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3. CALIBRATION
3.1 General Information
The DO 6 PLUS has three measurement modes; DO as % saturation, DO
as mg/L (or ppm) concentration, and temperature.
Dissolved oxygen levels vary with temperature, barometric pressure, and
salinity, so the calibration must be performed with consideration of these
factors.
It is necessary to set the proper temperature, barometric
pressure and salinity values prior to performing any DO calibration
or measurement.
See Section 3.2 —
Temperature Calibration
See Section 5.2 —
Automatic Temperature Compensation
See Section 5.9 —
Pressure & Salinity Adjustment
The DO 6 PLUS will accept two % saturation calibration points; 100%
using saturated air or air-saturated water, and 0% using a zero oxygen
solution. When the 100% calibration is performed, the corresponding
concentration is adjusted simultaneously. Therefore, it is not necessary
to calibrate the concentration mode. If calibrating for 0% oxygen, note
that the meter will take several minutes to reach 0% saturation value and
constant stirring is not required.
The following table lists calibration values in % saturation calibration
mode with two different barometric pressures. Note that the saturation
value (92.1%) has decreased due to the lower barometric pressure
entered.
% Saturation (per
factory default value)
Calibration Value
(760mmHg)
Calibration Value
(700mmHg)
less than 10%
0%
0%
10.1% to 49.9%
Err.1 (error 1)
Err.1 (error 1)
50% to 200%
100%
92.1%
If calibration is attempted from 10.1% to 49.9%, the “Err.1” message will
be shown. The calibration will be rejected and the display will return to
the measurement mode.
The DO 6 PLUS will accept one calibration point in concentration mode.
The minimum value is 2 mg/L (ppm), and the calibration window is
±40% of the factory default value.
Temperature and % saturation calibration should take place
before
attempting to perform mg/L (ppm) concentration calibration.
Calibration of the concentration mode will only replace the previous
concentration calibration and does not affect the % saturation calibration.
