GLOSSARY

All of SDI's Accelerometers are precision instruments built for demanding applications and feature low noise, minimal bias and scale factor errors, and excellent accuracy. Use the Glossary to learn about these and other accelerometer terms.

What's the difference between the various Surface Mount Accelerometer chips?

The 1521 is SDI's flagship and great for most applications. It's rugged, easy to use, dependable, and has a track record of success in thousands of applications. The 1522 is the upgraded sister of the 1521, also for use between -55°C and +125°C. They’ve been individually temperature tested to have improved performance under more temperature-intensive applications with only half of the bias and scale factor over temperature than the 1521. The 1522 is ideal for applications that swing rapidly through the temperature range or persist at the hot or cold ends for long periods of time. The 1531 has the same performance specifications of a 1521 but is specially designed to withstand temperatures up to +175°C and keep working. It’s built with high-temp materials and tested to make sure it stays dependable at extra high temperatures that other accelerometers wouldn’t dare try. The 1525 is SDI’s high-end industrial-inertial grade accelerometer with an average bias repeatability of 5 mg. That means it was designed to provide the high level of long-term stability required by intensive inertial-related applications for operation in -40 to +85°C environments, like backup systems for light to medium weight aircraft and helicopters. With an average bias repeatability better than 2 mg, the 1527 is SDI’s tactical-grade inertial measurement accelerometer. Years of exhaustive R&D have generated an exceptional MEMS accelerometer with superb Allan Variance, long term bias repeatability, scale factor stability, axis misalignment and vibration rectification error.
Which G-level should I choose?

The g-range of your sensor should accommodate the maximum g-force of acceleration the measured object will experience but not be excessively higher. Choosing a g-range too high will unnecessarily sacrifice detail and clarity, while choosing too low of a G-level means the sensor will saturate when the G’s exceed its measurement range. Anything sitting still on the surface of the Earth is constantly subjected to approximately 1G of gravity. DC accelerometers, such as those produced by Silicon Designs, will typically read 1G in the vertical direction when not in motion, as they are designed to measure the Earth’s gravitation pull on the MEMS sense element. However, in free-fall conditions, an accelerometer will measure zero G’s until it comes to an abrupt halt, at which time it will measure the force of the impact. Driving around a corner in a car is usually less than 0.5G. Humans normally lose consciousness at about 6-8G. Seismic applications typically incorporate accelerometers with 2G ranges or lower, while automotive safety test requirements may call for an accelerometer with range of 200G or greater. Make sure to factor in frequency range capabilities when choosing your accelerometer, too. SDI accelerometers are known to have the lowest noise in the industry because the MEMS sense element in every sensor is specific to the G-range. The customized geometry and damping also mean the sense elements have different frequency ranges, because a high-G accelerometer will require more movement than low-G model, and vice versa. Check the sensor’s DATA SHEET for specific frequency range information.
Should I choose the Low-Cost modules or the High-Performance modules?

If they’ll be used in an environment that a person could comfortably withstand without wearing special gear, use SDI's Low-Cost Modules. They’re built with standard SDI accelerometer chips and are great for most applications. Rugged and dependable, they have a track record of success in thousands of applications. They work from -55°C and +125°C, use 8-32V DC excitation, individually calibrated, and serialized for traceability. 1-AXIS: 2210, 2260, 2266 3-AXIS: 2460, 2466 If your application involves rapid swings in temperature or long periods of time at the far ends of the temperature range, use the High-Performance Modules. They use the SDI 1522 accelerometer chips, which have been individually tested and temperature corrected to provide half the bias and scale factor over temperature in addition to all the standard benefits of SDI accelerometers. 1-AXIS: 2220, 2240, 2276 3-AXIS: 2470, 2476
What if I need to move things around, tend to destroy cables, or need a long cable length?"

If NO, an integrated cable will work beautifully: 1-axis 2210, 2220, and 2260, or 3-axis 2460and 2470. If YES, you would be better off with a detachable cable. Consider modules with connectors and choose your own cable length: 1-axis2266and 2276, or 3-axis 2466, and 2476 If YES, BUT... you want a longer integrated cable. No problem, we can buildthem with long cables with minimum custom build lot size of 10 pieces.
What if the surrounding physical environment is pretty brutal?

Make sure your accelerometer can withstand the conditions around it. Is it an environment a person could comfortably withstand without wearing special gear? Save money and consider a Low-Cost Universal Module: 1-AXIS:2210, 2260, 2266, or 3-AXIS:2460 or 2466 Is it extra hot or cold? If yes, SDI recommends a High-Performance model with upgraded Bias & Scale Factor Temperature Coefficients: 1-AXIS: 2220and 2276 or 3-AXIS: 2470and 2476 Is it dirty, extra humid, or high/low pressure? If yes, SDI recommends a Specialty Hermetic model in a titanium case: 1-AXIS: 2240 or3-AXIS: 2480
Which modules do I use if my power supply provides +8-32V DC for excitation?

SDI's Universal Test & Measurement accelerometer modules work with +/- 8-32 V DC excitation, support both single-ended and differential outputs, and we usually have them in stock. 1-AXIS: The 2210 is our most popular module. It uses the SDI 1521 accelerometer chip, a traditional 1”x1” package, and a 3’ integrated cable. 1-AXIS: The 2220 is the upgraded version of the 2210 and ideal if your application involves rapid swings in temperature or long periods of time at the far ends of the range. It uses the SDI 1522 accelerometer chips, which have been individually tested and temperature corrected to provide half the bias and scale factor over temperature. It uses a traditional 1”x1” package with a 3’ integrated cable. 1-AXIS: The 2240 is the 2220 in a hermetic, titanium case and has a connector. 1-AXIS: The 2260 is electrically the same as the 2210, but built in a small-footprint package. 1-AXIS: The 2266 is the 2260 with a connector instead of a 3’ integrated cable. 1-AXIS: The 2276 is electrically the same as the 2220 but built in a small-footprint package with a connector instead of a 3’ integrated cable. It’s the upgraded version of the 2266. 3-AXIS: The 2460 is the 3-axis version of the 2260 and has a 3’ integrated cable. 3-AXIS: The 2466 is the 3-axis version of the 2266 and has a connector. 3-AXIS: The 2470is the 3-axis version of the 2220 and has a 3’ integrated cable. 3-AXIS: The 2476is the 3-axis version of the 2276 and has a connector. 3-AXIS: The 2480is the 2476 in a hermetic, titanium case and has a connector.
Which modules do I use if my power supply provides +5V DC for excitation?

SDI's Specialty Low Voltage Modules only need +5V DC excitation to support DAQ systems with limited power supply functions. 1-AXIS: The 2012 uses the SDI 1521 accelerometer chip, a traditional 1”x1” package, and a 3’ integrated cable. 3-AXIS: The 2422 is the 3-axis version of the 2012 and has a 3’ integrated cable. 3-AXIS: The2422H is a 2422 in a hermetic, titanium package and has a connector.
Which modules do I use if my mounting location has size or mass constraints?

If Yes: SDI has small footprint 1-axis modules that are 33% smaller than traditional packages. Save space with SDI’s small footprint 1-axis modules: 2260, 2266,and 2276. If No: save a little money with SDI’s traditional 1-axis modules in standard 1"x1" packages with integrated cables: 2210and 2220.