In addition to making these measurements in the absence of any light sources, the PV cell should also be properly shielded and low-noise cables used in the test setup.

Keithley's low Level Measurements Handbook provides more information about using coaxial and triaxial cables and connectors, including low noise cables, and cable and connector assembly.

The dark pulses also transmit through certain fiber optic cables faster and with less noise than light pulses.