CHAPTER 4 Data acquisition
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C H A P T E R 4
Data acquisition
Introduction
One of the characteristics of electrochemical detection is its tremendous
dynamic range. In amperometric detection peak heights may vary from micro-
amperes down to the pico-ampere range. The DECADE covers such a wide
range from 5 µA down to 10 pA full scale, without being limited by electronic
noise.
The DECADE is equipped with two output connections for data acquisition,
the recorder (‘REC’) and the integrator output (‘INT’). The
integrator
output
has been designed to supply a non-manipulated, analog signal from the I/E
converter which is as close as practically possible to the working electrode
(WE). The
recorder
signal is manipulated by the CPU of the DECADE. The
details on data acquisition in the various ranges will be discussed for both
output channels.
Internal organisation
At the working electrode (WE) in the electrochemical flow cell the electron
transfer takes place due to an oxidation or reduction reaction. The resulting
electrical current is amplified by the current-potential (I/E) converter (Fig. 4).
Fig. 4. DECADE signal processing from electrochemical flow cell to REC and
INT output. R is a selectable resistor of 100, 10 or 0.1 MOhm corresponding
to the pA, nA and µA range respectively.
In the I/E converter a range of 10, 100 or 10000 nA full scale (FS) can be
selected, which corresponds to the so-called pA, nA and the µA range,
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