Chapter 2 __________________________________________________________ Product Overview
VAISALA_______________________________________________________________________ 21
Humidity and Temperature Measurement
(Option)
An optional HMP155 humidity and temperature probe is available for
the PTB330TS. HMP155 provides reliable humidity and temperature
measurement in a wide range of applications. Humidity measurement is
based on the capacitive thin film polymer sensor HUMICAP®180R.
Temperature measurement is based on resistive platinum sensors
(Pt100). Both the humidity and temperature sensors are located at the
tip of the probe, protected by a sintered Teflon filter.
The MI70 indicator is used as the display, and the MI70 indicator also
provides the operation power for the probe. The PTB330 and HMP155
can be connected to the MI70 indicator simultaneously. The HMP155
version that is offered for the PTB330TS has RS-485 digital output.
Additional Temperature Probe
(Option)
The HMP155 can be ordered with an additional temperature probe. The
T-probe is attached to the HMP155 with a two meter cable.
When the HMP155 is equipped with the additional T-probe, it
calculates the relative humidity value based on the dewpoint (T
d
) value
obtained from the humidity probe and the T
a
value obtained from the T-
probe. This means that when you measure relative humidity (RH),
mixing ratio (x) or wetbulb temperature (T
w
) using HMP155 with T-
probe, it is important to make sure that the humidity probe and the T-
probe are placed in the same conditions in order to get accurate
readings.
