Inexpensive coulometers for integration of sensor output: measurement of solar radiation

The expert measurement of sunlight on plants requires expensive instrumentation and considerable knowledge of physics, as can be seen in recent editions of Agricultural and Forest Meteorology. Nevertheless, it seemed that a simpler system could be devised that would yield data within, for example, 10 percent of state-of-the-art accuracy at a fraction of the cost. This notes describes such a method, specifically designed for monitoring photosynthetically active radiation (PAR) in multiple tropical forest sites over periods of days or weeks. Of particular interest were habitats occupied by epiphytes in remote areas where the weight and bulk of instrumentation and its susceptibility to damage pose serious problems.