Sartorius LMA316PA Betriebsanleitung Seite 29

WLM6009-a10081
6. Calibration
A one-off calibration must be carried out for each product for which moisture or density is to be
measured.
The measurement procedure is an indirect procedure. It returns a value which is set by means of
the calibration process in relation to actual values which have to be determined in a laboratory
analysis.
6.1 What must be taken into account when calibrating
Condition of samples
The samples which are used for calibration should be in the same condition as when measure-
ment takes place.
Calibration samples should cover the entire moisture range for which measurements will be taken
later. It is an advantage if the moisture value of some samples is outside the later measuring
range.
Make sure the samples are equally moist at all points.
Possible calibration mistakes
The moisture range and ambient conditions for the calibration must be the same as the conditions
for the subsequent measurement process.
The temperature of the samples during the calibration should be as similar as possible to their
temperature during the subsequent measurement process. Temperature compensation is not
required if temperatures differ by no more than +/- 5°C.
In the case of deviations greater than 5°C, the temperature must be measured and taken into
account.
Make sure that there is no water condensation on the sensor. If necessary, wipe the sensor with
a dry cloth.
When working with a measuring beaker, make sure that the beaker is not moist on the outside.
Do not work with wet hands. Always entirely fill the sensor or measuring beaker.
Information on determining reference values
Calibration measurements using the LMA3xxPA / PMD3xxPA must be carried out with exactly
the same samples as were used for determining the reference moisture by means of a direct lab-
oratory method.
The material moisture of the samples must not change between the calibration measurement and
the determination of the moisture values in the laboratory, i.e. the comparative measurement
should be carried out in real time (as promptly as possible).
This is particularly important in the following cases:
– If the temperature of the sample is higher than the ambient temperature
– If hygroscopic substances are being analyzed
– If the substances being analyzed emit moisture
Hot samples must cool down in moisture-impermeable closed containers before the reference
measurement is taken.
Number of calibration points
Five calibration points with different degrees of moisture are usually required.
Two points are sufficient provided that the following prerequisites apply:
LMA316PA / LMA321PA
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