of weight. The principle used for GFS flow measurements.
Reference Gas
Cylinder
The cylinder that is weighed by the GFS balance as gas in flowing out of it through the other system
components.
TH probe
Temperature and humidity probes used to measure the conditions of the air surrounding the reference
gas cylinder assembly.
Catenary
The natural curve adopted by a length of cable, rope, or chain of uniform density, hanging between two
points; the shape used for the flow conveyance loop between the reference gas cylinder and the GFS
draft enclosure.
IR (Infrared)
Radiation of wavelength just longer than visible light. IR sensors can be used to measure a surface
temperature.
PRT
Platinum Resistance Thermometer. The element used to measure temperature inside the AMH-
GFS2102 platform near the balance.
Air buoyancy
The upward force on a body which much be compensated for in mass measurements, related to
the density and volume of air displaced by the body.