Specifications

27
CUSTOMIZE YOUR INSTRUMENT
(Also see easy-to-use order form)
Vaisalas unique microprocessor design and modular-
ity allow you to customize the HMP 231 at time of
purchase:
 Selection of output parameters:
- relative humidity - absolute humidity
- dewpoint - mixing ratio
- temperature - wet bulb temperature
- enthalpy
 Selection of:
- local display and keypad
- serial bus type (RS 232, 422/485 or digital
current loop)
- type of sensor protection (variety of filters 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 param-
eters 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 +50°C corresponds to 1 to 5V)
RECOMMENDED FOR CHANGING
ENVIRONMENTS
The HMP 231 is ideal for critical areas and applica-
tions where humidity, temperatures, or dewpoints
tend to fluctuate. The unit is fully temperature
compensated and provides unsurpassed accuracy
over the entire temperature range of -40°F to +140°F
(-40°C to +60°C).
NEW GENERATION HUMICAP®
The HMP 231 incorporates the latest generation of
Vaisalas patented thin-film HUMICAP
®
sensor.
Vaisala has pioneered the field of humidity since it
developed the first HUMICAP
®
humidity sensor more
than 20 years ago. Intensive in-house R&D has now
produced a sensor which measures humidity more
accurately (up to ±1%) and reliably at temperatures
higher than other sensors. The sensors tolerance to
high temperature; its ability to operate in condensing
environments; its resistance to harsh chemicals and
contaminants; and its excellent long-term stability are
of great value in monitoring and controlling critical
environments.
HMP 231 Smart Humidity/Dewpoint
Transmitter for High Performance
Wall-Mount Applications
ON-SITE, ONE-POINT CALIBRATION
By utilizing a reference RH (or temperature) probe
for comparison, routine maintenance and/or calibra-
tion of the HMP 231 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.
NEW FEATURE: RE-GAINING
This option makes the HMP 231 transmitter more
accurate and stable in environments where high
concentration of chemicals or cleaning agents are
present. In re-gaining, activated by a software
command, the sensor is returned to normal following
the evaporation of the chemicals from the sensor.
HMP 231 shown with optional display and
keypad. Supplied with NIST traceable
certificate of calibration