Thermo Scientific APEX 100 User Manual 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)
50 / 55
100 / 105
200 / 205
500 / 505
750 / 755
1000 / 1005
1500 / 1505
2000 / 2005
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
Thermo Scientific APEX User's Guide
Resolution (f/m)
98.4–108.3
98.4–103.3
99.7–102.2
99.9–100.9
99.9–100.6
99.9–100.4
99.8–100.2
99.8–100.1
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