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<< Click to Display Table of Contents > MOTF Multiplier |
  
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<< Click to Display Table of Contents > MOTF Multiplier |
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The MOTF multiplier is the central factor to translate encoder counts into mm. To calibrate this multiplier very well is crucial for correct vector compensation and encoder based distance measurements which are used by ScMotfOffset objects for example. The calibration routine is card specific and described in the following chapters. However, some general remarks and notes are given here.
There are two ways to determine the correct value for the MOTF multiplier:
1. By theory:
▪In the manual of the encoder, the increments per rotation is specified, in the following defined as "I" in the unit counts/360°.
▪The circumference of the wheel that is attached to the encoder is known as "U". The unit is mm/360°. The circumference is calculated over the radius of the encoder with the unit mm.
▪Then, the multiplier F is calculated as the ratio of (4 times I) and U. Please find an example for I = 2000 counts/360° and U = 2π * 50 mm/360° below:
▪Card specific calculations can be found in the following chapters (Hardware setup).
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A possible slack between the wheel and the conveyor is not considered. However the calculation gives a good approximation. The factor I must be multiplied by 4 because each rising and falling edge of both tracks counts. Please have a look at figure 352 for further details on the MOTF signals. |
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2. By experiment:
