RKI Instruments Digester Gas Monitor - Manual (Page 72)

66 • Viewing Maximum Spans Digester Gas Monitor Operator’s Manual
9. Repeat step 8 for each selected channel. When the last selected channel’s calibration
gas concentration has been accepted, the Digester Gas Monitor will begin to draw
sample through the Calibration Gas Fitting. The two screens shown below will
alternate.
10. Connect the tubing from the demand flow regulator to the Calibration Gas Fitting.
NOTE: Verify that the calibration gas cylinder contains enough sample by checking the
regulator gauge.
11. If necessary, adjust the flow rates as described in “Adjusting the Flow Rates” on
page 33.
12. Allow the Digester to draw calibration gas for 1 minute.
13. Press and release the ENTER button. For methane, oxygen, and carbon dioxide
channels, the solenoids will click and the flow to the sensors will be stopped for 15
seconds to allow for a stabilization period. The hydrogen sulfide channel does not
need a stabilization period.
14. The Digester Gas Monitor will perform a gas adjustment on the channels and indicate
GAS ADJUST PASSED for each channel. If the gas adjustment was not successful
for any channel, the display will indicate GAS ADJUST FAILED for that channel. The
Digester Gas Monitor will then return to the Select Operation screen.
15. Disconnect the tubing from the Calibration Gas Fitting.
16. Unscrew the demand flow regulator from the calibration cylinder.
17. Repeat step 1 through step 16 for the other detector(s) you wish to calibrate.
18. Use the UP/YES and DOWN/NO buttons to scroll to EXIT CAL MENU. Press and
release the ENTER button to exit Calibration Mode and return to Standby Mode.
19. Initiate a manual cycle and set the flow rates as described in “Adjusting the Flow
Rates” on page 33.
NOTE: Be sure to set the sample flow rate after exiting Calibration Mode. If the sample
flow rate is not set, the H
2
S dilution ratio will not be correct.
Viewing Maximum Spans
This operation allows you to see how much gas response adjustment remains after a
calibration is performed. This is a useful gauge for whether or not a sensor is nearing the
end of its life. When you enter the VIEW MAX SPANS screen, the Digester Gas Monitor
displays the maximum possible adjustment that the Digester Gas Monitor could have
made to the response reading with the calibration gas that was used for the most recent
successful calibration. So if a 0 - 100 %LEL channel is calibrated using 50 %LEL gas and
the maximum indicated span in the VIEW MAX SPANS screen is 95 %LEL, this means
that there was enough adjustment left on that channel to set the reading to 95 %LEL when
Apply CAL GAS
To Gas Detectors
- > ENTER when Done
- > ESCAPE to Abort 1: METHANE 49 %VOL
2: OXYGEN 12.0 %VOL
3: CO2 15.3 %VOL