I accepted a sponsorship from Gretim International LLC. One of the problems they are interested in is the design of a durable, easy-to-use device for finding the level in an opaque 55gal drum. I chose to work with this problem.

The original project summary provided by Gretim included several requirements: the gauge must accurately determine the amount of fluid in the drum. It must be resistant to chemicals, corrosion, and rust. Ideally, it would have no moving parts. It also needs to be resistant to shock, and easy to install and use. Perhaps most importantly, it needs to protect the user from the chemical it measures, because the primary customer groups work with many corrosive or otherwise dangerous chemicals.

In the early stages of the design process, I generated many wildly different concepts for determining the amount of fluid in the drum. Each design had to detect, analyze, and report the amount of the chemical to be measured without compromising the safety of the user, but there are many ways of doing so. After developing nine possible designs, I finally chose the concept named the "Re-Calibrated Standard Gauge" for its inclusion of an off-the-shelf pressure gauge as the main component.

The final design has four components: the all-important gauge itself, the "barrel," the "foot," and a connector. The device senses the static fluid pressure at the bottom of the barrel by means of the corresponding pressurization of the sealed air column. The pressure is related to the depth by the equation P=rgd. With a correctly calibrated dial face in place, the reading on the pressure gauge tells the depth of the fluid as measured from the fluid surface to the top of the teeth of the foot.

The prototype functions well, clearly demonstrating the viability of the concept. However, if it were to go into production, different materials would need to be used. The corrosion resistance of the gauge is dependent on material selection. 304 stainless steel and nylon are the materials of choice, along with bronze as a cheaper corrosion-resistant material for the "wetted" parts of the pressure gauge. It might be necessary to manufacture the pressure gauge instead of purchasing an existing model, because I have not been able to find a gauge that is sufficiently rugged and has the correct operating range. In spite of this, I believe that the gauge can be produced for a lower cost than many of its competitors. It has the potential to meet and even exceed its requirements in the final design.