Development of MEMS Pressure Sensor based Pressure Calibrator for Ground Testing of Baro-Altimeters of UAVs

A pressure calibrator is a device that is used to check the accuracy of pressure gauges, sensors, etc. It uses a highly accurate pressure sensor which is used as a reference to check the performance of the device under test (another pressure sensor or gauge). To test the working of a Baro-altimeter

Project Title

Development of MEMS Pressure Sensor based Pressure Calibrator for Ground Testing of Baro-Altimeters of UAVs

Project Area of Specialization

Mechatronics Engineering

Project Summary

A pressure calibrator is a device that is used to check the accuracy of pressure gauges, sensors, etc. It uses a highly accurate pressure sensor which is used as a reference to check the performance of the device under test (another pressure sensor or gauge). To test the working of a Baro-altimeter the pressure calibrator relates to the pitot tube of the air vehicle and pressure is decreased to create the scenario where the aircraft is up in the air. The Baro-altimeter of the aircraft then gives the height corresponding to the pressure. After creating flight-like conditions it is required that the aircraft's measurements are tested and calculated for any error. Concerning the scope of this equipment, we need to compare the given air pressure between both the air vehicle's sensor and the testing equipment sensor. The vehicle's sensors are calibrated accordingly and the reasons why the altimeter is giving faulty readings. The equipment would consist of one high accuracy MEMS pressure sensor that measures the artificially created pressure and calibration of sensors under consideration is performed. Furthermore, the equipment would also extract different properties (hysteresis, non-linearity, repeatability, span, accuracy, etc.) of the device under test to identify the reason why it is not working properly.

Project Objectives

Initially, the design of the equipment is to be proposed and manufactured. Later working on the project is divided in 4 stages. 1st stage involves proposing a suitable model for the equipment and having it approved. 2nd stage involves designing a required schematic and PCB Layout of the equipment and manufacturing it. 3rd stage involves the data acquisition with the extraction of parameters like nonlinearity, repeatability, hysteresis, accuracy, etc. The final stage involves designing and manufacturing a 3D model of the external housing of the equipment.

Project Implementation Method

Implementation of the desired project is done with the help of certain components which will be arranged in an orderly manner to fulfill the objectives. The main components of the pressure calibrator are:

• Vacuum Pump

• Actuation Valves

• Pneumatic Tubes

• Microcontroller (STM32)

• Analog to Digital Converter (ADS1248)

• MEMS Pressure Sensor

• Device Under Test (Another Pressure Sensor)

• Keypad and LCD

A vacuum pump relates to the actuation valves with the help of pneumatic tubes. The main purpose of the pneumatic tubes is to create a vacuum which in turn helps to create an environment of higher altitudes. MEMS Pressure Sensor is connected to the tubes and its reading is being taken by the microcontroller with the help of an analog to digital convertor. A microcontroller is also being used to control vacuum pumps and actuation valves. The keypad is being used to get input regarding altitude or pressure from the user while LCD is being used to show the results.

First, the device will get input from the user about the pressure to be created in the tubes. Then microcontroller will start the vacuum pump and open the valves to create the required pressure. MEMS Pressure Sensor will provide the run time value of the pressure in the tubes and the controller will compare it with the required value. Once the required pressure is obtained, the controller will close the valves and turn off the pump. Now the device under test will be connected to the tubes and its reading will be fed to the controller with the help of an analog to digital convertor. Now, the values of the device under test and MEMS pressure sensor will be compared and the error will be calculated. After this, the causes of the error in the device under test will be addressed by computing the non-linearity, repeatability, hysteresis, and accuracy of the device under test.

In this way, the device under test will be calibrated with the help of our product.

Benefits of the Project

Currently, the equipment is not being manufactured in Pakistan and the imported ones come at an almost unaffordable cost. Manufacturing this equipment locally would create an opportunity of being able to manufacture an equally efficient device when compared with the imported ones in the future. All the components that are being used in this equipment can be locally procured. The equipment would help in flight-line testing of the air vehicles and can also be used for calibration of any kind of pressure sensor other than the ones used in air vehicles.

Technical Details of Final Deliverable

The final product will consist of a system with a keypad and an LCD for display. The equipment will be powered by a 12V DC adapter. Connections for the device under test are placed on one side of the equipment housing body. While on the interior of the equipment, all the electronics, and mechanical parts will be mounted on specified slots made within the housing body of the system. Since the need of using a vacuum chamber was eliminated and vacuum creation within the tubing was adopted. The approach was to keep the tubing routes straight and of smaller size which also helped keep the equipment size even more compact and all these arrangements helped with a better calibration of the device under test with more accuracy and efficiency.

Final Deliverable of the Project

HW/SW integrated system

Core Industry

Others

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Partnerships to achieve the Goal

Required Resources

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