NSD Varlimit VS-212DN, User Manual

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6-5
6.3.3 Scale length and minimum current position value setting
The detection range is determined by the scale length and the minimum current position value.
Therefore, consider the relationship of these items. When either the scale length or the
minimum current position value is set, be sure to set the parameters that affect the distance again.
(1) SCALE LENGTH (I/O address: 16394 [16458])
This refers to the maximum distance over which the ABSOCODER sensor can execute absolute
detection. The scale length can be designated in units which match the machine's travel amount
(mm, inches, degrees, etc.). For multi-turn type ABSOCODER sensors (MRE Series), the scale
length will be the machine's travel amount which corresponds to the prescribed number of sensor
shaft turns (32, 64, 128, 160, 256, 320).
Example:
When a 32-turn MRE Series sensor is linked to a machine which moves 10 mm per each sensor
shaft revolution, and when the minimum setting unit of machine's drive unit is 0.01 mm, the scale
length would be as follows:
Actual detection distance = 10 mm/turn
×
32 turns = 320 mm
Scale length (L) = Actual detection distance/Minimum setting unit Or, L = 320/0.01 = 32000
Important
Absolute detection of the current position is possible only within the detection range.
If this range is exceeded, the current position value will immediately change by the amount
of the entire scale length.
Therefore, it is essential that the machine's travel range not exceed the scale length.
(2) MINIMUM CURRENT POSITION VALUE (I/O address: 16395 [16459])
This is the minimal value of the scale length which can be displayed. This value can be
designated as desired within the following range: -99999 to [1000000 - scale length].
Example:
Given the same conditions as those described in the 'Scale Length' item above, and with the actual
minimum position value of the machine detection range being -10 mm, the following will apply:
Minimum current position value (K) = actual minimum position value/minimum setting unit
Or, K = -10/0.01 = -1000
Note:
The “scale length” and “minimum current position value” settings by the external setting unit
(VS-T62 or VS-T62B) must always be designated as a pair.