How
does the Super Hybrid Sensor (SHS) work?


The
basic principle of the GX device is force
restoration motor. Any change in the load on the weighing
pan causes a position beam lever to pivot on two fulcrum flexures
(refer to diagram below). Attached to this beam is a bobbin
(wound with fine wire), called the "force coil."
This bobbin floats in a permanent magnet called the force motor.
At the end of the position beam lever, there is a small hole
which allows light from a light-emitting diode (LED) to pass
through to two photodiodes (light measuring diodes) as it moves
up or down. At zero weight, the light detected by the
upper photodiode is equal to that detected by the lower photodiode.
These three diodes make up the position detector.
When
the force coil is pulled up by the leverage exerted from a mass
on the weighing pan, the position detector detects a change
in the position of the force coil as the light reaching the
upper photodiode will be greater than that reaching the lower
one. The balance then feeds the force coil with more voltage
to pull it back until the light measured by the two photodiodes
is equal, and the mechanism is once again balanced. This
is accomplish by the analog module receiving photocurrent from
the photodiodes, converting it to voltage and sending it back
to the force coil. As the voltage increases, so does the
magnetic power pulling the force coil back until the position
detector reads equilibrium (balance).
The
current flowing through the force coil generates a voltage proportional
to the load weight on the pan. This is read back through
the analog module, first being filtered -- then the analog to
digital converter digitizes this measuring voltage, the resulting
value is counted and then fed to the microprocessor.
Temperature
affects the magnet and weight data. So temperature coefficient
for weight is measured and saved beforehand. The balance
eliminates the temperature effect by using the present temperature
measured by the temperature sensor and the coefficient.
The output from the temperature sensor is converted digitally
and sent to the CPU by the analog module.
The
CPU performs a mathematical operation in connection with each
parameter, such as temperature, linearity coefficient, and calibration
data. Also, the user can specify how the calculated information
should be displayed by using the keyboard. For example:
they can have the CPU perform special functions such as conversion
into other measuring units or counting of small parts.
Finally, the results are displayed on the fluorescent
display, or sent through the RS-232C
interface.
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