Communication 
  11.5 Calibration procedure 
SIWAREX WT241 
Manual, 05/2015, A5E36046748Aa  109 
 
Step 1 
Use a tape measure or length measuring device to determine the exact conveyor belt length. 
You can usually measure the distance between the axes of the deflection pulleys. The length 
is then twice the distance between the axes plus half the circumference of the deflection 
pulley and half the circumference of the drive pulley. Exact determination of the belt length is 
the basis for good accuracy of the belt scale. 
Step 2 
Make a temporary marking on the conveyor belt, e.g. using chalk or adhesive tape. 
This marking is used to measure one belt revolution. The conveyor belt has run for a certain 
warm-up time and is empty. Once the marking has passed a defined point, start the 
measurement of the belt revolution using the command "Start speed/pulse detection" (70). 
Terminate the measurement when the point is passed again (if only one belt revolution is 
parameterized for the measurement) using the command "Stop speed/pulse detection" (71). 
The following parameters are calculated by SIWAREX as a result of the measurement, and 
output in DR4 as a recommendation for acceptance: 
●  When using a speed sensor: 
–  Design speed 
–  Pulses per length unit 
–  Pulses per belt revolution 
●  Without speed sensor: 
–  Design speed 
Using command 85 you can apply the determined (nominal) speed, using command 87 the 
determined pulse parameters. 
Note 
Starting and stopping of the belt measurement can be carried out exactly if an electric 
switching signal (+24 V) – for example from a proximity switch – is used to signal a belt 
revolution.  
You can parameterize digital input DI.1 of the SIWAREX module as start/stop trigger (DR7 
command "Trigger for belt revolution detection on DI" (75)) and use it to measure the belt 
revolution. The defined number of belt revolutions is recorded following enabling by the 
command "Enable belt revolution detection on DI (74)".