Function Description - KERN 440...N Service Manual

5.2 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, parts counting, RS232 interface,
overload indication, low battery indication, tare, 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. If rechargeable battery is installed, it can be
charged up by the charging circuit.
7. Keyboard
The keyboard provides on user interface. [On/Off], [Mode/Cal], [Set/M], [Print] and
[Tare] keys are employed to operate the scale.
8. RS232 Interface
The RS232 serial interface provides the communication to the external computer or
printer.
6 440...N-SH-e-0840