 Michell Instruments % RH sensors feature a
capacitive thin-film polymer sensor. These sensors provide a high accuracy,
excellent long-term stability and negligible hysterisis. They are insensitive
to contamination by particulate matter, are not permanently damaged by liquids, and are
resistant to most chemicals.
OPERATING PRINCIPLE
A
capacitive humidity sensor works like a plate capacitor. The lower electrode is
deposited on a carrier substrate, often a ceramic material. A thin polymer
hygroscopic layer acts as the dielectric, and on top of this is the upper
plate, which acts as the second electrode but which also allows water vapour to
pass through it, into the polymer. The water vapour molecules enter or leave
the hygroscopic polymer until the water vapour content is in equilibrium with
the ambient air or gas. The dielectric strength of the polymer is proportional
to the water vapour content. In turn the dielectric strength affects the
capacitance, which is measured and processed to give a relative humidity
measurement. By also measuring temperature a dew point or absolute humidity
value can also be obtained. |
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PCMini52
Relative humidity and temperature transmitter mini probe.. |
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PCMini70
Relative humidity and temperature mini probe... |
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PC33, 52 & 62
Relative humidity and temperature transmitter analogue and digital... |
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PFMini72
Relative humidity and temperature transmitter... |
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PF211
Relative humidity and temperature transmitter... |
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SF52
Dew-point transmitter... |
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RM33 & 52
Relative humidity and temperature transmitter, HVAC room mount... |
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WM33 & 52
Relative humidity and temperature transmitter, multi unit... |
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WM261
Relative humidity transmitter... |
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WM281
Digital relative humidity/temperature transmitter for wall mounting... |
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WM291
Relative humidity/temperature digital transmitter for wall mounting... |
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DT262
Relative humidity transmitter... |
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DT269
Relative humidity transmitter... |
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DT282
Digital relative humidity and temperature transmitter for duct installation...
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DT284
Digital relative humidity and temperature transmitter remote version... |
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DT722
Rugged industrial relative humidity and temperature transmitter... |
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WR283
Digital relative humidity and temperature transmitter remote version for high temperatures... |
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WR285
Digital relative humidity transmitter with remote probe for pressurised locals... |
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WR293
Digital relative humidity and temperature transmitter remote version... |
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WR295
Digital relative humidity and temperature transmitter for applications at pressures up to 30 bar (3MPa)... |
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H3000
Capacitive humidity sensor... |
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DM509 & 535
Hand-held relative humidity and temperature transmitters... |
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S503
Humidity calibrator... |
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S904
Relative humidity and temperature calibrator... |
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SCI
Sensor communication interface... |
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