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Capacitive Technology |
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 Michell Instruments %RH sensors feature a
capacitive thin-film polymer sensor. These sensors provide a high accuracy,
excellent long-term stability and negligible hysteresis. 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
Digital relative humidity and temperature mini probe with analogue output... |
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PCMini70
Relative humidity and temperature mini probe... |
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PC62 & 62V
Digital relative humidity and temperature probe with digital or analogue output.. |
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PC33 & 52
Analogue relative humidity and temperature probe... |
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PF211
HVAC Relative humidity probe... |
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SF52
Dew point transmitter... |
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WM33 & 52
Relative humidity and temperature transmitter, wall mount... |
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WM261
Digital relative humidity and temperature transmitter, wall mount... |
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WM281
Digital relative humidity and temperature transmitter, wall mount... |
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WM291
Digital relative humidity and temperature transmitter, wall mount... |
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DT269
Digital relative humidity and temperature transmitter, duct mount... |
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DT282
Digital relative humidity and temperature transmitter, duct mount...
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DT284
Digital relative humidity and temperature transmitter, duct mount... |
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DT722
Rugged industrial relative humidity and temperature transmitter, duct mount... |
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MDM25
Portable, battery-operated handmeter, available with a number of different probe configurations.... |
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PFMini72
Relative humidity and temperature probe... |
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RM33 & 52
Relative humidity and temperature transmitter, HVAC Room Monitor... |
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WR283
Digital relative humidity and temperature transmitter - remote probe for high temperatures... |
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WR285
Digital relative humidity transmitter - remote probe for pressurised applications up to 30 bar... |
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WR293
Digital relative humidity and temperature transmitter - remote probe for high temperatures... |
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S503
Relative humidity generator for calibrations... |
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S904
Relative humidity generator for calibrations... |
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