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4. Calibration
4.1 Calibration Procedure
1.
Switch the
miniCHEM-Redox
on. Set the function switch to
STANDBY
, to
ensure that the (optional) relay output is not activated when placing the
Redox sensor into standards.
2.
Connect the Redox sensor and ensure that a solution guard rod is fitted. (see
section 3.4). Remove the wetting cap from the Redox sensor.
3.
Rinse the Redox sensor and guard rod in distilled water and blot them dry.
4.
Make up a 1:1 solution of ZoBell Part A and ZoBell Part B. If a small vessel
is used for calibration, around 10mL of each should suffice.
5.
Place Redox sensor and guard rod into the ZoBell standard. Ensure that the
Platinum tip and reference junction are both covered (see diagram below).
6.
When the reading has stabilised, adjust the
ZERO
control until the display
shows the value of the ZoBell standard. This will be one of the following…
a) 229 mV for Ag/AgCl reference systems filled with saturated KCl.
(All of the Redox sensors listed in section 1.2 are this type.)
b) 192 mV for Ag/AgCl reference systems filled with 1 Molar KCl.
c) 192 mV for Calomel reference systems.
7.
Rinse the Redox sensor and guard rod in distilled water and blot them dry.
8.
Discard the used made-up ZoBell standard.
9.
The
miniCHEM-Redox
is now calibrated and ready for Redox
measurements. Calibration should be performed at least monthly. Of course,
more frequent calibration will result in greater confidence in results.
