Model 81I; Figure 1-1. Model 80I Flow Diagram - Thermo Scientific Mercury Freedom 80i Manual

Introduction

Model 81i

Model 81i
1-2 Mercury System Manual
Figure 1–1. Model 80i Flow Diagram
Either the Total or Elemental sample is introduced into the fluorescence
chamber, where UV light from a high energy Hg line source lamp excites
the Hg atoms. The UV light is directed to the fluorescence chamber by a
rejection mirror/beam splitter combination. A reference detector monitors
the lamp intensity by viewing the transmitted light from the beam splitter.
As the excited Hg atoms decay back to the ground energy state, they emit
UV light that is proportional to the Hg concentration. The Hg
fluorescence is monitored by a solar blind photomultiplier tube (PMT)
placed at a right angle to the exciting radiation. The PMT detects the UV
light emission from the decaying Hg atoms.
Calibration gas from the Hg calibrator (Model 81i) is plumbed to the zero
air and cal gas bulkheads on the rear panel of the Model 80i. The zero or
span gas is routed through an internal critical orifice, through either the
NO or NC port of Solenoid S4, through the NC port of Solenoid S3 and
into the fluorescence chamber. During this time, both Total and Elemental
Hg samples bypass the chamber and are sent to the external pump exhaust.
The Model 80i outputs the Total Hg or Elemental Hg concentration to
the front panel display, the analog outputs, and also makes the data
available over the serial or Ethernet connection.
The Model 81i Mercury (Hg) Calibrator generates known concentrations
of gas phase elemental Hg by combining the output flow of a temperature
controlled, saturated Hg vapor source with a flow of Hg-free dilution air or
nitrogen. The Model 81i is normally configured as one component of an
integrated Hg Continuous Emission Monitoring System (CEMS). The
Thermo Scientific Mercury Freedom ™ System is comprised of a Hg
analyzer (Model 80i), a Hg calibrator (Model 81i), a Hg probe controller
Thermo Fisher Scientific