Page 89 - Lehrbuch Neigungsmessung deutsch 2018.indd

COMPENDIUM INCLINATION MEASUREMENT
WYLER AG, WINTERTHUR / SWITZERLAND

• Voltage stabilizer
• Digital frequency counter
• Calibration data memory
Pendulum • Asynchronous serial port Design of ZEROTRONIC:
• Sensor including pendulum held by
Archimedes helical springs
• RC oscillator
• Voltage stabilizer with level-shifter
• Digital frequency counter with calibra-
tion data memory and asynchronous
serial port
• Housing and mounting bracket

Connector for
RS 485

Electrodes RC oscillator Housing welded
gastight
7.1.1.1 MEASURING PRINCIPLE OF DIGITAL MEASURING SYSTEMS
The pendulum, suspended by the Archimedes helical spring, is mounted between two electrodes. De-
pending on the inclined position of the system, the pendulum will swing out of the zero position and in
doing so change the capacitance between the pendulum and the two electrodes. These capacitances are
transformed into different frequencies through the RC-oscillator. The ratio of the two frequencies returned
is used as the primary signal for detecting the required angle. The system is patent protected in most
countries.
Ideally, the mechanical dampening of the pendulum’s movements is provided by gases, normally by
nitrogen. The viscosity change of gases in the temperature range between -40 °C and +70 °C is marginal.
Therefore dampening with gases is superior to dampening with other substances such as liquids. The
best possible results in dampening are achieved by the ratio between the surface of the pendulum and the
size of the aperture of the Archimedes helical spring. In addition, mathematical smoothing can be done by
integrating the results over a period of time. This is highly scalable by adjusting the individual parameters.
Depending on the switched-on electrode and the resulting capacitance, one RC oscillator supplies the
required frequency between 250,000 and Voltage
350,000 Hz. Because of the alternating Selector stabilizer Connector
engagement of both of the electrodes Pendulum Oscillator V cc
through a selector switch and always RTA
using one oscillator only, it is assured that Signal treatment and asynchronous serial port RS485
the temperature influence is limited to a RTB
minimum. This configuration has proved
to be superior in terms of long-term sta- GND
bility over other existing applications. The C 1 C 2
short distances between the electrodes SIGNAL
and the oscillator and the stable connec- Position
tions between the critical electronic ele- “SELECTOR“
ments further improve the system’s capa- Output
bility. frequency
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