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DAQmx Create Virtual Channel (Counter Input » Angular Encoder) (G Dataflow)

Version:
    Last Modified: February 6, 2017

    Creates a channel that uses an angular encoder to measure angular position. With the exception of devices that support multi-counter tasks, you can create only one counter input channel at a time with this node, because a task can contain only one counter input channel. To read from multiple counters simultaneously, use a separate task for each counter. Connect the input signals to the default input terminals of the counter, unless you select different input terminals.

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    task in

    task in specifies the task to which to add the virtual channels this node creates. If you do not specify a task, NI-DAQmx creates a task for you, and adds the virtual channels this node creates to that task.

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    counter

    counter specifies the name of the counter to use to create the virtual channel. The DAQmx physical channel constant lists all physical channels, including counters, for devices installed in the system.

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    name to assign

    name to assign specifies a name to assign to the virtual channel this node creates. If you do not wire a value to this input, NI-DAQmx uses the physical channel name as the virtual channel name.

    If you use this input to provide your own names for the virtual channels, you must use the names when you refer to these channels in other NI-DAQmx nodes, such as the source input of the DAQmx Trigger node.

    If you create multiple virtual channels with one DAQmx Create Virtual Channel node, you can specify a comma-separated list of names to assign to the virtual channels. If you provide fewer names than the number of virtual channels you create, NI-DAQmx automatically assigns names to the virtual channels.

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    units

    units specifies the units to use to return angular position measurements from the channel.

    Name Description
    Degrees

    Degrees.

    From Custom Scale

    Units a custom scale specifies. If you select this value, you must wire a custom scale name to the custom scale name input.

    Radians

    Radians.

    Ticks

    Timebase ticks.

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    error in

    error in describes error conditions that occur before this node runs. This input provides standard 'error in' functionality.

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    z index

    z index specifies the Z indexing settings for the channel.

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    z index enable

    z index enable specifies whether to use Z indexing for the channel.

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    z index value

    z index value specifies in units the value to which to reset the measurement, when signal Z is high, and signal A and signal B are at the states you specify with z index phase.

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    z index phase

    z index phase specifies the states at which signal A and signal B must be while signal Z is high for NI-DAQmx to reset the measurement. If signal Z is never high while signal A and signal B are high, for example, you must choose a phase other than A High B High.

    When signal Z transitions to high, and how long it stays high, varies from encoder to encoder. Refer to the documentation for the encoder to determine the timing of signal Z with respect to signal A and signal B.

    Name Description
    A High B High

    Reset the measurement when signal A and signal B are high.

    A High B Low

    Reset the measurement when signal A is high and signal B is low.

    A Low B High

    Reset the measurement when signal A is low and signal B high.

    A Low B Low

    Reset the measurement when signal A and signal B are low.

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    custom scale name

    custom scale name specifies the name of a custom scale for the channel. If you want the channel to use a custom scale, wire the name of the custom scale to this input, and set units to From Custom Scale.

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    pulses per revolution

    pulses per revolution is the number of pulses the encoder generates per revolution. This value is the number of pulses on either signal A or signal B, not the total number of pulses on both signal A and signal B.

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    initial angle

    initial angle is the starting angle of the encoder. This value is in the units you specify with the units input.

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    decoding type

    decoding type specifies how to count and interpret the pulses the encoder generates on signal A and signal B. X1, X2, and X4 are valid for quadrature encoders only. Two Pulse Counting is valid only for two-pulse encoders.

    X2 and X4 decoding are more sensitive to smaller changes in position than X1 encoding, with X4 being the most sensitive. However, more sensitive decoding is more likely to produce erroneous measurements, if vibration exists in the encoder or other noise exists in the signals.

    Name Description
    Two Pulse Counting

    Increment the count on rising edges of signal A. Decrement the count on rising edges of signal B. If you select this value, z index phase is ignored.

    X1

    If signal A leads signal B, count the rising edges of signal A. If signal B leads signal A, count the falling edges of signal A.

    X2

    Count the rising and falling edges of signal A.

    X4

    Count the rising and falling edges of signal A and signal B.

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    task out

    task out is a reference to the task after this node runs. The task contains any newly created virtual channels. If you did not wire a value to task in, NI-DAQmx automatically creates the task this output refers to.

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    error out

    error out contains error information. If error in indicates that an error occurred before this node ran, error out contains the same error information. Otherwise, error out describes the error status that this node produces.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: LabVIEW NXG does not support FPGA devices


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