Pressure and weight strain gauges are those devices from the field of weighing technology that are capable of converting the mechanical deformation of objects and bodies into a conventional electrical signal, which subsequently allows you to determine the level of compression / extension of a certain body. By itself, such a sensor is a resistive transducer and is positioned as one of the main components of high-precision weighing equipment. These devices are used in any electronic type scales: from household floor scales to ultra-precise laboratory ones.
The principle of operation of the strain gauge is as follows: when an object is placed on the scales, under its influence (weight) the resistor on which the strain gauge is installed changes (deforms).In turn, the sensor measures the force and strain of the resistor and transmits this data to the control board. Thus, the weight of the item on the loading platform is calculated. In weighing equipment, one or more sensors can be used.
Correctly, such sensors in the engineering environment are called weight meters for scales, and in the common people they are called "beams".

Content
Any load cell has a certain set of characteristics that affect the scope and limits of its application. These include:
When selecting a sensor for use for specific purposes, it is also necessary to pay attention to additional characteristics, which include:
In general, the described device is a single elastic system consisting of a resistor and an electrical circuit, which is connected to a weighing batcher. When the resistance of the resistor changes, the strain level is set, after which the data obtained are transformed into the required mathematical and physical quantities and displayed on the scales display. This is how all electronic weighing equipment functions. Its sufficient accuracy will be maintained even in the event that one of the sensors fails, because the schemes used today involve duplication of measurements.
Depending on the type of the weighing bowl (or rather, the load receiving platform), there are the following types of strain gauges:
The main requirements for strain gauges are moisture resistance, low susceptibility to aggressive environments, and calculation for a long service life. In addition, the sensors must be sensitive to any increased mechanical load.
If the dimensions of the weighing equipment itself are too large, then it may happen that the connection between the sensor and the analog-to-digital converter of the equipment will be made using extended wires. Therefore, the electrical resistance of the wires themselves will begin to affect the readings.
This problem can be resolved in two ways:
IMPORTANT: On the weighing device "MASSA-K" of the "VT" series, "know-how" was applied, and the converter was installed directly on the sensor, which made it possible to do without wires and solve the issue of resistance. However, at the engineering level, a miscalculation was made, namely: the calibration toggle switch was not moved beyond the boundaries of the load cell, which led to the complication of verification procedures.

Without these holes, the total load would be equally distributed over the entire surface, and, accordingly, it would be more difficult to establish the deformation. Due to the fact that the resistors are placed in the places where the greatest stress is concentrated, the place of integration of the latter is specially made thin so that the load applied to the edge of the beam would be expressed to the maximum in these places. Thus, the orientation of the resistors is relative to the thinnest point.
An important issue in creating a successful and accurate weighing system using load cells is the organization of shielding and grounding. A competent solution of such a problem is the key to the correct functioning of the tensometric device in the field of low-current signal generation. At the same time, device cables must have a shielding braid that would protect them from electrostatic and other interference, provided it is properly installed.
The main and inviolable rule in this case should be the principle of avoiding "earth" loops, which means the need to ground the device at ONE and COMMON point. If you connect the cable screen at both ends, then the occurrence of a loop is inevitable. Thus, if the sensor body is securely connected and correctly fixed to the screen, then this will be enough, otherwise, it is possible to connect the screen to ground from only ONE of any end, for example, in the electrical panel. It is worth remembering that it is highly not recommended to use "neutral" as a "ground electrode".
If the sensors are connected in parallel, then you must not forget to connect the screen cable braids to each other, using the associated terminal contact in the junction box. After connecting, immediately "ground" them simultaneously with the body of the box itself.
Also, on ONE side, it is necessary to connect the common cable passing from the device to the junction box to the ground, while the formation of an "earth" loop must not be allowed. It is preferable to implement this circuit from the side of the receiver, i.e., near the entrance to the measuring device.
Right on top of the sensor cable insulation (approximately 4-5 cm from the equipment terminal), it is necessary to snap in a ferrite filter in order to block various interferences on the "ground". These filters are available for cables of various sizes and diameters. They can also be installed on other extended lines, such as RS-485, both on the transmitter and receiver. Sometimes it may happen that the inductance of a single filter may not be enough. Then it will be necessary to additionally and sequentially snap the filters at a certain distance from each other. This will increase the inductance to the desired level and reliably reduce the level of interference.
Due to the fact that strain gauge devices are not particularly complex in their design, it is better to focus on the price, and not on the manufacturer, when buying. Thus, although today's market is full of various price and brand offers, there is no big difference between economy class and premium.Expensive sensors should be purchased only when they are really needed for high-precision measurements, for example, in the food industry or for laboratory experiments. Otherwise, this purchase will not require large expenditures and will cost the standard price relative to standard measurement errors.
Regarding the Asian manufacturer of the products in question. As the analysis shows, the measurement accuracy of sensors from Taiwan, China, Korea is in no way inferior to the most popular firms. However, the material of their manufacture is often not durable and it happens that the deformation of the beam on Chinese devices can be seen with the naked eye immediately after a couple of several measuring procedures.
The model is intended for use in electronic scales at public catering establishments and in grocery stores. It has an improved design, access to the analog-to-digital converter (ADC) is carried out through a single wire, which does not cause a difference in resistance. More like a spare part.

