Tuesday, December 13, 2005

Accelerometers: Compact, Low Cost



Rieker’s line of accelerometers are small capacitive spring mass-based accelerometers with integrated electronics that do not require external amplifiers. The B Series - B1, B2, B3 – are static accelerometers for acceleration measurements in the frequency ranges from 0Hz to 550Hz. The BD and BDK Series are dynamic accelerometers for measurements in the frequency ranges from 1Hz to 1.5kHz. The units are available with analog DC output, digital pulse-width, or frequency- modulated outputs and have a very high resistance to extreme acceleration overloads and shocks (up to 10,000g). Light weight and compact in size (less than 24mm or .93”), these accelerometers can be configured to measure acceleration due to gravity (inclination) or radial acceleration (centrifugal force) in single, dual, or tri axial packages.

These accelerometers are characterized by very high overload resistance, linear frequency response with minimal resonance peaking (resonant peaks are minimised by means of a special gas-dynamic damping in the primary transformer), low distortion factor, low-impedance signal output, high signal to noise ratio, very low cross-axis interference, very low output-signal hysteresis, hermetically sealed, and very short settling time. Because of the low power consumption, these sensors have very low drift and long-term stability. Galvanic isolation, choice of housing style, and long connection leads are options.

Typical applications are for measuring or determining machine vibration, vehicle acceleration, seismic activity, inclination, and safety levels. These can be also be used for process control, stress control, shock control, crash testing, vibration analyzing, and dynamic rate determination. Certain accelerometers can measure both tilt and acceleration simultaneously.

Rieker Instrument Co Inc is one of the leading manufacturers of accurate, durable, weatherproof measuring, and leveling instruments, since 1917.

Tuesday, November 01, 2005

Structure of Capacitive Accelerometers

the Structure of:

Capacitive accelerometers sense a change in electrical capacitance, with respect to acceleration, to vary the output of an energized circuit.

When subject to a fixed or constant acceleration, the capacitance value is also a constant, resulting in a measurement signal proportional to uniform acceleration, also referred to as DC or static acceleration.

Monday, October 31, 2005

Acceleration

the Definition of:

The rate of change of velocity. Measurement of acceleration breaks into two main categories: for large moving objects, the acceleration is a very low frequency measurement proportional to the change in velocity of the entire object, such as a car or aircraft. For example, we speak of the acceleration of an automobile from 0 to 100 km/h (or 0 to 60 mph).

The second category is primarily used in vibration measurements, where the dynamic changes of the surface of an object are measured. For example, the resonance of an automobile muffler may result in vibrations at a frequency of 67 Hz.

Function of Capacitive Accelerometers
Capacitive accelerometers sense a change in electrical capacitance, with respect to acceleration, to vary the output of an energized circuit. The sensing element consists of two parallel plate capacitors acting in a differential mode.

These capacitors operate in a bridge circuit, along with two fixed capacitors, and alter the peak voltage generated by an oscillator when the structure undergoes acceleration. Detection circuits capture the peak voltage, which is then fed to a summing amplifier that processes the final output signal.