Abstract: A resistance strain sensor is a sensor manufactured using the resistance strain effect of metals to measure small changes. Strain sensor is a type of sensor that measures the strain generated by the deformation of an object under force. The resistance strain gauge is the core part of the resistance strain sensor, which directly affects various performance indicators of the sensor. The working principle of resistance strain gauges is the strain effect of metals. The phenomenon where the resistance of a metal conductor changes with the magnitude of its mechanical deformation is called the resistance strain effect of the metal. In the existing aircraft strength testing, the measurement principle of resistance strain gauge is commonly used, and an electric wire is pasted at each strength assessment point

A resistance strain sensor is a sensor manufactured using the resistance strain effect of metals to measure small changes. DAPC100 3ASC25H203 strain gauge sensor is a sensor based on measuring the strain generated by the deformation of an object under force. The resistance strain gauge is the core part of the resistance strain sensor, which directly affects various performance indicators of the sensor. The working principle of resistance strain gauges is the strain effect of metals. The phenomenon where the resistance of a metal conductor changes with the magnitude of its mechanical deformation is called the resistance strain effect of the metal.

In existing aircraft strength testing, the measurement principle of resistance strain gauges is commonly used. A resistance strain gauge is attached to each strength assessment point. During the test, the strength of the aircraft body nodes is obtained by reading the strain value. Ordinary aircraft use approximately 6000 to 12000 strain gauges per aircraft, while larger aircraft have more. Each strain gauge has 3 electrical wires, resulting in tens of thousands of wires, occupying a large area, complicated wiring, and severe entanglement of the wires, causing confusion at the testing site. Once a strain gauge encounters a problem, on-site investigation will be very difficult, greatly increasing the complexity and cycle of strength testing.

This article uses optical fibers for strain signal transmission. DAPC100 3ASC25H203 adopts a modular design and cascades between modules to increase the number of strain gauges that can be collected geometrically. It converts tens of thousands of electrical signals into one or several optical signals for transmission, with only one optical cable from the testing site to the monitoring room.

Moreover, due to the use of modular design, once a signal has a problem, it can be directly plugged and replaced with power, greatly reducing the cycle of identifying the source of the problem during the monitoring process. The introduction of fiber optic technology promotes the reliability and structural optimization of aircraft strength monitoring systems.

1 System Design

1.1 Structural Design

The system structure is shown in Figure 1. The components are divided into three parts: transmitter, fiber optic, and receiver. The transmitting end consists of a first level module, a second level module, and a third level module. The first level module is used to collect strain signals, and each first level module can collect up to 16 strain signals; The second and third level modules are used for data multiplexing and communication. Each second level module can connect up to 16 first level modules and collect up to 256 strain signals; Each level 3 module can connect up to 16 level 2 modules and collect up to 4096 strain signals. A maximum of three Level 3 modules are required for an aircraft to achieve the purpose of collecting all nodes. Level 3 modules convert the collected 4096 stress signals into optical signals and transmit them to the remote end through optical fibers. At the remote end, they are then converted into electrical signals through photoelectric conversion and receive, decode, extract, and send them to the upper computer for processing. Moreover, this product can increase or decrease the number of modules according to the number of strain signals to be collected. If hundreds of strain signals need to be collected, only a few first and second level modules are needed. If dozens of strain signals are collected, several first level modules can meet the requirements and can be combined freely. If a module fails to work properly, it can be replaced directly without affecting the operation of the whole system.