20
3.0
OPERATION
This section provides a basic overview of the ECD TC80 Total
Chlorine Analyzer. It covers physical and chemical influences on
the measurement and the menu structure of the analyzer.
3.01
I
NFLUENCES ON THE
M
EASUREMENT
P
H
V
ALUE
The TCS measures Total Chlorine and the total chlorine
concentration does not change with changes in the pH, there is
always the same amount of Total Chlorine. The output of the
sensor is however pH dependent, see figure 2.1, the output of the sensor decreases 5%/pH as the pH increases.
The T80 transmitter uses the pH signal from the S80 pH sensor to compensate for the decreasing output. The
measured value and the pH value are combined and the corrected Total Chlorine concentration is displayed.
The highest accuracy is attained when calibrations are performed at neutral pH values and higher chlorine
concentrations.
Figure 3.1
3.02
I
NFLUENCES ON THE
M
EASUREMENT
F
LOW
The TCS consumes chlorine to produce the signal. The area near the sensing tip will become depleted of chlorine
without adequate flow to replenish the sample. The sensor requires a minimum velocity of 0.5 ft./sec past the
membrane. Below this value the sensor will indicate a lower concentration than the actual value. Higher flow
rates have little to no effect on the measurement. See Figure 3.2.
70
80
90
100
110
120
130
3
4
5
6
7
8
9
10
11
12
13
% Output
with pH8
= 100%
pH
TCS output vs. pH value