Chapter 1 -- Introduction -- Potentiostat Schematic Diagram
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The PCI4/300 and PCI4/750 are two members of Gamry Instruments’ PCI4 Potentiostat family. They share a
number of characteristics with the other members of this family, especially in the areas of signal generation and
signal preconditioning prior to A/D conversion.
PCI4 features include 9 decade current auto-ranging, electrical isolation from earth ground, current interrupt iR
compensation, and extensive filtering. A sine wave generator on the PCI4 allows its use for impedance
measurements at frequencies up to 300 kHz.
The PCI4 consists of two printed circuit cards that install directly into a computer. Each card requires one
expansion slot in an AT compatible computer. The cards are interconnected by one ribbon cable. Depending
on the number of available slots, up to four PCI4 card sets can be installed in one computer.
The first card is called the Potentiostat Card. It contains the analog potentiostat circuitry and its associated
isolated power supply. This card is not directly connected to the computer's AT bus, except for the 5V power
and its ground. It communicates with the computer over serial lines isolated by opto-couplers on the other
card. The Potentiostat card can be switched to act as a high performance Galvanostat or as a ZRA (Zero
Resistance Ammeter).
The second printed circuit card will be referred to as the Controller Card. It contains a PCI bus interface, opto-
coupled serial transfer logic, an isolated power supply, a signal generator, and a high performance measurement
system.
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The PCI bus interface communicates with the rest of the PCI4 over opto-coupled serial lines. There is no
ground connection between the PCI bus circuitry and the analog circuits in the PCI4.
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Each card contains an isolated DC/DC converter. The power supply on the Controller card converts the
computer’s 12 volt supply into the voltages needed to power its own analog circuitry. The power supply on
the Potentiostat card converts the computer’s 5 volt supply into a variety of voltages.
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The standard "DC" signal generator on the Controller Card uses two 16 bit D/A converters. A DDS sine
wave generator is packaged on a small "piggyback card" that plugs into the Controller card.
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The Controller Card measurement circuitry includes signal filtering, offset, and switchable gain on two
independent measurement channels. The output of these channels is measured using a 16 bit A/D
converter.
Potentiostat Schematic Diagram
If you are not familiar with electronic schematics or potentiostats, you probably want to skip this section. This
information is for expert use only and is not required for routine use of the PCI4 Potentiostat.
Figure 1-1 is a highly simplified schematic diagram. It shows the analog portion of the Potentiostat in its
potentiostatic control mode.
