7
GG-NH3
Operation
Start-Up
Sensor can be response tested and/or span calibrated
immediately after power up. Allow 60 seconds for
power up time delay of sensor to end (green power
LED will flash during power up).
Start-Up test:
1) One person exposes each sensor to calibration gas.
2) The second person stays at the control panel to
determine that each sensor, when exposed to the
gas, is connected to the proper input and responds,
causing appropriate alarm functions.
LED Functions
(see
Figure 2
on page 8)
Calibration
The GG-NH3 sensor comes factory calibrated and
should require only minimal adjustment after
installation. There are two pots on the preamp that
are used for calibration (see
Figure 2
).
Note:
Never measure sensor output in mA. Always
use mVDC or VDC voltmeter settings.
Zero Calibration:
After the sensor is installed and has
been powered up for a minimum of 8 hours, the unit
can be zero calibrated by the following:
• Be sure the unit is in clean air.
• Adjust the zero pot until the sensor outputs 40 mV
from Test [-] to Test [+] (see
Figure 2
).
Note:
To
zero the sensor immediately after power up or cell
replacement, unplug cell from the transmitter and
adjust signal to 40 mV.
Span Calibration
: DO NOT ADJUST THE SPAN POT
WITHOUT CERTIFIED CALIBRATION GAS! If span
adjustment is required, use the following procedure:
•
To enter calibration mode (disables all filtering and
averaging), turn the Zero pot clockwise 1/4 turn and
then back again. Successful entry into calibration
mode will be indicated by the Power (green) LED
blinking twice per second. Calibration mode will
time out automatically after 4 minutes.
• Apply span gas at 0.5 to 0.8 L/min (span gas must
be in air, not nitrogen or other carrier).
• Sensor should react to gas within 15 seconds.
• Once the output signal has peaked (or 2 minutes
maximum) adjust the Span pot until the correct
output is achieved (see Figure 2). With full-scale
span gas, the calculated span value is 200 mV.
((span gas / sensor range * 16 + 4) (
mA output)
)
Note: Below are a few response characteristics which
may be an indication that the gas sensor is at or near
the end of its useful life. If any of these characteristics
are observed, the cell should be replaced.
• Slow response to / recovery from calibration gas.
• Failure of the output to reach 50% of the calibration
gas value prior to span adjustment.
• Unable to achieve correct output during span.
• Output at 0.5 mA due to SafeCell test failure.
