Ahlborn ALMEMO 6290-7B, Operating Instructions Manual, Page: 31 / 53

Zero Point Adjustment
Many sensors must be adjusted at least once or at regular intervals to
compensate for instabilities. For this purpose, a specific
zero point
adjustment is available, in addition to the ´Set Measured Value to Zero´
mentioned above, as some sensors require an additional scaling (e.g. pH
probes). In this function the zero point error is not stored as base value but as
zero point correction (special cases and slope correction, see 6.5). In this case,
the locking mode must be set below 4 (see 6.7). The zero point correction is
performed using the following keys:
Function
MEASURE
: Zero point adjustment: ,
MEASURE
ENTER
If a base value is programmed the measured value is not indicated
as zero but as the negative base value after the adjustment.
7.1.4 Atmospheric Pressure Compensation
Some measuring variables depend on the environmental atmospheric pressure
(see 6.2 measuring range list ´w. PC´). As a result, higher deviations from the
normal pressure of 1013mbar can cause corresponding measuring errors:
e.g. error per 100mbar: rel. humidity psychrometer approx. 2%
dynamic pressure approx. 5%
O
2
saturation approx. 10%
Therefore, the atmospheric pressure should be considered (approx.
-11mb/100m over mean sea level, MSL) especially during use in a
corresponding height above sea level. It can either be programmed or
measured with a sensor (see manual 6.7.2).
Function ATMOSPHERIC PRESSURE ´
mb
´
Selection with key: ... Input mbar, see 5.4
FUNCTION
1 0 1 3
m b
With each reset the atmospheric pressure is set to 1013mb. It can be set to the
actual value by the usual data entry.
ALMEMO

6290-7B 30
Continuous Measurement of a Measuring Point