Chapter 2 __________________________________________________________ Product Overview
VAISALA _______________________________________________________________________ 19
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the features and advantages of the Vaisala
DRYCAP
®
Dewpoint Transmitters DMT345 and DMT346.
Introduction to DMT345 and DMT346
The DMT345 and DMT346 transmitters incorporate the advanced
Vaisala DRYCAP
®
technology, which enables reliable and accurate
dewpoint measurement. Both transmitters also feature the AutoCal
function which provides excellent long term stability of the
measurement.
The DMT345 is designed for measurement of relative humidity in
temperatures up to 180 °C. The transmitter outputs dewpoint/frostpoint
(Td/f), mixing ratio (x), volume concentration (ppm), relative humidity
(RH), and temperature (T).
The DMT346 is a high-performance instrument for measurement of
dewpoint and mixing ratio in temperatures up to 350 °C.
DMT346 also outputs sensor saturation rate (SSR) and temperature (T
S
=
T
Sensor
) of the cooled Vaisala DRYCAP
®
sensor. Because the sensor is
cooled, these values do not represent true process conditions, hence they
cannot be used for process control. Nevertheless, they provide a valuable
aid for calibration and for checking the cooling effect.
For quantities measured by DMT345, see Table 3 below. For the optional
calculated quantities measured by DMT345, see Table 4 on page 20.
For quantities measured and calculated by DMT36, see Table 5 on page
20.
Table 3
Output Quantities and Their Abbreviations for Vaisala
DRYCAP
®
Dewpoint Transmitter DMT345
Quantity
Abbreviation Metric Unit
Non Metric Unit
Dewpoint/frost point temperature (T
d/f
) TDF
ºC ºF
Mixing ratio (x)
X
g/kg
gr/lb
Relative humidity RH
RH
%RH
%RH