CTI GG-VL2-NH3, Installation And Operation Manual

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8
GG-VL2-NH3
Span Calibration: Do not adjust the span pot
without certified calibration gas! If span adjustment is
required, use the following procedure (see Figure 3):
• Unscrew calibration port cover and connect cal gas
hose to hose barb fitting
• Press the CAL switch once to enter cal mode.
• Apply 1% NH3 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 (200 mVdc).
• Shut-off gas, remove hose and replace cover.
• Press the CAL switch to exit cal mode.
• Calibration is now complete.
Note: Allow up to an hour for the signal to return back
to 4 mA after exposure to high concentrations.
Note: If correct output during span adjustment is
unachievable, replace the sensor element. See sensor
replacement procedure on page 10 if a replacement
sensor element is needed.
Note: Gas exposures well above the 0-1% NH3 range
of the sensor can shorten the life of the sensor
element, and typically results in a "zero signal shift",
where the signal is stuck at full-scale levels. Make sure
no ammonia gas is present and simply re-zero the
sensor following the Zero Calibration procedure on
the previous page.
4mA adjustment: Sometimes a fine adjustment of the
4mA signal may be desired to compensate for a slight
positive or negative zero-signal reading on the control
panel.
• Make sure the sensor is NOT in calibration mode.
• Adjust the 4mA pot until the control panel reads
zero.