LABEC M-MIA-LA - Manual (Page 91)

Ultrasonic milkanalyser
Operation manual 04.11.09 89/107
For pH electrodes, originally supplied with milk analyser read the
following information:
Temperature compensations
The output of pH electrodes varies with temperature in manner, predicted by
theory. When needed, Sensorex can supply electrode holders with build-in
automatic temperature compensators. The need of automatic compensation
depends on the temperature variation, the pH value being measured. At pH
of about 7 there is no error due to temperature and, of course, at a constant
temperature there is no error. As shown in the following table, the pH error
due to temperature is a function of both the temperature and the pH value
being measured. At a pH of about 7 there is no error due to temperature and,
of course, at a constant temperature there is no error. The more the
temperature changes from the ambient calibration temperature and the more
the pH departs from 7 the greater is the pH error.
pH temperature error table
pH °C
2 3 4 5 6 7 8 9 10 11 12
5 .30 .24 .18 .12 .06 0 .06 .12 .18 .24 .30
15 .15 .12 .09 .06 .03 0 .03 .06 .09 .12 .15
25 0 0 0 0 0 0 0 0 0 0
35 .15 .12 .09 .06 .03 0 .03 .06 .09 .12 .15
45 .30 .24 .18 .12 .06 0 .06 .12 .18 .24 .30
55 .45 .36 .27 .18 .09 0 .09 .18 .27 .36 .45
65 .60 .48 .36 .24 .12 0 .12 .24 .36 .48 .60
75 .75 .60 .45 .30 .15 0 .15 .30 .45 .60 .75
85 .90 .72 .54 .36 .18 0 .18 .36 .54 .72 .90
0 pH Error Range
Less than .1 pH Error Range
5. PH helpful hints
For greatest accuracy in pH measurement, follow these guidelines:
- Use the same technique to measure samples, which was used for
calibration.
- Be consistent with stirring rates, times and conditions.
- Calibrate with buffers, which are close in temperature to that of the
sample.
- Calibrate the pH electrode regularly, e.g. once a day for accuracy to
within 0.05 pH.