Tuesday, January 30, 2024

How to Improve Reliability of Tilt Sensors



 1. How to ensure the reliability index of the tilt sensor

For the technical indicators and performance indicators of the tilt sensor, there are usually clear and quantitative index requirements, which can be directly measured and tested when the product leaves the factory. For reliability indicators, it is generally impossible to implement direct measurement and inspection, and it is necessary to carry out reliability design and control of the whole process of product development and production to ensure that the reliability indicators meet the requirements. We mainly discuss the reliability supervision and control, design and evaluation and test of tilt sensor in the development, production and use stage.

2. Reliability design
The development stage of inclinometer sensor can be divided into demonstration stage, scheme stage, development stage and finalize stage. According to the technical requirements of the tilt sensor, the MTBF task value θS of the sensor is determined in the demonstration stage, and the θS is preliminarily demonstrated according to the reliability level of the sensor product.
When the inclinometer sensor is in the project stage, it is necessary to design according to the tactical technical index of the inclination sensor and work out the functional block diagram of the sensor. According to the block diagram of tilt sensor, the internal logic relationship in the block diagram is analyzed, and the reliability block diagram of the newly developed inclination sensor is compiled. According to the reliability block diagram of the inclinometer sensor, the reliability indicators are assigned to each subsystem of the sensor, or the reliability indicators on the technical requirements are weighted, and the results after allocation must meet the reliability indicators of the whole system. After the reliability block diagram is prepared and the reliability index is assigned, the estimated reliability value θP is estimated for the components used in the hardware circuit. According to the obtained θP value, the part of the hardware circuit that affects the reliability of the sensor is designed and changed. At last, the functional block diagram, reliability block diagram, reliability distribution index and reliability predicted results prepared according to the technical requirements of the inclination sensor are reviewed periodically in order to improve the design of the defects that affect the reliability of the sensor. In the reliability design of the tilt sensor, the design needs to be considered as shown in Figure 1.

Reliability design structure of tilt sensor

2.1 Reliability design of hardware circuit
After the inclinometer sensor enters the development stage, the hardware circuit is designed according to the functional block diagram and reliability block diagram.
In the design of hardware circuit reliability, the aspects that need to be considered are shown in Figure 2.

Tilt sensor Hardware circuit reliability design structure diagram

In the process of hardware circuit design, components are the basis of circuit reliability design. In the actual sensor hardware circuit, due to different environments, load changes and a series of reasons such as the design of the sensor drift fault, therefore, in the actual design of the hardware circuit should be integrated into the margin design, after the completion of the hardware circuit design, before the data transmission, it is required to check the integrity of the components in the hardware circuit to ensure that the sensor is powered on. Correct and intact data transmission between each unit. In addition, limit testing and reasonableness testing are performed on all analog and digital inputs and outputs in the hardware circuit.
2.2 Software program reliability design
In the design of the hardware interface software of the sensor, the failure detection of the external input or output device must be considered first, and when the failure is detected, the software can restore the interface to a certain safe state, and the hardware failure mode involved is also required to be considered. When the sensor transmits data, in order to ensure the authenticity and reliability of the data received by the receiver, the data sent by the sender is required to use a specific format and content, so that the sender and the receiver can use the agreed method for verification. In the process of software design, its reliability design structure is shown in Figure 3.

