Electronic weighbridge

Industrial Instrument applications for electronic weigh bridge

1. Electronic Weighbridge Prepared by : Shubham Bharadia

2. 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 .

3. 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: H ydraulic load cells P neumatic load cells & Strain gauge load cells.

4. Specification Of The Load Cell 1. Rate Load Capacity 10,15,20,30,50 tons 2. Input Resistance 800 +/- 30  W 3. Output Resistance 700+/- 5  W 4. Excitation Recommended Max 15 Volts 5. Rated Output 3.0 +/- 10% mv/v 6. Non-Linearity +/- 0.03% of applied load 7. Hysterisis +/- 0.03% of applied load 8. Thermal Effect on Zero 0.05% of applied load/10 deg C 9. Thermal Effect on Sensitivity 0.03% of applied load/10 deg C 10. Insulation Resistance > 1000 m  W 11. Creep at 20 Minutes +/- 0.05 % of applied load 12. Temperature Range Operative 0 deg. C to 50 deg. C 13. Safe Load 150% of rated capacity 14. Ultimate Load 300% rated capacity 15. Protection Clause IP 67

5. 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.  

6. Principle The 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

7. Principle Signal 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.

8. Types Pit type weighbridge This 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 platform is in flush with ground Level.

9. 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.

10. Uses They 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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