Model 2280A
19
shows prompts associated with the calibration procedure. During Calibration Check
Mode, the digital display shows the gas concentration as a flashing digit, or pair of digits.
When a channel enters into a fault condition a 0mA signal is generated by this output.
During a fault, the display shows a fault code.
If the sensor attached to the channel is seeing gas in excess of 100% of full-scale, the
output generates a signal between 20 and 21.7mA (not proportional).
3.5 Calibration Preparation Instructions
Before a full calibration or calibration check is begun, ensure the sensor assembly is
seeing “clean air”. If the atmosphere at the sensor contains a low background of H
2
S
observe the following procedure:
1. Obtain a GMI field calibrator plastic bottle (P/N 50000). Assure that it contains no H
2
S
by flushing it with clean air. Place your hand or a cover over the bottle’s open end
and take it to the sensor.
2. Place the bottle over the sensor.
3. Wait a few minutes for the sensor to become permeated with clean air.
4. Remove the sensor from the bottle.
After each use of the field calibrator bottle, clear the bottle of residual H
2
S gas by flushing
it with clean air.
3.5.1 Gas Application Options
3.5.1.1 Breaker Bottles and Ampoules
General Monitors offers ampoules with breaker bottles as a method of reliably introducing
calibration gas to the Model 2280A. The ampoule is placed inside the breaker bottle into
the breaker slot, and the breaker bottle is placed over the sensor. The ampoule should
contain 50% full-scale of H
2
S of the sensor range. For example, 100 ppm full-scale is a
50 ppm ampoule. Check the date code on the ampoule to make sure the expiration date
has not passed. Follow the calibration procedure below in Sections 3.6 and 3.7.
To apply gas using Breaker Bottles and Ampoules:
1. Remove cap and flush breaker bottle with fresh air.
2. Insert one ampoule into the ampoule holder. Replace the cap.
3. Place cap over the sensor and rotate bottle for a tight fit.
4. Turn knob clockwise until ampoule breaks.
5. Allow the sensor to see the gas for 1 to 2 minutes.
3.5.1.2 Portable Purge Calibrator
An alternate method for introducing calibration or test gas to the Model 2280A is
available. The H
2
S Portable Purge Calibrator is a compact, practical, accurate and safe