Real-Time Electronic Measurement of Alcohol Content in Distilled Spirits Production

RF absorption is used to determine the alcohol content of spirits in real time during distillation. Alcohol concentration is a health issue and a quality parameter in alcoholic spirits production and must be presented in bottle label. The transducer is a coaxial transmission line cell designed to be impedance matched to the instrumentation as empty. It can be attached to the condenser output. Another configuration is to attach it to the tank collecting the heart cut or fraction. The distilled fluid flows into the cylindrical region in-between the conductors. An RF signal is injected into the coaxial cell. The incident and the transmitted signal power are measured by the attached circuitry. Two independent demodulating log amplifiers are used to convert the incident and the transmitted signals into dc voltages. Two A/D converter channels collect the voltages from each demodulating log amplifier, and the converted signal data are stored in the computer to estimate the alcohol content. As a proof concept, the instrument was tested in an artisanal alembic output in a cachaça plant in the Brazilian countryside.