National Instruments Quadrature Input Module FP-QUAD-510 - Manual (Page 8)

FP-QUAD-510 8 www.ni.com
The velocity range is the maximum velocity that can be measured
for a given timebase. The velocity register uses a 15-bit counter,
which gives a maximum number of counts of 2
15 , or 32,768. So, the
velocity range for a given timebase is calculated using the
following formula:
where V
rng
is the velocity range in counts per microsecond and T is
the timebase in microseconds.
The velocity resolution is the velocity accuracy for a given
timebase and is determined using the following formula:
where V
res
is the velocity resolution in counts per millisecond and
T is the timebase in microseconds.
Index Status Channel Operation
The FP-QUAD-510 includes four discrete input channels, channels
12 through 15, which contain the status of the Index signal for axes
0 through 3 respectively. This signal is latched to a 1 when the
condition at the axis inputs is Phase A = 0, Phase B = 0, and
Index = 1. This bit remains latched until it is read, at which point it
is cleared automatically.
Table 2. Velocity Ranges
Length of Timebase
(in µs)
Velocity Range
(in counts/µs)
Velocity
Resolution
204.8 ±160 4.883 counts/ms
409.6 ±80 2.441 counts/ms
819.2 ±40 1.221 counts/ms
1638.4 ±20 610.4 counts/s
3276.8 ±10 305.2 counts/s
6553.6 ±5 152.6 counts/s
13107.2 ±2.5 76.29 counts/s
26214.4 ±1.25 38.15 counts/s
V
rng
32768
±
T
------------------ =
V
res
1000
T
------------ =