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DAQmx Create Virtual Channel (Analog Input » Rosette Strain Gage) (G Dataflow)

Last Modified: September 18, 2017

Creates channels to measure two-dimensional strain using a rosette strain gage.

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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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physical channels

physical channels specifies the names of the physical channels to use to create the strain gage virtual channels necessary to calculate the rosette measurements channels.

For each rosette sensor, the node creates one strain virtual channel for each strain gage in the rosette, and one rosette virtual channel for each measurement specified in the rosette measurements array. For the Tee Rosette type, at least 2 physical channels are required. For the Rectangular Rosette and Delta Rosette types, at least 3 physical channels are required. You are also able to specify a multiple of the required number of physical channels to create the virtual channels necessary for multiple rosette sensors. The order of these channels is critical for proper rosette measurements and should be in the order of the gages in the rosette. The gages in the rosette are typically labeled as A, B, and C or 1, 2, and 3 which is the order required by DAQmx. The DAQmx physical channel constant lists all physical channels on devices and modules installed in the system. You also can wire a string that contains a list or range of physical channels to this input. If you have an array of physical channels, use the DAQmx Flatten Channel String node to convert the array to a list.

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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 creates a default channel name.

The format of this name is rosette#_TYPE, where # is an index number incremented to the first unique value, and TYPE is the channel type.

rosette#_strainGage1 Strain gage 1.
rosette#strainGage2 Strain gage 2.
rosette#strainGage3 Strain gage 3.
rosette#principalStrainAngle Principal strain angle.
rosette#cartesianStrainX Cartesian strain X.
rosette#cartesianStrainY Cartesian strain Y.
rosette#cartesianShearStrainXY Cartesian shear strain XY.
rosette#maximumShearStrain Maximum shear strain.
rosette#maximumShearStrainAngle Maximum shear strain angle.

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 nodes.

If you create multiple virtual channels with one DAQmx Create Virtual Channel nodes, 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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rosette configuration

rosette configuration specifies information about the rosette configuration and measurements.

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rosette type

rosette type specifies the type of the rosette.

Name Description
Rectangular Rosette

A rectangular rosette consists of three strain gages, each separated by a 45 degree angle.

Delta Rosette

A delta rosette consists of three strain gages, each separated by a 60 degree angle.

Tee Rosette

A tee rosette consists of two strain gages oriented at 90 degrees with respect to each other.

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gage orientation

gage orientation specifies, in degrees, the orientation of the gage with respect to the preferred X axis. This parameter applies only to Cartesian measurements.

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rosette measurements

rosette measurements specifies the virtual channels to create for the rosette measurements. For each rosette sensor, the node creates one strain virtual channel for each strain gage in the rosette, and one rosette virtual channel for each measurement specified in the rosette measurements array.

Name Description
principal strain 1

The maximum tensile strain coplanar to the surface of the material under stress.

principal strain 2

The minimum tensile strain coplanar to the surface of the material under stress.

principal strain angle

The angle, in degrees, at which the principal strains of the rosette occur with respect to the preferred X axis. The range is -180 degrees to 180 degrees, where negative values are angles below the X axis. For tee rosettes, this value is 0 degrees.

cartesian strain X

The tensile strain coplanar to the surface of the material under stress in the X coordinate direction.

cartesian strain Y

The tensile strain coplanar to the surface of the material under stress in the Y coordinate direction.

cartesian shear strain XY

The strain coplanar to the cross section of the material under stress in the XY coordinate direction.

maximum shear strain

The maximum strain coplanar to the cross section of the material under stress.

maximum shear strain angle

The angle, in degrees, at which the maximum shear strain of the rosette occurs with respect to the preferred X axis. The range is -125 degrees to 225 degrees, where negative values are angles below the X axis. Maximum shear strain angle occurs at an offset of 45 degrees relative to the principal strain angle. For tee rosettes, this value is 45 degrees.

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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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bridge information

bridge information specifies information about the bridge configuration and measurement.

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strain configuration

strain configuration specifies the bridge configuration for the strain gages.

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Note  

Typical rosette sensors use the Quarter Bridge I strain configuration.

Name Description
Full Bridge I

Full Bridge I.

Full Bridge II

Full Bridge II.

Full Bridge III

Full Bridge III.

Half Bridge I

Half Bridge I.

Half Bridge II

Half Bridge II.

Quarter Bridge I

Quarter Bridge I.

Quarter Bridge II

Quarter Bridge II.

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voltage excitation source

voltage excitation source specifies the source of excitation.

Name Description
External

Use an excitation source other than the built-in excitation source of the device. If you select this value, you must use the voltage excitation value input to specify the amount of excitation.

Internal

Use the built-in excitation source of the device. If you select this value, you must use the voltage excitation value input to specify the amount of excitation.

None

Supply no excitation to the channel.

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voltage excitation value

voltage excitation value specifies in volts the amount of excitation supplied to the sensor. Refer to the sensor documentation to determine appropriate excitation values.

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lead wire resistance

lead wire resistance is the amount of resistance in ohms in the lead wires. Ideally, this value is the same for all leads.

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strain gage information

strain gage information contains information about the strain gage and measurement.

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gage factor

gage factor specifies the sensitivity of the strain gages and relates the change in electrical resistance to the change in strain. Each gage in the bridge must have the same gage factor. Refer to the sensor documentation to determine this value.

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nominal gage resistance

nominal gage resistance is the resistance in ohms of the gages in an unstrained position. Each gage in the bridge must have the same nominal gage resistance. The resistance across arms of the bridge that do not have strain gages must also be the same as the nominal gage resistance. Refer to the sensor documentation to determine this value.

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poisson ratio

poisson ratio is the ratio of lateral strain to axial strain in the material you are measuring.

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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 the maximum strain you expect to measure. This value applies to each strain gage in the rosette.

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minimum value

minimum value specifies the minimum strain you expect to measure. This value applies to each strain gage in the rosette.

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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

Web Server: Not supported in VIs that run in a web application


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