Noncontact Material Identification and Distance Measurement Using Effective Capacitance With CdS Cells
We propose a novel noncontact sensing method for material identification and for detection of the distance between the sensor and the surface of a material by using its electrical and optical properties. In the proposed method, capacitance between the terminals of a pair of CdS cells, called the effective capacitance, is measured, and several capacitance values are obtained by changing the emission strength of the light emitting diode, thus changing the resistance value of the CdS cells. From these values, it is possible to identify the materials and to detect the distance between the CdS cells and the material. In this paper, we compare four kinds of effective capacitance measurement methods using a pair of CdS cells and describe the proposed measurement method. In addition, this paper discusses the measurement accuracy of effective capacitance values in the proposed method and demonstrates its ability to identify six material samples-clear, white, and black acrylic, clear vinyl chloride, brown bakelite, and aluminum-and to detect the distance between the CdS cells and the material.
Noncontacting low-cost instrument for film thickness measurement
The authors present a noncontact, nondestructive technique for measuring the thickness of thin liquid or solid films and coatings in real time by utilizing the resonance properties of microstrip structures based upon the work of Hurley, Kaufman, and Roy (see Review of Scientific Instruments, 61, Sept. 1990). This work is extended by confining all microwave aspects of the system internal to the instrument, thereby eliminating the need for any microwave test equipment. Only a low-voltage DC source, such as a 9-V battery, is required to power the unit, while the output is again a DC voltage or current. Using linear modeling equations, the system successfully determines the film thicknesses of water, enamel paint, and silicone rubber up to 0.8., 1.5, and 2 mm, respectively. Copper sheet metal up to 0.9 mm in thickness is also measured.<<ETX>>
Optical sensors for strain measurement on moving V-belts
Measuring the strain of an object provides information about axial loads which it is exposed to. In many cases, this information is wanted not from still-standing but from linearly moving objects. For the special application of combustion engine V-belts e.g. strain measurement permits to investigate their operational behavior. For this purpose, new noncontact measuring methods using optical sensors are being developed. The sensors detect periodic patterns on the moving V-belt surface. Provided that the V-belt speed is measured, the belt strain can be determined from a frequency analysis of the sensor signal.