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Use the SVL Limit Testing VI to perform limit testing. You can enter an upper limit mask, lower limit mask, or both to the SVL Limit Testing VI to define a pass range that varies in shape and level based on acceptable results at any given point in the measurement. You also can create a discontinuous mask which enables you to perform limit testing on only a part of the results while ignoring the rest.

You must enter at least one limit, or the SVL Limit Testing VI returns an error. You can visually display the input signal, failures, upper limit, and lower limit by creating an indicator from the output values output.

The upper limit and lower limit inputs to the SVL Limit Testing VI must be compatible with the input signal. The following table lists the criteria for each input signal type that is compatible with the SVL Limit Testing VI.

Input Signal Type	Criteria on Input Limit Masks
Waveform Data Type (t0, dt, [signal])	dt > 0 dtS ? ?dtU = dtL NS = NU = NL
Frequency Spectrum (f0, df, [spectrum])	f0S =  f0U = f0L dfS =  dfU = dfL NS = NU = NL
Octave Spectrum, Swept Sine Spectrum, XY data ([X], [Y])	[X]S  = [X]U = [X]L NS = NU = NL
Identified Peaks, Harmonic Components, Multitone Phases [(frequency, amplitude)]	f(i) S = f( i)U = f(i) L NS  = NU = NL

The following abbreviations apply in the previous table:

• dt is the time spacing, in seconds, between elements
• df is the frequency spacing, in hertz, between elements
• N is the number of elements in the array
• f(i) is the i^th frequency element
• S is the signal
• U is the upper mask limit
• L is the lower mask limit

Limit testing covers a broad range of data testing from range detection to discontinuous mask testing of a swept-sine frequency response spectrum. The following block diagram shows a range detection test using the SVL Limit Testing VI.

In the previous block diagram, scaled waveform data and upper and lower limits are input to the SVL Limit Testing VI. This VI checks that the data falls within the envelope that the upper and lower limits specify. The following front panel shows the output results for the range detection test.

The following block diagram shows a pass/fail test on a measured total harmonic distortion (THD).

In the previous block diagram, the test checks only the upper limit of the measurement; therefore, only the upper limit is wired to the SVL Limit Testing VI. The upper limit must have the same units as the input measurement. Both the THD and the upper limit are expressed as percentages. The following front panel shows the THD test output results.

The following block diagram shows a continuous mask test on a power spectrum.

In the previous block diagram, formula nodes define both the upper and lower limits in the SVL Limit Testing VI. The following front panel shows the output graph for the power spectrum continuous mask test.

The following block diagram shows a discontinuous mask test on a swept-sine frequency response.

The following front panel shows the output graph for the discontinuous mask test.

A discontinuous mask test can track and test the results at different magnitudes and ranges, as well as stop testing at defined intervals. For example, you can use the envelope that the upper and lower limit masks defines in the previous discontinuous mask test for a device under test such as a notch filter.