In various modern spheres of human activity, there is a need to control different structures by measuring the parameters and the current state of this element. Strain gauge sensors are indispensable assistants in this matter.
Leading technologies are increasingly using electronic strain gauges, among which strain-resistive device models are most widely used. Strain gauge elements can measure weight, force, pressure, movement, etc.
Strain gauges are widely used for scales, industrial machines, various engines, used in the construction industry and many other areas.
Types of sensors
In various industries, a huge variety of strain gauge transducers are used. There are the following types of devices:
- force measurement tools - sensors scan for changes in force and load parameters;
- devices for measuring acceleration projection - accelerometers;
- measuring means for moving test materials;
- tensometric pressure devices - characterized by the control of pressure parameters of various elements in differentenvironments;
- strain torque transducers.
For scales, load cells are the most typical structural element. Depending on the application of the structure of the cargo receiving surface, the following types of sensors are used:
- console type devices;
- measuring instruments in the form of the Latin letter S;
- puck-shaped load cells;
- Measuring devices that vaguely resemble the shape of a barrel.
There is a classification of measuring strain gauges, depending on the design features - the sensitivity element. The source material defines the following models:
- wire - created in the form of a wire, the material is two-component nichrome, elemental compound fechral, thermostable alloy constantan;
- foil strain gauges - use thin strips of foil;
- semiconductor sensors - made from chemical elements such as silicon, gallium, germanium.
Operating principle
The principle of the device is based on the tensor effect. Its essence lies in changing the working resistance of semi-conductive elements during their tension or compression - mechanical deformation.
Strain gauges are a constructive set of strain gauge, which has a communicative point on the panel. The latter is connected to the material for measurement. Functional diagram of operationstrain gauge is that there is an impact on the sensitivity element. The device is connected to a power source using electrical outlets that are in contact with the sensitive plate.
Contact points are characterized by the presence of constant voltage. The load cell takes over the part through a special substrate. The mass of material interrupts the circuit due to deformational distortions. The resulting process is transformed into an electrical current signal.
The strain gauge pressure sensor is often used with AC strain gauges. In this system, amplitude modulation of the voltage is performed, which is fed directly to the transducer sensors.
Load cell device
Strain measuring instrument consists of:
- elastic element;
- strain gauge;
- device case;
- sealed connector.
Under the elastic element is meant a body that takes on the load. It is mainly made from special steel grades that have been heat treated in advance. This has an impact on obtaining stable readings. The manufacturing form is presented in the form of a rod, ring or console. The bar structure is more in demand and widespread.
A strain gauge is a wire or foil resistor assembly that is glued to a rod. This part of the strain gauge sensor changes its resistance relative to the deformation of the rod, and the deformation distortion, in turn, is proportional toload.
The body of the measuring device protects the internal structure from all kinds of mechanical damage, including the negative effects of the environment. The housing conforms to the international standard and has various shapes.
The hermetically sealed connector is required to communicate the sensor with additional equipment (balances, amplifiers, etc.) via a cable. There are various connection schemes. Design features of some load cells provide for cable replacement.
Force Measurement Sensors
Strain force sensors have another common name - dynamometers. These measuring instruments are an integral part of the weighing equipment. Their need can hardly be overestimated, since they function in all automated technological systems of any production. They have been used in agriculture, medicine, metallurgy, automotive industry, etc.
In this method of measurement, many manipulations occur, and in accordance with this, several types of load cells are distinguished:
- tactile - subdivided into transducers of effort, slippage and touch;
- resistive - use a strain gauge and have a linear output signal;
- piezoresonant - characterized by direct and reverse effect, which provides a special sensor - resonator;
- piezoelectric - resistant to ambient temperature, high strength, uses a direct piezo effect;
- magnetic –operate on the phenomenon of magnetostriction, which changes the geometry of dimensions in the magnetic region;
- capacitive - parametric type measuring instruments, which are a capacitor.
Weight measurement sensors
Strain load cells consist of three elements:
- Strain gauge.
- Bend beam.
- Cable.
Sensors are used in industrial and personal weighing equipment. These measuring instruments are more popular in manufacturing areas and have the following types:
- console devices - billets of aluminum or steel. Steel can be made in the form of a barrel or a washer, have a high tightness;
- beam devices - measure loads on platform and bridge structures.
Benefits of load cells
They are:
- High-precision measurements of parameters.
- Do not allow distortion of information.
- Compatible with voltage measurements.
- Compact overall dimensions.
The disadvantage can be considered the loss of sensitivity of functioning elements during critical temperature changes.
