After I explained that a Keithley source-measure unit can be used as a potentiostat, I got a quick call back saying “So how do you hook it up?”
The 2450-EC potentiostat has four (4) connections on the front panel: FORCE HI, SENSE HI, FORCE LO, and SENSE LO. The FORCE terminals are like the output terminals of a power supply. The SENSE terminals do the measurement and can adjust the signal on the FORCE lines. This connection scheme is called 4-wire sense. It can compensate for potential drops in the FORCE leads. This all makes sense (no pun intended) to an electrical engineer. Fortunately, electrochemists do not have to worry about this.
For a 3 electrode cell, just connect:
- FORCE HI to the working electrode (WE)
- SENSE HI to the working electrode (WE) (Yes, both HI connections go to WE)
- FORCE LO to the counter electrode (CE)
- SENSE LO to the reference electrode (RE)
This connection scheme will give results (graphs and data) according to the IUPAC redox voltage and current convention (positive potential to the right of the graph; positive / oxidizing current at the top of the graph).
Keithley provides a cable their 2450-EC and 2460-EC potentiostats to simplify the connection between the instrument and 2, 3, and 4 electrode electrochemical cells.
Read more on the Keithley 2450-EC and the 2460-EC potentiostats.
Bill Pelster is the Director of Quality for the Keithley product line of Tektronix, Inc. He has been with the company for 37 year and has worked in engineering, applications, service, product safety, and quality. He has developed application software for testing high temperature superconductors and is now a member of the Keithley electrochemistry team. Bill holds a BEE degree from Cleveland State University (Fenn College) and an MBA from CWRU (Weatherhead School).