Several methods for producing multiple known concentrations are available to use, such as connecting
multiple certified gas cylinders at different concentrations. However, Ecotech strongly recommends
the use of a dilution calibrator and a certified cylinder of CO at an appropriate concentration.
1. Connect your calibration system to the Calibration Port of the instrument (Ecotech recommends
the Serinus Cal 1000 as a minimum, refer to Figure 111).
2. Generate and record the displayed span concentrations for (at least) six stepped points (of known
concentrations) evenly spaced across the instruments measurement range (refer to the example
below).
3. Then using a program such as MS Excel, create an X Y scatter plot of expected concentration versus
the recorded instrument response and use linear regression to calculate the line of best fit and the
correlation factor (R
2
) – refer to the users local applicable standards.
Example for an instrument measurement range of 75 ppm:
a. For the 1st concentration, set the gas dilution calibrator to supply 60 ppm CO gas to the
instrument.
b. Allow the instrument to sample the calibration gas until a prolonged stable response is
achieved (the amount of time this takes is impacted by the calibration setup). Record the
instrument response.
c. Repeat the above steps using concentrations of 50 ppm, 30 ppm, 20 ppm, 10 ppm and a Zero
point.
Note: To highlight hysteresis errors, it is advisable to run the multipoint check in both descending
and ascending order - refer to applicable local standards.
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