NI C Series - Regulatory Information; United States; Canada

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For a two-pulse encoder, when a pulse is detected on Channel A, a positive value is

returned. When a pulse is detected on Channel B, a negative value is returned. The

following figure shows an example of velocity measurement using a two-pulse

encoder. The Divisor count is set to 1 and the Measurement Time is disabled.

Figure 27. Two-Pulse Encoder Velocity Measurement

Encoder Count

Counter Timebase

Counter Value

Current Measurement

Read Value

Ch A

Counter

Read

Ch B

1 2 3 4 1 2 3 1

4 –1

3 –1

Encoder Velocity: –1 / (4 * Counter Timebase) = –25 Mcount/s

Channel Settings

You can configure the following counter properties:

■

Decoding Type: Configurable to two-pulse decoding for two-pulse encoder

or X1, X2 or X4 decoding for quadrature encoder.

■

Input terminal of A signal.

■

Input terminal of B signal.

■

Maximum Measurable Count Period—You can set the maximum measurable

count period of the signal. If the encoder count value changes slower than this

value, the counter returns a measurement value of zero for both N

ticks

and

counts

. Use this property to get updated measurement data when the

encoder slows down or is stopped instead of previous measurements. To

disable this feature, set the Maximum Measurable Count Period to zero. When

this feature is disabled, the counter keeps measuring until a valid

measurement is detected, the counter overflows, or the user stops the

counter.

NI-9361 Getting Started

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