MoTeC PLM - Manual (Page 20)

20 Sensor Calibration
Calculate from O2 Concentration (Free Air)
This calibration method uses the known oxygen concentration of free air to
calibrate a sensor. Re-calibration using this method allows a sensor to maintain
accuracy as it ages.
To perform the free air calibration, the PLM must be powered up and connected
to a PC (with a serial cable) running the PLM Setup software. The configuration
in the PLM must match the sensor type being used for the calibration. Free air
calibration must be done in the open air – not in a workshop or dyno room
where there will be large amounts of hydrocarbons in the atmosphere.
The O2 Concentration parameter specifies the actual % concentration of
Oxygen in the atmosphere and should be entered if known. A nominal value of
20.94% is given, but the more accurately this is known for current atmospheric
conditions (temperature, pressure) the more accurate the calibration will be.
To start the calibration process, click the ‘Calibrate’ button. The following dialog
is displayed while the sensor readings stabilize.
When the sensor reading is stable the calibration can be stored by clicking the
Store button, as shown below.
The new calibration value is displayed as both a gain factor and an equivalent
resistor calibration. This calibration can be recorded against the sensor serial
number to allow the sensor to be used with another PLM unit by simply entering
the calibration value.