2.2 Function description
1. Load cell
This is the heart of the whole system. Four load cells, located in the four corners of the
platform, are arranged as a bridge. The resistance change of the bridge elements is
proportional to the load applied on the load cells. Therefore the output of the load cells
is an analogue signal, which is proportional to the load applied on the platform.
2. Amplifier
The analogue signal from the load cell is very small, of the order of micro-volt. Hence,
a linear and stable amplifier is applied to amplify the analogue signal to an appropriate
level.
3. A/D Converter
In order for the analogue signal can be input to the microprocessor, this part converts
the analogue signal to its digital equivalent. The operation of the analogue to digital
converter is using a VOLTAGE TO FREQUENCY technique and is controlled by the
microprocessor.
4. Microprocessor
The microprocessor controls all the functions of the balance, such as auto zero, A/D
conversion, timings, weight calculation and display, overload indication, low battery
indication, memory / tare function, etc.
5. Display
This is the part where the weight is shown out on the LCD display in digital form. The
whole display is driven by the microprocessor.
6. Power regulator and low battery detector
This part contains the ON/OFF power control. In order for the external power can be
used by other parts of the balance, a regulator is used to regulate the supply. A low
battery detector is employed to make sure that the power supply is strong enough for
normal operation of the balance.
7. Keyboard
The keyboard provides the user interface. ON/MEMORY, MODE, TARE and OFF
keys are employed to operate the balance.
DE-SH-e-0111
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