For a project we needed to use a specific device (Bio-Rad Gene pulser) to electroporate mammalian cells. We set up the instrument with the following settings:
Voltage = 1.9kV (we had to use this voltage for a particular reason)
Capacitance = 25 uF
Resistance = 200 ohm
And proceeded with electroporating cells (COS7 and CHO) in 0.4 cm chambers (Bio-rad) in PBS (800 uL). Interestingly, with different cell lines and cell densities, we had identical time constants (0.8 ms). We were shooting for a relatively low time constant as I read in another RG post (