Absfruct-A fully integrated bridge-output-to-frequency converter has been realized as signal-conditioning circuitry for a onechip smart thermal maskflow sensor. The frequency converter reads out four separate mistor bridges of the air-flow sensor in order to realize high sensitivity and direftional flow measurement over the f d angle range of 360". The converter selects the sensor bridges individually by means of a microprocessorcontrolled analog multiplexer. The flow velocity and direction are also calculated by the micropmcesaor. The relative measurement cancels all W-order errors. The center frequency is 10 kHz and the sensitivity 1 IW@VN). A bridgeoffset of 10 mVN is allowed, and the linearity error is 0.1%.
A fully integrated bridge-to-frequency converter is presented as signalconditioning circuitry for a one-chip smart thermal flow sensor. The converter reads out four separate bridges by means of a multiplexer to realize high sensitivity and directional flow measurement over the full range of 360°. Multiplexer control and output signal are microprocessor compatible. The relative measurement cancels all linear errors. The centre frequency is 10kHz. The sensitivity is lHz/(|iV/V). A bridge-offset of 10mV/V is allowed. The linearity error is 0.1%. The supply voltage is5V.
Guarding safety and security within industrial, commercial and military areas is an important issue nowadays. A specific challenge lies in the design of portable surveillance systems that can be rapidly deployed, installed and easily operated. Conventional surveillance systems typically employ standalone sensors that transmit their data to a central control station for data-processing. One of the disadvantages of these kinds of systems is that they generate a lot of data that may induce processing or storage problems. Moreover, data from the sensors must be constantly observed and assessed by human operators. In this paper, a surveillance concept based on distributed intelligence in wireless sensor networks is proposed. In this concept, surveillance is automatically performed by means of many small sensing devices including cameras. The requirements for such surveillance systems are investigated. Experiments with a demonstration system were conducted to verify some of the claims made throughout this paper.
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