How to calculate the frequency measurement accuracy of the GTX22x0 series of Time Interval Counter PXI Cards

Knowledge Base Article # Q200171

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Summary How to calculate the frequency measurement accuracy for the GTX22x0 series
Many factors can effect the accuracy of frequency measurements taken on any instrument. Main factors that effect accuracy are
1) Signal noise
2) Instrument timebase accuracy
3) Gate time used to measure the signal
4) Calibration cycle.

The frequency measurement accuracy for the GTX2200 series can be found using the following formulas:

Slew Rate
Slew Rate (SR) = 2 x PI x Vp x f
      where PI = 3.14159265
                  Vp = peak amplitude of the sine wave being measured (in volts)
                   f = frequency of the signal being measured

Trigger Error
Error due to noise superimposed on the input signal from both internal and external sources

How to calculate the frequency measurement accuracy of the GTX22x0 series of Time Interval Counter PXI Cards

En = rms noise of input signal (100MHz bandwidth)

Least Significant Digit (LSD)
How to calculate the frequency measurement accuracy of the GTX22x0 series of Time Interval Counter PXI Cards

Resolution (Hertz)
How to calculate the frequency measurement accuracy of the GTX22x0 series of Time Interval Counter PXI Cards

Accuracy (Hertz)
How to calculate the frequency measurement accuracy of the GTX22x0 series of Time Interval Counter PXI Cards


The following Excel file can be used to calculate the accuracy GTX22x0 Accuracy Spreadsheet .The values for Signal Frequency, Signal Noise (En), Measurement Gate Time and Instrument Timebase accuracy can be adjusted to observe the effects of these parameters on the overall measurement accuracy.

Article Date 7/10/2009 12:04:19 PM     Updated: 4/21/2016 2:02:43 PM
Keywords GTX2200, GTX2210, GTX2220, GTX2230, accuracy

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