Institute for Telecommunications Technology, Darmstadt University of Technology, Merckstrasse 25, D-64283 Darmstadt, Germany.
J Acoust Soc Am. 2011 Jun;129(6):3682-9. doi: 10.1121/1.3585833.
Electret microphones are produced in numbers that significantly exceed those for all other microphone types. This is due to the fact that air-borne electret sensors are of simple and low-cost design but have very good acoustical properties. In contrast, most of the discrete structure-borne sound sensors (or accelerometers) are based on the piezoelectric effect. In the present work, capacitive accelerometers utilizing the electret principle were constructed, built, and characterized. These electret accelerometers comprise a metallic seismic mass, covered by an electret film, a ring of a soft cellular polymer supplying the restoring force, and a metallic backplate. These components replace membrane, spacer, and back electrode, respectively, of the electret microphone. An adjustable static pressure to the seismic mass is generated by two metal springs. The dynamic characterization of the accelerometers was carried out by using an electrodynamic shaker and an external charge or voltage amplifier. Sensors with various seismic masses, air gap distances, and electret voltages were investigated. Charge sensitivities from 10 to 40 pC/g, voltage sensitivities from 600 to 2000 mV/g, and resonance frequencies from 3 to 1.5 kHz were measured. A model describing both the charge and the voltage sensitivity is presented. Good agreement of experimental and calculated values is found. The experimental results show that sensitive, lightweight, and inexpensive electret accelerometers can be built.
驻极体麦克风的产量远远超过其他所有类型的麦克风。这是因为空气传播驻极体传感器的设计简单且成本低廉，但具有非常好的声学性能。相比之下，大多数离散结构传播声音传感器（或加速度计）基于压电效应。在本工作中，构建、制造和表征了利用驻极体原理的电容式加速度计。这些驻极体加速度计包括一个金属振动物体，其上覆盖有一层驻极体薄膜，一个提供恢复力的软蜂窝聚合物环，以及一个金属背板。这些组件分别取代了驻极体麦克风的膜片、间隔物和背电极。通过两个金属弹簧向振动物体施加可调节的静态压力。使用电动振动器和外部电荷或电压放大器对加速度计进行了动态特性研究。研究了具有不同振动物体质量、气隙距离和驻极体电压的传感器。测量了从 10 到 40 pC/g 的电荷灵敏度、从 600 到 2000 mV/g 的电压灵敏度以及从 3 到 1.5 kHz 的谐振频率。提出了一个同时描述电荷和电压灵敏度的模型。实验值和计算值之间存在良好的一致性。实验结果表明，可以制造出灵敏、轻巧且廉价的驻极体加速度计。
