User Manual

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.
Ty
pe 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 c
r
ystal 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
agre
e
ment between theory and measurement during liquid immersion experiments. Polished crystals are
also required to obtain
measurements reproducibility from crystal to crystal
2
.
Non-polished c
r
ystals (R
a
=1.8 microns) are also available at reduced costs for applications that do not
require the accura
c
y 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, Titani
u
m, etc. INFICON also offers Gold electrode crystals with an additional SiO2 outer layer to
create a
h
ydrophilic surface needed for some biological applications.
Pag
e
8