We want to use the Biologic potentiostat SP200 as an ammeter (as e.g. a Keithley 6485 or a classic multimeter), meaning that we want to read out the current without interfering in the system.
A measurement like chronoamperometry between WE and CE=RE always requests a voltage to be applied, and even applying 0 Volts would change the system.
Is this even possible with a classic potentiostat?
Dear Robin Bonné ,
it is uncommon, but it might be possible with a classic potentiostat your inquire, by selecting the OCV (vs time) mode in a (software) schedule program. The OCV on an Ohmic Resistor, R, might be[1] an (alternative[2], lower accuracy) ammeter, i (i = OCV / R), for some special cases.
1. Take special care about 'ground' electrode of your potentiostat, because it is not floating, like a classic multimeter (Keithley 6485, etc.).
2. Alternative, ammeter of rather lower accuracy (multimeter) than Keithley 6485.
Thank you for your answer, Ioannis Samaras!
OCV over a resistor was also our backup option, but since we're working with very small currents, not the ideal one.
Currents would be up to a few nA, and we want to measure 10-100 pA differences. Our Biologic SP200 potentiostat can handle this, but the software doesn't seem to allow to be operated as an ammeter. (We use a Keithley picoammeter now, but prefer the potentiostat because of readout issues.)
Dear Robin Bonné ,
do you have, also, the optional current booster, ULC (Ultra-Low-Current[1]) unit ?
1. Ultra Low current (down to aA resolution) https://www.biologic.net/products/ultra-low-current-down-to-aa-resolution/
Dear Ioannis Samaras
No we don't have the module, but it is still possible to reach that 10 pA precision, needed for our studies.
You might want to pre-test, with a (common 4-electrodes) CV[1] (VHigh_Low:+-0.1V, and low rate, say, 1mV/s) on two, same, not interconnected, (dummy) Resistors, R (about 100kO). So, you ignore the (dummy) Voltage (V vs time) and you keep, only, the data for current, (i vs time, graph).
1. Alternatively, try amperometry using a)one R1 (for current), same as before, and then
b)replace it (R1) with a (very low power) photocell, to verify if/how the graph i(t) synchronizes with the (external) light.
https://www.researchgate.net/figure/A-Potentiostatic-amperometry-at-V-0-V-by-periodic-light-chopping-for-the-cell-with_fig10_350295197
We will do that. Thanks a lot for your answers and time investment here.
- Badges
- Science topic
- Similar topics
- Instrumentation Engineering
- Instruments