Specifications

31
CUSTOMIZE YOUR INSTRUMENT
(Also see easy-to-use order form)
Vaisalas unique microprocessor design and modular-
ity allow you to customize the HMP 234 at time of
purchase:
 Selection of output parameters:
- relative humidity - absolute humidity
- dewpoint - mixing ratio
- temperature - wet bulb temperature
- enthalpy
 Selection of:
- power supply (24 VDC/VAC; 115 VAC, 230 VAC)
- local display and keypad
- serial bus type (RS 232 or 485/422, or digital
current loop)
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 +80°C corresponds to 1 to 5V)
FOR PRESSURIZED SPACES/
CHANGING ENVIRONMENTS
The HMP 234s sensing head facilitates installation in
pressurized processes to 10 MPa (1450 psi). This
instrument is ideal for critical areas and applications
where humidity, temperatures, or dewpoints tend to
fluctuate. It is fully temperature compensated and
provides unsurpassed accuracy over the entire
temperature range -40°F to +356°F (-40°C to +180°C).
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 234 shown with optional display and
keypad. Supplied with NIST traceable certificate
of calibration
NEXT GENERATION HUMICAP
®
The HMP 234 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.
ON-SITE, ONE-POINT CALIBRATION
By utilizing a reference RH (or temperature) probe
for comparison, routine maintenance and/or calibra-
tion of the HMP 234 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 234 Smart Humidity/Dewpoint
Transmitter for High Performance in
Pressurized Spaces
HMP 234