| Name | Index |
|---|---|
| Manufacturer country | South Korea |
| Structural type | Cantilevered |
| Weight, kg | 0.23 |
| Dimensions, mm | 190x58x53 |
| Price, rubles | 2100 |
Multifunctional sample of S-shaped design. It can be used in various types of scales designed for medium loads. Easy to install, can be paired with other sensors.With the help of a stranded wire, stable communication with the ADC is ensured.

| Name | Index |
|---|---|
| Manufacturer country | China |
| Structural type | S-shaped |
| Weight, kg | 1.5 |
| Dimensions, mm | 94x86x35 |
| Price, rubles | 3800 |
This sensor is designed for weighing packing and other bulk products, it is not designed for heavy loads. Extremely easy to install and made from durable alloy steel for extended life. Additionally, it has a class of protection against dust and moisture (as a separate element of equipment for weighing).

| Name | Index |
|---|---|
| Manufacturer country | Russia |
| Structural type | single point |
| Weight, kg | 1.3 |
| Dimensions, mm | 130x25x22 |
| Price, rubles | 5600 |
Alloy steel probe with nickel plated surface. It has a predominantly industrial purpose and is used for medium and high loads (weighing concrete mass at a construction site, weighing hot asphalt when laying a roadbed, etc.). Can work both in tension and compression.

| Name | Index |
|---|---|
| Manufacturer country | Switzerland |
| Structural type | S-shaped |
| Weight, kg | 12 |
| Dimensions, mm | 150x100x98 |
| Price, rubles | 11100 |
This device is intended for use on relatively large loading platforms - from 80x80 cm, and can also be used in bunker and packing scales. It is an example of a single-point design, therefore it can only be used in a single version.

| Name | Index |
|---|---|
| Manufacturer country | Russia |
| Structural type | single point |
| Weight, kg | 5 |
| Dimensions, mm | 45x54x79 |
| Price, rubles | 16300 |
A professional measuring device designed to check the weight of cars and various special equipment. It can be used at stationary traffic police posts in order to determine the permissible weight of vehicles for travel, as well as at customs posts.

| Name | Index |
|---|---|
| Manufacturer country | South Korea |
| Structural type | Cantilevered |
| Weight, kg | 7 |
| Dimensions, mm | 85x70x95 |
| Price, rubles | 17600 |
The design of the elastic element of this sensor allows accurate readings to be transmitted even if the load is placed on the edge of the platform. The tightness of the body is ensured by the installation of special helium gaskets. The kit comes with a protective sleeve, cover and caps.The device is designed for precise work with almost any weight - from small values to extra large ones.

| Name | Index |
|---|---|
| Manufacturer country | Russia |
| Structural type | single point |
| Weight, kg | 8.1 |
| Dimensions, mm | 76x79x95 |
| Price, rubles | 33500 |
The model is intended for industrial use, for example, for weighing bulk and liquid materials of large volumes on enlarged platforms (determining the weight of prepared concrete in a concrete plant). Easy to calibrate, housing made of stainless steel.

| Name | Index |
|---|---|
| Manufacturer country | South Korea |
| Structural type | single point |
| Weight, kg | 15 |
| Dimensions, mm | 84x83x45 |
| Price, rubles | 57000 |
The low profile round sensor is capable of handling extra heavy loads up to 100 tons. At the same time, the model has a margin of additional NPI of about 150%. It can function both in compression and in tension. The design uses a 4-core cable with a polyurethane protective braid, which guarantees high linearity and accuracy of data transmitted to the ADC. The system has its own moisture and dust protection, mounted according to the European standard.

| Name | Index |
|---|---|
| Manufacturer country | South Korea |
| Structural type | "washer" |
| Weight, kg | 30 |
| Dimensions, mm | 307x278x90 |
| Price, rubles | 70000 |
In order to save money, you can also order and purchase strain gauges through Internet sites. The popularity of this method is also due to the fact that on the websites of sellers and manufacturers it is very convenient to search for the desired model according to the specified parameters. Separately, it is worth noting that, unlike retail, prices on the Internet will be much lower. Moreover, if a wholesale supply of a large amount of goods is required (for example, to supply an industrial facility), then a branded specialized store may well provide a discount. In addition, sensors are a product that is hardly possible to spoil even in conditions of extremely careless shipment, so there is nothing to fear by and large.