The instrument generates, from a combined array of light emitting diodes (LED), non-periodical flashes of variable spectral composition and of user-defined timing, energy and duration. In a standard application, the instrument is used to excite photochemistry in photosynthetically active samples by strong single-turnover flashes and to follow the elicited electron-transfer reactions using weak non-periodic measuring flashes. The energy of the measuring flashes is low so that their contribution to the photochemistry is negligible and, yet, it is sufficient to excite easily detectable fluorescence emission and to allow detection of photochemistry-reflecting absorption changes in the range of A approximate to 10(-3). The minimal timing-definition step for a trigger or measure event is 300 ns and the minimal interval between two measurements is 10 mu s for each of the two independent input channels. The data are read with 16 bit resolution.
