Particulate Systems HPVA Series, Руководство оператора, Страница: 103 / 124

Mar 2011 B-1
B. Performing a Cryogenic Analysis
Description
This appendix contains instructions for performing an analysis with the optional Cryogenic Kit, avail-
able from Particulate Systems.
Due to helium interaction with samples at cryogenic temperatures, it is difficult to find the true analy-
sis free space of the sample tube with the sample present. Therefore, we recommend that you first find
the ambient and analysis free space volumes of the empty sample tube to be used in the analysis. After
you perform the free space routine, you can then put the sample into the sample tube and prepare it for
analysis. The HPVA software allows you to enter the ambient and analysis free space values previ-
ously found prior to the adsorption/desorption routine.
When the volumetric calculations are performed by the HPVA Excel macro, the mass and density of
the sample are used to find the sample’s physical volume. This volume is subtracted from the ambient
and analysis free space values originally entered into the HPVA software. This corrects the blank sam-
ple tube free space values for the volume of the sample and provides accurate volumes to be used for
the isotherm calculations.
When the HPVA is performing an experiment or being operated in
manual control mode, the valve switches on the front panel should be
placed and remain in the closed (down) position.
If a switch is placed in the opened position during a software
operation, it will override the software and may damage the
instrument.