VICI 235 Dynacalibrator - Manual (Page 5)

1
Introduction
General Description
VICI Metronics Dynacalibrators ® use Dynacal ® permeation devices to generate
the precise gas concentrations necessary for calibrating air pollution analyzers,
monitors, and other instruments that measure gas concentrations in the parts-
per-million range and lower.
Dynacalibrators are available in three models, each with a large variety of
optional features to fit a wide range of calibration requirements. All critical
factors, such as permeation rates, gas flow rates, and permeation chamber
temperatures are calibrated against standards traceable to the National Institute
of Standards and Technologies.
Model 235 specifications are listed on page 3.
Dynacal Permeation Devices
Metronics Dynacal permeation devices are the simplest and most reliable
method for supplying a source of trace quantities of various gases. They can
accommodate virtually any requirement for generating low concentrations of
gases. Permeation rates from thousands of ng/min down to fractional parts of a
ng/min are possible. The devices can be supplied filled with any one of hundreds
of different compounds, both organic and inorganic.
How to Use This Manual
This manual provides installation, operation, and maintenance information for
all configurations of the Model 235. The identification tag on the rear panel of
every Dynacalibrator is stamped with the unit’s complete model number, which
reflects the exact unit configuration. A chart on the last page of the manual
explains the model numbers.
Basic Design
The Model 235 contains two mass flow controlled (MFC) systems – the carrier
system and the dilution system. The carrier gas system is typically a fixed flow
which passes through the permeation chamber containing the permeation device.
The temperature of the chamber, which controls the permeation rate of the
calibration gas from the permeation device, is tightly regulated to provide both
accurate and precise results. The chamber temperature is adjusted from 30°C (or
2°C above ambient, whichever is higher) to 110°C. The carrier stream mixes with
the calibration gas in the chamber and is then fed forward to the mixing tee.
In standard models (Figure 1) the dilution gas stream is controlled and measured
by the diluent MFC, and feeds forward to the other side of the mixing tee. The
mixture of the carrier and the diluents is then fed to the distribution tee, which
allows the flow to move to the Span Out and the Overflow bulkhead connectors
for distribution.