User Guide

21
TEMPERATURE-RESISTANCE
CORRELATION FOR HANNA
pH SENSITIVE GLASS
The resistance of glass electrodes partially
depends on the temperature. The lower the
temperature, the higher the resistance. It
takes longer time for the reading to stabilize
if the resistance is higher. In addition, the
response time will suffer to a greater degree
at temperatures below 10°C.
Since the resistance of the pH electrode is
in the range of 200 Mohm, the current across
the membrane is in the pico Ampere range.
Large currents can disturb the calibration of
the electrode for many hours.
For these reasons high humidity environ-
ments, short circuits and static dis-
charges are detrimental for a stable pH
reading.
The pH electrode's life also depends on the
temperature. If constantly used at high tem-
peratures, the electrode life is drastically
reduced.
-
20
-
20
-10
0 +10+20 +30+40 +50+60+70 +80+90
°
C
-10
-10
Ω
-10
-10
-10
-10
2x10
9
1x10
9
2x10
8
1x10
8
2x10
7
1x10
7