Capacitive Technology


Capacitive TechnologyMichell 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.

MDM50 MDM50
Designed to make high-speed spot check measurements to -50°C dew point as simple as possible, simply connect your sample gas, turn on the instrument and it will automatically begin to measure the dew point of the applied sample.
PCMini52 PCMini52
ø12mm highly compact probe with dual voltage outputs.
PCMini70 PCMini70
ø22mm compact transmitter with stainless steel housing, for OEM applications. Voltage %RH output, direct 3-wire PRT temperature measurement.
PC62 & 62V, 52 PC62 & 62V
ø19mm probes with voltage or RS232/RS485 outputs.
PC33 & 52 PC33 & 52
ø19mm probes with voltage or current loop outputs.
MDM25 MDM25
Portable, battery-operated handmeter, available with a number of probe configurations. Displays relative humidity, temperature and one calculated value, making it suitable for a wide range of applications.
SF52 SF52
The SF52 is a fast-responding, cost effective dew-point transmitter designed for use in harsh industrial dryer applications. Available with G1/2" or 1/2" NPT process connections.
WM33 & 52 WM33 & 52
Compact transmitters, with optional integrated display. Current loop or voltage outputs.
WM261 WM261
ø12mm fixed probe, with voltage or current loop %RH outputs, optional direct 3-wire PRT temperature measurement.
WM281 WM281
ø19mm fixed probe with voltage, current loop, or RS485 outputs.
WM291 WM291
ø19mm fixed probe with voltage, current loop, or RS485 outputs. Integrated display.
DT269 DT269
ø19mm fixed probe with voltage or current loop %RH outputs, optional direct 3-wire PRT temperature measurement.
DT282 DT282
ø19mm fixed probe with voltage, current loop, or RS485 outputs.
DT722 DT722
ø19mm fixed probe for high temperature applications. Current loop outputs. Optional integrated display.
PFMini72 PFMini72
ø18mm probe for outside installation with voltage outputs, optional direct 3-wire PRT temperature measurement.
RM33 & 52 RM33 & 52
Low-cost transmitters with voltage or current loop outputs.
WR283 WR283
ø12mm remote probe for high temperature applications. Voltage, current loop outputs or RS485 outputs.
WR285 WR285
ø18mm remote probe for pressurised applications up to 30bar. Voltage, current loop outputs or RS485 outputs.
WR293 WR293
ø12mm remote probe for high temperature applications. Voltage, current loop outputs or RS485 outputs. Integrated display.
H5000 & 5100 H5000 & 5100
Fast-responding capacitive relative humidity element, ideal for integration into OEM equipment.
H6000 & 6100 H6000 & 6100
Corrosion-resistant, PTFE-coated capacitive relative humidity element, ideal for integration into OEM equipment.
I7000 & 7400 (Hygrosmart) HygroSmart I7000 Series
The HygroSmart I7000 Series is interchangeable without the need for recalibration. The small size allows its integration into any equipment while the plug-and-play system allows fast replacement even by untrained staff.
S503 S503
The S503 is a compact and highly portable humidity calibrator, perfect for on-site calibrations.
S904 S904
The S904 is a stand-alone and transportable humidity calibrator, for dew-point and relative humidity sensors.
DT284 DT284
ø12mm fixed probe for high temperature applications. Voltage, current loop or RS485 outputs.