29
CALIBRATION - 5
Martek Instruments, Inc.
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
DOWN
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:
Then will ask you to:
The voltage value for span should ap-
proximate +0.5000 volt.
Once the displayed voltage has stabilized,
press the
SELECT
key. The display will
prompt with the following message:
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:
and the "pH" option will be flashing.
The Mark 22 is now calibrated for con-
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-
ductivity
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. You can pur-
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
o
C."
PLACE SENSOR IN
HI COND STANDARD
HIT KEY W/STABLE
+0.5120 VOLT
INP 5 DIGIT STD.
HI C = 1.0000 uS
TEMP
COND
pH
TIME
