Thermo Scientific APEX 100, User Manual

Page: 125 / 442

Thermo Scientific APEX User’s Guide
Page 125
Overview of Set Up
Some conveyor systems, especially those that can be set to run at variable speeds, have
a built-in speed encoder. A typical speed encoder is constructed using a disk-shaped
gear with teeth around the periphery, and is attached to a roller on the conveyor. The
teeth of the gear pass in front of a photo eye, giving a square signal (as shown in the
figure below) whose frequency is proportional to the speed of the conveyor. In a typical
conveyor set up, the signal from the speed encoder is hard wired to Input 1 on the
detector’s wiring board. Input 1 on the APEX is the dedicated physical input for the
speed-encoder signal. For wiring details, see page 289.
In order for the speed-encoder function to work optimally, the speed-encoder gear
should be large and have a large number of teeth, so that the maximum conveyor speed
produces a signal of at least 500 Hz but no greater than 2,000 Hz. In addition, any
signal from the speed encoder should not fluctuate or have missing pulses. A nice steady
signal is required. A fluctuating signal will cause large changes in the speed display and
will adversely affect all speed-related parameters.
Acceptable Values for Inputs from the Speed-Encoder
The following table shows the resolution at the calibrated frequency.
Frequency (Hz) Resolution (f/m)
50 / 55 98.4–108.3
100 / 105 98.4–103.3
200 / 205 99.7–102.2
500 / 505 99.9–100.9
750 / 755 99.9–100.6
1000 / 1005 99.9–100.4
1500 / 1505 99.8–100.2
2000 / 2005 99.8–100.1
f/m = feet per minute
Calibrating the Speed-Encoder Function
You must calibrate the speed-encoder function before you can use it.
1)
Turn on the conveyor and set the belt speed to maximum. Use a tachometer to
record the speed.
2)
Go to the product-speed function in the Main Menu, as described on page 27, and
key in the reading for maximum belt speed. (We keyed in 100 feet per minute.)
Product Speed