Automatic Switch Off; Device Locking; Atmospheric Pressure Compensation - Ahlborn ALMEMO 2490-2 Operating Instructions Manual

12.3 Automatic switch OFF

In menu item ´AOFF´ the device can be programmed to switch OFF automatic-
ally if no key is touched for a certain settable number of minutes; this will help
save the batteries. This automatic device switch OFF will not take effect if the
setting is ´- -´ or if a mains adapter or interface cable is connected. If the
device is powered from an external supply manual switch OFF can be preven-
ted by selecting the setting ´noOFF´. To switch OFF in this case the external
power supply would have to be unplugged.

12.4 Device locking

The measured value in the main field of the display can be manipulated by
pressing key
CLR
ferent ways or even switched off in cases where there is a risk of accidentally
activating relative measuring by zero-setting the measured value.
Loc parameter :
0 The offset is saved in RAM, base or zero-point - depending on locking
1 The offset is saved in RAM only.
2 Relative measuring is locked

12.5 Atmospheric pressure compensation

Measured variables dependent on the ambient atmospheric pressure (see
Manual 6.3.3 Measuring range list ´with PC´) may, in the event of large devi-
ations from normal pressure (1013 mbar), involve certain measuring errors.
e.g. Error per 100 mbar
Rel.humidity psychrometer
Mixture ratio, capacitive
Dynamic pressure
O saturation
2
It is advisable therefore, especially when taking measurements at appreciable
heights above sea level to take due account of the atmospheric pressure (ap-
prox. -11 mbar / 100 meters above mean sea level, MSL).
The appropriate atmospheric pressure can be entered in parameter 'mb'either
in device programming or it can be measured using an atmospheric pressure
sensor (reference sensor with designation ´*P´, see Manual 6.7.2).
and setting it to zero. This function can be evaluated in dif-
Compensation range
approx. 2%
approx. 10 %
approx. 5%
approx. 10%
Automatic switch OFF
500 to 1500 mbar
Vapor pressure VP up to 8 bar
800 to 1250 mbar (error < 2%)
500 to 1500 mbar
ALMEMO ® 2490 29