Proving Ring type Load Cell

                                      

                                        

The proving ring is a device used to measure force. It consists of an elastic ring of known diameter with a measuring device located in the center of the ring.

Proving rings come in a variety of sizes.They are made of a steel alloy. Manufacturing consists of rough machining from annealed forgings, heat treatment, and precision grinding to final size and finish.

Proving rings can be designed to measure either compression or tension forces. Some are designed to measure both. The basic operation of the proving ring in tension is the same as in compression. However, tension rings are provided with threaded bosses and supplied with pulling rods which are screwed onto the bosses.

The proving ring consists of two main elements, the ring itself and the diameter-measuring system, shown on the right in the exploded view of a proving ring.  Forces are applied to the ring through the external bosses. The resulting change in diameter, referred to as the deflection of the ring, is measured with a micrometer screw and the vibrating reed mounted diametrically within the ring.

The micrometer screw and the vibrating reed are attached to the internal bosses of the ring. In modern rings, the upper and lower internal and external bosses are machined as an integral part of the ring to avoid mechanical interferences during the application of the force.

To read the diameter of the ring, the vibrating reed is set in motion by gently tapping it with a pencil. As the reed is vibrating, the micrometer screw on the spindle is adjusted until the button on the spindle just contacts the vibrating reed, dampening out its vibrations. When this occurs a characteristic buzzing sound is produced. At this point a reading of the micrometer dial indicates the diameter of the ring.

The number of divisions on the micrometer dial and the graduation of the vernier index vary by type of proving ring. Typically, proving rings are designed to have a deflection of about 0.84 mm (0.033 in) to 4.24 mm (0.167 in). The relative measurement uncertainty can vary from 0.075 %  to about 0.0125 %.

Cantilever Beam type Load Cell

                 

The Cantilever load cell is a strain gauge based low profile bending beam load cell and is for precision single point load applications. It is designed for eccentric load sensitivity. Its alloy steel construction is very rugged to withstand shock load. These load cells can be used in Tank Weighing, Hopper Weighing, Truck weighing etc.

Epoch compression series-Load cell is a high precision force sensor for stringent load measurement. The innovative design of this sensor offers high degree of accuracy towards force measuring techniques. A precision machined flexure with superior quality strain gauges is used as the load sensing element. The unique feature of this design brings high accuracy, full temperature compensation and high over Load Protection.

These load cells finds the application in hopper weighing, tank weighing, tension/compression measurements, crane weighing, platform scales, weigh bridges, silo weighing etc.,

Strain Gauge Load cell

A load cell is a transducer that is used to create an electrical signal whose magnitude is directly proportional to the force being measured.

 The various types of load cells include hydraulic load cells, pneumatic load cells and strain gauge load cells.

Strain gauge load cell

Before Read Watch this Video : http://www.rdpe.com/ex/hiw-sglc.htm 

Through a mechanical construction, the force being sensed deforms a strain gauge. The strain gauge measures the deformation (strain) as a change in electrical resistance, which is a measure of the strain and hence the applied forces. A load cell usually consists of four strain gauges in a Wheatstone bridge configuration. Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available. The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used. The output of the transducer can be scaled to calculate the force applied to the transducer.

Strain gauge load cells are the most common in industry. These load cells are particularly stiff, have very good resonance values, and tend to have long life cycles in application. Strain gauge load cells work on the principle that the strain gauge (a planar resistor) deforms/stretches/contracts when the material of the load cells deforms appropriately. These values are extremely small and are relational to the stress and/or strain that the material load cell is undergoing at the time. The change in resistance of the strain gauge provides an electrical value change that is calibrated to the load placed on the load cell.

Strain gauge load cells convert the load acting on them into electrical signals. The gauges themselves are bonded onto a beam or structural member that deforms when weight is applied. In most cases, four strain gauges are used to obtain maximum sensitivity and temperature compensation. Two of the gauges are usually in tension, and two in compression, and are wired with compensation adjustments. The strain gauge load cell is fundamentally a spring optimized for strain measurement. Gauges are mounted in areas that exhibit strain in compression or tension. The gauges are mounted in a differential bridge to enhance measurement accuracy.^[2] When weight is applied, the strain changes the electrical resistance of the gauges in proportion to the load.^[3] Other load cells are fading into obscurity, as strain gauge load cells continue to increase their accuracy and lower their unit costs.

Application of Load Cell & Strain Gauge

Engineering

Test Rig Force Monitoring

Strain Gauging of Components

Robotic—Weighing of components

Specialised load cells

General weighing

Machine control

Repair & Calibration

Cranes & Lifting

Overload / Under load Protection

Weighing

Pile Load Monitoring

Radio Telemetry

Repair & Calib

Research & Development

Evaluation of new products using load cells, strain gauging and logging facilities on listed fields of industry

Strain Gauging of Components

General weighing

Repair & Calibration

Civil Engineering

Bridge Lifting

Strain Gauging of Components

Structural Testing

Repair & CalibrationChemical

Press force monitoring

Strain Gauging of Components

Robotic—Weighing of components

Silo weighing load cells

General weighing

Repair & Calibration

Packaging

Web Tension

Process control

Strain Gauging of Components

General weighing

Repair & CalibrationAerospace

Airframe Test Rigs

Strain Gauging of Components

Aircraft Weighing

Landing Gear Test Rigs

Torsion Test

Repair & Calibrationration

Automotive

Component Test Rigs

Crash Tests

Production Quality Processes

Strain Gauging of Components

Special Sensors

Aerodynamics

Repair & Calibration