Laurel Electronics LAUREATE SERIES COUNTER_TIMER - Manual (Page 34)

13.2 QUADRATURE DECODING
The quadrature decoder board generates up(+) and down(-) counts that are arithmetically
totalized on the main counter board and then displayed. The decoder board has input circuitry
that may be jumpered for either single-ended input signals or balanced line driver signals. It
will accept the normal A & B quadrature signals and, if present, a zero index signal. The A &
B signals are 90 deg out of phase and the phase relationship of A & B determine whether up
counts or down counts are produced. Up counts add to the total and down counts subtract from
the total.
Since incremental optical encoders may have a different A & B phase relationship to indicate
up and down, the board has a jumper E7 (BPOL) on the B signal to allow selection of the desired
phase. Without the jumper, Up output pulses are created when the B signal has a positive
transition while the A signal is at a positive level (A leads B). With the jumper installed, Up output
pulses are created when the B signal has a negative transition while
the A signal is at a positive level (B leads A).
A With the phase shown
E7 open - Counts up
B
E7 jumpered - Counts down
With the opposite phase shown, the effect of E7 reverses.
The board has jumpers that allow counting by 1, 2 or 4 counts per cycle of the A or B signals.
The edges that are counted are:
X1 = positive transitions of the A signal.
X2 = positive and negative transitions of the A signal.
X4 = positive and negative transitions of both the A and the B signals.
Digital filtering is provided for the A & B signals to reduce the probability of noise providing false
counts.
Some optical encoders create a zero index signal once per revolution that indicates when the
encoding wheel is at its zero position. Each time this signal is created, the total count should
be a multiple of the number of counts per revolution of the coding wheel. If this feature is
enabled in the counter, the counter checks to see if the total counts is an exact multiple of the
counts per revolution. If so, it does nothing, and if not, it changes the total to the closest exact
multiple. The counts per revolution are entered into the counter via the menu item Pulses. From
0 to 59,999 pulses may be entered. If X2 or X4 counting is enabled on the board, then the value
entered into Pulses should be the counts (or pulses) per revolution of the encoder multiplied
by this factor of X2 or X4. Also, if Scale is a factor other than 1, include it as a multiplying factor
when determining the value of Pulses to enter.. Do NOT include the value of Offset1.
For example:
If the encoder produces 256 cycles per revolution and X2 counting is selected by a jumper
on the board, and from the front panel Menu of the counter, SCALE1 is set to 3 and OFFSET1
is set to 100, then from the front panel menu set PULSES = 256 * 2 * 3 = 1536.
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