Metrohm 726 Titroprocessor - Manual (Page 160)

8.5 SEC
726 Titroprocessor, Instructions for use 154 154
8.5 SEC
Conditioning to a preset endpoint is implemented as an independent mode.
Its own set of parameters makes the conditioning mode SEC independent
from SET modes. In this way conditioning is very versatile.
A SEC mode does not produce a measuring point list and therefore no
curves can be shown. No facilities for calculations are provided.
If a SEC mode is used in preparation for a SET titration then care must be
taken that the parameters of both modes do not differ too much from each
other.
Four different SEC modes are available for rapid conditioning to a preset
endpoint; they differ only in the measured quantity:
SEC_PH* measured quantity pH
SEC_U* measured quantity mV
SEC_UPOL* measured quantity µA (selectable pol.voltage in mV)
SEC_IPOL* measured quantity mV (selectable pol.current in µA)
The following information applies to all SEC modes. Any variations are
noted.
SEC_PH* Conditioning to preset endpoint
Reagent Sensor
Concentr. Meas. input A1
Dos. drive A1
applies to ⇒ SEC_PH*, SEC_U*, SEC_UPOL*, SEC_IPOL*
SEC modes create the following system variables:
COV Conditioning volume; reagent consumption for conditioning
DRC Volume drift in conditioned state
$CRF Conditioning flag; correctly conditioned yes/no (1 or 0)
These system variables can be used to apply an automatic drift volume re-
duction:
Formula:
Drift red. R1=DRC/60*(ITD+MD)/1000 mL
EP corr. R2=EP1-R1 mL
Here it is assumed that owing to external influences a volume drift is effec-
tive during the sample titration whose value corresponds to the volume drift
in a conditioned state (variable DRC). Its duration is equivalent to the period
between conditioning switch-off and sample titration switch-off
(ITD+MD * ).