Encoder resolution definition

Question

How is encoder resolution defined?

Answer

The encoder resolution is defined in mm/tick in the Gocator web GUI. This is equivalent to mm/count or mm/pulse.

This value converts encoder counts (otherwise known as ticks or pulses) to a linear displacement in mm.

The Gocator detects every single rising edge of encoder quadrature pulse (A+ / A- / B+ / B-) thus one quadrature pulse is counted as 4 ticks; one on each of the 4 transmission lines.

Many encoder specification sheets define an encoder resolution in either PPR or CPR. CPR typically stands for Counts Per Revolution. PPR can either stand for Pulses Per Revolution or Periods Per Revolution. It is important to know which term is being used. 

Both of the below calculation methods assume:

1. All four differential channels (A+ / A- / B+ / B-) are used.

2. The ratio of drive roller rotations to encoder shaft rotations is 1:1.

3. The thickness of the conveyor belt on top of the roller is negligible or taken into account with the "roller radius".

Calculate Encoder Resolution - Pulses/Counts per Revolution on Spec Sheet

If your encoder is defined in either Counts Per Revolution (CPR) or Pulses Per Revolution (PPR) and your encoder is mounted to the same shaft as your conveyor drive wheel (or equivalent), then you will perform the following math to determine your encoder resolution:

1. (Total Linear Distance Traveled by Conveyor Roller in 1 Revolution) / (Pulses Per Revolution) = (Encoder Linear Resolution)

Pro Tip: for most users the (Total Linear Distance Traveled by Conveyor Roller in 1 Revolution) is typically the circumference of the roller.

         Pulses Per Revolution = 8000 ppr

          Roller Radius = 25.4 mm

          Roller Circumference = 2*Pi*r = 159.66 mm

          (159.66 mm) / (8000 ppr) = 0.01955714 mm/tick or mm/pulse

Calculate Encoder Resolution - Periods per Revolution on Spec Sheet

If your encoder is defined in Periods Per Revolution (PPR) and your encoder is mounted to the same shaft as your conveyor drive wheel (or equivalent), then you will perform the following math to determine your encoder resolution:

1. (Periods Per Revolution) * (Number of Transmission Lines) = (Pulses Per Revolution)

          Ex. 2000 ppr * 4lines = 8000 ppr

2.(Total Linear Distance Traveled by Conveyor Roller in 1 Revolution) / (Pulses Per Revolution) = (Encoder Linear Resolution)

Pro Tip: For most users the (Total Linear Distance Traveled by Conveyor Roller in 1 Revolution) is typically the circumference of the roller.

          Roller Radius = 25.4 mm

          Roller Circumference = 2*Pi*r = 159.66 mm

          (159.66 mm) / (8000 ppr) = 0.01955714 mm/tick or mm/pulse