Accelerometers are widely used sensors in engineering, aerospace, automotive, manufacturing, and even mobile devices. They measure acceleration forces—both static (like gravity) and dynamic (such as vibrations or motion). However, to ensure that the data gathered by these devices is reliable and accurate, regular accelerometer calibration is essential.
What Is Accelerometer Calibration?
Accelerometer calibration is the process of verifying and adjusting the sensor’s output to match a known standard. It involves comparing the measured acceleration from the accelerometer with a precise reference signal under controlled conditions. Calibration corrects any discrepancies or errors, ensuring that the accelerometer provides accurate, linear, and traceable results.
Calibration is especially important in high-precision environments like aerospace testing, structural health monitoring, vibration analysis, and scientific research.
Why Calibration Is Important
Accuracy
Without calibration, accelerometers may drift or give biased readings over time. Accurate calibration ensures the readings are reliable and reflect true acceleration.
Traceability
Calibration links measurement results to international standards (like those maintained by NIST or ISO), allowing data to be compared across systems and locations.
Compliance
Many industries require compliance with standards such as ISO/IEC 17025, which mandates periodic calibration of instruments used in testing and measurements.
System Performance
Sensors are often part of larger data acquisition or monitoring systems. Uncalibrated accelerometers can compromise the entire system’s accuracy and performance.
Types of Accelerometer Errors Addressed in Calibration
- Bias (Offset) – A constant error added to all measurements.
- Scale Factor Error – Incorrect sensitivity or gain that skews data.
- Linearity Error – Output that does not linearly follow input.
- Cross-Axis Sensitivity – Influence from directions other than the primary sensing axis.
- Temperature Drift – Changes in output due to temperature variations.
Calibration adjusts for or identifies these errors to ensure measurement precision.
Accelerometer Calibration Methods
1. Back-to-Back Comparison Method
One of the most common methods, this involves mounting the test accelerometer on top of a reference accelerometer on a shaker table. Both are subjected to the same sinusoidal vibration, and their outputs are compared.
- Ideal for periodic field calibrations
- Typically performed at discrete frequencies (e.g., 80 Hz, 160 Hz)
2. Reference Standard Method
Uses a laser Doppler vibrometer or other highly accurate motion detection system to measure the movement of a calibrated shaker table. The accelerometer’s output is compared against this motion.
- Provides very high accuracy
- Common in national labs and certified calibration facilities
3. Earth’s Gravitational Field (Static Calibration)
This method uses the known value of gravity (9.81 m/s²) by orienting the accelerometer in different positions (e.g., +1g, 0g, -1g).
- Simple and low-cost
- Suitable for MEMS sensors and basic applications
Standards for Accelerometer Calibration
Calibration procedures should comply with recognized international standards to ensure consistency and traceability. Commonly used standards include:
- ISO 16063-21 – Methods for the calibration of vibration and shock transducers
- ISO/IEC 17025:2017 – General requirements for the competence of testing and calibration laboratories
- ANSI S2.11 – American standard for accelerometer calibration
Calibration reports issued by accredited labs must include uncertainty values, traceability to national standards, and environmental conditions during calibration.
Calibration Frequency
The calibration frequency for an accelerometer depends on several factors:
- Usage Environment: Harsh environments (high temperatures, shock, moisture) may require more frequent calibration.
- Criticality of Measurement: Devices used in aerospace or safety-critical applications should be calibrated more often.
- Manufacturer Recommendation: Follow OEM guidance, typically once every 6 to 12 months.
- After Major Impact: Accelerometers subjected to shock or damage should be recalibrated immediately.
Steps in the Calibration Process
- Preparation
- Visual inspection of sensor
- Identification of model and serial number
- Documentation review
- Mounting
- Proper attachment to the shaker or reference device
- Use of adapter blocks and couplings
- Testing
- Apply controlled vibration
- Record outputs at various frequencies and amplitudes
- Analysis
- Compare test readings with reference
- Determine sensitivity, bias, and error margins
- Adjustment (if applicable)
- Some systems allow digital correction of calibration factors
- Report Generation
- Include calibration date, technician, traceability, environmental conditions, and uncertainty
Choosing a Calibration Service Provider
When selecting a provider for accelerometer calibration:
- Ensure ISO/IEC 17025 accreditation
- Confirm traceability to national or international standards
- Look for detailed calibration reports with uncertainty values
- Prefer labs with experience in your specific industry (automotive, aerospace, etc.)
Conclusion
Accurate accelerometer measurements are critical to many industries and applications. Regular accelerometer calibration ensures the reliability, compliance, and performance of these sensors over time. Whether for laboratory testing, industrial monitoring, or high-tech manufacturing, investing in professional calibration services backed by international standards is essential for data integrity and operational excellence.
Make calibration a core part of your maintenance strategy and ensure your measurement systems are always performing at their best.