The photoinduced transient displacement current (PTDC) technique is based on measuring the displacement current caused by formation of dipolar species in solution and their reorientation in external electric field.
Three essential elements of a transient dc conductivity apparatus are:
- an excitation source - laser (only one photon is shown in the picture above)
- a measuring cell (represented by two parallel plates in the picture) with a power supply
- an oscilloscope/digitizer (also shown in the picture).
Resulting sensitivity and time resolution depend on all three components.