Variable volume piezometer for measurement of volumetric properties of materials under high pressure

Abstract

A piezometer was designed to measure volume change of foods and other biomaterials as a function of pressure, and calibrated and tested up to 700 MPa at 25°C. The sensor was constructed from a polycarbonate tube, sealed with a plug on one end and a removable piston on the other. Samples were placed inside the tube. Upon pressurization, the piston displaced inside the tube, transmitting pressure to the sample; impedance in a magnet wire coil on the outside of the tube was measured to characterize volume change. Sensor calibration with water yielded a polynomial that characterized volume as a function of impedance. Sensor precision is 0.3% of measured volume; its resolution allows measurement of sub-microliter volume changes. Testing with ethanol and sucrose solutions yielded data within 1% of previously reported values. The sensor's applications include measurement of volumetric properties of liquid and solid biomaterials, and chemical reaction volumes.

Keywords:

• density
• compressibility
• piezometer
• volume

Acknowledgements

The authors would like to acknowledge research support provided by USDA-CSREES-NRICGP grant 2005-35503-15365, by the Ohio Agricultural Research and Development Center (OARDC), by the Ohio State University and by the Center for Advanced Processing and Packaging Studies (CAPPS). References to commercial products or trade names are made with understanding that no endorsement or discrimination by the Ohio State University is implied.