Teledyne MD300 Operating/Service Instructions Manual page 19

Portable Oxygen Monitor
connect to a supply of pure dry oxygen flowing at 1-2 liters
per minute.
5. Wait about 20 seconds to insure the sample line is completely
purged with the calibration gas. Press the CAL key. The
LCD will count down from 9 to 0. During this time the
microprocessor is measuring the sensor output to determine
the gas concentration and selects the calibration range i.e.
100% or 20.9%. When the calibration is complete the LCD
will display the gas value. Press the LOCK/UNLOCK key to
save the calibration data.
Note: The AD300 and MD300 can only be calibrated using 100%
oxygen or room air 20.9%. Improper calibration or use of
other gas concentrations will activate the
indicator. To repeat the calibration press the
LOCK/UNLOCK key and press the CAL key.
6. Remove the sensor from the oxygen supply and confirm the
LCD reads less than 22% in room air. It is not necessary for
it to read exactly 20.9%.
7. It is important to perform the calibration carefully and
thoroughly, using calibration gases that are free from
contaminates. Wait for a stable reading before locking in
calibration point. The accuracy of the instrument is only as
good as the procedure used to calibrate it.
Note: A single point air calibration is not recommended unless
the sensor can be exposed to a known source of fresh
outdoor air. Confined areas such as rooms where high
concentrations of oxygen are released may be enriched
with excess oxygen, which will introduce errors into the
calibration. Air calibration should only be used for
monitoring oxygen levels between 21% and 40% and
should never be used where a high degree of accuracy
is needed.
CAUTION: DO NOT ADJUST THE CALIBRATION SETTINGS IN
AIR AFTER THE 100% CALIBRATION, AS THIS WILL
CANCEL THE MORE ACCURATE 100%
CALIBRATION. THE 100% CALIBRATION MAY BE
REPEATED AS MANY TIMES AS DESIRED.
Teledyne Analytical Instruments
Operation
SENSOR
19