Gemini 4100 Instruction Manual page 23

[43 4] SEPARATE INPUT - In this mode, the two counters, A & B, are
independently controlled by the inputs. Input 1 serves as the Counter A input
and Input 2 serves as the Counter B input.
[43 5] QUADRATURE COUNTING - Quadrature counting modes are primarily
used in positioning and anti-jitter applications. The reason this mode works is
due to the manner in which two pickups are positioned relative to each other.
The signal on Input 2 is a pulse train signal shifted 90° away from the signal on
Input 1. These two signals are processed by the Gemini as follows:
Input 1 serves as the count input, while Input 2 serves as the quadrature input.
For quadrature with single edge counting, the counters will count in a positive
direction when Input 1 is a negative going edge and Input 2 is at a low level.
The counters will count in a negative direction when Input 1 is a positive going
edge and Input 2 is at a low level. All transitions on Input 1 are ignored when
Input 2 is at a high level. These logic rules provide the basis for anti-jitter
operation which will prevent false counts from occurring due to back-lash,
vibration, chatter, etc.
When two edge counting is used, the quadrature mode works the same as with
single edge counting when Input 2 is low. But when Input 2 is at a high level,
counts at Input 1 are no longer ignored. Instead the logic rules for Input 1 are
complemented, allowing both edges of Input 1 to be counted. This doubles the
effective resolution of the encoded input.
[43 6] QUADRATURE TIMES 4 - This mode takes the quadrature mode, with
two edge counting, one step further. In quadrature times 4, both Input 1 and
Input 2 serve as the count or quadrature input, depending on their state. In one
instance, Input 1 will serve as the count input and Input 2 will serve as the
quadrature input. In another instance, Input 1 will be the quadrature input and
Input 2 will be the count input. This enables each edge, positive and negative
going, of both inputs, 1 and 2, to be counted. This results in a resolution four
times greater than in the basic quadrature x1 mode.
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CODE 44 - COUNTERS A & B NUMBER OF COUNT EDGES
The counters of the Gemini can be programmed for either single or two edge
(x2) counting. The number of count edges cannot be set when the count mode is
programmed for quadrature x4 operation. The Gemini will ignore any attempt to
enter function command code 44, when set for quadrature x4.
[44 1] SINGLE EDGE COUNTING (x1) - The unit counts on the negative going
(falling) edge of the count input signal. The Inputs 1 & 2 Response mode
descriptions describe how each mode uses this method of edge counting.
[44 2] TWO EDGE COUNTING (x2) - This mode is used when doubling of the
count signal input is required. The unit counts on the positive going (rising)
edge of the count input signal, as well as, the negative going (falling) edge.
CODE 45 - COUNTER B SCALE MULTIPLIER
There are four "Counter B Scale Multipliers" that are available. They
effectively divide the internal count B value by 1, 10, 100, and 1000 respectively,
to yield the displayed Counter B value. Note: Use of a small scale multiplier in
conjunction with a small Scale Factor could cause the internal count value to be
exceeded before the 6-digit display value is exceeded. See "Programming the
Presets, Scale Factors, Timed Outputs & Counter Load Values" section for
more details.
[45 1] x1
[45 2] x0.1
[45 3] x0.01
[45 4] x0.001