Electronic Weighbridge

Prepared by :Shubham Bharadia

What is weighbridge ?weighbridge is a large set of scales, usually

mounted permanently on a concrete foundation, that is used to weigh entire rail or road vehicles and their contents. By weighing the vehicle both empty and when loaded, the load carried by the vehicle can be calculated.

The key component that uses a weighbridge in order to make the weigh measurement is load cells.

Load cells 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:

I. Hydraulic load cellsII. Pneumatic load cellsIII. & Strain gauge load cells.

Specification Of The Load Cell 1. Rate Load Capacity 10,15,20,30,50 tons2. Input Resistance 800 +/- 30 W3. Output Resistance 700+/- 5 W4. Excitation Recommended Max 15 Volts5. Rated Output 3.0 +/- 10% mv/v6. Non-Linearity +/- 0.03% of applied load7. Hysterisis +/- 0.03% of applied load8. Thermal Effect on Zero 0.05% of applied load/10 deg C9. Thermal Effect on Sensitivity 0.03% of applied load/10 deg C10. Insulation Resistance > 1000 m W11. Creep at 20 Minutes +/- 0.05 % of applied load12. Temperature Range Operative 0 deg. C to 50 deg. C13. Safe Load 150% of rated capacity14. Ultimate Load 300% rated capacity15. Protection Clause IP 67

Load cells are mounted with the help of unique mounting arrangement. This arrangement offers following advantages

• A unique suspension design allows the platform to swing in the direction of the movement of vehicle.• Absorbs lateral and transverse breaking force, which improves the life of the load cell.• Easy to install and hence reduced time of maintenance. 

PrincipleThe Electronic Static Weigh-bridge is made

up of a framework of girders reinforced with transverse beams.

The entire framework is mounted on strain gauge Ball-Cup Type Load Cell/ Compression Type Load Cells (4, 6, 8 &10 No's. Load Cells), depending on length of the platform.

The shear stress produced by the load is detected by a strain gauge, full bridge circuit and converted into an analog electrical signal

PrincipleSignal from each loadcell is fed to Junction

Box. Output from Junction Box is fed to

microprocessor based weighbridge Microprocessor.

The processing electronics of terminal digitizers the signal from the Junction-box using an ADC, based on time proven quad slope integration technique and weight is registered on LED display.

Types 1. Pit type weighbridgeThis type of weighbridge is most suitable for places with limited space e.g. non-hilly areas where the construction of pit is not a costly affair.Benefits

Lesser Space Required Rickshaws & Tractor Trolleys can also be weighed as platformis in flush with ground Level.

2. Pitless weighbridge This type of weighbridge is most suitable where the excavation work for foundation is difficult or construction of pit is expensive. Benefits Costly Pit construction is

eliminated. Platform above ground level-

No water logging during rainy season

Problem of pit maintenance is eliminated.

UsesThey are used in industries that manufacture or move bulk

items, such as in mines or quarries, garbage dumps / recycling centres, bulk liquid and powder movement, household goods, and electrical equipment.

Since the weight of the vehicle carrying the goods is known they are a quick and easy way to measure the flow of bulk goods

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