Data
75
Conditions for sample
Effect of sample pH
As mentioned above, the chemical form of free residual chlorine changes with the pH value of
the sample.
The sensitivity change versus pH of the sample water is shown in Fig. 3. As shown in Fig. 3,
the reading decreases according to the increase of pH. The percentage in the Fig. 3 is based
on the sensitivity at pH 7. Therefore, if the sample pH is different from the pH of the last
calibration time, the reading will be affected. If the pH of the sample water is controlled
constant, the reading will be more stable.
Fig. 3 Changes in the reading depending on the pH value of the sample
Tip
For the RA-10, the pH electrode can be installed on the overflow cell.
For the electrodes that are available for this installation, contact our sales personnel.
Effect of electrical conductivity of sample
Electro chemical reaction is needed to measure residual chlorine for the HR-200. The
sensitivity is affected by the conductivity less than a specified level (Fig. 4).
Add electrolyte for example sodium chloride to keep the conductivity more than 100
S/cm for
low conductive sample. It is rare to treat sample with electrolyte because conductivity of tap
water or swimming pool water is more than 100
S/cm in general.
Fig. 4 Changes in the reading depending on the electrical conductivity of the sample
Pe
rce
nt
age
at p
H 7.0
[
]
pH
9
7
8
5.5
6.5
7.5
8.5
6
180
160
140
120
100
80
60
40
20
0
Sample conductivity [
S/cm]
Re
sidua
l chl
orine
concen
tratio
n [mg
/L
]
0
100
200
300
400
500
600
3.5
2.5
1.5
0.5
1
2
3
h19136 | UTC 2020/03/30 3:34:51
CONFIDENTIAL
