Biosys, a startup company with an expertise in microbiology needed help in refining a novel bacteria detection system and packaging it into a marketable product. The development required an incubator capable of testing 32 vial samples with an accurately controlled temperature while maintaining a small temperature delta between the test positions. The optical detection system had to be precisely aligned to the vial and be capable of detecting a .2% change in light intensity.

Solution: EPI engineers adapted a standard PID temperature control algorithm for operation on an 8-bit micro-controller. The algorithm and the use of solid-state heating elements allowed for accurate temperature stability. EPI optimized the heat transfer paths from the two heating elements to the vial incubator and improved the temperature uniformity across the chamber by more than a factor of two.

        Improvement in the stability and accuracy of the optical measuring system was accomplished using a combination of machined parts and precision injection-molded plastics. An LED calibration routine was written to remove gain variations in the detector and emitter elements allowing for the use of a wide range of components.

        Larger laboratories require the ability to process hundreds of samples each day. EPI designed an enclosure that holds four incubators in a 2x2 array of drawers. Each drawer tests 32 samples at independently adjusted temperatures allowing up to 128 samples to be evaluated at the same time. Each drawer is mounted on slides to allow for easy loading and unloading. Drawer latches were designed to limit the number of open drawers to one so that mechanical stability was guaranteed.

Results: EPI’s engineering effort improved the temperature uniformity and optical performance. Incubator packaging and design were tested successfully against several safety requirements.

The resulting system met the goals for laboratory environments and has proven successful in multiple worldwide applications.