
2. Product overview
2.1 Vaisala HUMICAP Humidity and Temperature
Probe HMP155
HMP155 measures relative humidity and air temperature. Humidity measurement on the sensor
is based on the capacitive thin film polymer HUMICAP sensor. Temperature measurement is
based on platinum resistance (Pt100) sensors. Both the humidity and temperature sensors are
located at the tip of the probe, protected by a removable filter.
HMP155 is installed inside a radiation shield, which ensures proper ventilation while protecting
the sensor from solar radiation and precipitation. The shield provides ventilation while
blocking both direct and reflected solar radiation.
2.1.1 HMP155 models
There are 3 HMP155 models: A, D, and E.
• Active output models
• Model A has 2 analog voltage outputs
• Model E has RS-485 digital output
• Passive output model
• Model D has a 4-wire temperature measurement (passive) and an analog voltage
output for relative humidity measurement
All HMP155 models have RS-485 interface for the service use.
Table 3 HMP155 models
Feature
HMP155A
HMP155D
HMP155E
Digital RS-485 output
✔
Voltage output for RH
✔
✔
Voltage output for T
✔
Passive 4-wire for T
✔
RS-485 for service use
✔
✔
✔
Chapter 2 – Product overview
9
Содержание HUMICAP HMP155
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