Moisture Measurement - Sensing Application
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 | | The moisture measurement sensing
requirement is often the need to detect levels of moisture in a particular
material without being able to contact it to permit control of a drying
process. | |
Measuring moisture content allows control of the drying process such that
drying is carried out until a specific level of moisture content is achieved
rather than for a fixed time period.
Standard domestic tumble dryers have for many years simply used timers to
set the duration of their drying cycle. Drying time and energy requirement can
vary considerably depending on ambient air humidity, the dampness of the
clothes to be dried and the temperature of drying. Using "one time fits all" in
anything other than ideal conditions, is likely to result in either a waste of
energy or clothes that have not been thoroughly dried.
In industry, moisture content of a material can effect it's ability to
successfully be processed by some subsequent task. Fine drying control may be
required to maintain quality of production as well as control the costs
involved.
Capacitive sensing is very suitable for economic moisture measurement, water
has a high dielectric value and is consequently easily detectable with
capacitive techniques having as it does a significant effect on electric
fields.
Required conditions for the application of capacitive sensing for moisture
content measurement include a significant difference between the carrier
material completely dry and 100% waterlogged. The type size, mass and density
of the carrier material will have a bearing on this.
Examples:
- High speed high temperature extrusions: Sensatech have produced sensors for
continual in process moisture measurement of an extruded material passing the
sensor at high speed and in a high temperature environment. In this application
the moisture content of the material had a significant correlation with the
quality of the end product as it significantly affected the results from
subsequent processes.
- Soil moisture measurement: for irrigation control.
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