Thermo Fisher Scientific
Model 48
i
Instruction Manual
4-1
Chapter 4
Calibration
This chapter describes the procedures for performing a standard zero/span
calibration and a multipoint calibration of the Model 48
i
. The information
described here is more than adequate to perform the calibration. However,
if greater detail is needed, please refer to the
Quality Assurance Handbook for
Air Pollution Measurement Systems
1
.
The following sections discuss the required apparatus and procedure for
calibrating the instrument.
The following equipment is required to calibrate the instrument:
A cylinder of CO in air containing an appropriate concentration of CO
suitable for the selected operating range of the analyzer under calibration is
necessary. The assay of the cylinder must be traceable either to a National
Institute of Standards and Technology (NIST) CO in Air Standard
Reference Material (SRM) or an NIST/EPA approved gas manufacturer's
Certified Reference Material (CRM).
A recommended protocol for certifying CO gas cylinders against a CO,
SRM or CRM is given in the
Quality Assurance Handbook
1
. The CO gas
cylinder should be recertified on a regular basis determined by the local
quality control program.
Calibration requires zero air that is free of contaminants which will cause a
detectable response on the CO analyzer. The zero air should contain <0.01
ppm CO. Since the Model 48
i
is virtually interference free, it is only
necessary to ensure that CO has been removed.
It should be noted that zero air as supplied in cylinders from commercial
suppliers typically contains CO concentrations in the 0.1-0.3 ppm range.
So cylinder zero air should be scrubbed of the residual CO prior to its use
in the Model 48
i
as a dilution gas or a zero standard. Room air which has
been scrubbed of CO can also be used as the zero air source.
It is not necessary to remove SO
2
, NO, NO
2
, CO
2
, water vapor, or
hydrocarbons, since the Model 48
i
does not respond to these molecules. If
Equipment Required
CO Concentration
Standard
Zero Air Generator
