A Robust Sensor for Monitoring the Operational Status of Agricultural Ventilation Fans

Abstract

A new vibration sensor for monitoring the operational status of exhaust fans in confined animal feeding operations (CAFOs) and other ventilated structures was developed and tested. The sensor utilizes integrated Micro Electro Mechanical Systems (iMEMS) technology to accurately and reliably detect the vibration of agricultural fans, an indicator of fan operating status. When coupled with a sensor to measure pressure drop across the fan and an appropriate fan performance curve, the vibration sensor can enable the collection of real-time building ventilation airflow data. The sensor integrated an iMEMS accelerometer along with signal conditioning components to convert the cyclic acceleration signal into a filtered TTL digital signal appropriate for a wide variety of data acquisition equipment. Sensor current draw was 0.9 mA, which allowed multiple devices to operate from a single power bus. Laboratory and field testing has shown that the sensor is 99% effective in determining the total on-time of agricultural fans when compared with existing methods. Testing has also shown that the sensor response is not affected by changes in operating environment temperature. Sensor installation takes only a few minutes and requires only a single hole placed in the existing fan mounting structure. Furthermore, by encapsulating the sensor in a potting compound, all critical electronic components can be sealed from the corrosive effects of moisture and gases common to CAFOs and other ventilated structures.