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sample temperatures are rarely maintained
at precisely 25 degrees C. The Mark 22 is ca-
pable of providing raw parameter data, tem-
perature , and temperature corrected data all
in one display screen. The temperature ele-
ments for all Martek probes are rated to 100
deg. C and with the exception of pH, all sen-
sors can be subjected to sample water with
temperatures up to this limit.
For ultrapure conductivity measurement, the
Mark 22 can utilize one of three different tem-
perature compensation formulas. The three formu-
las are:
Marsh and Stokes:
−
EC Tc
0 05498 2 9326 10
.
=
EC
°
25 C
Truman Light:
−
EC Tc
exp
10858
=
EC
°
25 C
GE:
−
=
EC Tc
0 0545 0 55
.
.
EC
°
+
25 C
1
where
=
EC
electrical conductivity at 25 C
°
25 C
=
EC
electrical conductivity at T
Tc
=
T
sample temperature ( C)
c
a
= slope coefficient (1/ C)
Martek Instruments, Inc.
−
+
×
−
3
.
(
T c
25
×
7
72158
.
0 20004 10
.
−
+
.
+
+
2
T
273
(
T
273
)
c
c
+
−
1
a T c
(
25
)
−
exp ( .
0 0363
T
)
0 36297
.
+
c
0 0545
.
−
a T c
(
25
)
°
c
°
°
The slope coefficient a can also be ad-
justed within the Mark 22 software. The co-
efficient is typically 2.0%/°C for neutral salt
solutions.
sures acidic streams, slope coefficients be-
tween 1.0 and 1.6%/°C are more appropri-
ate for cation conductivity samples.
Mark 22 is used to calibrate on-line instru-
mentation, match the temperature-compen-
sation formula and slope coefficient to those
applied by the on-line instrumentation.
more information about temperature com-
pensation of conductivity, see "Temperature
Compensated Conductivity—A Necessity for
Measuring
Zabarsky, Ultrapure Water, Jan/Feb 1992, pp.
56-60.
−
+
×
−
5
2
)
6 0629 10
.
(
T c
25
)
+
−
1
a T c
(
25
)
×
9
0 31968 10
.
−
+
3
+
(
T
273
)
c
0 05479
.
OPERATION - 4
Since cation conductivity mea-
High-Purity
Water"
−
+
×
−
7
3
4 2690 10
.
(
T c
25
)
If the
For
by
Oscar
+
0 05498
.
17
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- Conductivity Calibration
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