Conductivity - Moisture measurement
Measurement of how a specific material conducts electricity.
Can measure the capacitance,conductance or resistance of a material.
Water is a poor conductor.
The change of how a material reacts to electricity can be used to quantify the amount of water.
Benefits of conductivity moisture measurement
easy to use
Limitations of Conductivity moisture measurement
Blind to changes in the chemical makeup of a solution.
High maintenance:frequent replacement
Detection limit of 30-40% of water content.
Inaccurate measurement for samples with 4-6% of moisture
Difference in sample density and temperature affect measurement
Microwave - Moisture measurement
Measurement of microwave energy.
Water is an excellent absorber in the microwave region.
Water absorption can be used to directly quantify water concentration.
Benefits of Microwave moisture measurement
Able to detect moisture at the surface and core of the product
Precise measurement within a small area.
sensors can be installed directly on the production line.
Limitations of Microwave moisture measurement
Needs dryer to operate
Mostly for conveyor belt,not during the process
Not applicable for liquids
Dependent on electrical permitivity of analyte
Can be limited by temperature
Analyzing time is greater than milliseconds
Optical methods - Moisture measurement
Optical analysis methods measure the emitted,absorbed/transmitted or reflected light from a sample.
Photometry - Measures the overall magnitude of the light intensity.
Spectroscopy - Spatially disperses the different wavelengths of light and and measures the intensity of the light at the discrete wavelength.
Benefits of Photometry
Smaller number of calibration
Non destructive to the sample
Tuned for a specific application
can be used for solids,liquids and powders
easy to use
Cost can be lower than a spectrometer
Limitations of Photometry
They will not work for other applications that require different wavelengths unless modified.
For applications only where chemistry does not change over time.
Only 2-3 parameters can be measured.
Need to be initially calibrated for analyte of interest.
Benefits of Spectroscopy
Monitor reaction process in real-time.
Acquisition cost has come down to photometer levels with new technology offering.
Extremely low cost of ownership.
Can be used for solids,liquids and powders.
Can be used for more complex chemistries.
More measurement parameters can be added with software.
Non-destructive to the sample.
Measures in millisecond.
Enhanced spectral processing.
Built in chemometric modelling on latest technologies
Easy to use
Limitations of Spectroscopy
Instrument choice dependent on chemistry.
Needs to be initially calibrated for analyte of interest.