Vaisala HMP155 - Manual (Page 13)

Chapter 2 __________________________________________________________ Product Overview
VAISALA _______________________________________________________________________ 11
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the features, advantages, and the product
nomenclature of the Vaisala HUMICAP
®
Humidity and Temperature
Probe HMP155.
Introduction to HMP155
The HMP155 probe provides reliable humidity and temperature
measurement in a wide range of applications. Humidity measurement is
based on the capacitive thin film HUMICAP
®
polymer sensor.
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 removable filter.
The HMP155 comes in active and passive output models where the
relative humidity voltage output is similar, but the temperature output is
either active or passive (resistive). Active output version has either two
analog outputs or an RS-485 digital output. Passive output version has 4-
wire temperature measurement and an analog voltage output for relative
humidity measurement.
The quantities measured by HMP155 are presented in Table 3 below.
The quantities calculated from the measured quantities are presented in
Table 4 on page 12.
NOTE Calculated quantities are not available with the passive output version.
Table 3 Quantities Measured by HMP155
Quantity Abbreviation Metric
Unit Non-Metric
Unit
Relative humidity (RH) RH %RH %RH
Temperature (T) T ºC ºF
Additional T-probe temperature
(T
a
)
T
a
ºC ºF