hello all,

Janusz Mlodzanowski wrote:

>I would like to build a PIC based Redox measurement unit.
>I could not find any information about the signal conditioning path.
>I know that AC over DC is a preferred method. What about frequency
>range, and voltage required.
>What signal magnitude (uV vs mV) can be expected
>from the probe?
>I would appreciate any comments.
>Janusz


i have just developed a measurement system for electro chemical potentials
based on a 16F877.

redox measurement is basicly dc voltage measurement from -1V to +1V and is
accomplished with
best choice high impedance opamps (like LMC6082) with an additional
overvoltage/burst protection
circuit in the first stage.
the 16f877 does the main work to compute linearity by means of linaer
regression and the display/keypad interface.
with an additional Pt100-measurement you can compensate the temperature
error.

the voltage developped at the electrode pair depends on a variety of
parameters like material of the electrodes (the
reduction and oxidation participants), the pH-value of solution, the
temperature etc.

btw: the developed measurement system could also be used as a pH-meter and
to measure the conductivity.



best regards
Dieter Baltruschat

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