Air Displacement Volumeter | June 2015

Over the summer of my sophomore year at Dartmouth, I designed and built a machine which could calculate the volume of an object by measuring the amount of air it displaced from a chamber. This project was meant to correct some of the limitations of the liquid displacement method of measuring volume, and I reached out to Professor Ronald Lasky in the Thayer School to advise the work for course credit. The final prototype was able to successfully measure the volume of objects within 2% of there actual volume, and I have applied for a U.S. patent on my designs.

The concept of my design was that if you equalize a pressure differential between two chambers, you can determine the ratio between their free volumes.

This procedure can then be used to calculate the volume of an object inside one of the chambers if the free volumes of the two chambers are known.

Design Concept for the Air-Displacement Volumeter

The final prototype of the device was novel, in that it was able to perform this procedure using one air compressor and one pressure gauge. The machine could also take many measurements quickly, allowing the operator to average several data points to get a better estimate of the object's volume. I also created a simple calibration procedure to calculate the volume of two chambers, by running the process with an object of known volume.

Air-Displacement Volumeter Prototype

The main drawback of the prototype, however, was that it required a fair amount of work on the users part to operate: calculating the volume of the object required the operator to toggle valves and enter pressure reading into a Microsoft Excel program. While this procedure only takes about a minute to perform, I would prefer that the process is fully automated such that the user could simply hit one button and the machine could calculate the volume of the object on its own. I have begun work on fully automated air-displacement volumeter, and hope to complete this prototype in the coming months.

Current State of the Automated Air-Displacement Volumeter Prototype

The current prototype is powered by a 12V AC to DC converter, and the original bulky air compressor has been replaced with small motorized pump. An Arduino microcontroller triggers solenoid valves and displays calculated values on an LCD screen. I plan to replace the Arduino with a more specialized microprocessor once the device is fully operational.