Influence of the Wheatstone bridge configuration and the magnitude of the calibration weight in the uncertainty of the load measurement using a low-cost instrumentation

The strain gauge (SG) is widely used for measurement of strains, or even of loads, in mechanical or structural components, mostly due to their low-cost, easy application and good accuracy. However, the literature is lacking in relation to studies concerning the determination of measurement uncertainty. This work presents a discussion of the influence of the SGs configuration in the Wheatstone bridge and the magnitude of the calibration weight applied to the measurement of load in a bending load (whose design is similar that used in load cells). Were compared ¼, ½ and full bridge configurations to linear SGs with 350Ω resistance. Low-cost instrumentation was used with the HX711 converter module and the Arduino microcontroller board. The measuring system was calibrated with two different weights: one of approximately 10% of the maximum value of the system operating range and another one of approximately 85%. Some conclusions can be highlighted, such as the influence of the amount of the SGs on the Wheatstone bridge and the magnitude of the calibration weight on the uncertainty of load measurement. Adding up, these results helpful to discuss a relation between a measurement uncertainty and the implementation cost.