Tilt angle sensors are used to measure the tilt angle of objects relative to the horizontal plane. They are widely used in various fields such as platform leveling, mechanical manufacturing, safety protection, and precision measurement. There are also many manufacturers, but the market's understanding of the accuracy of tilt angle sensors is vague and even biased.
This article will take the tilt sensor based on acceleration sensing principle as an example to describe in detail the factors that affect the accuracy of the sensor. An accelerometer measures the component of gravity acceleration on the sensitive axis of the accelerometer and converts it into angle data, that is, the inclination value and acceleration value have a sine relationship.
The measurement accuracy of the inclination sensor is closely related to the following indicators:
Noise - depends on the inherent characteristics of the core sensitive device, but is also associated with frequency response, also known as amplitude frequency characteristics. Generally speaking, the higher the frequency response, the greater the noise. Noise determines the resolution of the sensor. If the angle change is so small that it is almost submerged in noise and cannot be distinguished, we consider the angle change to be the resolution of the tilt sensor.
Zero bias stability - depends on the inherent characteristics of the core sensitive device, which refers to the fact that the sensor's measured output is not zero in the absence of angle input (such as absolute horizontal plane), and the actual output angle value is the zero bias. The impact of zero bias on the accuracy of sensors is not frightening, as zero bias can be eliminated through calibration. However, zero bias usually drifts with time and temperature changes, and this drift is called zero bias stability. This drift is usually difficult to eliminate, so it can cause accuracy degradation.
Nonlinear - can be corrected through subsequent calibration, depending on the number of calibration points. The more correction points there are, the better the nonlinearity. Although nonlinearity can be corrected through subsequent correction methods, there is also a drift phenomenon in nonlinearity, which cannot be eliminated and can cause accuracy degradation.
Cross coupling error refers to the error generated when a sensor is coupled to its output signal when a certain acceleration is applied perpendicular to its sensitive axis or tilted at a certain angle. For a single axis tilt sensor with a measurement range of ± 30 ° (assuming the X direction is the tilt measurement direction), when there is a 10 ° tilt perpendicular to the X direction in space (at this time, the actual measured tilt angle in the X direction remains unchanged, such as+5 °), the output signal of the sensor will produce additional errors due to this 10 ° tilt, which is called cross coupling error. This additional error varies depending on the product. When the cross coupling error of the tilt sensor is 3% FS (FS: full scale), the additional error generated is 3% × 10 °=0.3 °, while the actual output angle of the sensor is estimated to be 5.3 ° (=5 °+0.3 °). At this point, even if the nonlinear error of the tilt sensor reaches 0.01 °, compared to the cross coupling error, this nonlinear error can be ignored. In other words, as the measurement accuracy of the tilt sensor, the cross coupling error cannot be ignored, otherwise it will cause significant measurement errors.
Installation error - When installing and measuring sensors, the measuring axis should coincide with the sensitive axis of the sensor. However, in actual installation and measurement, it is always difficult to accurately match. For example, if the angle between the installation measurement axis and the sensor sensitive axis is 1 degree, the measured value is the projection of the actual angle change on the sensitive axis. If the angle changes by 30 degrees, the measured value is 30 * cos (0.1)=29.995 degrees, with an error of 0.005 degrees. Therefore, for high-precision applications, it is very important to maintain the alignment between the measurement axis and the sensor sensitive axis.
Repeated measurement accuracy depends on the inherent characteristics of the core sensitive components and cannot be improved through subsequent corrective measures.
The influence of temperature on zero point and sensitivity - including drift and repeatability of temperature curves, which depend on the inherent characteristics of the core sensitive device and cannot be improved through subsequent corrective measures. In the case of determined repeatability, subsequent calibration can be carried out depending on the number of calibration points (angle points and temperature points). The more calibration points there are, the better the temperature drift accuracy.
Range - Due to the sinusoidal relationship between inclination measurement and acceleration, the relationship between angle measurement error and acceleration measurement error satisfies the following equation:
Among them, d α is the inclination measurement error, da is the acceleration measurement error. When the range approaches 90 degrees, the acceleration a approaches the gravitational acceleration g, which is close to infinity. Therefore, a slight acceleration error causes a large inclination measurement error.
From this, it can be seen that the system error of the tilt sensor includes noise, zero bias, repeatability, and temperature drift repeatability, which cannot be corrected or compensated for; Random errors include cross coupling errors, input axis misalignment, nonlinearity, and temperature drift linearity, which can be improved through correction and compensation measures. Therefore, to measure the measurement accuracy of a tilt sensor, it is necessary not only to measure nonlinearity, but also to synthesize the system error and random error of the sensor before measurement.
Therefore, the error of the tilt sensor should include nonlinearity, repeatability, noise, zero bias drift, zero nonlinear drift, and cross coupling error.
Due to the many factors involved in accuracy, Wuxi Huilian Information Technology Co., Ltd. eliminates and corrects different error causes one by one, so that users do not need to deeply consider these indicators. Users only need to follow some basic installation requirements to meet the accuracy indicators. This can greatly reduce the workload of users.
The technical advantages and capabilities of Huilian Technology's tilt sensor
1. Huilian Technology's tilt sensor has excellent angle measurement performance. Huilian Technology's products calibrate and eliminate multiple factors that affect product accuracy indicators, such as nonlinearity, drift, and cross axis coupling. Make it convenient and easy for users to use tilt sensor products.
2. Truly achieve full angle range measurement. The Huilian tilt sensor does not have a significant increase in+-90 degree error, and can achieve accurate measurement in all directions and attitudes. High accuracy and good consistency throughout the entire measurement range.
3. Temperature zero drift and nonlinear compensation enable accurate measurement of products even when temperature changes occur.
4. Adopting advanced sealing technology to reduce the impact of harsh environments such as temperature, humidity, and vibration on the product and improve its environmental adaptability.
5. Tilt angle sensors that are tested strictly in accordance with relevant domestic and international standards (including GB, GJB, MIL, IEC, ISO, EN, etc.).
6. Multiple invention patents, utility model patents, appearance patents, and software copyrights in the field of inclination measurement.
7. Equipped with independently patented automated testing technology for tilt angle sensors, reducing the impact of human factors on quality and maintaining consistency in quality.
8. Possess core research and development capabilities, including three PhDs and five masters, and can customize tilt measurement products for customers with special requirements.
