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
Well not to be mean but I seeing as questions about operating your instrument has nothing to do with LabVIEW.
I suggest you ask your question on the Keithley support forum.
Then once you know how to properly operate your instrument, come back show us your code and someone here can probably help you with LabVIEW.