Foxcroft FX-300-F, Инструкция по эксплуатации

Страница: 30 / 45

27
5.4 2-point slope calibration procedure
We do not recommend 2-point slope field calibration for new sensor installations; for most if not all
applications the factory set slope will provide the best results.
The 2-point calibration should only be done when the sensor begins to lose response or sensitivity. The
1-point offset is the only calibration required on a regular basis.
Performing calibration with fluoride standards will not get the inline installation dialed-in. This can only
be done with a proper grab sample offset calibration.
NOTE: Always use the more stable TISAB II rather than TISAB III total ionic strength
adjusting buffer for both self prepared and premixed solutions purchased from a lab
supply company.
1.
Fill a 250 ml beaker with enough standardization solution so that the entire tip of the Fluoride
sensor will be submersed.
2.
Place the sensor into the first low ppm ISE standard solution.
3.
Allow a minimum of 3 – 5 minutes for the sensor to stabilize once it has been removed from the
process and placed into the low standard solution (low ppm).
4.
Parameter No. 01 is a “lock” that must be set to ‘Off’ to change ANY parameter, including the
temperature, offset and slope calibrations.
5.
Press the ‘Mode’ key to select ‘Offset’.
6.
Adjust the reading using the Up/Down keys until the display shows the correct value for the first
low ppm ISE solution standard.
7.
When done press the “Mode” key until the PPM (Run) mode indicator lights, indicating the run mode.
8.
Rinse the sensor in distilled or deionized water, blot dry with a paper towel and place the sensor
into the second high ppm ISE standard solution.
9.
Allow a minimum of 3 – 5 minutes for the sensor to stabilize between the low and high Calibration
Solutions (low ppm to high ppm).
10.
Press the “Mode” key to select SLOPE.
11.
Use the Up/Down keys until the display reads the second desired value for the second high ppm
ISE solution standard.
12.
Press the “Mode” key until the PPM (Run) mode indicator lights, indicating the run mode.
13.
CAUTION: When finished you must verify that your calibration has resulted in a slope (parameter
#15) that is at or near the default fluoride slope of -57.2. If it is not the calibration was not
performed correctly; either re-calibrate or re-set the transmitter back to the default slope of
negative 57.2 using parameter #15.
14.
CAUTION: Before returning the calibrated sensor into service you must perform the 1-point offset
calibration to ensure agreement with grab sample analysis.
5 Calibration