Page 11 of 16
M-GDA-4350 V12 Rev 1.1
6. Calibration:
Sensors are issued tested & pre-calibrated under controlled lab conditions. Changes to
humidity, temperature, and other environmental factors affect the sensor accuracy and may
need a re-set of the fresh air zero point when introduced to new environments.
The GDA 4350 is an auto calibrating device and under most cases will auto calibrate to new
environment over time.
Functional testing may be carried out with a suitable test gas to ensure that the 4-20mA o/p
corresponds with the gas level. This should be undertaken when the unit is fully assembled
and using a flow rate of ~0.5L/min of the target gas. Test gas and equipment are available
from Gas Detection Australia.
6.1.
Fresh air Zero point Calibration:
A manual fresh air zeroing (span) of the sensor can be performed when the sensor has been
powered for a minimum of one hour. The fresh air zero can be performed when the sensor is
in a known fresh air. The sensor must be in the fresh air conditions for a minimum of five
minutes or until the output has reached a stable point.
To perform a manual fresh air zero (span) point calibration:
1. Remove the GDA 4350 from the wall to access the back of the sensor unit;
2. Add a jumper to pins 1 and 3 of
P3
see picture below, This enters Manual Calibration
Mode (see table for LED sequence);
3. Press and hold the
SPAN/ Fresh Air Zero
calibration button
S1
for 1 to 2 seconds
(see table for LED sequence):
If the Fresh Air Zero was successful (see table for LED sequence)
If the Fresh Air Zero was
NOT
successful (see table for LED sequence). Repeat step 3
after ensuring that the sensor is in fresh air and stable.
Note: Do not press the ZERO button as it will perform a Nitrogen zero.
4. When successfully zeroed remove the Manual Calibration jumper from header
P3
and
return to normal operation.
Mode
LED Light Sequence
Manual CAL Mode
Solid while jumper in Manual
CAL position
Performing Zero
0.5 sec
Alternate blinking at once per
second for ~ 4 sec
Zero Successful
0.1 sec
Fast blink for ~ 2 sec
Zero Failed
Solid for > 2 sec
Table 4: Calibration LED sequence
