This Small Business Innovation Research (SBIR) Phase II project aims to develop a micro-electro-mechanical system (MEMS)-based moisture (dew point) measurement instrument. Trace moisture measurements are needed in a variety of industrial sectors including natural gas production and distribution, semiconductor manufacturing, pure gas supply, aerospace, and petrochemical processing. Commercially-available moisture sensors are either very expensive, or alternatively lack the required accuracy, long-term stability, and responsiveness for many existing applications. The innovative aspect of the proposed approach is the utilization of micro-electro-mechanical resonant balances coupled with a cooling element. The instrument will measure dew point using the highly accurate chilled surface technique to deposit a layer of moisture on the surface of the resonant balances, hence combining the accuracy of the chilled surface measurement technique the with small size, low power consumption and affordability enabled by MEMS. The MEMS resonant balances are capable of detecting as little as a few femto-grams of deposited moisture. Therefore, only a very small amount of gas needs to be chilled for a short period of time (i.e. low power/battery operation) to deposit sufficient water to indicate the dew point. The self-zeroing capability of the measurement technique eliminates the need for frequent maintenance and calibration.
The broader impact/commercial potential of this project includes a significant leap forward in the moisture measurement technologies that have experienced no major development over the past several decades. The proposed new class of dew pointers offers higher accuracy, responsiveness, stability, and robustness currently unavailable at the same price range. An important immediate market with great national significance is the measurement of moisture in natural gas. In cold climates excess water in the gas pipeline can freeze the pipe shut, rendering the pipeline useless until the frozen point can be identified and cleared. Furthermore, due to the variability of the moisture content and the complete lack of suitable and affordable measurement equipment, wet gas is being used as the pricing standard in the natural gas industry, leading to pricing errors of up to 1.74%. The proposed battery- or solar-powered sensors will permit unattended operation and data transmission capability and will be installed at the natural gas wellheads as well as different points along the distribution network where these types of measurements are in high demand.
