Humidity Sensors

this is a training module on

well humidity sensors welcome to the

training module on honey while humidity

sensors this training module introduces

humidity sensor technology and their

applications the technologies and

situations most often associated with

humidity sensors are thermoset and

thermoplastic sensors bulk thermoplastic

and bulk alo three sensors lithium

chloride sensors and thermoset polymer

capacitors sensors humidity sensors can

be constructed from a variety of

materials however the features and

benefits of the materials used influence

the effectiveness of the sensor and the

diversity of its applications

here is a comparison table for humidity

sensors constructed from different

materials thermoset and thermoplastic

sensors also referred to as thin film

capacitive sensors work on the role that

relative humidity changes the

capacitance of a sensor in a measurable

and consistent way these capacitance

based sensors can measure zero to one

hundred percent with application

temperatures ranging from minus 40 to

200 degrees Fahrenheit bulk

thermoplastic and bulk alo three sensors

also called bulk polymer resistance

sensors function on the basis that a

change in resistance over a polymer

element fluctuates with relative

humidity in a measurable and consistent

way these sensors can typically measure

zero to one hundred percent relative

humidity with application temperatures

between minus 20 to 140 degrees

Fahrenheit lithium chloride film

humidity sensors can contain a thin

layer of lithium chloride that sits on

an insulator which has two palladian

coils while side by side because the

film is hygroscopic it will attract

moisture from the surrounding atmosphere

when the humidity increases there is a

direct change in the resistance of the

film between the two Palladium coils

the thermoset polymer capacitors fu

manatee sensor works through absorption

water is absorbed down through the top

of the sensor through the porous

platinum top layer to effect the layer

of thermoset polymer between the two

layers of palladium this chart

illustrates the primary features and

benefits of the honeywell thermoset

polymer Hema nate'd sensors the

thermoset polymer relative humidity

sensors use an industry proven thermoset

polymer three layer capacitance

construction platinum electrodes and

except for high-temperature versions on

chips silicon integrated voltage output

signal conditioning these humidity

sensors are laser trims so that they

eliminate calibration other features

include low current power design stable

low drift performance fast response high

linearity and long term stability

in Adam surface transportation

automotive onboard applications manned

space vehicles require systems to cool

and dehumidifier cabin air to do this

they use a temperature and humidity

control system the system circulates and

filters air removes water in the form of

humidity and maintains a constant

temperature any water that is collected

goes to the water recovery and

management system automotive HVAC

control units rely on vital signals from

different sensors to main a comfortable

environment inside a vehicle one of the

conditions that is monitored is the

amount of water vapor in the cabin air

along with humidity as a comfort level

water vapour levels are important in the

fogging up and D fogging of the

windshield a humidity sensor inside the

cabin of the vehicle continuously

monitors the amount of water vapor

present this allows the HVAC unit to

regulate the blowout air temperature

adjust blower speeds and open

recirculation vents to control and help

prevent windshield fogging

in appliance consumer applications the

humidity sensor and control circuit

monitors the ambient condition of the

room air and controls the blower fan to

maintain a constant humidity there are a

number of benefits for the use of

humidity sensors in the areas of

information technology because they are

chemically resistant humidity sensors

are able to withstand the inks and

chemicals used in the printing process

the stable low drift performance of the

sensors is called upon when doing long

run productions and even during those

long run productions the low-power

design ensures the sensors are energy

efficient for the medical

instrumentation market humidity sensors

offer low energy efficient power design

their fast response time works to ensure

the patient's physical comfort and


this table shows the humidity offerings

from Honeywell each sensor is designed

to provide enhanced sensitivity response

time stability and reliability

configured with integrated circuitry to

provide on ships signal conditioning

offered on all products absorption based

humidity sensors provide both

temperature and relative humidity

packages are chemically resistant and

operating ranges of minus 40 to 85

degrees C performing in most harsh

environments these humidity sensors

offer interchangeability of plus or

minus three percent accuracy for

potential applications as diverse as

heating ventilation and air conditioning

equipment refrigeration office

automation and medical equipment for the

hih 4000 dash 2001 and hih 4000 303

Honeywell recommends mil max socket 3109

31 32 dash for one dash 2001 or similar

for hih 4000 dear oh dear oh 2 and h IH

4000 304 Honeywell recommends melmax

socket 8 5 193 dash 0 3 2 1 0 dash 2001

or similar

you can answer the questions in the

chart one is signing on the humidity