Motion-sensing applications detailed in this article have reference the model ADXL330 monolithic integrated-circuit (IC) accelerometer from Analog Devices (www.analog.com) as an example of a three-axis device with suitable range for many wireless-related functions. The ADXL330 is one of the company's integrated microelectromechanical system (iMEMS ) lines of accelerometers that first revolutionized automotive airbag systems over 15 years ago. The devices are fabricated with a surface micromachining process that has been used to ship over 200 million sensors for automotive safety, consumer, and industrial applications. The iMEMS accelerometers are used to measure position, motion, tilt, shock, and vibration in a broad array of applications.

The ADXL330 is a three-axis accelerometer with signal-conditioned voltage outputs fabricated on a single IC (see figure). It is designed to measure acceleration over a minimum full-scale range of ±3 g, and can survive shock levels to 10,000 g. The typical full-scale measurement range is ±3.6 g.

The acceleration measurement nonlinearity is typically ±0.3 percent. The crossaxis sensitivity is ±1 percent. Package alignment error is typically ±1 deg. while inter-axis alignment error is typically ±0.1 deg. The ratiometric sensitivity at the x, y, and z output ports is typically 300 mV/g for a supply voltage of +3 VDC. Changes in sensitivity as a function of temperature are only ±0.015 percent/°C. The ADXL330 is rated for operating temperatures from ?25 to +70°C.

Operators can select the accelerometer's bandwidth by using capacitors for each of the x, y, and z directions at the respective output pins for those directions. The bandwidth can be selected to suit a particular application over a range of 0.5 to 1600 Hz for the x and y axes and 0.5 to 550 Hz for the z axis.

The ADXL330 is designed for single-supply operation, running on voltages from 2 to 3.6 V. It draws a mere 200 µA current from a typical supply voltage of +2 VDC. It is supplied in a low-profile 16-lead plastic lead-frame chip-scale package (LFCSP_LQ) measuring 4 × 4 × 1.45 mm. Analog Devices, Inc., One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106; (781) 329-4700, FAX: (781) 461-3113, Internet: www.analog.com.