Ahlborn ALMEMO 2490-1, Operating Instructions Manual

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Automatic switch OFF
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
and setting it to zero. This function can be evaluated in dif-
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 Compensation range
Rel.humidity psychrometer approx. 2% 500 to 1500 mbar
Mixture ratio, capacitive approx. 10 % Vapor pressure VP up to 8 bar
Dynamic pressure approx. 5% 800 to 1250 mbar (error < 2%)
O
2
saturation approx. 10% 500 to 1500 mbar
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).
ALMEMO ® 2490 29