Tilt sensor Software reliability design structure diagram

When the software program of the sensor is written, the first thing to consider is the robustness of the software. In software robustness design: First, the power module of the inclinometer sensor may have intermittent failure at the moment of power supply, so that the inclinometer sensor into a potential unsafe state, in order to avoid this state, it is required that the software safely shut down the sensor when the sensor power supply fails, in addition, the power supply of the inclination sensor may have abnormal fluctuations. Software is also required to handle it; Second, the software design must take into account a self-test when the sensor is powered on, verifying that the sensor system itself is safe and can operate normally, and when necessary, the sensor can carry out periodic self-testing; Third, the inclination sensor needs to work normally in electromagnetic radiation, static interference and other environments, which requires the sensor hardware circuit design to be processed according to the technical requirements, so that the sensor can control the external interference within the specified range, when there is external interference, the software is reset again, so that the sensor can still operate normally. Secondly, it is necessary to carry on the margin design when writing the sensor operation program. While ensuring the storage capacity and data channel transmission capacity of each module of the software, the software margin of the inclination sensor should be planned to ensure that the software margin meets the requirements. According to the specific state of each subsystem during software running, the arrangement of various cycles and working time series of software is determined to ensure that sufficient margin is reserved between software working time series.
Finally, consider the data definition when the sensor program is written. When defining the data in the software operation process, it is necessary to ensure that the defined data must be within a reasonable range, so that the sensor can ensure the size and error of the value within the specified range during the data operation process to ensure the accuracy of the data operation. In addition, reasonableness checks are also carried out at the entrance, exit, and other key locations of the software.
2.3 Structural reliability design
In addition to the protection of the external environmental stress, the electromagnetic compatibility of the inclinometer sensor is mainly optimized in the structure of the sensor. Under modern conditions, electromagnetic interference is everywhere, in this environment to make the sensor normal operation, it is required to optimize the sensor in hardware circuit, overall structure, manufacturing process, etc., in order to reduce the sensitivity of the sensor for interference, so that the external entry and internal leakage of electromagnetic interference can be controlled in a acceptable range.
2.4 Process reliability design
Process reliability design is mainly divided into printed board reliability design, electrical interconnection design and “three defenses” design. The reliability design of the printed circuit board requires the layout of the entire circuit board to be reasonable, and a single functional module or functional circuit is placed on a panel as far as possible, which is more convenient for later troubleshooting and maintenance. The circuit board should be rationally arranged on the circuit board, the circuit at all levels should be arranged and combined according to the distribution of the schematic diagram, the input and output of the sensor should be arranged separately, the analog circuit module and the digital circuit module should be isolated, the layout and wiring should be reasonable as far as possible, and the generation of parasitic coupling electromagnetic interference should be suppressed. When placing electronic components on the circuit printed board, it is required to be as suitable as possible for visual inspection of the entire circuit printed board, to facilitate the inspection of the nominal value of electronic components and fault location. When placing large and heavy components on the circuit printed board, it is necessary to reinforce them to prevent damage to components caused by vibration and impact of the sensor and make the sensor unable to operate normally. The design of electrical interconnection requires the sensor process specification to specify the installation and welding temperature and time of the components, the welding specifications of the inserted components and the operating conditions of the welding operators. The “three defenses” design requires the developer to fully understand the use environment of the sensor, master the characteristics of the sensor use environment and the law of change, analyze the stress conditions of the sensor failure in its use environment, and finally choose the suitable defense for the sensor
Enclosures, materials and sensor manufacturing processes.
3 Summary
By analyzing the reliability of inclinometer sensors in the process of development, production and use, we integrate the reliability design of wireless ER-TS-12200-Modbus and single-axis ER-TS-3160VOER-TS-4150VO and other tilt sensors into the development and production of sensors. Through the reliability information collected by customers during the use of such products, the reliability assessment of the sensor is carried out, and the reliability improvement of the tilt sensor is finally completed. 

MEMS-IMU error calibration compensation method that does not rely on precision turntable

https://www.ericcointernational.com/application/mems-imu-error-calibration-compensation-method-that-does-not-rely-on-precision-turntable.html

Research on MEMS-IMU signal denoising technology

 https://www.ericcointernational.com/application/research-on-mems-imu-signal-denoising-technology.html

High Performance Navigation MEMS IMU

 ER-MIMU-02 (0.05 deg/hr)

1. 3 axis gyroscope & 3-axis accelerometer;
2. High performance and small size;
3. Gyro bias instability: 0.05 deg/hr.

