12. Sensors
12.2.1 Set measured value to zero
One very useful function is to zero the
measured value at certain locations or
points in time as a reference value
from which to observe subsequent de-
viations. For this purpose touch on
the measured value in question and
confirm via selection box ´
Zero-set
´. The measured value is then saved as
base
value
and thus set to zero. To save the relative reference value to RAM on a
temporary basis only, option 'Temp. zero-setting' must be used. (
Display 'REL'
)
Whenever, instead of the actual measured value, the display indi-
cates a deviation from the base value, the symbol will appear.
To obtain the actual measured value again the base value must be
cleared. (see 13.2.11).
12.2.2 Zero-point adjustment
Many types of sensor need to be adjusted either once or at regular intervals to
compensate for various instabilities. This can be done with the above-men-
tioned ´Set measured value to zero´ - but also with the special zero-point ad-
justment, which does not influence scaling. For this purpose touch on the
measured value again and confirm via selection box ´Adjustment´. This en-
sures that the zero-point error is saved not as base value but as zero-point
correction. (see 13.2.10) If the function is locked at level 3 or above (see
13.2.6), a help box states that it can be unlocked temporarily; this ensures that
the correction values are remain permanently stored on the connector.
As soon as the request is confirmed, adjustment is performed.
If a base value has been programmed, the measured value indicated
after adjustment is not zero but the negative base value.
In the case of dynamic pressure probes the zero-point error is al-
ways written to the calibration offset temporarily (i.e. until you switch
off) even if the channel is locked.
12.2.3 Sensor adjustment for chemical sensors and probes
With the following sensors the adjustment (s. 12.2.2) will automatically take the
form of a two-point adjustment. The appropriate calibration setpoints should
already be entered but these can also be modified.
Probe Type Zero point Gain
pH probe
ZA 9610-AKY: 7.00
4.00
or 10.00 pH
Conductivity
FY A641-LF: 0.0 2.77 mS/cm
FY A641-LF2: 0.0 147.0 uS/cm
FY A641-LF3: 0.0 111.8 mS/cm
O
2
saturation
FY A640-O2: 0 101 %
With pH probes ´Zero-set´ (s. 12.2.1) restores the connector to de-
fault programming.
42 ALMEMO
®
710
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