35-3001A-10 Oxygen/Carbon Monoxide Sample-Draw Detector • 25
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a calibration
frequency of every 3 months is adequate for most sample draw detector applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends a
calibration frequency of every 3 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment, and calibration adjustments are minimal at calibration, then a calibration frequency of
every 6 months is adequate.
If an application is very demanding, for example if the environment is not well controlled, then more
frequent calibration than every 3 months may be necessary.
Calibration, Oxygen Sensor
This section describes how to calibrate the oxygen sensor in the sample-draw detector. It includes
procedures to prepare for calibration, set the fresh air reading, set the zero reading, and return to
normal operation.
NOTE:
Calibrating the sample draw detector may cause alarms. Be sure to put the controller into its
calibration program or disable external alarms before continuing.
NOTE:
This procedure describes calibration using a demand flow regulator.
Preparing for Calibration
NOTE:
If you can verify a fresh air environment, it is not necessary to use a zero air calibrating
sample to set the fresh air reading at the controller.
1. Follow the instructions in the controller’s operator’s manual for entering calibration mode.
2. Screw the regulator into the zero air calibration cylinder.
3. Open the housing door.
4. Set a voltmeter to measure in the millivolt (mV) range and plug the leads into the oxygen
amplifier.
Plug the positive lead into the red (+) amplifier test point; plug the negative lead into the black (-)
amplifier test point.
Setting the Fresh Air Reading
1. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet
fitting.
This step is not necessary if you verified a fresh air environment earlier in this
procedure.
2. Allow the sample draw detector to draw sample for one minute.
3. Verify a voltmeter reading of 434 mV (± 2 mV).
