6.2.1 Setting the measured value to zero,
It is possible - a very useful function - to zero the measured value at certain lo-
cations or at certain times in order then to observe the deviation from this refe-
rence value. This function can be activated in the MEASURED VALUE function
by means of the following key combination :
Zero-setting by pressing keys:
,
PROG
CLEAR
1: `0 0 0.0´
CL
When the
PROG
key is pressed in function ´
CL
´ the measured value 000.0 flas-
hes; when the
CLEAR
key is then pressed, the measured value is saved as base
value and set to zero.
So long as the deviation from the base value is shown (rather than
the actual measured value), the
CORR
arrow appears in the display.
If only a ´C´ appears as function, this means that the base value function
is locked at level 5 or above; (see Section 7.2). In this case the new ba-
se value is not saved to the connector’s EEPROM but only to the RAM;
i.e. once the device is switched off, then the next time it is switched on,
this will be restored to its original value.
pH,- conductivity- and O
2
probes cannot be zero-point setting,
but to adjusted only permanently.
If you prefer to have the new zero-point saved more permanently, then,
before zero-setting, briefly and temporarily lower the locking mode to
level 3 by switching on the device with the
PROG
and
FUNCTION
keys held
down. When you switch off, the base value will then be retained; (the
locking mode, however, will be restored to its original level).
In order to obtain the actual measured value again the base value must be
cleared. If the ´
BA
´ function is not currently activated, you need only to switch
off and on again; (see above). If the ´
BA
´ function is available, it can be se-
lected by pressing the
FUNCTION
key; the base value can then be cleared by
pressing key combination
PROG
,
CLEAR
; (see Section 7.5).
6.2.2 Sensor adjustment, zero-point, and gain
Many types of sensor need to be adjusted at least once or at regular intervals to
compensate for various instabilities. There is, for this purpose, in addition to the
above-mentioned procedure for “setting the measured value to zero”, a specific
zero-point adjustment, which does not affect scaling with base value and factor
(e.g. pH probes). This function does not save the zero-point error as base va-
lue but as a zero-point correction; (see Section 9.7). Zero-point adjustment is
executed by pressing the following key combination:
Zero-point adjustment:
,
,
e.g.
PROG
▼
PROG
1: `0 7.0 0´
AJ
ALMEMO
2390-5
25
Measuring operations
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