6.2 Function Description
1. Load cell
This is the heart of the whole system. The load cell itself is arranged as a bridge.
The resistance change of the bridge elements is proportional to the load applied
on the load cell. Therefore, the output of the load cell is an analog signal,
which is proportional to the load applied on the scale.
2. Amplifier
The analog 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 analog signal
to an appropriate level.
3. A/D Converter
In order for the analog signal can be input to the microprocessor, this part
converts the analog signal to its digital equivalent. The operation of the analog
to digital converter is using a SIGMA DELTA technique and under the control
of the microprocessor.
4. Microprocessor
The microprocessor control all the functions of the scale, such as auto zero,
A/D conversion, timings, weight calculation, display, overload indication,
low battery indication, 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 scale, 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 scale.
7. Keyboard
The keyboard provides on user interface. [On/TARE], [OFF] keys are employed
to operate the scale.
EMB-SH-e-0933
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