Psion Teklogix Vehicle-Mount Computer 8590 User Manual page 178

Appendix D: Mechanical Dynamic Loading
Determining Insulating Effects
Excitation Frequency Natural Frequency
10Hz
20Hz
Approx. 28Hz
40Hz
60Hz
80Hz
Based on this table, we can clearly expect very good insulation for excitation
frequencies that are twice as high as the system's natural frequency.
Consequently, the amplitude of the reaction accelerations of the 8580/8590 still only
reaches 66% of the amplitude of the excitation accelerations, which actually have an
effect twice that of the natural frequency.
The table also demonstrates the costs of achieving this, namely that all excitation
frequencies below the natural frequency are amplified - to a maximum when
resonance occurs.
Implication For Designing Computer Mounts:
• If high energy excitation frequencies mainly occur 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 mainly occur above the
natural frequency, it is recommended that you use passive vibration insula-
tion for the computer. This applies to unsprung fork lifts with solid rubber
tires or for unbalanced machines with relatively constant and correspond-
ingly high operating speed.
Random samples of fork lift rotors were taken and the field excitations measured:
D-8 8580/8590 Vehicle-Mount Computer User Manual
20Hz 0.5
20Hz 1
20Hz 2
20Hz 2
20Hz 3
20Hz 4
Degree Of Insulation
-33% Warning! Amplification
Warning!Resonance, approx. – 500%
and greater! High amplification!
0, no insulation
66%
88%
93%