Owner's Manual

GDX-350 Sensor Transmitter
30 P/N: 5600-9001 Rev 2
Follow these GDX-350 calibration guidelines:
• Calibration accuracy is only as good as the calibration gas accuracy. Bacharach, Inc.
recommends calibration gases with NIST (National Institute of Standards and Technology)
traceable accuracy to increase the validity of the calibration.
• Do not use a gas cylinder beyond its expiration date.
• Calibrate a new sensor before use.
• Allow the sensor to stabilize before starting calibration (approximately 5 minutes).
• Calibrate on a regular basis. (Bacharach, Inc. recommends once every 3 months, depending on
use and sensor exposure to poisons and contaminants.)
• Calibrate only in a clean atmosphere, which is free of background gas.
Use the following step-by-step procedure to perform ZERO and SPAN calibrations.
The flow chart in Figure 4-2 illustrates the following procedure. UP, CAL, NEXT and EDIT labels indicate
keystrokes using the magnetic wand. The CAL MODE information screen (located on the top of the
chart) is available for advanced users to see Offset/Gain calibration constants and live analog to digital
converter (A/D) counts. Span Gas calibration values may also be edited from this screen. Holding the
UP key for 5 seconds during CAL MODE displays this screen.
Calibration history records are logged and may be viewed in the Sensor Information menu (see Section
5.6 on page 39).
Step
ZERO and SPAN Calibrations
1.
To enter the CAL MODE from either of the data displays, press the DOWN/CAL key and within 5
seconds press the EDIT key.
2.
Using the Cal-Cup, apply a clean ZERO gas or be sure there is no background target gas in the
monitored area. After the reading is stable, (approximately 1 minute) press the EDIT key to
perform a ZERO calibration.
3.
If the ZERO calibration is successful, press the NEXT key to proceed to the SPAN check. Once
ZERO CAL is successful, the unit automatically proceeds to SPAN CHECK. If NEXT is pressed
now, it will exit the CAL routine. However, if NEXT is pressed when first in CAL, it will skip
ZERO CAL and go to SPAN CHECK.
4.
Apply the correct SPAN gas at 0.5 liters/min. After the reading is stable (approximately 1
minute), press the EDIT key to perform a SPAN calibration.
WARNING: The SPAN gas used must match the value specified since this is
what the GDX-350 will indicate after a successful SPAN calibration. The Cal Span
Value may be edited if it becomes necessary to apply a different gas concentration
(see Cal Span Value in Section 5.3 on page 35).
5.
Once the SPAN calibration is successful, the display flashes “REMOVE CAL GAS” and starts
the CAL PURGE delay.
6.
CAL MODE will be complete after the end of the CAL PURGE delay.