Thermo Electron 48C, Instruction Manual

Page: 110 / 204

Chapter 4 Calibration
4-8
HI AND LO MULTI-POINT CALIBRATION
The Model 48C CO Analyzer can be calibrated using a dual three-point calibration. The
calibration points are divided into a “low” range and a “high” range consisting of three
points each Cal Point 1, Cal Point 2, and Cal Point 3. The customer decides the ranges
and TEI recommends calibrations points of 80% (Cal Point 1), 50% (Cal Point 2), and
20% (Cal Point 3) of the range selected.
To use the Multi-Point calibration program dipswitch 8 must be in the on position and a
zero adjust needs to have been done (see page 4-4).
The equipment used, pre-calibration and Calibration-Connect Instrument are the same for
the Multi-Point calibration as they are for a standard calibration (see pages 4-1 to 4-4).
Default Coefficients
NOTE: If performing a Multi-Point calibration after changing ranges or a “bad”
calibration it is recommended to start off with default values for the Cal point
coefficients.
To set default values from the “Main Menu” select “Service Mode”. From “Service
Mode” select “Hi Multi-Point Cal” or “Lo Multi-Point Cal”. From “Hi or Lo Multi-Point
Cal” select Default Coef”. Press
ENTER
. The analyzer will automatically reset the default
values.
Cal Point 1, 2, and 3 Adjust
1. Adjust the zero air flow and the CO flow from the standard CO cylinder to provide a
diluted CO concentration of approximately 80% of the upper range limit (URL) of the
analyzer. The total air flow must exceed the total demand of the analyzer connected to
the output manifold to ensure that no ambient air is pulled into the manifold vent. The
exact CO concentration is calculated from:
)
F
+
F
(
)
F
x
]
[CO (
= ] [CO
CO D
CO
STD
OUT