Specifications

33
HMP 235 Smart Humidity/Dewpoint
Transmitter for Demanding High
Temperature Applications
CUSTOMIZE YOUR INSTRUMENT
(Also see easy-to-use order form)
Vaisalas unique microprocessor design and modular-
ity allow you to customize the HMP 235 at time of
purchase:
 Selection of output parameters:
- relative humidity - absolute humidity
- dewpoint - mixing ratio
- temperature - wet bulb temperature
- enthalpy
 Selection of:
- power supply type (24 VDC/VAC; 110 VAC, 220 VAC)
- cable length (2, 5, or 10 meters)
- local display and keypad
- serial bus type (RS 232, RS 485/422 or digital
current loop)
- mounting flange type (aluminum or stainless
steel)
- type of sensor protection (variety of filter types
available)
After purchase, you can directly program either via
computer or local display and keypad:
 Units (metric or non-metric)
 The two output parameters corresponding to
analog channels 1 and 2 (note: all output para-
meters selected by users are also available via
serial output and display)
 Selection of the following output signals:
 4 to 20 mA  0 to 1V
 0 to 20 mA  0 to 5V
 0 to 10V
 Scaling of measurement parameters and output
signals (e.g. -10°C to +80°C corresponds to
1 to 5V)
NEW FEATURES:
 Re-Gaining
This option makes the HMP 230 transmitters more
accurate and stable in environments where high
concentrations of chemicals or cleaning agents are
present. With Re-Gaining, activated by a software
command, the sensor returns to normal following
the evaporation of the chemicals from the sensor.
 Alarm Relays
For applications where adjustable on/off alarm
control is needed, this option is the solution. These
relays are easy to adjust with a display keypad or
through RS 232.
HMP 235 shown with optional display and
keypad. Supplied with NIST traceable certificate
of calibration. Operating temperature range of
-40°F to +356°F (-40°C to +180°C).
Note: Sensor can withstand temperatures up to
392°F (200°C) for short periods. Cable available
in lengths of 2 meters, 5 meters and 10 meters.
Optional mounting flange available in either
stainless steel or aluminum.
FULL TEMPERATURE COMPENSATION
The HMP 235 transmitter provides accurate measure-
ment with full temperature compensation over the
entire humidity range (0 to 100% RH) at temperatures
from -40°F to +356°F (-40°C to +180°C). Additionally,
the stainless steel sensor head can withstand tem-
peratures up to 392°F (200°C) for short periods, and
can be positioned directly in the environment being
measured: ducts, kilns, and dryers, for example. The
sensor is connected to the transmitter via either a 2,
5, or 10 meter cable, allowing the electronics and
housing to be located outside of the hostile environ-
ment.
ON-SITE, ONE-POINT CALIBRATION
By utilizing a reference RH (or temperature) probe
for comparison, routine maintenance and/or calibra-
tion of the HMP 235 can be performed on site within
a matter of minutes without disturbing transmitter
operation. This unique one-point calibration feature
will save down time, reduce service costs, and ensure
high accuracy operation.
HMP 235