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CHAPTER 6
Calibration
Gas Sensors
TSI
®
recommends testing the accuracy of gas sensor measurements
each time the instrument is used. This is a common practice within
the gas measurement community which includes IAQ consultants
and industrial hygienists. Due to the nature of the sensors along with
other environmental factors such as altitude, temperature, and
relative humidity, the zero value and sensor sensitivity can shift over
time requiring you to perform a field calibration.
Gas Sensor Verification
Verifying the accuracy and
performance of a sensor can easily
be accomplished in the field by
comparing it to certified ZERO and
SPAN calibration gases (also
referred to as a “Bump Test”). To
do this, attach a calibration cap to
a bottle of the recommended
ZERO gas and place the cap onto
the gas sensor being checked. If
the probe reads a number outside
of the sensor accuracy after the
measurement has stabilized, the
sensor has drifted and needs to be
recalibrated. Perform the same
procedure with the recommended
SPAN gas to check the sensor
measurement against the certified
SPAN bottle concentration and
determine if a user calibration is
necessary. See Table 1 for recommended ZERO and SPAN gases.
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