PROGRAMMING & CALIBRATION
3-5
to Table 5 and then apply a source of mixed standard reference
gases*. The display will count down from 60 to 0 seconds, and
then show the name of each sensor, the message “cal’ed!” and
the calibrated value for each gas. The readings should be very
close to the span gas values.
To select other sensors to calibrate, press
[N/-]
after entering
Multiple Sensor Calibration. The display shows all the sensors
selected for multiple sensor calibration with the cursor blinking
at the first sensor location. Press
[Y/+]
or
[N/-]
to select or de-
select a sensor as indicated by an asterisk “*”.
CO* - - - -
H
2
S*
LEL* pick
OXY
Note:
Oxygen span calibration is normally done during fresh
air zero, so oxygen is not selected in this multi-gas calibration.
See Single Gas Calibration to calibrate the oxygen sensor.
*
Cross Sensitivity:
some sensors show cross sensitivity to
other gases; therefore, it is important to choose the gas mixture
carefully to avoid erroneous calibration due to cross sensitivity.
For example, H
2
and some organic gases are known to cause
a response on the CO sensor, and H
2
S responds on the NH
3
sensor.
3.2.3. Single Sensor Calibration
This procedure determines the second point of the sensor
calibration curve for a single sensor. Enter Single Sensor
Calibration according to Table 5 and press
[MODE]
to select
the desired sensor. Preapply the gas for the times shown in
Table 2 (if necessary) and press
[Y/+]
to initiate calibration.
Oxygen Sensor Calibration
The O
2
sensor allows 2-point or 3-point calibration type. The 3-
point calibration gives greater accuracy for oxygen near 19.5%,
a common alarm limit for warning of oxygen depletion. First set
this type in Section 3.2.6. Span calibration at 20.9% O
2
is
