User manual

F-8 8580/8590 Vehicle-Mount Computer User Manual
Appendix F: Mechanical Dynamic Loading
Determining Natural Frequencies
Implication For Designing Computer Mounts:
• Suppose that high energy excitation frequencies occur mainly in the region of the
natural frequency of the 8580/8590 with its mounting, which can be found, for example,
in a vehicle chassis tuned to a low frequency. In this case a spring mounting of the
8580/8590 should be avoided.
• However, if high energy excitation frequencies occur mainly above the natural fre-
quency, it is recommended that you use passive vibration isolation for the computer.
This applies to unsprung fork lifts with solid rubber tires or for unbalanced machines
with relatively constant and correspondingly high operating speed.
Random samples of fork lift rotors were taken and the field excitations measured:
These values can be assigned to operation class 5M3.
F.8 Determining Natural Frequencies
There are several ways of determining a system's natural frequencies:
• Take field measurements with acceleration sensors and frequency analyses (very time-
consuming, but produces accurate results for all spatial axes)
Track: Warehouses with loading thresholds, potholes and
pallet splinters.
Amplitude of the excitation
accelerations:
Mean value ±1g to ±2g for all three spatial axes
with peak values ±5g approximately twice each
minute and ±8g to ±13g occasionally.
Excitation frequencies: 5Hz to 200Hz
Important: The basic 8580/8590 is designed for operation class 5M3. Depending on
the equipment (e.g. 24-key keyboard) and mounting types (e.g. with
elastomer springs), the operation class can be reduced to 5M2 or 5M1.
If you have any questions regarding the permissible operation class,
please contact the Psion technical service department.