E-M-HP22-V1_21
Rotronic AG
Bassersdorf, Switzerland
Document code
Unit
HygroPalm HP22 hand-held indicator:
User Guide
Instruction Manual
Document Type
Page
10
of 16
Document title
© 2009-2010; Rotronic AG E-M-HP22-V1_21
4.4 Changing the parameters shown on the display
When the menu is not active, press the ENTER key to change which parameters are shown on the display:
o
Relative humidity and temperature
o
Relative humidity, temperature and calculated parameter (when calculated parameter is enabled)
4.5 Changing the unit system
The unit system of the HP22 (metric or English) can be changed from the keypad (Menu > Settings > Unit).
Press the MENU key to show the internal menu on the display
With the menu item Settings highlighted, press the ENTER key
With the menu item Unit highlighted, press the ENTER key
Use the UP or DOWN key to change the unit system as desired
Press the MENU key twice to exit the menu and return the HP22 to normal operation
The optional HW4 software can also be used to change the unit system:
4.6 Low battery indicator
When the battery is down to about 20% of its initial charge,
“Low Battery” appears at the bottom of the display.
4.7 Practical advice for measuring humidity
The most common source of error when measuring relative humidity is a difference between the
temperature of the probe and the temperature of the environment. At a humidity condition of 50 %RH, a
temperature difference of 1 C (1.8 F) typically results in an error of 3 %RH on relative humidity.
When using the HP22 hand-held indicator, it is good practice to monitor the display for temperature
stability. The probe should be given sufficient time to equilibrate with the environment to be measured. The
larger the initial temperature difference between the probe and the environment to be measured, the more
time temperature equilibration requires. This time can be shortened, and errors avoided, by using the probe
configuration that fits best for your application.
In extreme situations, condensation may occur on the sensors when the probe is colder than the
environment. As long as the humidity / temperature limits of the humidity sensor are not exceeded,
condensation does not alter the calibration of the sensor. However, the sensor has to dry out before it can
provide a valid measurement.
Non-moving air is an excellent insulator. When there is no air movement, surprising differences in temperature
and humidity can noted over short distances. Air movement at the probe generally results in measurements
that are both faster and more accurate.
