Datalogic AMT58 Series, Manual

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ENCODER PARAMETERS
70
AMT58...PN
RED ZONE
The so-called “Red Zone” problem occurs when the Number of revolutions (i.e. the Total
measuring range / Measuring units / Revolution) is not a power of 2.
When this problem arises, the device must operate within the “red zone” for a certain
number of positions. The size of the “red zone” is variable. To calculate it we must sub -
tract the overall set resolution from the overall physical resolution of the device as many
times as until the difference is less than the overall set resolution. When the encoder
crosses the limit of the last value in the overall physical resolution, a counting error
occurs, i.e. a jump in the position count. The problem is represented graphically in the
following Figure.
Example
AMT58...13X14PN multiturn encoder
Physical resolution:
• Singleturn physical resolution = 8,192 counts/rev. = 13 bits (2
13
)
• Multiturn physical resolution = 16,384 revolutions = 14 bits (2
14
)
• Overall physical resolution = 134,217,728 = 27 bits (2
27
)
Set values:
• Measuring units / Revolution = 8,192 = 2
13
• Total measuring range = 122,880,000 = it is NOT a power of 2
It results from this:
• Number of revolutions = 15,000 = it is NOT a power of 2
This can be proved easily:
It follows that for 11,337,728 positions (134,217,728 - 122,880,000 * 1 = 11,337,72), i.e.
for 692 revolutions, the encoder will work within the limits of the so-called “red zone”.
After position 11,337,728 (i.e. at the end of the “red zone”) a position error (namely, a
“jump” in the position count) would happen as the following position would be “0”. See
the Figure in the previous page.
Overall physical resolution
=
134,217,728
= 1.092...
Overall set resolution 122,880,000