Hello All,
I am using Keithley 2450 SMU for performing a simple potentiometry. I have an electrode with three terminals Working electrode(WE), Reference Electrode (RE) and Counter electrode (CE). My application is to supply 200mV , 1 Amp across WE and CE, at the same time, I need to measure the Voltage across the WE and RE. I have used the LabVIEW drivers availabe at NI website. I have the following queries.
1) Which measuement option I need to use for the above applicaton, 2 wire mode or 4 wire mode
2) I have tried 2 wire mode and found that, what ever source voltage we are providing across the electrodes (WE and CE), I am getting the same from the Source meter measurement panel.Same from LabVIEW code also. For eg, if I give 200mV I am getting same 200mV across the RE and WE. But when I measure the voltage across (WE and RE) using a multimeter, I am getting around 155mV. Why it is not showing in Source meter?Why SMU is not showing the voltage drop across the RE and WE?
3) Then, I tried with 4 wire mode (200mV ,1 Amp) and I am getting 200mV across WE and CE and same across WE and RE. But when I measure the voltage across WE and CE using multimeter, I am getting 320mV and across WE and RE I am getting 200mV. I think in 4 wire mode the SMU is compensating the drop across the WE and RE and it is trying to maintain 200mV across it.But I dont want this behaviour. I need the voltage (the dropped voltage) across the WE and RE.
I am attaching the connection diagram of SMU with the electrode.
Expecting your suggestions and inputs
Thanks