RKI Instruments GD-K8A - Manual (Page 16)

12 • Model GD-K8A Diffusion Detector Head
Calibration
This section describes how to calibrate the GD-K8A. It includes procedures to prepare for
calibration, set the zero reading, set the response reading, and return to normal operation.
Preparing for Calibration
NOTE: This procedure describes calibration using a fixed flow regulator with an on/off
knob.
1. Put the controller into its calibration program or disable external alarms to avoid
unwanted alarms during calibration.
NOTE: If you can verify that the GD-K8A is in a fresh air environment, you do not need
to apply zero air to set the zero reading.
2. Connect the calibration kit sample tubing to the calibration adapter and to the fixed
flow regulator.
3. Open the GD-K8A’s door and attached the calibration adapter over the sensor face.
4. Use small test clips to connect a milliampmeter to the output check pins.
5. Use the following formula to determine the correct GD-K8A response output for the
calibrating sample.
Response Output (mA) = (calibrating gas/fullscale) X 16 + 4
For example, if you have a cylinder of 5 ppm calibration gas with a GD-K8A full scale
of 10 ppm:
12 mA = (5 ppm/10 ppm) X 16 + 4
Setting the Zero Reading
1. Screw the zero air calibration cylinder onto the fixed flow regulator.
2. Turn the regulator’s on/off knob counterclockwise to open it. Gas will begin to flow.
3. Allow gas to flow for two minutes and verify a milliampmeter reading of 4.0 mA. If
necessary, use the zero pot to adjust the reading to 4.0 mA.
4. Turn the regulator’s on/off knob clockwise to close it.
5. Unscrew the zero air calibration cylinder from the fixed flow regulator.
Setting the Response Reading
1. Screw the calibration gas cylinder onto the fixed flow regulator.
2. Turn the regulator’s on/off knob counterclockwise to open it. Gas will begin to flow.
3. Allow calibration gas to flow for two minutes and verify that the milliampmeter
reading matches the response reading you determined earlier. If necessary, use the
span pot to adjust the reading to match the correct response reading.
4. Turn the regulator’s on/off knob clockwise to close it.
5. Unscrew the calibration gas cylinder from the fixed flow regulator.
6. Remove the calibration adapter from the sensor face, disconnect the calibration kit
sample tubing from the regulator.