T.S. Sanfelippo

Publications (2)1.37 Total impact

• Article: Surface acoustic‐wave device for measuring rate of gas flow

  J. G. Brace, T. S. Sanfelippo, S. G. Joshi
  [show abstract] [hide abstract]
  ABSTRACT: The use of a surface acoustic wave (SAW) device for measuring rate of gas flow is described. A delay‐line stabilized SAW oscillator is heated above the ambient by using a novel approach in which radio frequency (rf) energy is converted to heat via acoustic dissipation. This ‘‘self‐heating’’ arrangement eliminates the need for a separate heater and associated circuitry. Convective cooling caused by gas flow results in a change in the substrate temperature and thereby the oscillator frequency. The frequency of a 75‐MHz oscillator fabricated on a 128° rotated Y‐cut, X‐propagating lithium niobate substrate is found to vary by more than 55 kHz for variation in flow rate from 0 to 500 cm³/min. A dual‐oscillator configuration is implemented to provide temperature compensation and a convenient low‐frequency output corresponding to flow rate. Adequate flow‐sensing response is achieved with only modest (15 mW) oscillator loop power.
  Review of Scientific Instruments 02/1991; · 1.37 Impact Factor
• Conference Proceeding: Mass flow sensing using surface acoustic waves

  J.G. Brace, T.S. Sanfelippo, S.G. Joshi
  [show abstract] [hide abstract]
  ABSTRACT: A novel approach for measuring mass flow of gases is reported. A SAW (surface acoustic wave) delay line is heated above the ambient by absorbing RF power from an oscillator loop in which it also serves as the frequency-control element; forced convective cooling due to gas flow induces substantial frequency shifts. Utilization of RF power in the sensor is analyzed by applying a simple equivalent-circuit model. A mass-flow sensing configuration that utilizes dual SAW delay-line oscillators to provide temperature compensation and a convenient low-frequency output corresponding to mass-flow rate is described. For low flow rates, oscillator frequency increases linearly with the rate, and a normalized sensitivity greater than 4×10^-6/sccm at 150 mW input power has been obtained for nitrogen gas. Simplicity, high sensitivity, digitally compatible output, and low fabrication cost are some of the attractive features of this sensor
  Ultrasonics Symposium, 1989. Proceedings., IEEE 1989; 11/1989