Laboratory-scale moisture analyzers use halogen or infrared heaters as part of a procedure to determine moisture content in products to ensure they are in compliance with federal or industry regulations. As with all precision analytical scales and balances accuracy is a paramount requirement for a moisture analyzer.
In the case of moisture analyzers, two calibration processes must be performed: one for weighing accuracy and one for temperature accuracy.
Why Moisture Analyzers Must be Calibrated
It takes very little in the way of disturbances to impact the accuracy of a moisture analyzer balance. For example, the effect of gravity is not the same everywhere on Earth, meaning that newly purchased analyzers must be calibrated on location before being used.
Moreover, changing environmental conditions in the laboratory or wherever moisture analyzers are used can impact accuracy, as can moving a unit to another location, even if it’s only to another worktable. The worktable should be isolated from vibration caused by moving carts across the floor and from temperature fluctuations caused by proximity to heating or air conditioning ducts.
“External calibration” is the process used to check the accuracy of Kern moisture analyzers available from Tovatech. This is performed by using the recommended adjustment weight (such as 50 g) for the particular moisture balance being tested. Calibration procedures are outlined in the operating instructions accompanying various models of moisture analyzers.
Once the unit has been tared to accommodate the weight of the sample pan the calibration weight is placed on the pan. If there is a discrepancy between the exact weight and what the moisture analyzer displays, the analyzer will automatically correct itself and the exercise is completed.
Optional temperature calibration sets are available to check the accuracy of the heaters. But before tests are conducted the moisture analyzer should be cooled for 3 hours. Following the instruction manual insert the temperature probe as close as possible to the thermal sensor. Temperature tests are conducted at two points and take longer than the weight calibration exercise. If there is a discrepancy between the temperature displayed on the probe and the analyzer instructions are provided to perform the correcting adjustment(s).
In summary, a moisture balance can only provide accurate readings if it is calibrated on a regular basis. Personnel using the moisture balance should be familiar with calibration procedures and timetables.
What procedures does your organization follow in calibrating moisture analyzers?