INFICON CHC-15 Crystal Holders GC-15 Glass Cell - Manual (Page 16)

CHC-15 CRYSTAL HOLDER & GC-15 GLASS CELL
The figure below shows a INFICON 1” diameter as seen from the front side.
Figure 6. 1" Crystal - as Seen From The Front Side
2.2.2 CRYSTAL PARAMETERS
Polished one-inch diameter crystals that are commonly available for liquid work have the typical values
as listed below.
Type Frequency
Range (MHz)
Electrode
Material
Resistance
(ohms)
Q Factor
5 MHz 4.976 – 5.020 Gold ~10 120,000
9 MHz 8.976 – 9.036 Gold ~7 55,000
2.2.3 CRYSTAL SURFACE FINISH
Studies have shown that electrode surface roughness can cause large apparent mass loadings due to the
liquid that is trapped within pores at the crystal surface 1 . INFICON’s crystals are optically polished to 50
Å average surface roughness to minimize this effect. Polished crystals are required to obtain good
agreement between theory and measurement during liquid immersion experiments. Polished crystals are
also required to obtain measurements reproducibility from crystal to crystal 2 .
Non-polished crystals (R
a
=1.8 microns) are also available at reduced costs for applications that do not
require the accuracy and reproducibility of the polished crystals.
2.2.4 CRYSTAL ELECTRODE MATERIALS
INFICON’s crystals are available in a variety of electrode materials including Gold, Platinum, Aluminum,
Silver, Titanium, etc. INFICON also offers Gold electrode crystals with an additional SiO2 outer layer to
create a hydrophilic surface needed for some biological applications.
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