2.4 Instrument Description
22
2.4.9 Tachometer
The tachometer is used to measure the conveyor speed. It is sup-
plied with power by a separate power supply unit. The evaluation
unit LB 442 can process signals from pulsed tachometers with 500
pulses/rev or 5000 pulses/rev as well as current signals (0/4 - 20
mA) proportional to the speed.
For measurements on a conveyor belt, a running wheel having a
diameter of 160 mm is attached to the tachometer. In this case,
the tachometer including the flexible holder has to be installed in
such a manner that the wheel is running on the lower belt.
For measurements on chain and screw conveyors, the tachome-
ter is attached to a rotating axle via a flexible coupling. The driving
axle should have a diameter of 12 mm.
Provided the conveyor speed is constant, the speed need not be
monitored on-line. Several experiments and statements by manu-
facturers of conveyor systems show, however, that the speed is
not constant immediately after starting the conveyor.
See also information on Tachometer Installation in the Appendix
on page 130.
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