Chapter 2 __________________________________________________________ Product Overview
VAISALA _______________________________________________________________________ 19
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the features, advantages, and the product
nomenclature of the Vaisala HUMICAP® Humidity and Temperature
Transmitter Series HMT330.
Introduction to HMT330
The HMT330 transmitter provides reliable humidity measurement in a
wide range of applications. Analog outputs can be chosen between
current and voltage signals. Alternatively, digital outputs RS-232
(standard) or RS-422/485 (optional) can be selected.
The quantities measured and calculated by HMT330 are presented in
Table 3 below. The quantities available as an option are presented in
Table 4 below.
Table 3
Quantities Measured by HMT330
Quantity
Abbreviation Metric Unit Non-Metric Unit
Relative humidity (RH)
RH
%RH
%RH
Temperature (T)
T
ºC
ºF
Table 4
Optional Quantities Measured by HMT330
Quantity
Abbreviation Metric Unit Non-Metric Unit
Dewpoint / Frostpoint
Temperature (T
d/f
)
TDF ºC ºF
Dewpoint Temperature (T
d
) TD
ºC
ºF
Absolute humidity (a)
A
g/m
3
gr/ft
3
Mixing ratio (x)
X
g/kg
gr/lb
Wetbulb temperature (T
w
) TW
ºC
ºF
Humid air volume / dry air
volume (by volume or by
weight) (H
2
O)
H2O ppm
v
/ppm
w
ppm
v
/ppm
w
Water vapor pressure (P
w
) PW
hPa
lb/in
2
Water vapor saturation
pressure (P
ws
)
PWS hPa
lb/in
2
Enthalpy (h)
H
kJ/kg
Btu/lb
Difference of T and T
d/f
(
∆
T) DT
ºC
ºF
