In various modern spheres of human life there is a need to control different designs by measuring the parameters and current state of this element. Indispensable assistants in this matter are strain gauge sensors.
Leading technologies are increasingly using electronic strain gauges, among which the most widespread are strain-resistant device models. Strain gauges can measure weight, force, pressure, movement, etc.
Widely used are load cells for scales, industrial machines, various engines, they are used in the construction field and many other areas.
Types of sensors
A wide variety of strain gauges are used in various industrial sectors. The following types of devices are distinguished:
- force measuring instruments - sensors scan changes in force and load parameters;
- instruments for measuring the projection of acceleration - accelerometers;
- measuring instruments for moving test materials;
- tensometric pressure devices - characterized by the control of pressure parameters of various elements in different environments;
- strain gauge torque converters.
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 appliances;
- measuring instruments in the form of the Latin letter S;
- washer-shaped strain gauges;
- measuring instruments remotely resembling the shape of a barrel.
There is a classification of measuring strain gauges, depending on the design feature - the sensitivity element. The source material identified such models:
- wire - are created in the form of a wire, the material is two-component nichrome, the elemental compound fechral, thermostable constantan alloy;
- foil strain gauges - thin foil strips are used;
- semiconductor sensors - are made of such chemical elements as silicon, galium, germanium.
Principle of operation
At the heart of the principle of the device is the strain effect. Its essence is to change the working reaction of semi- and conductor elements during their tension or compression - mechanical deformation.
Strain gages are a structural set of a strain gauge, which has a communicative point on the panel. The latter is connected to the material for measurement. The functional diagram of the actuation of the strain gauge is that there is an effect on the sensitivity element. The device is connected to the power source using electric taps that have 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 chain due to deformation distortions. The resulting process is transformed into an electrical current signal.
A strain gauge pressure transmitter is often used with alternating current strain gauges. In this system, amplitude voltage modulation is performed, which is fed directly to the conversion sensors.
Load cell device
The tensometric measuring instrument consists of:
- elastic element;
- strain gauge;
- instrument case;
- sealed connector.
By an elastic element is meant a body that takes on a load. It is mainly made from special grades of steel that have previously been heat treated. This has an effect on obtaining stable readings. The manufacturing form is presented in the form of a rod, ring or console. The core structure is more in demand and widespread.
A strain gauge is a wire or foil resistor assembly that adheres to a rod. This part of the strain gauge changes its resistance to the deformation of the rod, and the deformation distortion, in turn, is proportional to the load.
The body of the measuring device protects the internal structure from all kinds of mechanical damage, including the negative effects of the environment. The case complies with international standards and has various forms.
A sealed connector is required for communication of the sensor with additional equipment (scales, amplifiers, etc.) via a cable. Variable connection schemes exist. Design features of some load cells include cable replacement.
Force sensors
Strain gages of force have another common name - dynamometers. These measuring instruments are an integral part of weighing equipment. Their need is difficult to overestimate, since they function in all automated technological systems of any production. They found application in the field of agriculture, medicine, metallurgy, automotive, etc.
In this measurement method, there are many manipulations, and in accordance with this, several types of load cells are distinguished:
- tactile - are divided into converters of effort, slippage and touch;
- resistive - use a strain gauge and have a linear output signal;
- piezoresonance - are characterized by a direct and inverse effect, which provides a special sensor - a resonator;
- piezoelectric - resistant to ambient temperature, high strength, uses the direct piezoelectric effect;
- magnetic - operate on the phenomenon of magnetostriction, which changes the geometry of sizes in the magnetic region;
- capacitive - means of measuring the parametric type, which are a capacitor.
Weight sensors
Strain gages weight sensors consist of three elements:
- Strain gauge.
- Bending beam.
- Cable.
Sensors are used in industrial weighing equipment and personal use. These measuring instruments are more popular in the manufacturing fields and have the following types:
- cantilever devices - aluminum or steel billets. Steel can be made in the form of a barrel or washer, have a high tightness;
- beam devices - measure loads on platform and bridge structures.
Strain Gauge Advantages
They are as follows:
- High precision measurements.
- Do not allow distortion of information.
- Compatible with voltage measurements.
- Compact overall dimensions.
A disadvantage can be considered the loss of sensitivity of the functioning elements during critical temperature drops.