ER-MIMU-02 uses MEMS accelerometer and gyroscope with high quality and reliability, RS422 and external communication, baud rate can be flexibly set between 9600~921600, through the communication protocol to set the user’s required communication baud rate. With X, Y, Z three-axis precision gyro, X, Y, Z three-axis accelerometer with high resolution, can be output by RS422 X, Y, Z three axis of gyroscope and accelerometer’s original hexadecimal complement data (including gyro hexadecimal complement the numerical temperature, angle, the accelerometer hexadecimal temperature, the acceleration hexadecimal complement number); It can also output float dimensionless values of the gyroscope and accelerometer processed by the underlying calculation.

Application areas
Antenna and Line of Sight Stabilization Systems
Integrated Navigation Systems & Inertial Guidance System
Flight Control & Guidance System
Attitude Heading Reference Systems (AHRS)
Stabilization of Antennas, Cameras & Platforms
Aerial and Marine Geo-mapping / Surveying




Monday, January 29, 2024

Tilt sensors are booming



Introduction

ER-TS-3160VO Voltage Single Axis Tilt Meter is an analog voltage single axis tilt sensor. Users only need to collect the sensor voltage value which can calculate the current object tilt angle. The built-in (MEMS) solid pendulum measures the change of static gravity field, which is converted into the change of inclination, and the change is output through the voltage (0~10V, 0.5~4.5V, 0~5V optional).
The product adopts the non-contact measuring principle, which can output the current attitude and inclination angle in real time. The operation is simple, there is no need to look for two faces with relative changes. It has the characteristics of small size and strong shock and vibration resistance, especially suitable for harsh industrial environments.

More details: https://www.ericcointernational.com/tilt-sensor/single-axis-tilt-sensor.html

Features
Single axis tilt monitoring
Full range accuracy 0.01°, resolution 0.001°
Output 0~5V, 0.5~4.5V, 0~10V (optional)
Wide voltage input DC 9~36V
Wide temperature working -40~+85℃
Measuring range: 0~±180° (optional)
High vibration resistance>20000g
IP67 Protection
Can output RS232 at the same time, RS485 optional
Small volume (90*40*27mm) (customizable)

Applications
Railway gauge ruler, gauge instrument
Satellite solar antenna positioning
High altitude working vehicle
Mining machinery, oil logging equipment
Medical equipment
Tripod head levelling  
Hydraulic lifting platform
Inclination monitoring
Angle control of various construction machinery
Inspection of bridges and dams

Thursday, January 25, 2024

Tilt Sensor Automatic Calibration System



Full text: https://www.ericcointernational.com/application/tilt-sensor-automatic-calibration-system.html 

1. Tilt sensor calibration method

Tilt sensor is widely used in the field of engineering measurement, and its measurement accuracy is often related to the evaluation of the deformation of structures, which is of great significance to the construction quality control and safety production management of construction engineering site. The manual two-point calibration method is commonly used to calibrate the inclinometer sensor, which describes the relationship between the output voltage and the Angle through a straight line, and is usually only suitable for the inclination sensor with low accuracy requirements. If the sensor has relatively high accuracy requirements, it is necessary to use a higher precision inclination chip and calibration method. Multi-point calibration is an effective calibration method to improve the accuracy of sensors, but in the case of a large number of fixed points using manual trigger, reading and calculation calibration method, not only low efficiency, and by human factors interference, is not conducive to the large-scale production of sensors. By designing an automatic calibration system for tilt sensor based on programmable electric Angle station, we realize the automatic change of Angle, reading and result output in the calibration process of inclinometer sensor, improve the calibration efficiency and sensor accuracy, and reduce the dependence of the calibration process on the technical level and experience of the operator.

