Description acceptable. In one class of these devices, the conversion of AC signals to DC signals causes vibrational rectification error. They're not seismographs, but a type of these devices invented by Lucien LaCoste contain over-coiled springs that behave as if they have (*) "zero-length." Measurement systems consisting of coupled examples of these devices measure a quantity expressed as a 3 by 3 tensor whose components are measured in eotvos (“ert-versh”). Microelectromechanical designs for these devices typically consist of a damped cantilever with a test mass. These devices are the sensors in a car airbag system. The combination of a gyroscope, a magnetometer, and one of these devices compose inertial navigation systems. For 10 points, name these devices used in smartphones to detect shaking and tilting, which measure a quantity with units of meters per second squared. ■END■