Introduction
A load cell is a transducer used to convert a physical quantity (force) to electrical quantity (voltage). A strain gage is one of the commonest types of load cells. In these types of load cells, gages are connected to a structure that bends on the application of a force. A Wheatstone bridge circuit is a four type strain traducer that gives a maximum sensitivity as well as temperature compensation (Westwood 38). A quarter or half bridge are used to perform the same purpose. In the Wheatstone bridge device, two gages are under tension while the other two are in compression. The arms are connected to compensation adjustments. Weight is applied to the structural member; strain modifies the gage resistance proportionally to the load. Strain gage built load cells have high accuracy (0.03% - 0.25%) full scale. They have a low unit cot and are suitable for most industrial uses.
A Wheatstone bridge circuit is suitable for gauging the change in resistance in strain gages. The device operates on the principle defined by the equation:
. (1)
Where L is the gage length, A is the gage cross-sectional area, and R is the gage resistance. Figure 1 below illustrates the wire connection of a Wheatstone machine while Figure 2 illustrates a load cell model.
Figure 1: Wheatstone bridge circuit
Figure 2: A load cell transducer
Methods
After downloading and installing Arduino IDE on the computer, the load cell, the HX711 breakout board and the Arduino UNO were connected as shown in figure 3 below.
Figure 3: load cell, HX711 breakout board, and Arduino UNO connection
The Arduino UNO board was connected to a laptop computer using a USB bus.
Figure 4: Computer Arduino UNO connection
The Arduino IDE was opened on the computer. The default blank code was substituted with the code that was downloaded from the blackboard and saved.
For the computer to communicate with the Arduino board, the right port was selected. The code was uploaded to the Arduino board and the magnifier selected to open the serial monitor. A speed of 9600 baud was set for the serial monitor.
The load cell was set up as shown in figure 5 below. Without weighing the device, the sketching was started. After displaying the readings, a weight was placed on the scale. The a/z button was pressed to make adjustments of the calibration factor.
A “LoadCell.ino” code was downloaded from the blackboard. The “calibration factor” variable was substituted with the given number. The “Load Cell.ino” code was uploaded to the Arduino board and readings monitored with the Serial Monitor. Three weights were placed on the cell and the readings and their standard masses recorded.
Results
Discussion
The load cell setup was used to familiarize on strain gage and load cell. In the setup, the load cell device was used to measure mass and force and conduct load measurement tests. The load cells have an internal or external amplifier to reduce noise (Braidot and Alejandro 38). For the best resolution, the signal is amplified to. The bandwidth of the signal is made faster (about 1 kHz). The Arduino.UNO board is loaded with the ino Code from the computer machine to act as a microcontroller.
Work Cited
Braidot, Ariel, and Alejandro Hadad. Vi Latin American Congress on Biomedical Engineering Claib 2014, Paraná, Argentina, 29, 30 & 31 October 2014. , 2015. Internet resource.
Westwood, James D. Medicine Meets Virtual Reality 22: Nextmed/mmvr22. , 2016. Internet resource.
