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DAQmx Create Virtual Channel (Counter Input » Linear Velocity) (G Dataflow)

Version:
    Last Modified: February 6, 2017

    Creates a channel that uses a linear encoder to measure linear velocity. 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 signal to the default input terminal of the counter unless you select a different input terminal.

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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 in which unit to return velocity measurements from the channel.

    Name Description
    in/s

    Inches per second.

    m/s

    Meters per second.

    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.

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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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    measurement range

    measurement range specifies the minimum and maximum values you expect to measure.

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    maximum value

    maximum value specifies in units the maximum value you expect to measure.

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    minimum value

    minimum value specifies in units the minimum value you expect to measure.

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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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    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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    distance per pulse

    distance per pulse is the distance to measure for each pulse the encoder generates on signal A or signal B. This value is in the units you specify with the units input.

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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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