Teledyne T100 Instruction Manual page 172

Calibration Procedures
6.1.1.2. SPAN GAS
IMPORTANT
6.1.1.3. CALIBRATION GAS STANDARDS AND TRACEABILITY
172
Devices such as the API Model 701 zero air generator that condition ambient air by
drying and removal of pollutants are available. We recommend this type of device for
generating zero air.
Span gas is specifically mixed to match the chemical composition of the gas being
measured at about 80% of the desired full measurement range. For example, if the
measurement range is 500 ppb, the span gas should have an SO
400 ppb.
Span gases should be certified to a specific accuracy to ensure accurate calibration of the
analyzer. Typical gas accuracy for SO
in nitrogen.
Teledyne ML offers an IZS option operating with permeation devices. The accuracy of
these devices is about ±5%. Whereas this may be sufficient for quick, daily calibration
checks, we strongly recommend using certified SO
Applications requiring US-EPA equivalency do not allow permeation devices to be used
as sources of span gas for calibration of the analyzer.
All equipment used to produce calibration gases should be verified against standards of
the National Institute for Standards and Technology (NIST). To ensure NIST
traceability, we recommend acquiring cylinders of working gas that are certified to be
traceable to NIST Standard Reference Materials (SRM). These are available from a variety
of commercial sources.
Table 6-1: NIST-SRM's Available for Traceability of SO
4
NIST-SRM
1693a
1694a
1661a
Teledyne ML - T100 UV Fluorescence SO2 Analyzer
gases is 1 or 2 %. SO
2
2
TYPE
Sulfur dioxide in N
2
Sulfur dioxide in N
2
Sulfur dioxide in N
2
concentration of about
2
standards should be mixed
2
span gases for accurate calibration.
Calibration Gases
2
NOMINAL
CONCENTRATION
50 ppm
100 ppm
500 ppm