Fence Sensor Research Articles

The Architectural Nervous System

The Architectural Nervous System

Buried cable sensor with intruder location

A buried cable sensor has been added to the Intrepid family of outdoor perimeter intrusion sensors. The sensor with the trademarked name "MICROTRACK" is similar to the "MICROPOINT" fence sensor with precise detection location, sensitivity leveling, and free format zoning. Intruder location is accomplished with low-power ultra wideband frequency stepped radar driving the sensor cables. Target range resolution also allows the use of sensitivity leveling for each individual range bin. This will compensate for differences in soil conductivity along the length of the cable and for metal objects, which may be located in the near field radiation. The design of the MICROTRACK sensor was presented at the 2002 Carnahan Conference in Atlantic City. It has been described as FM-CW radar, however it differs from the generic form in that the frequency is stepped rather than continuously swept and phase code modulation is added to discriminate against interference. The wide bandwidth of the MICROTRACK sensor fills in the nulls typical of a single frequency radar and provides a more uniform field profile along the entire length of the sensor cables. This describes the testing that has been performed to characterize the system for different environmental conditions. Southwest Microwave, Inc. has procured an open field site of 31 acres of flat desert land for testing the buried cable. Another site in Canada is used for testing with an additional set of weather and soil conditions. Detection patterns, proximity to stationary objects, and various environmental factors will be discussed. Extensive measurements of both electric and magnetic fields along the length and perpendicular to the sensor cables show a detailed map of the multiple frequency surface wave. When the cables are buried, the uniformity of the field is degraded slightly but no deep nulls are observed. Site testing has confirmed major benefits of the MICROTRACK sensor: - Uniform Detection Zone - Elimination of Deep Nulls - Precise Target Location - Sensitivity Leveling.

A second generation MEMS surface fence sensor for high resolution wall shear stress measurement

The measurement of the wall shear stress in fluid mechanics has important implications for the investigation of turbulent flow phenomena. An advanced version of the MEMS silicon surface fence sensor that measures this stress is presented herein. This sensor consists of a cantilever structure with a length of 5 mm, a height of 315 μm, and a thickness of 10 μm. Fluid flowing towards this structure causes it to bend. The resulting bending stress in the cantilever is measured with four piezoresistors, and this stress is correlated to the wall shear stress. The offset voltage has been reduced significantly. The sensor operates over a range of approximately −1 to +1 N/m 2 with a resolution of 10 mN/m 2.

A MEMS skin-friction sensor for time resolved measurements in separated flows

A MEMS surface fence sensor for skin-friction measurements in separated flows has been developed and tested successfully in low-speed flows. The new sensor is able to distinguish between forward and reverse flow and features a temporal resolution of up to 1 kHz. Calibrations of the sensor have been obtained in the range of –0.7 N m-2≤τw≤0.7 N m-2 with a resolution of 0.02 N m-2. Comparative measurements with the wall-pulsed wire technique in a reverse-flow region show excellent agreement with respect to the mean skin-friction coefficient cf but also reveal some discrepancies for the fluctuating part cf′.

Fiber optic fence sensor developments

Many detection technologies have been employed for perimeter detection, to sensitize a barrier. These outdoor perimeter fence detection sensors must reliably detect intruders attempting to cut or climb the barrier, while ignoring the effects of environmental noise, including nearby activity. In recent conference proceedings, the new IntelliFIBER/spl trade/ fiber optic based product was introduced and compared with previous technologies. IntelliFIBER is designed to provide the advantages of a nonconductive "dielectric" cable sensor, e.g., resistance to electromagnetic interference and the ability to provide longer cable zones. It utilizes the proven processor of the Intelli-FLEX/spl trade/ triboelectric cable fence sensor, which provides relay or bidirectional networked serial communications and is compatible with its calibration module. IntelliFIBER also capitalizes on the Intelli-FLEX's adaptive detection algorithms that were developed through extensive field-testing, to provide exceptional immunity to environmental alarms while still detecting the skilled intruder.

A micro surface fence probe for the application in flow reversal areas

Abstract The wall-shear-stress is the force parallel to a surface caused by a flow, which propagates parallel to the surface. Although there are several methods in use, there is a lack of sensors able to provide a high time resolution as well as the detection of flow reversals. This paper presents a micromechanical surface fence sensor, which consists of a 100–300 μm high and 7–10 μm thick silicon fence and a “body” for contacting and packaging. Four piezoresistors, connected to a Wheatstone bridge, measure the deflection of the fence and transform it into an electrical signal. Different fence geometries have been designed, simulated by FEA, fabricated and tested in a probe system as well as in a wind tunnel. With the most sensitive design, a resolution of 20 mN/m 2 has been achieved. With this performance, the device is suitable for a number of applications in aerodynamic research.

Evaluation of the Naval Space Surveillance Fence Performance Using Satellite Laser Ranging

An experiment is described in which the performance of the Naval Space Command Fence Receiver Suite is evaluated using satellite laser ranging. Fence measurement accuracy and precision is presently assessed based on cataloged orbits,which are notsufe ciently accurateforrigorouscalibrationand trend identie cation. Satellitelaser ranging is a well-known high-precision data type, which can provide submeter reference positions routinely. Two methods of sensor evaluation are investigated. One is an ephemeris-based approach, where a truth reference orbit is determined from laser ranging data from a number of different satellites at different altitudes. Fence-based residuals are then computed from this truth. The second is a geometric method, which computes satellite positions directly using ranging data and angle data from the telescope. A mathematical treatment of the geometric dilution of precision for both methods is included in the discussion. The overall experiment showed that the fence sensor suite isoperating to within 14 ‐17 times its noisee oorof 10 πrad atzenith. We believe thatthis is the most extensive measurement of the fence performance utilizing an external and independent data type, and due to the precision of the data type, its overall response and error trends are identie ed.

Electric fence sensor

Electric fence sensor