Hach-Lange FP 360 sc Basic User Manual - Manual (Page 14)

English 14
The measurement conditions can change in terms of
•
Composition of PAH or oil impurities
• Distribution of impurities in water
• Temp
• Measuring medium composition
• Measurement sensor and measurement window
Determination of factors and adjustment of slope
To adjust the slope:
1.
At the sensor installation site, draw a lab sample of the measuring
medium and promptly analyze the sample for PAH and oil content.
2. Make a note of the measurement value shown on the controller at
the time of the sample being taken. Make sure the correct unit is
shown for the measurement value, e.g. as ppm oil.
3. Repeat steps 1 and 2 several times.
4. Use the sample value and the value shown on the controller at the
time of sampling to calculate a factor.
5. Find an average value from the factors.
6. Enter the factor as the slope (refer to Adjust the slope (FACTOR)
on page 15 ).
It is advisable to adjust the slope if the following conditions apply:
•
If the measuring sample is PAH-/oil free, the measurement value
must almost be zero.
• The factors calculated from the lab values must enable a sensible
average value to be derived.
If these conditions do not apply, do a multi-point calibration.
Note: If both the zero point and the slope must be changed, use a 2-point
calibration (refer to
Multi-point calibration (2 to 5-point calibration) on
page 15 ).
Multi-point calibration
In the event of a multi-point calibration, enter the lab value as the target
value and the value shown as the actual value. Make sure that all values
are entered in the same unit, e.g. oil in ppm. (refer to
Multi-point
calibration (2 to 5-point calibration) on page 15 ).
Check the zero point
• Medium: ultra-pure water
• Target value: < 1 ppb. Clean the window in the event of deviations.
Use a glass container (not plastic) large enough to enable the
measurement to be taken with an 8 to 10 cm distance between the
measurement window and the base (e.g. a 1000 mL glass beaker).
Place a black, non-reflective underlay under the container and switch off
artificial lights during the measurement process.
Note: In air, the measurement value displayed is not exactly zero due to
reflections on the window surface. This is standard sensor behavior and
not an indicator of malfunction.
Note: Always use ultra-pure water. Distilled water and demineralized
water are not suitable as these can contain organic compounds.
Example for engine oil Example for naphthalene
Lab value: 4.0 ppm oil
Measurement value shown
1 :
2.4 ppm oil
Calculated factor: 1.67
1 At the time of sampling
Lab value: 420 ppb PAH
Measurement value shown
1 :
120 ppb PAH
Calculated factor: 3.5