User manual

PicoScope 6 User's Guide 169

9.1.2

Spectrum measurements

To add a spectrum measurement, open a spectrum view and then click the Add

Measurement button. You can use these measurements in either scope mode or

spectrum mode .

Frequency at peak. The frequency at which the peak signal value appears.

Amplitude at peak. The amplitude of the peak signal value.

Average amplitude at peak. The amplitude of the peak signal value averaged over a

number of captures.

Total power. The power of the whole signal captured in the spectrum view,

calculated by adding the powers in all of the spectrum bins.

Total Harmonic Distortion (THD). The ratio of the sum of harmonic powers to the

power at the fundamental frequency.

Total Harmonic Distortion plus Noise (THD+N). The ratio of the harmonic power

plus noise to the fundamental power. THD+N values are always greater than the THD

values for the same signal.

Spurious-free Dynamic Range (SFDR). This is the ratio of the amplitude of the

specified point (normally the peak frequency component) and the frequency

component with the second largest amplitude (call it "SFDR frequency"). The

component at the "SFDR frequency" is not necessarily a harmonic of the fundamental

frequency component. For example, it might be a strong, independent noise signal.

Signal+Noise+Distortion to Signal+Noise Ratio (SINAD). The ratio, in decibels,

of the signal-plus-noise-plus-distortion to noise-plus-distortion.

Signal to Noise Ratio (SNR). The ratio, in decibels, of the mean signal power to the

mean noise power. Hanning or Blackman windows are recommended because of their

low noise.

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