Secondary Moisture measurements are ones that measure a property of the variable (moisture) rather than the variable directly. All continuous moisture analyzers utilize secondary measurement principles and must be calibrated against a primary reference technique. They have the advantage of continuous or rapid sampling measurement and may be used for real-time process monitoring and control.

Without continuous measurement capability, a typical process would be controlled by taking product samples and performing laboratory analysis. These methods are time consuming. By the time a result is obtained, the process may well have changed substantially.

In its simplest form, a continuous moisture analyzer will provide trend information between laboratory sampling, even if left uncalibrated. In this form the instrument is a useful set point controller, where the process set point may be adjusted after each laboratory sample.

There are numerous online moisture measurement techniques.  Dielectric Measurement and Near InfraRed Reflectance are two that have proven to be accurate and reliable in many industries.