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Generates a white noise signal with uniform or Gaussian distribution.

Details  

Dialog Box Options

Block Diagram Inputs

Block Diagram Outputs

Dialog Box Options

Parameter	Description
White Noise Type	Contains the following options: Uniform—Generates a uniformly distributed, pseudorandom pattern whose values are in the range [–a:a–1], where a is the value of Amplitude. Gaussian—Generates a Gaussian-distributed, pseudorandom pattern.
Execution Mode	Contains the following options: Inside single-cycle Timed Loop—For uniform signals, select this option to guarantee that the VI executes in one cycle. For Gaussian signals, select this option to provide a new output value every nth call to the VI. For the n–1 cycles between valid outputs, the data ready? output returns FALSE. If you select this option and place the VI outside a single-cycle Timed Loop, the Code Generation Errors window reports an error. Outside single-cycle Timed Loop—For Gaussian signals, select this option to return an output after every call to the White Noise Generator Express VI. If you select this option and place the VI inside a single-cycle Timed Loop, the Code Generation Errors window reports an error.
Scaling	Contains the following options: Show amplitude terminal—Creates an amplitude input on the White Noise Generator Express VI. This option only appears if you select Uniform as the White Noise Type. You can save resources on the FPGA if you do not place a checkmark in the Show amplitude terminal checkbox. Amplitude—Specifies the amplitude of the uniform white noise. The default is 32768, so the white noise out output is uniformly distributed between –32768 and 32767. You can set Amplitude to any value from 0–32768. This option only appears if you select Uniform as the White Noise Type. Set to default—Sets Amplitude to the default value of 32768 or RMS to the default value of 4096. Show RMS terminal—Creates an RMS input on the White Noise Generator Express VI. This option only appears if you select Gaussian as the White Noise Type. You can save resources on the FPGA if you do not place a checkmark in the Show RMS terminal checkbox. RMS—Specifies the root mean square (RMS) value of white noise out. The default is 4096. You can set RMS to any value from 0–6000. This option only appears if you select Gaussian as the White Noise Type. Expected peak value—Returns the theoretical peak value based on the RMS value. The peak value is six times the RMS value or 32767, whichever is smaller.

Block Diagram Inputs

Parameter	Description
initialize	Sets the VI to the initial state determined by the seed input. The default is FALSE.
seed	Specifies the starting point in the internal pseudorandom pattern.
amplitude	Specifies the amplitude of the uniform white noise. The default is 32768, so the white noise out output is uniformly distributed between –32768 and 32767. If you wire a value greater than 32768 to the amplitude input, the VI coerces the value to 32768. The value you wire to this input overrides the value in the configuration dialog box.
RMS	Specifies the root mean square (RMS) value of white noise out. The default is 4096. You can set RMS to any value from 0–6000. If you wire a value greater than 6000, the VI coerces the value to 6000. The value you wire to this input overrides the value in the configuration dialog box.

Block Diagram Outputs

Parameter	Description
data ready?	Specifies if white noise out is valid. The data ready? output appears only if you configure the VI to generate a Gaussian signal inside a single-cycle Timed Loop. The data ready? output returns TRUE every nth call to the VI. To ensure code executes only when white noise out is valid, wire the data ready? output to a Case structure and include the code you want to execute in the TRUE case.
white noise out	Returns the uniformly distributed or Gaussian-distributed, pseudorandom pattern as a 16-bit integer.

White Noise Generator Details

For Gaussian signals, the White Noise Generator Express VI calculates the sum of n samples of uniform white noise and scales the result to fit the range. If RMS is 4096, the theoretical peak value is 24576 and the crest factor is 6. So, the maximum possible output value is 6 standard deviations above 0. Output values saturate if the peak value is greater than 32767. If RMS is 6000, the peak value is 32767 and the crest factor is 5.46. The following graph shows a comparison between an ideal Gaussian curve and the curve the White Noise Generator Express VI returns.

The White Noise Generator Express VI cannot guarantee that the mean is zero.