How they work
The two basic components of a load cell are the sensing element and the circuit. The sensing element is responsible for receiving mechanical pressure, and the circuit part converts this pressure into electrical output. Generally speaking, the load cell in the load cell manufacturer is operated by the pneumatic method, hydraulic method, or strain gauge technology.
The sensing element in the load cell is usually a strain gauge. Strain gauges are usually composed of thin metal wires or metal foils (in the form of coils or grids), which are installed at specific locations on structural elements and bonded to specific locations. (Some piezoelectric sensors using crystals can be considered as strain gauges.) Therefore, strain gauges can be considered as dedicated microcircuit boards. They work by converting the internal deformation of the combined elements into electrical signals through changes in their own resistivity. The change of meter resistivity is directly related to weight, force or strain, so that weight, force, or strain can be accurately measured. It should be noted that different strain gauges have different sensitivity to mechanical strain. The special sensitivity of the meter is called the meter factor (GF). Strain gauges are essential for many types of load cells and many types of applications. For example, compression and tension sensors use a large number of strain gauges, and push-pull force gauges and flow measurements rely on strain gauges.
This circuit is the connection of the meter or sensor of the entire load cell. The most basic design consists of four meters that make up the measurement circuit. (More complex, more detailed sensors can have up to 30 gauges as part of the measurement circuit. Since the increase in gauge corresponds to the increase in sensitivity, advanced load cells require many gauges to accurately record and monitor changes in measurement.) The equation consists of 4 gauges arranged in a square; the voltmeter extends between the two corners of the square because its power/ground is connected to the other diagonal. The Wheatstone bridge equation is widely used because it is an effective way to amplify the apparent resistivity and corresponding electrical output changes. at the same time,
After the load cell converts the mechanical stress into electrical energy, the information monitored by the load cell will be signaled to the recorder or other computer data collection system. Load cell output includes analog voltage, analog current, analog frequency, switch or alarm, serial and parallel. When a load cell is used to measure any changes in some ongoing system, the load cell can issue an alarm or shut down the system itself until the difference is corrected. Although strain gauge load cells are the most popular type of load cell, they are not the only type.
Piezoresistive load cell and strain gauge technology overlap significantly. They work by directly measuring the electrical charge accumulated in the piezoelectric crystal by the applied mechanical force. Other types of load cells measure force through changes in magnetism, frequency (for example, vibrating load cells), and the ability to hold a charge (for example, capacitor load cells). It was pointed out earlier that the first load cell was operated on pneumatic and hydraulic principles. This ball-type load cell is still in use today.
The hydraulic load cell relies on the force exerted on the piston to increase the pressure in the oil-filled cylinder. Such pressure changes are then transmitted (for example via a hose) to the sensing element of the load cell (for example a Bourdon tube).
The pneumatic load cell relies on the forced deflection of the air applied to one of the ends of the diaphragm sensing element. When this deflection occurs, it changes the pressure inside the load cell and the pressure of the airflow escaping from the bottom of the load cell.
Hydraulic load cells are ideal for situations where conventional power sources cannot be used, while pneumatic load cells can be used where safety and/or sanitary conditions need to be improved.