17
OPERATION - 4
Martek Instruments, Inc.
EC
25 C
EC
Tc
T
a T
c
c
°
−
−
+
−
=
+
0 0545 0 55
0 0363
0 36297
1
25
0 0545
.
.
exp ( .
)
.
(
)
.
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. Since cation conductivity mea-
sures acidic streams, slope coefficients be-
tween 1.0 and 1.6%/°C are more appropri-
ate for cation conductivity samples. If the
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. For
more information about temperature com-
pensation of conductivity, see “Temperature
Compensated Conductivity—A Necessity for
Measuring High-Purity Water” by Oscar
Zabarsky, Ultrapure Water, Jan/Feb 1992, pp.
56-60.
EC
25 C
EC
Tc
T
c
T
c
T
c
a T
c
°
−
+
×
−
+
×
−
+
×
−
+
−
=
+
−
−
−
0 05498
2 9326 10
25
6 0629
10
25
4 2690 10
25
1
25
3
5
2
7
3
0 05498
.
.
(
)
.
(
)
.
(
)
(
)
.
EC
EC
T
a
25 C
Tc
c
°
=
°
=
=
°
°
electrical conductivity at 25 C
electrical conductivity at T
sample temperature ( C)
= slope coefficient (1/ C)
c
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:
Truman Light:
GE:
where
EC
25 C
ECTc
T
T
T
a Tc
c
c
c
°
−
−
+
+
×
+
−
×
+
+
−
=
+
exp
.
.
.
(
)
.
(
)
(
)
.
10858
72158
273
0 20004 10
273
0 31968 10
273
1
25
7
2
9
3
0 05479
