National Instruments Quadrature Input Module FP-QUAD-510 - Manual (Page 7)

© National Instruments Corp. 7 FP-QUAD-510
Reset on Index Capability
You can configure each position counter to reset each time the
index condition is met. An index-initiated reset resets both the
upper and lower 16-bit registers associated with that axis. This
is useful in applications in which only the position within one
rotation of the encoder is important to the user. In this mode of
operation, any count errors that occur are canceled when the index
condition is met.
Commands
Channels 0 through 3 (the lowest 16 bits of the position counter)
each support a control command with one action—reset. The
control-reset command resets the target counter. The control
command ignores the index reset setting. This command also resets
the upper 16 bits of the position counter.
Velocity Data Channel Operation
The FP-QUAD-510 uses a timebase counter as a basis for
determining the rate of change of position—the velocity—for each
axis. The four velocity data registers, channels 8 through 11,
contain 16-bit velocity data for axes 0 through 3 respectively. The
data in each register represents the velocity of the axis in number
of counts per microsecond. A positive number indicates motion in
the forward direction, and a negative number indicates motion in
the reverse direction. Each register can be independently
programmed with one of eight velocity ranges as shown in Table 2.
Each range is based on a different timebase length and has a
different resolution.
Note While the ranges available reach speeds of
160 counts per microsecond, the module inputs are still
limited to 1,000,000 counts per second (1 count per
microsecond) maximum. The higher ranges are used to
measure velocity over shorter timebases. With these
ranges, the velocity data is averaged over a much shorter
time period and, therefore, is more instantaneous.
However, the data from these ranges has a coarser
resolution. The slower ranges have a finer resolution, but
the data is an average velocity over a longer period
of time.