2. Principle of automatic calibration of inclination sensor
The calibration of the sensor means that the measured value of the inclinometer sensor with higher precision is input to the inclination sensor to be calibrated as the standard value, and the feedback value of the sensor to be calibrated is obtained for data fitting processing. The common calibration method only calibrates the inclination sensor by two fixed points, and describes the error Angle relationship of the sensor by a straight line. This method is easy to operate and is suitable for tilt sensors with low precision.
However, if the inclinometer sensor with a measuring range of -15°~+15° collects data every 1°, and the error of each Angle is obtained as shown in Figure 1, it can be found that the error of the sensor is not linear with the Angle when the Y-axis interval is set to 0.01°. Therefore, if the sensor is calibrated by multi-point calibration method, the error of the sensor is not linear with the Angle. The accuracy of the sensor can be further improved by fitting a curve to describe the error characteristics of the sensor.

tilt Sensor error distribution

Therefore, this paper adopts the multi-point calibration method that sets 1 fixed point every 1°, and the third-order fitting method based on the principle of least squares to compensate the sensor error. The error fitting model is as follows:
Δφ = a1x3 + a2 x 2 + a3x + a4 (1)
In the formula, Δφ is the error value of the inclination Angle, x is the acquired value of the sensor to be calibrated, and a1, a2, a3 and a4 are the coefficients of the fitting polynomial.

3.Overall system scheme
The automatic calibration system is composed of three parts: electric Angle station, standard inclination sensor and PC calibration software, as shown in Figure 2.

tilt sensor Composition diagram of automatic calibration system

During calibration, the tilt sensor to be calibrated and the standard value sensor are fixed parallel to the electric Angle platform, the electric Angle platform is connected to the PC calibration software using RS485, and the tilt sensor to be calibrated and the standard value sensor are connected to the PC calibration software through the RS232 of the lora module at the receiving end. The calibration software at the PC end sets the Angle of the fixed point, the calibration software automatically controls the electric Angle station to find the corresponding fixed point, and continuously collects data at each fixed point to analyze whether the Angle data of the tilt sensor and the standard value sensor to be calibrated is stable (the difference between the last 10 sets of data collected does not exceed 0.003°). Record the readings of the tilt sensor and the standard value sensor to be calibrated, and automatically rotate to the next set point until all 31 set points are collected, and the software automatically calculates each parameter of the fitted curve according to the collected data.

4. System testing and analysis
4.1 Functional Testing
In order to verify the function of the automatic calibration system, an inclination sensor with a factory accuracy of 0.1° was placed in the system for calibration. The resulting data are shown in Table 2.

tilt Sensor data before calibration

It can be seen from Table 2 that before calibration, the maximum error of the sensor X axis is -0.037°, and the maximum error of the Y axis is 0.031°. The error fitting curve of the sensor calculated by the calibration software is shown in Figure 6.

tilt sensor-Scatter plot of error curve

4.2 Accuracy Verification
In order to verify the accuracy of the calibrated sensor, the automatically calibrated inclination sensor is sent to a professional measuring institution for measurement. The measurement accuracy is required to be 0.01°, and the measurement data are shown in Table 3.

Measurement data of tilt sensors

The measurement results show that the maximum error of X axis and Y axis is 0.006° and 0.009°, respectively, satisfying the accuracy index of 0.01°. The accuracy of the sensor is improved by one order of magnitude after calibration by the automatic calibration system.
5.Conclusions
We demonstrate the design direction of an automatic calibration system for inclinometer sensor, and carry out the calibration and performance test of the system. During the design and implementation of the automatic calibration system, the following conclusions are obtained:
(1) The automatic calibration system based on the programmable electric Angle station can realize the automatic calibration of the inclinometer sensor, effectively improve the calibration efficiency and save labor costs.
(2) The selection of the resolution of the electric Angle station should fully consider the mechanical structure characteristics of the Angle station. Compared with the resolution of 0.007° and 0.00036°, the resolution of 0.0007° can ensure the calibration accuracy while having higher calibration efficiency. The resolution of the ER-TS-12200-Modbus is 0.0005°, and the resolution of the ER-TS-22800 is 0.0008°, so the ER-TS-22800 can achieve higher calibration efficiency while ensuring calibration accuracy.
(3) The experimental results show that compared with the traditional two-point calibration method, using the multi-point calibration method to calibrate the inclinometer sensor and using the third-order curve to fit the error characteristics of the sensor can effectively improve the accuracy of the inclinometer sensor.  

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