10. Measuring operations
24
10.4
Relative measuring
One very useful function is to zero the meas-
ured value at certain locations or at certain
times as a reference value in order then to ob-
serve only the subsequent deviations. This
function is independent of the locking status
and does not modify the programming param-
eters in the connector. (Special cases,
see 10.5 and Locking, see 12.4).
To zero-set the measured value press key :
CLR
To display relative measuring with arrow :
REL
.
Return to normal measured value by pressing and holding down key :
CLR
.
Setting to zero automatically deletes the maximum and minimum val-
ues for this channel. The
MAX
,
MIN
, and
MEM
functions are thus also
available for relative measurement.
10.5
Sensor adjustment
Many types of sensor need to be adjusted at least once or at regular intervals
to compensate for various instabilities. With
dynamic pressure probes
(ranges
L840 and L890, units Pa) the zero-point must be temporarily adjusted by press-
ing key
CLR
, i.e. until switching off, even if the channel is locked.
With the following
chemical probes
automatic two-point adjustment can be per-
formed :
Probe
Type
Zero
point
Gain
pH probe
ZA 9610-AKY: 7.00
4.00
10.00
pH
or
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 %
1. Open locking
For adjustment purposes, since these sensors are by default locked, locking
must be temporarily deactivated. To do so when switching ON press and hold
down the two keys
MAX
and
MIN
. The arrow
FREE
should then light up
indicating that adjustment is now possible. After the device is switched off the
sensor will be locked again as normal.
2. Zero-point adjustment
To perform
zero-point adjustment
the measured value must first be physi-
cally set to zero, i.e.
● pH probe must be immersed in a buffer solution pH 7.0.
● Conductivity probe must be withdrawn from the liquid and dried.
● O
2
probe for water must be held in a zero solution.
Zero-point adjustment
is performed in 2 steps :
