H
2
0
2
H
2
0
2H
2
0
0
2
2H
2
0
2
H
2
0
2
1
3
2
3
A
B
Figure 3 Operating principle of PEROXCAP measurement
A
HUMICAP sensor with a catalytic layer (under the probe filter). This sensor only senses
water vapor.
B
HUMICAP sensor without a catalytic layer (under the probe filter). This sensor senses the
air mixture with both hydrogen peroxide vapor and water vapor.
1
Catalytic layer over the thin film polymer. This layer catalyzes hydrogen peroxide into
water and oxygen and prevents it from entering the sensing polymer.
2
Thin film polymer between two electrodes.
3
Alumina substrate.
In addition to measuring vaporized H
2
O
2
concentration, HPP272 provides measurement for
relative saturation, relative humidity, and temperature. Relative humidity (RH) is a parameter
that indicates the humidity value derived from water vapor only, whereas relative saturation
(RS) indicates the humidity percentage derived from water vapor and H
2
O
2
vapor together.
When relative saturation reaches 100 %RS, the vapor mixture starts to condense.
Chapter 3 – H2O2 Measurement
15