Hanna Instruments HI 9810 Instruction Manual Download

Page: 6 / 11

The TDS value in aqueous solutions is directly proportional to conduc-
tivity. The ratio between the two parameters depends on the solution.

HI 9810

has a fixed conversion factor set to 0.5. This means that

1 µS/cm is equal to 0.5 mg/L of TDS.

EC/TDS CONVERSION FACTOR

The conductivity of an aqueous solution is the measure of its ability to
carry an electrical current by means of ionic motion.

The conductivity invariably increases with increasing temperature.

It is affected by the type and number of ions in the solution and by
the viscosity of the solution itself. Both parameters are temperature
dependent. The dependency of conductivity on temperature is ex-
pressed as a relative change per degree Celsius at a particular
temperature, commonly as percent per C.

For common ionic solution, this value is about 2%/ C. Acids, alkalis
and concentrated salt solutions have somewhat lower value, typically
1.5%/ C.

Since a small difference in temperature causes a large change in
conductivity, it is necessary to compensate for conductivity readings at
high and low temperature. The readings are usually normalized at
25 C.

HI 9810 automatically compensates for temperature differences with
a built-in temperature sensor circuitry. With this compensation, the
display shows the readings at 25 C (77 F).

TEMPERATURE COMPENSATION

For temperature compensation during calibration, please refer to the
following chart.

pppppH VALUES AT VARIOUS

H VALUES AT VARIOUS

TEMPERATURES

TEMP

pH VALUES

°C

°F

4.01

6.86

7.01

9.18

10.01

0
5

10
15
20
25
30
35
40
45
50
55
60
65
70

32
41
50
59
68
77
86
95

104
113
122
131
140
149
158

4.01
4.00
4.00
4.00
4.00
4.01
4.02
4.03
4.04
4.05
4.06
4.07
4.09
4.11
4.12

6.98
6.95
6.92
6.90
6.88
6.86
6.85
6.84
6.84
6.83
6.83
6.84
6.84
6.85
6.85

7.13
7.10
7.07
7.04
7.03
7.01
7.00
6.99
6.98
6.98
6.98
6.98
6.98
6.99
6.99

9.46
9.39
9.33
9.27
9.22
9.18
9.14
9.10
9.07
9.04
9.01
8.99
8.97
8.95
8.93

10.32
10.24
10.18
10.12
10.06
10.01

9.96
9.92
9.88
9.85
9.82
9.79
9.77
9.76
9.75

For instance, if the buffer temperature is 25 C, the display should
show pH 4.00 or 7.00 or 10.00.
If the buffer temperature is 10 C, the display should show pH 4.00
or 7.10 or 10.20.
If the buffer temperature is 50 C, the display should show pH 4.10
or 7.00 or 9.80.