LABEC M-MIA-A - Manual (Page 88)

Ultrasonic milk analyser
For Sensorex pH electrodes, originally supplied with The 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 an hour for accuracy to within
0.01 pH, or once a day for accuracy to within 0.1 pH.
Use fresh buffers for calibrations. Avoid contamination of the stock buffer
solution and do not use it beyond the expiry date.
Keep all connections dry.
Operation manual MRC.VER.01-02.10