162 Appendix D
Calibrating Sensors
EVM Series User Manual
An accurate flow meter (i.e., bubble-flow meter) and tubing is required to perform
this calibration. The tubing and flow meter are connected to the back outlet or in
the turret.
An accurate temperature sensing instrument (i.e., thermometer) is required to
perform this calibration. The instrument is then placed in the location where you
will log and the calibration is conducted. *NOTE: when calibrating temperature,
ensure the unit is not charging by unplugging the external power cord before
proceeding.
An accurate temperature sensing instrument (i.e., psychrometer) is required to
perform this calibration. The instrument is then placed in the location where you
will log and the calibration is conducted. *NOTE: when calibrating relative
humidity, ensure the unit is not charging by unplugging the external power cord
before proceeding.
**NOTE: before performing a user calibration, ensure that your calibration is performed in an area known not to contain
hazardous or interfering gases if ambient air will be used as the zero gas for operation. If this is not possible, pure bottled air
(Nitrogen is recommended) should be substituted.
About Zero Calibration: A Zero calibration is advised each time you log a session to adjust for drift in the sensor’s sensitivity
which occurs over time and after use.
About Span Calibration: A span calibration proceeds a zero calibration and is used to set the linear measuring range. The
span should be a sizeable fraction of the selected full scale range of the gas.
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