AB Quality Allen-Bradley 1771-IJ, Руководство пользователя

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2–2 Preliminary Adjustments
Publication 1771ĆUM006B-EN-P - June 2002
Count resolution (switches 2 and 3) - In the encoder mode, the
accuracy of a quadrature type encoder can be improved by allowing
the module to count the pulse trains at both channel inputs. This
doubles the number of pulses counted for the same degree of rotation
at the encoder. A further improvement can be made by letting the
module count the leading and trailing edges of both pulse trains,
thereby counting four times (times 4) for the same degree of rotation.
Certain applications may need the actual count and module should be
set for times 1 (the pulse is counted on its rising edge as high true).
The count resolution setting affects the total count kept at the module
and as it is sent back in the status word. Programming manipulations
of the status word and the preset values must account for the
multipliers. The count resolution setting may also be limited by the
program scan time if the carry or borrow bits are used to cascade
counters.
Note : In the counter mode, the count resolution setting (Table 2.B)
has no effect on the count.
Table 2.B
Count Resolution Settings
Multiplier Switch 2 Switch 3
Times 1 On On
Times 2 On Off
Times 4 Off Off
Encoder/counter selection (switch 4) - In the encoder mode, the
module counts the number of input pulses entering on channel A
from a quadrature type encoder. By comparing the phase
relationship between input pulses on channel A and pulses appearing
at channel B, it knows whether to add or subtract the incoming count
from the total (that is, whether to count up or down). The phasing
(Figure 2.1) between the channels is determined by the direction in
which the encoder is turned. To use the module in the encoder mode,
switch 4 must be set to encoder (on).
Count Resolution
Encoder Counter Selection