The item to be weighted is placed on a platform. The weight is determined by the machine and displayed on 7-segment Led display. Figure shows the schematic block diagram of microprocessor based electronic balance. It consists of load cell, amplifier, analog to digital converter and 7-segment LED display.
The electronic balance has a load cell pressure transducer. It converts the weight in to a proportional electrical signal. The sensing resistance in the load cell forms a Wheatstone bridge. With no load on the platform, the bridge is balanced. On placing the load, the resistance of one arm will change. This produces an output of the order of few millivolts. The small signal is amplified by an instrumentation amplifier. This amplifier provides an output signal to the required level of analog to digital converter.
The ADC converts the analog voltage into digital form as needed by the microprocessor. Through an I/O port, output of the ADC is connected to the microprocessor. The microprocessor reads the data, converts it into BCD digits. The measured weight is displayed on 7-segment LED display in Kg, gm, etc.
Features:
- Easy to operate.
- High speed of response, low settling time and hence rapid weighing.
- Compact and small in size.
- Both analog and digital output with printing facility is available.
- High accuracy even under most adverse environmental conditions such as dust, corrosive, heat and cold.
- High stability and ruggedness.
- High resolution.
- Long equipment life.
- No technical skill is required to operate.
- Greater reliability.
Limitation
Relatively high cost.