General Eastern Humidity Sensor

The EMD-4000 is a bulk resistance-type humidity sensor based on the impedance change of a thin-film polymer due to water vapor absorption. The polymer is deposited on Bismuth alloy terminals, which are set on a ceramic substrate. The sensor is excited by a low voltage alternating current and the impedance measured as a function of relative humidity.
The thin-film polymer consists of chemical functional groups that disassociate into ionic species as water vapor is absorbed. This results in increased electrical conductance through the sensor or a decrease in impedance. The impedance is an inverse exponential function of the surrounding humidity.

FEATUREs
• Excellent interchangeability
• Available in 5% accuracy
• Economical
• Recovers from condensation
• Good resistance to chemical vapors
• Fast response
• Low hysteresis