Vaisala HMT120 - Manual (Page 11)

Chapter 2 ___________________________________________________________ Product Overview
VAISALA _________________________________________________________________________ 9
CHAPTER 2
PRODUCT OVERVIEW
This chapter introduces the features, components and accessories of the
HMT120 Series.
The Vaisala range of relative humidity measurement instruments covers
all the applications from ventilation to process control in demanding
conditions. For more information about other Vaisala relative humidity
instruments, please contact your Vaisala representative or visit
www.vaisala.com .
Introduction to the HMT120 Humidity and
Temperature Transmitter
HMT120 measures relative humidity and temperature and converts it to
analog current loop outputs. Other quantities, such as dewpoint (Td) can
be calculated from the basic RH and T values according to the device
configuration. HMT120 is powered with a 10 ... 30 VDC external loop
voltage (20 ... 30 VDC when R
L
<500 ohms) and it outputs two analog
current signals with nominal 4 ... 20 mA range.
HMT120 transmitter's output quantities are configurable. Available
quantities for outputs are limited to two at the time. These two quantities
can be used freely at any outputs (display, service port and analog current
loop outputs).
Available quantities are RH, T, Td, Td/f, a, x, h, Tw, pws, and pw.
The default output quantities are set at the factory during order time.
These factory preset quantity selections can be changed afterwards via
service port if necessary.
The HMT120T and HMT120H models are single-parameter transmitters.
The only output quantity of HMT120T is temperature. The output of the
HMT120H can be configured to be any one of the humidity-related
quantities (RH, Td, Td/f, a, x, h, Tw, pws and pw).