7.4 Reference measurement and correction
of measured values
In the
MEASURE
function by pressing the
CLEAR
key you can set the current
measured value temporarily to zero (if the channel is locked at level ? 5). The
current measured value is saved as reference value and the difference with re-
spect to this reference value is displayed; it is thus possible e.g. to read out at
random points the respective difference with respect to the reference point.
To indicate that this differential mode is activated, the 'CORR' arrow flashes.
Set measured value to zero :
CLEAR
HOLD
MIN
MAX
CORR
M
DIM
Setting to zero automatically deletes the maximum and minimum values for
this channel. The
MAX
,
MIN
, and
HOLD
functions are also available in conjuncti-
on with reference measurement.
The way in which the zero-setting function operates depends on the
locking mode for the measuring point in question (Man. Sec. 6.3.12).
If the locking mode is set to level 5 or higher, the reference value will
be lost when the device is switched OFF.
If the locking mode is set to level 4, the reference value will be saved
as base value in the connector EEPROM.
If the locking mode is set to level 3 or low, the sensor will be adju-
sted and the correction values will be saved in the connector EE-
PROM; see below..
Deleting the reference value
The reference value for a channel can be deleted by pressing and holding
down the
CLEAR
key - even in the course of normal operation; (this does not
apply with dynamic pressure); (and this is only if also unlocked in the EE-
PROM, see below). The maximum and minimum values are deleted and the
'CORR' arrow should stop flashing.
Return to normal measured values:
Press and hold down (appr. 1 s)
CLEAR
1s
Sensor adjustment
Many types of sensor have to be adjusted relatively often to compensate for
various instabilities. If the sensors are scaled with the base value and factor or
if the correction has to be saved ?*? more permanently, then
zero-point ad-
justment
must be performed using the
zero-point correction function
; (
see
Manual, Section 6.3.10). On probes with scaling the base value is thus re-
tained; i.e. a pH probe (base value 7.00) after adjustment will show not 0.00
but 7.00 pH. This function is activated automatically if the locking mode is set
to level ? 3 (see above). You can
briefly and temporarily lower the locking
mode down to level 3
by switching the device ON with the
M
▲
and
CLEAR
keys held down; after switching OFF the locking mode will be restored to the
level originally programmed.
ALMEMO
2390-3
19
Measuring operation