Page 16
4. Calibration
4.1 Calibration Procedure
1. Switch the
mini
CHEM
-DO
2
on.
2. Ensure that the Dissolved Oxygen sensor is correctly connected (see section
3.4).
3. Set the function switch to
STANDBY
, to ensure that the (optional) relay
output is not activated by the Dissolved Oxygen sensor’s response.
4. Rinse the Dissolved Oxygen sensor in distilled water and blot dry.
Zero Calibration
5. (a) Place the sensor into an oxygen-free solution. This solution may be
prepared by dissolving 2g of Sodium Sulphite in 100mL of distilled water.
A 50g bottle of Sodium Sulphite powder is supplied with new ED1M
and EDYSI sensors for this purpose (part number 123302).
(b) Allow the reading to stabilise at or near zero. This may take 2-3 minutes.
(c) Adjust the
ZERO
control until the display reads 0.00 ppM or 0.0 %
Saturation.
6. Rinse the Dissolved Oxygen sensor in distilled water and blot dry.
Span Calibration
7. (a) Hang the Dissolved Oxygen sensor in air. The tip of the sensor should be
pointing downwards.
(b) Allow the reading to stabilise. After a zero calibration, this may take up to
5 minutes.
8. (c) For % Saturation readout, adjust the
SPAN
control until the display reads
100.0.
For ppM readout, adjust the
SPAN
control for the ppM (mg/L) Dissolved
Oxygen value at the current air temperature, and the expected salinity value of
the sample solution. A table is provided in section 10.1 for this purpose.
If the expected salinity value of the sample solution is quite high, there may not
be enough adjustment in the
SPAN
control to calibrate the readout. If this is the
case, please see section 10.3 for details on how to set the internal jumpers to
allow for higher salinities.
9. The
mini
CHEM
-DO
2
is now calibrated and ready for Dissolved Oxygen
measurements.
