Vaisala hmt120 User Manual

2. Product Overview
2.1 Introduction to HMT120
HMT120 measures relative humidity and temperature and converts it to analog current loop
outputs. Other quantities, such as dewpoint (T
d
) 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 a time. These two quantities can be used freely at any outputs (display,
service port and analog current loop outputs).
Available quantities are RH, T, T
d
, T
d/f
, a, x, h, T
w
, p
ws
, and p
w
.
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, T
d
, T
d/f
, a, x, h, T
w
, p
ws
and p
w
).
Vaisala Relative Humidity Measurement Instruments
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.
2.2
Accessories
The following accessories are optionally available:
• Duct installation kit
• Rain shield with installation kit
• Rain/solar radiation shield installation kit (for pole installation)
• Probe mounting
flange
• Probe mounting clamp
• Constant output probe (HMP1100REF, gives constant RH and T values)
2.3
Fixed and Remote Probe Models
The transmitter is available either with a fixed probe directly attached to the transmitter
housing or a remote probe with dierent (3/5/10/20 m) cable lengths. All extension cables
can be easily cascaded in order to obtain longer reach: see Spare Parts and Accessories
(page 74).
Chapter 2 – Product Overview
9

Vaisala hmt120 Specifications

General

Brand	Vaisala
Model	hmt120
Category	Transmitter
Language	English