Development of an integrated fluid sensor

A new versatile device which warns of low fluid levels in various medical fluid containers is presented. The fluid-sensing part of the device is a novel type of electromagnetic (EM) coupler which senses the presence or absence of fluid in close proximity to it. The device is battery operated and is small enough to attach directly to the outside of many medical fluid containers. The EM coupler was characterized and optimized through network analyzer measurements, finite difference frequency domain (FDFD) and finite difference time domain (FDTD) computer simulations. Microwave oscillator and detection circuits were designed, constructed, and tested using the optimized EM coupler. The fluid-sensor was tested on a plastic milk container filled with water and the measured results are presented here. Qualitative results were also obtained on glass containers and actual intravenous (IV) bags.