Ohmart Vega W-4510, Technical Reference Hardware Manual

Page: 53 / 162

Installation
36 W-4510 Weigh Scale Technical Reference Manual
Auxiliary and optional equipment
Tachometer
The tachometer monitors the conveyor belt or screw speed. Use the tachometer when the
belt or screw speed variation exceeds
±
1%. Mount the tachometer correctly to maintain the
proper speed. The digital tachometer provides 1,200 pulses per revolution. The shaft
revolutions per minute (RPM) must be between 5 and 1,000 when line speed is at its
maximum. Use a step-up or step-down arrangement if the shaft RPM is not within this range.
The drive shaft (or idler roller) must have positive contact with the conveyor to ensure
accurate correlation of the speed. For accurate operation, select one of the following four
locations on the conveyor for driving the tachometer:
1.
The tail pulley
2.
The idler take-up roller where the conveyor has adequate tension and wrap-around to
prevent slippage
3.
The idler roller where there is adequate contact with the conveyor, even when the
conveyor is lightly loaded
4.
The pulley in contact with the underside of the conveyor. Only use this location if the first
three locations are inconvenient or impossible.
Ohmart does not recommend the following locations for the positioning of the tachometer:
•
Idler or pulley that is in contact with the side of the conveyor handling material. Material
build-up on the idler can cause a decrease in speed. This decrease in speed introduces
an error into the system.
•
Head pulley when there is a possibility of slippage. This slippage is prevalent on
conveyors that are too long, inclined, or heavily loaded.
Be careful when you make the mechanical connections from the idler to the tachometer.
Correct mechanical connections prevent any eccentricity of the gears or couplings causing
output signal variations. Ohmart provides a coupling adapter for each tachometer flexible
coupling. The three holes that you use for mounting the adapter are intentionally oversized to
permit necessary adjustments for centering on the shaft.
The installation drawings illustrate the dimensions of the tachometer and several methods of
coupling it to the conveyor.
Refer to the interconnect drawing on page 29 for general wiring information. Refer to the
certified drawings that Ohmart supplies for specific wiring details.