An automatic psychrometer sensor for poultry farming

A sensor was developed which utilized the psychrometric process and produced an output proportional to percent relative humidity compatible with existing industry control devices. The wet- and dry-bulb sensors were comprised of two temperature sensors which had already been used successfully for thermostats for poultry farming control systems. A mechanical timer was utilized to automate the psychrometric process. The wet- and dry-bulb signals were digitized, and the result was used to address a psychrometric table stored in read-only memory (ROM) chips. The output from the ROMs was then converted to an analog signal for display and for use by a control system. The testing of the sensor demonstrated that it would produce the proper output within a tolerance of 1% for a range of several known humidities.<>