Metal tube float flowmeter detailed introduction force sensor

1. Principle of force sensor:

The metal tube float flowmeter consists of three major parts: a force sensor: one or more elastic bodies that can deform after being subjected to force, a bridge circuit (such as a Wheatstone bridge) composed of a resistance strain gauge that can sense the deformation, an adhesive that can fix the resistance strain gauge on the elastic body and conduct the strain, and a sealant that protects the electronic circuit.

2. Working process of force sensor:

When subjected to external force, the strain gauge attached to the elastic body deforms and causes resistance changes. The resistance change causes the composed Wheatstone bridge to lose balance and output an electrical signal that changes linearly in proportion to the external force.

3. Material of force sensor:

3-1. Elastomer material:

The elastomer material of the force sensor is generally made of metal, and most of the available materials are aluminum alloy, alloy steel and stainless steel. The alloy material has both rigidity to ensure consistent deformation and deformation recovery, and good weather resistance and corrosion resistance. The main requirement of the elastomer is to be able to accurately transmit force information and maintain deformation consistency and complete reset under the same force.

3-2. Strain gauge and resistor element materials:

The composition of the resistance strain gauge is complex and it is a composite manufacturing product. The combination of the base material and the strain copper of the strain gauge is ever-changing. According to its strain requirements, there are currently nearly a thousand products. Generally, the base material is made of polymer film material, and the metal tube float flowmeter strain material is high-purity constantan. The constantan on the base material is optically treated and then etched with different resistance grid wires that sense deformation. Therefore, the quality of the resistance strain gauge is not only related to the base material and the purity of the composite metal, but also to the composite process, etching technology and process, etching chemical materials and post-processing process and materials and other factors.

3-3. Material of patch adhesive:

The adhesive for resistance strain gauge patch mainly adopts two-component polymer epoxy series adhesive. The performance of polymer chemical products is closely related to the physical and chemical indicators of each component, such as purity, structure and size of molecular chain, storage time, component ratio, molecular modification, mixing method, mixing and maturing time, curing time, curing temperature, additives and percentage, etc.

3-4. Sealant material:

In the early stage of force sensors when welding technology and equipment were not sufficient, a special series of silicone rubber sealants were used. Silicone rubber has long-term chemical stability, so it has excellent properties such as corrosion resistance, moisture resistance, aging resistance, and insulation, and has long been the preferred product of all sealants.

3-5. Material of the wire of the force sensor:

The wire is still part of the force sensor. The metal material of the force sensor wire has a personal experience of quality differences due to the use of wires in household appliances. After all, the wire is the path for bridge power supply, signal output, and long-line excitation voltage compensation. Silver-plated wire is definitely better than copper wire in terms of conduction effect, and copper wire is definitely better than aluminum wire in terms of conduction effect. Its role is self-evident.

With the increasing number of interferences such as various high frequencies and radio waves, excellent shielding of force sensors is also an important method to protect signal stability. In addition, environmental erosion, insect and rodent damage, fire retardancy, etc. also require the material of the sensor protection layer to be anti-corrosion, anti-insect, fireproof and explosion-proof, and even armor protection, casing protection and other methods are needed.

3-6. Wire sealing materials and methods:

Each component of the force sensor will affect the final technical performance of the sensor. Some force sensors only use a simple fixing method to prevent the movement of the sensor wires and damage the sensor's electronic circuit fixation. Some force sensors with a very short conduction distance even rely solely on glue sealing for fixation. However, if there is no proper wire fixing or sealing method for force sensors with larger volume and heavier weight, it will be the bottleneck that is most likely to cause failure of the force sensor. In particular, when installing a sealing head to fix the wires, the material and tightening strength of the fasteners will also affect the final technical performance of the force sensor. Observers have found that few fasteners are used to install sealing adhesives, which can avoid the residual stress caused by relying on the tightening force to fix, and the metal tube float flowmeter will not have leakage problems due to insufficient tightening force.