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.
A Multifunction Tactile and Proximity Sensing Method by Optical and Electrical Simultaneous Measurement
This paper presents a new single-unit tactile and proximity sensing method which simultaneously uses optical and electrical measurement. The proposed sensor consists of electrodes and a photodiode with a light-emitting diode. In the proposed method, the admittance between the electrodes and the photodiode is measured. The electrical properties of most objects vary with the distance between the sensor and the object, and in this sensor, they are measured from the admittance between the electrodes. Additionally, the optical properties of the sensor surface (indentation) are measured from the admittance of the photodiode. In the experiment, discrimination between six materials (acrylic, glass, aluminum, and sponges with three different hardness values) and detection of the indentation were demonstrated during contact, while the object proximity could also be detected. The proposed sensor may be useful as a tactile sensor in robots.
Electron Beam Test System for GHz-Waveform Measurements on Transmission Lines within MMIC
A system for measurements of waveforms on transmission lines within microwave integrated circuits based on a scanning electron microscope has been developed. For the first time it offers simultaneously a spatial resolution of less than 1Ovm, a temporal resolution better than 10ps, and in principle a frequency range up to 40GHz. Additionally, due to the use of a special phase-shift technique, the repetition rate of the electron beam pulses and the operating frequency of the MMIC can be chosen arbitrary. The performance of this test system is demonstrated by quantitative waveform measurements up to 24GHz. On coplanar transmission lines built on semiinsulating GaAs with center conductor widths of 40¿m and 20¿m, relative power levels could be estimated.