Accelerometer Technical Notes and FAQs

Precision Inertial Products Notes Index:

Our Technical Notes and FAQs (Frequently Asked Questions) area is designed to help you solve common questions and issues.

Technical Note #401 - Selecting Accelerometer Options

Technical Note #402 - MEMS Accelerometer Theory of Operation

Technical Note #403 - AC Coupling DC-Coupled Accelerometers

Technical Note #404 - Accelerometer Offset Drift Reduction Techniques

Technical Note #407 - Converting Unipolar to Bipolar Signals

Technical Note #408 - Establishing Digital Sensor Communications

Technical Note #409 - IRIG Encoding External Data (Inertial Measurement System)

Technical Note #410 - CRC16 Algorithm

Technical Note #411 - Acquiring Digital Sensor Measurements

Technical Note #412 - High-Speed Digital Sensor Measurements

Technical Note #413 - Compensating for Accelerometer Misalignment

Technical Note #414 - Reading Calibration Information from a Digital Accelerometer

Technical Note #415 - Reading Application Information from a Digital Sensor

Technical Note #416 - Units Conversions for Random Walk

Technical Note #417 - Digital Instrument Application Offset Compensation

Technical Note #418 - Acquiring Digital Sensor Measurements Using Scripts

Technical Note #419 - Processing CRC-8

Technical Note #420 - Setting Self-Test via RS485

Technical Note #421 - Converting Measurement Values to Engineering Units

FAQ #1

Can I use an Accelerometer to measure velocity or position?
Answer: Yes
These values can be obtained by integrating the accelerometer signal. Since integration introduces errors over time, the accuracy of the derived velocity and position values will decrease as the integration interval increases. For velocity measurements, the required accelerometer accuracy can be approximated based on the integration interval and the desired velocity accuracy by:

English Units
(v = ft/sec, t = sec, a = g's)
a = v / (32.17 * t)

Metric Units
(v = m/sec, t = sec, a = g's)
a = v / (9.807 * t)

Similarly, for position measurements, the required accelerometer accuracy can be approximated based on the integration interval and the desired position accuracy by:

English Units
(x = ft, t = sec, a = g's)
a = x / (32.17 * t * t)

Metric Units
(x = m, t = sec, a = g's)
a = x / (9.807 * t * t)

FAQ #2

Do I need to use differential inputs?
Answer: No
However, the use of differential inputs is recommended. Differential measurements provide a Kelvin connection and eliminate lead errors. When using an accelerometer with built-in cable, external noise pickup is also reduced because of twisted pair wiring.

When making single-ended measurements, lead error offsets must be considered. Since the supply current of our accelerometers is fairly constant, lead errors can be corrected by using offset compensation.

FAQ #3

Is CE Marking required for Components sold in Europe?
Answer: No
There has been some confusion as to whether electrical and electronic components to be sold in Europe require CE Marking. The following, which appeared in the the December 1997 "Test Clips" section of "Test and Measurement World", clarifies this issue:

The European Union has issued a "Guideline on the Application of Council Directive 73/23/EEC" clarifying that components should not bear the CE Marking. The CE Marking applies to products sold for end use, not products designed for integration into other products. Some exceptions include components used in building installations such as household switches, lamps, starters and some motors.

Manufacturers can design components that conform to the requirements of the CE Marking, but they may not apply harmonized safety standards to the product. So, even if a component conforms to the safety objectives of the Low Voltage Directive, manufacturers can't apply the CE Marking and, therefore, no presumption of conformity can exist. Some manufacturers may continue to apply the CE Marking for marketing purposes, but you should not assume that a component conforms to safety or EMC harmonized standard just because it bears the CE Marking.