GDS-68XP Operation & Maintenance Manual, Revision 3.4
Page 28
7
CALIBRATION
CALIBRATION OVERVIEW
Calibration is critically important to ensure correct operation of the GDS-68XP. The GASMAX CX built-in
CAL MODE function is designed to make calibration quick, easy and error free; a successful ZERO and
SPAN calibration requires only four keystrokes.
It is important to note that a
GASMAX calibration should only be performed during Purge/Hold mode
.
During each sample sequence, the GDS-68XP sequencer checks for a number of different error conditions,
including overrange, sensor fault, sample peak identification fault, and sensor non-return-to-zero. Since
the sequencer expects a valid output from the GASMAX at all times, if the GASMAX CX is placed in CAL
MODE at any time during the sample sequence, a CAL ERROR is generated. Always check to be sure that
the L2 (GREEN) indicator LED is flashing before performing a GASMAX calibration procedure.
Calibration can be performed in one of three ways. If certified calibration gas is available, the
Cal Port
Sample
calibration technique is the fastest and most convenient method. If a three-way valve is installed
in the sample stream inlet, the
Inlet Port Sample
calibration technique is preferred, as the calibration gas
passes through the filter, regulator, control valve, flow switch and flame arrestors, more closely
simulating the path taken by the actual sample gas. Finally, if calibration gas is not available, but the
stream contains a known amount of target gas, the
Stream
Sample
calibration technique is available.
In all cases, the GDS-68XP should be calibrated at least once every three months. Furthermore, during the
initial six months of operation, the GDS-68XP should be checked more often to verify that the sensor is
operating properly and that some component of the sample gas mixture has not damaged the sensor or
change the sensor’s response to the target gas compound.
IMPORTANT:
FOR MAXIMUM ACCURACY, USE CALIBRATION GAS WITH A CONCENTRATION VALUE THAT
IS GREATER THAN 25% OF FULL SCALE AND LESS THAN 75% OF FULL SCALE.
Before beginning calibration, make sure you have the following items: A cylinder of calibration gas, fixed
flow regulator and a length of flexible tubing.