Thermo Scientific Orion 310, Instruction Manual

Page: 36 / 81

PerpHecT ® Orion 310, 320, 330 Instruction Manual
32 Introduction to Patented digital LogR pH Measurement for Orion 320
Table 1 pH Error due to 1 ° C Temperature Change (in pH units)
A. What Is digital LogR?
PerpHecT pH meters allow for direct temperature measurement and
temperature compensation from your pH electrode. With simultaneous
measurement of pH and temperature, the patented Orion digital
LogR technology makes it possible using most standard glass pH
electrodes. The system is based on using the electrical resistance of the
glass sensing bulb as the temperature probe. The name comes from the
fact that the logarithm of the resistance of the bulb varies almost linearly
with the reciprocal of the absolute temperature (See
Figure 5 ). Almost all
common pH glasses show a similar decrease in resistance with increasing
temperature, and can be used with other types of meters. However, only
the exact shape of the curve for Orion PerpHecT electrodes is in the
meter’s memory.
To maximize system performance and accuracy, use PerpHecT ROSS and
PerpHecT pH electrodes.
2.7
-1 0 1 2 3 4 5 6 7
2.6
2.8
2.9
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
T
emperature (1000/Degrees K
elvin)
Figure 5
Log of Resistance
Cal Point Values
Calculated Values
10
20
30
40
50
60
70
80
90 0.004
0.003
0.003
0.003
0.003
0.003
0.003
0.003
0.003 0.011
0.010
0.010
0.010
0.009
0.009
0.009
0.008
0.008 0.007
0.007
0.007
0.006
0.006
0.006
0.006
0.006
0.006 0.014
0.014
0.014
0.013
0.012
0.012
0.012
0.011
0.011 0.018
0.017
0.017
0.016
0.015
0.015
0.015
0.014
0.014
pH 12
or pH 2 pH 11
or pH 3 pH 10
or pH 4 pH 9
or pH 5 pH 8
or pH 6
TEMP. ( ° C)