Different types of Moisture measurement Instruments

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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
Inexpensive
Low power
easy to use
Portable

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
Low power
easy to use
Portable
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
Low power
Easy to use
Portable

Limitations of Spectroscopy
Instrument choice dependent on chemistry.
Needs to be initially calibrated for analyte of interest.