Martek MARK 22 Operation Manual page 33

selected, select a cell constant of K = 0.0100
then press the CELL key again to return to
the monitoring mode.
Next, place the monitor in the lowest con-
ductivity range by pressing the
ARROW key until the decimal point is as far
to the left as possible.
Enter the calibration mode and choose the
"COND" option. Next, choose the "SPAN"
option and press the SELECT key. The dis-
play will prompt with the following message:
PLACE SENSOR IN
HI COND STANDARD
Then will ask you to:
HIT KEY W/STABLE
+0.5120 VOLT
The voltage value for span should ap-
proximate +0.5000 volt.
Once the displayed voltage has stabilized,
press the SELECT key.
prompt with the following message:
INP 5 DIGIT STD.
HI C = 1.0000 uS
Enter the value of 1.0000 uS by pressing
the SELECT key..
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 Mark 22 is now calibrated for con-
Martek Instruments, Inc.
DOWN
The display will
COND
TIME
CALIBRATION - 5
ductivity. The conductivity reference cell can
now be attached to the Mark 22 and mea-
surements taken. However, before doing so,
make certain that the specific cell constant
listed on the reference cell being used is cor-
rectly entered into the Mark 22. A condensed
version of the conductivity calibration pro-
cedure is located in Chapter 2.
The Dynamic Method of Spanning Con-
ducti v i t y
The Mark 22 conductivity calibration can
also be determined by the traditional method
of using reference solutions traceable to NIST
standards for accuracy.
When calibrating conductivity with this
method, special care must be taken to ensure
that the correct "K" factor range of measure-
ment is entered into the Mark 22 and that
the raw conductivity value of the reference
solution is used when inputting the conduc-
tivity span value.
Once you are certain that the correct "K"
factor has been entered within its appropri-
ate range for your particular reference cell,
you can proceed to span the Mark 22 con-
ductivity sensor.
The conductivity can be spanned using a
conductivity reference solution of potassium
chloride (KCL) equivalent to one of several
specific conductivity values.
chase this reference solution or mix it your-
self (Refer to a chemical handbook for po-
tassium chloride concentrations versus con-
ductivity values).
When using a reference solution, you
must remember the following:
"The conductivity value of the certified
reference solution is always measured at
25 C."
o
You can pur-
29