32
3.
If you wish to continue for low calibration, leave the probe in air, a visual
display of the raw data is seen on the LCD display. When the raw data D is
stable press
ENTER
, the salinity calibration coefficient will then be automatically
updated. You will be asked if you wish to calibrate high set point
ENTER
or
ESC.
4.
If you wish to continue for an upper calibration, immerse the probe in a
solution with a salinity of 30-40 ppt, Press
ENTER
; a visual display of the raw
data D is seen on the LCD display. When the data is stable press
ENTER
, then
use the UP/DOWN arrows keys to set the salinity value of the solution that was
used and then the calibration coefficient will be automatically updated and the
instrument will return to the calibration menu.
Low Conductivity calibration
1.
Select CAL C25 us/cm from the Cal Key and using ARROW Keys select Calibrate
instrument press ENTER after reading warning and use arrow keys to select E.C.
(us/cm) and press
ENTER
to continue or
ESC
and go to Cal High set point or Cal
Low set point. Follow the instructions on the LCD display and be sure that the
raw data “D” is stable before accepting the data.
2.
Leave the probe in air and press
ENTER
for zero conductivity calibration. You will
be asked if you wish to calibrate high set point
ENTER
or
ESC.
3.
If you wish to continue for an upper calibration, immerse -the probe in a KCl
solution. To prepare the solution, dissolve 0.7459 grams anhydrous KCl in
distilled water and make up the solution to 1 litre. This has an electrical
conductivity of 1413 umhos/cm. The raw data will be displayed on the display.
When the raw data D is stable press
ENTER
. Then use the UP/DOWN arrows
keys to set the conductivity value of the solution that was used and then the
calibration coefficient will be automatically updated and the instrument will
return to the calibration menu.
Other conductivities can be selected between 500 to 8000 us/cm. It is advisable to use
the solution of KCl which has the conductivity of 1413us/cm. The calculation for
temperature correction is at its optimum when this value is used. If other standards are
used the temperature changes in the sample will cause small changes in the displayed
conductivity.
Dissolved Oxygen calibration
Dissolved oxygen calibration is performed using solutions with zero % or 100% oxygen
saturation. To prepare a sample with zero % saturation, dissolve 26 grams of sodium
sulphite in 500 ml of water and add 0.2 grams of cobalt chloride. Stir the solution until
the crystals are dissolved. Discard the solution after 30 minutes as it will begin to absorb
oxygen. Alternatively an optional zero dummy probe may be used to obtain a zero point.
Содержание 615
Страница 47: ...47 Appendix 2 Compliance for probe N 10255...