IM 12B6C2-E-H
36
7-11. Temperature adjustment
ACCESS CODE
: 11 (see §7-2)
DISPLAY
: *T.ADJ
Adjustment
: Correction for cable
resistance
Explanation:
The temperature measurement is a two wire
resistance measurement. In this kind of
measurement the length of the connecting
cable can influence the accuracy of the tem-
perature indication. To compensate for the
extra resistance of the cable up to 551 can
be calibrated. Connect the correct tempera-
ture sensor to the EXA instrument and insert
it in a stable temperature bath of a known
value. Check the temperature indicated at
this setting in °C and adjust the value if
necessary. Now the EXA transmitter has
been calibrated to compensate for the cable
resistance.
7-12. Manual adjustment of ITP, slope
and asymmetry potential
ACCESS CODE
: 12 (see §7-2)
DISPLAY
: *ITP, *SLOPE, *ASPOT
Adjustment
: Set the value of the
isothermal point of
intersection (ITP),
slope and asymmetry-
potential.
Explanation:
The EXA PH200 can be programmed for pH
electrodes that do not have a standard ITP
(0 mV point) at pH 7.
In some applications special pH electrodes
are used (e.g. Emamel, Antimony, etc.)
which have a different construction and prin-
ciple than standard electrodes. The basic
parameters of these electrodes can be pro-
grammed in this section The isothermal
point of intersection (ITP) is the pH-value
where the electrode gives 0 mV. The slope is
the sensitivity of the electrode in percent of
theoretical value (59.10 mV/pH at 25°C).
The asymmetry potential is the offset in mV
of the reference system used.
Defaults
: ITP
= 7.00 pH
SLOPE
= 100%
ASPOT
= 0 mV
Limits
: ITP
:-1 to 15 pH
SLOPE
: 70 to 110%
ASPOT
: -120 to
+120 mV
With checks off:
SLOPE
: 25 to 199%
ASPOT
: -199 to
+199 mV
