Calibrating Fdom - Xylem EXO Series User Manual

Calibration
4.4 5.9
fDOM
This procedure calibrates fDOM RFU or fDOM QSU/ppb. If the user has both units selected, then this
procedure must be performed twice, once for each unit, to completely calibrate the parameter.
For 2-point calibrations, the first standard must be clear water (0 μg/L). The second standard should be a 300
μg/L quinine sulfate solution. (For detailed instructions for mixing this solution, see section 5.10.)
A
Do not leave sensors in quinine sulfate solution for a long time. A chemical reaction occurs with the
copper on the sonde (sonde bulkhead, copper tape) that degrades the solution and causes it to drift.
QSU – 1- or 2-point
Pour the correct amount of clear deionized or distilled water into the calibration cup. Immerse the probe
end of the sonde in the water.
In the Calibrate menu, select fDOM, then select QSU/ppb. Select either a 1- or 2-point calibration. Enter 0
for first standard value and 300 μg/L for second standard value.
Click Start Calibration. Observe the readings under Current and Pending data points, and when they are Stable
(or data shows no significant change for approximately 40 seconds), click Apply to accept this calibration point.
Remove the central wiper from the EXO2 sonde before proceeding to the next step.
Next place the sensors in the correct amount of 300 μg/L quinine sulfate standard in the calibration cup. Click
Proceed on the pop-up window. Observe the readings under Current and Pending data points. While stabilizing,
click the Wipe Sensors button to activate the wiper to remove any bubbles. When data are Stable (or data shows
no significant change for approximately 40 seconds), click Apply to accept this calibration point.
Click Complete. View the Calibration Summary screen and QC score. Click Exit to return to the sensor
calibration menu, and then the back arrows to return to main Calibrate menu.
RFU – 1- or 2-point
Pour the correct amount of clear deionized or distilled water into the calibration cup. Immerse the probe
end of the sonde in the water.
In the Calibrate menu, select fDOM, then select RFU. Select either a 1- or 2-point calibration. Enter 0 for
first standard value and 100 RFU for second standard value.
Click Start Calibration. Observe the readings under Current and Pending data points, and when they are Stable
(or data shows no significant change for approximately 40 seconds), click Apply to accept this calibration point.
Remove the central wiper from the EXO2 sonde before proceeding to the next step.
Next place the sensors in the correct amount of 300 μg/L quinine sulfate standard in the calibration cup. Click
Proceed on the pop-up window. Observe the readings under Current and Pending data points. While stabilizing,
click the Wipe Sensors button to activate the wiper to remove any bubbles. When data are Stable (or data shows
no significant change for approximately 40 seconds), click Apply to accept this calibration point.
Click Complete. View the Calibration Summary screen and QC score. Click Exit to return to the sensor
calibration menu, and then the back arrows to return to main Calibrate menu.
Rinse the sonde in tap or purified water and dry the sonde. Discard the used standard.
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