Thermo Scientific TVA-1000B Instruction Manual - Geotech ...

Instruction MI 611-183
March 1996
CENTURY ® TVA-1000 Toxic Vapor Analyzer
11.8 eV PID Lamp Capsules (Part No. CR011YZ)
IMPORTANT NOTE: This document contains essential information about
11.8 eV PID lamp capsules. PLEASE READ ENTIRE DOCUMENT BEFORE
USING AN 11.8 eV PID LAMP CAPSULE IN YOUR TVA-1000.
About 11.8 eV PID Lamps
The standard PID capsule supplied with the TVA-1000 contains a 10.6 eV lamp. This PID
lamp capsule is suitable for detection of many of the most commonly encountered hydrocarbons,
since their ionization potentials generally tend to fall below 10.6 eV. However, in cases
where you need to detect a compound with an ionization potential between 10.6 eV and
11.8 eV, the 11.8 eV PID lamp capsule is required.
NOTE: It is important that you recognize the disadvantages of using an 11.8 eV PID
lamp capsule prior to installing one in your TVA-1000.
With normal care and cleaning, a 10.6 eV PID lamp capsule should give you greater than
2000 hours of life. The 11.8 eV PID lamp capsule, however, is not so durable. Its expected life
is much shorter (often less than 100 hours) and is much more dependent on environmental
conditions and usage pattern. However, with proper care and use you can maximize the life of
your 11.8 eV PID lamp capsule and prevent premature failure.
Because of the high energy UV radiation used by the 11.8 eV PID lamp capsule, the same
magnesium fluoride material used in the 10.6 eV PID lamp capsule window is unsuitable. A
special window material (lithium fluoride) is required in 11.8 eV PID lamp capsules to allow
the short wavelength to pass through to the ionization chamber. Although lithium fluoride is
one of the few materials that will transmit 11.8 eV photons, its crystal lattice is slowly eroded
by the UV energy in a process called solarization. As the PID lamp capsule becomes solarized,
the window changes to a yellowish color and transmission of the photons is reduced dramatically.
Lithium fluoride is also a hygroscopic material, which means that it tends to absorb
moisture. Absorption of moisture due to high humidity or contact with liquid water will
severely degrade transmission, quickly reducing the usable life of the PID lamp capsule. The
use of a WATERTRAP* probe (Part No. CR013EA) is strongly recommended to prevent
ingestion of liquid water.
*Manufactured by INTEK Corporation South, Baton Rouge, LA. and A+ Corp., Prairieville, LA.