GASMAX ECx Instruction Manual
Revision 1.1
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In addition, alarm levels, Measurement Name ASCII fields and other variables may require
attention by users in order to best serve their application.
4.2.1 Initial Toxic / Oxygen Monitor “Span” Check
Prior to the initial
Routine Sensor Calibration
described in section 5.1, a coarse SPAN gas
reading verification should be performed after installation. Apply an upscale gas value of at least
25% of full scale to the sensor. For example, if 0-100ppm H2S is the measurement range, apply
at least 25ppm but not more than 100ppm. The indicated value should read within 15% of full
scale. Remember, this is only a coarse check and precision calibrations are performed in
Routine Sensor Calibrations
described in the following section 5.1. Section 7.4 describes
PREAMP GAIN adjustments that may be required if full-scale ranges are changed.
SECTION 5 – OPERATING INSTRUCTIONS
5.1
CAL MODE - Routine Sensor Calibration
Calibration is the most important function for insuring correct gas readings at the GM ECx. The
CAL MODE (flow chart shown in Figure 5-2) is designed to make calibration quick, easy and error
free. A successful ZERO and SPAN calibration requires only four keystrokes. The wireless 10-
bit output indicates CAL MODE by transmitting 75 counts. It then transmits 200 counts during the
subsequent CAL PURGE delay to prevent external alarms during calibration. CAL MODE
automatically exits if no keystrokes are detected after 5 minutes.
The GM ECx wireless 10-bit output range is 200 to 1000 counts for 0 to 100% of full scale. The
GM ECx indicates CAL MODE by transmitting 75 counts (-15.6% FS) to receivers on the network.
Toxic gas ranges transmits 200 counts (0% FS) during the subsequent CAL PURGE delay to
prevent external alarms during calibration. NOTE: To prevent activating A1 & A2 low trip alarms
at the controller, oxygen ranges transmit 884 counts (20.9% oxygen reading) upon entry into CAL
PURGE. CAL MODE automatically exits if no keystrokes are detected after 5 minutes.
Follow these GM ECX calibration guidelines:
•
Calibration accuracy is only as good as the calibration gas accuracy. GDS Corp
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 schedule. (GDS Corp 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.