Process Unit 73 LF - Knick

Process Unit 73 LF
Concentration Determination
You can only make use of concentration determination
if your unit is equipped with option 359,
360 or 382. Without these options, the menu
reads “Concentration (Optional)”. The line cannot
be selected.
The Process Unit 73 LF determines the substance
concentration from the measured conductivity and
temperature values in percentage by weight (% by
wt.) for H 2 SO 4 , HNO 3, HCl (Opt. 359) or HCl,
NaOH, NaCl (Opt. 382) (with option 360: customer-specific
substance mixtures).
Requirements for Concentration Determination
The following conditions (among others) are required
for reliable concentration determination:
For calculation of concentration, the medium
being measured must be a purely binary mixture
(e.g. water / hydrochloric acid). Presence
of other dissolved substances (e.g. salts) leads
to incorrect concentration values.
In the region of small slopes (e.g. at the range
limits) small conductivity changes can correspond
to great concentration changes. This
might lead to an unsteady display of the concentration
value.
Since the concentration value is calculated
from the measured conductivity and temperature
values, accurate temperature measurement
is very important. Therefore, you should
make sure that cell and process medium are in
thermal equilibrium.
Especially for concentration determination, you
should adjust the temperature probe to increase
accuracy (see page 4–5).
9–24 Capabilities