Martek MARK 22 Operation Manual page 34

5 - CALIBRATION
Therefore, unless solution temperature in
your conductivity reference cell is exactly
25 C, you must measure the solution tem-
o
perature and apply the following formula:
Solution Conductivity @ 25
Raw Conductivity
For example, let's say you are using a ref-
erence solution with a certified conductivity
value of 30 microsiemens/cm @ 25
measuring the solution with a thermometer,
you determine the temperature of the solu-
tion to be 19 C. If you input these numbers
o
into the formula stated above, the equation
will look like this:
30 uS/cm X [1 + .02(19 - 25)] = 26.4 uS/cm
After processing the equation your an-
swer should be 26.4 uS/cm. Again, this is
the raw conductivity value of the reference
solution and this is the value that you would
enter into the Mark 22.
To span the conductivity value, place the
reference solution in the conductivity refer-
ence cell. It is desirable that the solution be
flowing through the cell, but if this is imprac-
tical, fill the cell completely with solution and
seal the ends.
Now, enter the calibration mode and
choose the "COND" option. Next, choose the
"SPAN" option and press the SELECT key.
The display will prompt with the following
message:
PLACE SENSOR IN
Then will ask you to:
HI COND STANDARD
30
o C X [1 + .02(T - 25)] =
C. After
o
HIT KEY W/STABLE
+0.5120 VOLT
Once the displayed voltage has stabilized,
press the SELECT key.
prompt with the following message:
INP 5 DIGIT STD.
HI C = 0.0000 uS
Enter the raw conductivity value of the
reference solution by pressing the UP or
DOWN ARROW key.
forward to the next digit by pressing the
SELECT key and move back to a previous
digit by pressing the EXIT key. The position
of the decimal point will vary when other
cell constants are used.
NOTE: If the solution is not flowing through the
cell, the voltage displayed may slowly start in-
creasing due to polarization. Care should be
taken to press the SELECT key as quickly as
possible after the solution has been placed in the
reference cell and as soon as the voltage appears
to have stabilized.
Once the last digit has been entered, the
Mark 22 will automatically return to the cali-
bration menu:
TEMP
pH
and the "pH" option will be flashing.
The display will
You can then move
COND
TIME
Martek Instruments, Inc.