A Simple Psychrometric Apparatus for Bowen Ratio Determinations

Abstract

A simple apparatus has been devised which automatically reverses the vertical positions of two pairs of shielded and aspirated wet- and dry-bulb diodes. Analog voltage signals proportional to the dry and wet bulb temperatures T and T_w and to the differences ΔT and ΔT_w are provided. The diodes present a low source impedance, a linear response over normal ranges, a sensitivity of about 2.3 mV(°C)⁻¹, and as used here, a time constant of about one minute. From these measurements the Bowen ratio can be determined conveniently.