Ahlborn ALMEMO 2290-4 V5, Руководство по эксплуатации, Страница: 35 / 48

Sensor Adjustment
For some sensors special functions are available in this context:
1. With pH probes, if the two keys
START/STOP
and
F2
are pressed during switch-on,
the locking is only temporary, i.e. until the device is switched off and set to 3. An
undesired adjustment can then be avoided.
2. Dynamic pressure probes are very delicate and should be adjusted in an
unpressurized state before each use (i.e. disconnected hoses or Pitot tube out of
flow). The correction value must be entered before the conversion
'pressure-to-velocity' is performed. For the ranges L840 and L890 an adjustment is
possible even if the channel is locked. The zero point error is temporarily being
written into the calibration offset until the switch-off is performed.
3. With the following sensors the same key combination as for the zero point
adjustment can be used to automatically perform a slope adjustment if not the
zero value but the calibration value mentioned below is present:
pH probe: ZA 9610-AKY pH4 or pH10
Conductivity: FY A641-LF: 2.77 mS/cm,
FY A641-LF2: 147 µS/cm
FY A641-LF3: 111.8 mS/cm
O
2
saturation: FY A640-O2: 101 %
7.1.8 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 100 mbar: Compensation Range:
Rel. humidity psychrometer approx. 2% 500 to 1500 mbar
Mixture ration, cap. approx. 10 % vapour 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
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 (s. man. 6.7.2). The function ATM.PRESS. ´
mb
´ will be
automatically activated under the key F2 for the sensors mentioned (see 5.2).
Function ATM.PRESS. ´
mb
´
Selection with key ... Input mbar, see 5.4
F2
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 (see 5.4).
ALMEMO

2290-4 35
Continuous Measurement of a Measuring Point