RESUMO
Piezoelectric sensors have emerged as a versatile tool for measurement of various quantities such as pressure, acceleration, strain, or force across many industrial applications. When mechanically strained, electric charges are produced inside a piezoelectric transducer. These charges result in an electric field that may be measured as a voltage difference between two electrodes, from which the strain can be inferred. To measure this voltage the sensor must be interfaced with an external device that would typically have a finite input impedance. This, together with the capacitive nature of the piezoelectric sensor, results in an inability to measure strain at low frequencies. We propose a method, based on using a varactor diode in an oscillator circuit, which can result in accurate measurements of the piezoelectric voltage at ultra-low frequencies. We demonstrate successful measurements at 1 mHz.
RESUMO
In this paper, we discuss the hardware development of a UWB sensor node for wireless body area networks. A few unique UWB pulse generation techniques have been discussed. The sensor node transmits multiple pulses per bit to increase the average power of the transmitted signal in order to improve the bit-error rate (BER) performance. The multiple-pulse per bit technique is also used as the coding scheme to identify the individual sensor nodes when more than one sensor forms a network. The sensors nodes are able to transmit body signals up to 2 m with a BER lower than 10(-5).
Assuntos
Redes de Comunicação de Computadores/instrumentação , Monitorização Ambulatorial/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Telemetria/instrumentação , Transdutores , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
An implantable telemetry device is presented, inductively powered by a 5.8 mW 27 MHz ISM-band supply and received with a stacked-spiral implantable power coil. A 15th harmonic 405 MHz MICS-band data carrier is generated from the power signal, data-modulated, filtered and sent to a receiver via a wireless data link. The implantable module is tested in a biological environment, successfully proving the concept.
