PROGRAMMING & CALIBRATION
3-4
Diffusion Instruments
Q-RAE Plus diffusion monitors must be calibrated using a fixed
flow regulator with a flow rate between 0.5 and 1.0 liters per
minute. Diffusion monitors are supplied with a special
calibration adapter that covers the gas diffusion port.
Sensor Calibration Time
Slowly responding sensors listed in Table 2 may require pre-
exposure of the sensor to the gas immediately before initiating
the calibration sequence. Some firmware versions use a fixed
60-second calibration time; some newer versions automatically
apply the full calibration time. After completing the zero
calibration, expose the unit to the gas for the pre-exposure time
listed in Table 2 if a 60-second countdown time is programmed
in the unit.
If the firmware has the full calibration time programmed in, the
sensors must be calibrated in the Single Sensor mode to take
advantage of this feature. The calibration time is set at 60
seconds in the Multiple Sensor mode and may not be changed.
3.2.1. Zero (Fresh Air) Calibration
This procedure determines the zero point of the sensor
calibration curve. Expose the inlet to a clean air source with
20.9% oxygen and without any organic, toxic or combustible
gas impurities. This “Zero Air” can be from a cylinder, clean
ambient air, or ambient air purified through a charcoal filter.
Initiate “Fresh Air Calibration?” using the keystrokes in Table 5.
When the zero calibration is successful, the display should
show a reading of “20.9” for the oxygen sensor and “0.0,” or a
very small number, for all other sensors.
3.2.2. Multiple Sensor Calibration
This function simultaneously determines the second point of
the calibration curve for multiple sensors in the monitor. For
slowly responding sensors, preapply the gas for the times
shown in Table 2. Initiate Multiple Sensor Calibration according
