Accessory equipment for SECM

12 Block schematic of a nanocurrent source for use in SECM. WEI, WE2, AE, and RE refer to working, auxiliary, and reference electrodes. 

The lower part of the diagram is the switching circuit. Applying a ground potential to the input causes relay K1 (Hamlin HE721A0510) to become energized, lighting LED D2. K1 acts as a power switch for relays 

A separate relay power supply is needed to supply the large currents required by the relays. The relay power supply can be an inexpensive wall-wart. Note that the relay power supply and ground lines are completely isolated from the current supply section of the circuit. 

Some SECM experiments require an isolation amplifier to avoid electrical interference. One example occurs with a potentiometric tip and a potentio-static electrode, such as a pH-sensitive tip at a polarized corrosion test sam- 

The following is a listing of addresses and web pages for companies mentioned by name in the text. Also included are suppliers of material or equipment useful in constructing or maintaining a SECM. It is not an exhaustive list, and emphasis is on North American suppliers. Addresses are for the United States unless otherwise noted. 

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