Teledyne 335 - Analog control room monitor for personnel safety - Manual (Page 15)

3-3 TELEDYNE ANALYTICAL INSTRUMENTS
Oxygen Alarm Monitor Installation and Operation 3
The CAUTION and DANGER alarms are equipped with separate
relays. Each of these relays provides a single set of contacts rated for 2A
resistive load @ 28VDC or 2A @ 120VAC.
A 0-1VDC signal output is available as an option that must be specified
at the time of purchase. If you have chosen this option, the Oxygen Monitor
will generate a 0-1VDC signal as output to represent the 0-25% oxygen
range. This output signal is linear and proportional to the oxygen concentra-
tion within the 0-25% range. The output signal is available to the user from
a terminal block inside the enclosure. (See the Interconnection Diagram
included with the drawings at the rear of this document.)
3.3 Calibration
Prior to operating this instrument for the first time, the Oxygen Monitor
must be calibrated. If this instrument is to be used as a safety monitor,
routine calibration should be carried out on a weekly basis.
Calibration of a standard instrument is performed by exposing the
sensor to ordinary ambient air (not the monitored atmosphere) and adjusting
the “CALIBRATE” control until the meter pointer rests at the CAL mark on
its scale. This mark represents the normal oxygen concentration of air
(20.9%) under standard conditions, so be sure that the sensor is exposed to
fresh air when using the calibration mark.
If it is not feasible to use ordinary air as the calibration gas, then clean,
compressed instrument air can be used. It will probably be necessary to seal
the sensor in the piped-in calibration gas to isolate it from the surrounding
atmosphere. A flow-through adaptor can be purchased from TAI as an
accessory for those applications. Although a special calibration gas can be
used, the calibration results will be meaningless unless the oxygen concentra-
tion of the calibration gas is known, and the analyzer is adjusted to indicate
that concentration. To eliminate any error caused by the calibration gas,
always use a certified composition with an oxygen concentration between
80% and 90% of the full scale meter reading of the analyzer.
Calibration in the same atmosphere that is being monitored can
result in serious error. The analysis performed and the alarms, if
any, generated by this instrument when calibrated using the moni-
tored atmosphere or a span gas of unknown composition, will be
meaningless.
3.4 Operation
Once the instrument has been installed, calibrated, and the power turned
on, it will continuously monitor the oxygen level within the environment it is
NOTE: