The main application of strain gauges is the manufacture of force and pressure transducers, particularly load cells. A load cell is a type of transducer that measures the mechanical load on an object by converting it to readable electronic signals. They are used in various industries such as automation, process control, biomechanics, equipment monitoring, building integrity analysis, bulk material weighing, testing, and quality control.
Modern load cells work using a combination of the Wheatstone bridge equation and the strain gauge. The Wheatstone bridge equation was developed in 1833 by Samuel Hunter Christie, and improved upon and popularized in 1843 by Sir Charles Wheatstone. Wheatstone bridge circuits illustrate the concept of a difference measurement. Today, load cells are usually made up of four strain gauges in a Wheatstone configuration.
How to choose a load cell 1. Consider the load input direction. 2. Consider the object to be weighed: capacity, resolution, shape. 3. Consider the environment the Load Cell will operate in. 4. Consider the desired accuracy, error ratings, and ease of calibration. 5. Select the load cell type for the application.
Higher voltages through the resistive strain gauges (which comprise the Wheatstone bridge) will cause more current to flow and heat the strain gauges. The cell body acts as a heat sink to keep the gauges cool. If the maximum rated excitation voltage is exceeded, the heating will cause signal perturbation or gauge failure. Additionally, in battery operated devices, high excitation voltage (and thus, current) will cause the battery to deplete much faster than with lower excitation voltages through the circuit.
① Creep Recovery The change in no--load output occurring with time after removal of A load which had been applied for a specific period of time. Usually measured over a specific time period immediately following removal of rated load and expressed as a percent of rated output over a specific period of time. ② Deflection The change of length along the primary axis of the load cell between no--load and rated load conditions. ③ Drift A random change in output under constant load conditions.
① Ambient Conditions Humidity, pressure, temperature, etc. of the medium surrounding the load cell. ② Ambient Temperature The temperature of the medium surrounding the load cell. ③ Angular Load Eccentric A load applied eccentric with the primary axis at the point of application and at some angle with respect to the primary axis.
How to select the appropriate sensor When we provide sensing solutions, it is very important to choose the right products. There are so many kinds of sensors. Once the selection is not good, it will bring a lot of issues to the application.
A load cell is a sensor that converts force or weight into a measurable electrical output, the most common output signal is mV/V.
In Injection Moulding Machine, pressure transmitter and pressure control device installed in the mould inlet, make sure the product can be more stable, also prevent watste of material. Load cells and displacement sensors installed in the moving parts and fixation parts , offering high accuracy force and position measurement, to make sure high accuracy control, to prevent damage to equipment.
In press-fitting industry, parts are more and more using force-distance monitoring to guarantee product quality. It's an industrial trend in manufactory. Typically it has been widely used in automobile industry, significantly lower product cost, improve equipment availability, and greatly improve daily productivity.
