Question

Which accelerometer technology is the best?

Answer

No one accelerometer technology is really better than the other. The "best" accelerometer technology is dependent on the application. This brief article will review technologies outlining their relative strengths and weaknesses.

Piezoelectric (Charge Mode): A piezoelectric device offers excellent performance from a few Hz to about 10 kHz (higher in some cases). There are charge mode accelerometers that offer extreme temperature operation from 300°F (184°C) up to 1200°F (650°C). The shock range of these units is also very wide and they are ideal when the maximum range is unknown. The accelerometer can be paired with a charge amplifier where the gain can be adjusted based on the actual output requirements. Acceleration measurements are limited to dynamic acceleration as they do not respond to constant acceleration and low noise cable is recommended.

IEPE (ICP): These accelerometers also utilize piezoelectric technology, but combine it with a built-in electronic charge to voltage converter. They have characteristics similar to piezoelectric accelerometers, but feature a low impedance voltage output thus no charge amplifier is required. Due to the internal electronics, the high temperature is limited to 350°F (175°C). These accelerometers exhibit the same frequency and sensitivity characteristics as piezoelectric devices and also only measure dynamic acceleration. IEPE accelerometers are used for shock and vibration measurements and low noise seismic applications. This technology offers operator convenience and allows the use of ordinary coaxial cable. While this technology eliminates the need for a charge amplifier, a constant current source is required. Many data acquisition systems and FFT analyzers have built-in current sources making no additional conditioning necessary. Stand-alone power sources and conditioners are also available.

Piezoresistive: Piezoresistive accelerometers are usually a millivolt output device which makes them desirable for shock measurements. By using MEMS technology, they can be manufactured with a very high resonance frequency allowing for measuring frequencies >100 kHz. They are also "DC" responding allowing for observing long duration shock events. These sensors can be very small and lightweight, while also rugged in high shock environments. Piezoresistive accelerometers are especially useful for high shock measurements and automotive crash testing applications.

Variable Capacitance (VC): Their strength is the measurement of very low frequencies and motion with little low frequency phase shift. These devices can measure continuous acceleration with high sensitivity making them useable for measuring tilt angle and also acceleration produced during a rocket launch. VC accelerometers exhibit very stable zero offsets and amplitude stability. They have high sensitivity making them desirable for motion and vibration, but have a limited high frequency response to a few kHz.

Applications include ride studies, low frequency modal analysis, aircraft flutter applications. They are desirable for measuring whole body motion following a shock event.

It should be noted that all the above accelerometers, with the exception of the piezoelectric accelerometer, require excitation power.