Encoder Mode
TIP:
When using a counter for a trigger source, it is a good idea to use a pre-trigger with a value of at least 1.
The reason is that all counters start at zero with the initial scan; and there will be no valid reference in regard to
rising or falling edge. Setting a pre-trigger to 1 or more ensures that a valid reference value is present, and that
the first trigger will be legitimate.
Introduction
Rotary shaft encoders are frequently used with CNC equipment, metal-working machines, packaging
equipment, elevators, valve control systems, and in a multitude of other applications in which rotary shafts
are involved.
The
encoder mode
allows the 3000 Series board to make use of data from optical incremental quadrature
encoders. When in the
encoder mode
, the board accepts
single-ended
inputs. When reading phase A, phase
B, and index Z signals, the 3000 Series board provides positioning, direction, and velocity data.
The 3000 Series board can only receive input from up to two encoders.
The 3000 Series board supports quadrature encoders with a 16-bit (Counter Low), or a 32-bit (Counter
High) counter, 20 MHz frequency, and x1, x2, and x4 count modes. With only phase A and phase B
signals, 2 channels are supported; with phase A, phase B, and index Z signals, 1 channel is supported.
Quadrature encoders generally have 3 outputs: A, B, and Z. The A and B signals are pulse trains driven
by an optical sensor inside the encoder. As the encoder shaft rotates, a laminated optical shield rotates
inside the encoder. The shield has three concentric circular patterns of alternating opaque and transparent
windows through which an LED will shine. There is one LED for each of the concentric circular patterns
and likewise, one phototransistor. One phototransistor produces the A signal, another phototransistor
produces the B signal and the last phototransistor produces the Z signal. The concentric pattern for A has
512 window pairs (or 1024, 4096, etc.)
The concentric pattern for B has the same number of window pairs as A except that the entire pattern
is rotated by 1/4 of a window-pair. Thus the B signal will always be 90 degrees out of phase from the A
signal. The A and B signals will pulse 512 times (or 1024, 4096, etc.) per complete rotation of the
encoder.
The concentric pattern for the Z signal has only one transparent window and therefore pulses
only once per complete rotation. Representative signals are shown in the following figure.
DaqBoard/3000 Series User’s Manual
918494
Counter Input Modes 5-15
Summary of Contents for OMB-DAQBOARD-3000 Series
Page 7: ...This product requires one of the following Operating Systems Windows 2000 Windows XP ...
Page 14: ...IG 8 DaqBoard Installation Guide 918494 1033 0940 rev 8 0 ...
Page 36: ...2 8 Connections Pinouts 918494 DaqBoard 3000 Series User s Manual ...
Page 40: ...4 2 Calibration 918494 DaqBoard 3000 Series User s Manual ...
Page 80: ...6 12 Setpoint Configuration for Output Control 908794 DaqBoard 3000 Series User s Manual ...
Page 102: ...DBK215 pg A 14 948894 Appendix A ...
Page 104: ...B 2 Hardware Analog Level Trigger 90794 Appendix B ...