RKI Instruments GX-82 - Manual (Page 14)

10 • Calibration Model GX-82 Instruction Manual
NOTE: The combustibles measurement is flow-sensitive. If you are using a dispensing
valve on the gas cylinder instead of a regulator, use a flowmeter and set the flow
rate to 0.8 SCFH (0.4 l/m).
6. Watch the GX-82 display to verify the combustibles reading matches the
concentration of the calibrating sample. If the reading does not correspond with the
sample, slowly adjust the COMB SPAN control.
7. Expose the sensor to fresh air and verify that the combustibles reading returns to zero.
8. Repeat the exposure to the calibrating sample and verify that the combustibles
reading reaches the correct level. Repeat steps 5 through 8 until no further adjustment
is required.
NOTE: If the combustibles reading cannot be set high enough to agree with the
calibrating sample, replace the sensor.
Calibrating the oxygen channel
1. Use a calibration cup and gas cylinder to expose the oxygen sensor to a know oxygen-
free sample, such as 100% nitrogen (available from RKI).
2. Watch the display to verify that the O
2
reading decrease to 0.0. If the reading does not
reach 0.0, adjust the O
2
ZERO control.
NOTE: If the oxygen reading cannot be adjusted to 0.0, replace the oxygen sensor.
If the oxygen reading does not return to 20.9% the next time the GX-82 is turned
on, replace the oxygen sensor.
Calibrating the toxic gas channel
The H
2
S and CO circuits use the same procedure for span adjustment. Follow these steps
using the appropriate calibrating sample for the corresponding sensor.
1. Use a calibration cup and gas cylinder to expose the sensor to a calibrating gas
sample. The sample should represent the target gas at a midrange concentration. (The
RKI Calibration Kit is ideal for this application. See kit instructions for assembly and
use.)
2. Watch the display to verify the reading agrees with the concentration in the
calibrating sample. If not, adjust the corresponding control (H
2
S or CO SPAN).
NOTE: If the reading cannot be set high enough to agree with the calibrating sample,
replace the sensor.