Vaisala HMP42 - Manual (Page 6)

HMI41 AND HMP42
Operating Manual
M210317EN-A
2
The HMI41 indicator displays relative humidity, temperature and dewpoint
temperature readings. In addition to these, one of the following quantities can
also be chosen: absolute humidity, wet bulb temperature or mixing ratio.
The indicator also features an automatic power-off function which can be
disabled, and a continuously updated display. The display can be frozen to
show the current readings, and it can be used for checking the minimum and
maximum readings measured during data collecting. The automatic power-off
function is not active during data collecting even if it was previously selected.
The versatile HMI41 indicator also includes a data collecting feature. Data
collecting can be either automatic or manual, and it can be optimized for each
application: both the measurement interval and duration can be set by the user.
During automatic data collecting, the probe takes measurements only just
before storing each measurement. In order to minimize the consumption and to
maximize the battery life, the power is automatically turned off for the
measurement interval and the display is dim except when the readings on the
display are updated (once a minute). The stored readings can be transferred to
a PC via a serial interface (order code 19446ZZ) and then printed, if required.
The humidity measurement range is 0 - 100 %RH. The temperature measure-
ment range with the HMP42 probe is -40 - +100 °C. Relative humidity is
measured with the accurate and stable HUMICAP

MINI humidity sensor
which uses an operating principle based on the changes in the capacitance of
the sensor as its thin polymer film absorbs water molecules.