# A Low-Cost IoT-Based Bidirectional Torque Measurement System with Strain Gauge Technology
## 5 Discussion  
The practical results confirm that an affordable, IoT-enabled torque measurement system can deliver accuracy and reliability comparable to present commercial solutions. The use of strain gauges in a Wheatstone bridge configuration, combined with digital signal amplification, enables precise monitoring of shaft torque in real time. The high R2 values observed in both directions confirm the appropriateness of the polynomial regression model, while the low MAE and standard deviation values demonstrate the system's accuracy and repeatability. The bidirectional calibration approach distinguishes this work from many previous studies, making the system suitable for applications involving reversible or oscillatory loads. A further practical advantage is installation simplicity: because the strain gauges are surface-mounted, the sensor can be deployed on a drivetrain without any structural modification, eliminating the need to cut the half shaft or fit flange couplers. This capability is particularly important in automotive measurements, where torque sensors must reliably capture rapid changes in direction associated with acceleration, deceleration, and engine braking. In such scenarios, the torque experienced by drivetrain components frequently reverses due to shifting driving conditions, and a sensor calibrated only unidirectionally may yield significant errors or fail to capture the full dynamic behavior. Potential improvements include miniaturization of the electronics, waterproofing the enclosure for outdoor use, and implementing advanced signal processing algorithms to further reduce noise and enhance dynamic response. Future work will also explore the use of energy harvesting techniques, such as inductive power transfer, to enable continuous operation without battery recharging. To provide a comprehensive evaluation, Table 7 summarizes the main advantages and limitations of the developed IoT-based torque measurement system. The system's primary strengths include its low cost, modularity, and open-source design, which collectively enable rapid adaptation to diverse applications and facilitate integration with modern data acquisition workflows. The use of a high-order polynomial calibration model ensures accurate and repeatable measurements for both clockwise and counterclockwise torques, addressing the requirements of reversible and oscillatory load scenarios. However, the range of limitations that must be addressed differs with the scale and context of the planned deployment. The reliance on battery power restricts operational time between charges, and the current hardware is not yet waterproofed for harsh or outdoor environments. While the open-source approach encourages customization, it may pose challenges for users without technical expertise. Additionally, the calibration process, while robust, is more complex than simple linear methods and requires careful execution to maintain accuracy over time. Overall, the system offers a compelling balance of affordability, flexibility, and performance, but further improvements--such as enhanced power management, environmental protection, and streamlined calibration procedures--would increase its suitability for broader industrial adoption. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**ID** & **System** & **Calibration Method** & **Wireless** & **Enclosure** & **Distinct Strengths** \\ \hline
1 & Proposed System & Fifth-order polynomial & Yes & No & Yes \\
2 & Exoskeleton Sensor & Commercial torque-transducer comparison & Yes & Yes & Telemetry \\
3 & 1 N-m Sensor & Benchmarked to AT Delta Sl-330-30 & No & No & Economy for benchtop use \\
4 & 5 N-m Sensor & Benchmarked to AT Delta Sl-330-30 & No & Economy for benchtop use \\
5 & 20 N-m Sensor & Benchmarked to AT Delta Sl-330-30 & No & No & Economy for benchtop use \\
6 & Walking Robot Sensor & Six-axis load cell reference & Yes & Yes & IPG? enclosure \\
7 & Optical Sensor & Optical scale-factor fit & No & Yes & CNC-milled aluminum enclosure \\ \hline \hline \end{tabular}
\end{table}