Frequency

Frequency is defined as the inverse of the period (1/period). The measurement can be restricted to a region. Period is a determined by measuring the time between the first detected edge of a waveform and the next occurrence of the same type of edge. The edges are the middle threshold crossings which, by default, are set to the 50% level. Two annotation labels identify the threshold crossings on the waveform. Top-base levels are not used in the frequency calculation when threshold levels are set to absolute voltages. Frequency will not be calculated unless a complete waveform cycle is visible on the display. When measuring an optical channel, the measurement units are Watts.

The detected edges can be either rising or falling. Frequency is determined as follows:

• Rising edge

• Falling edge

Configurable Measurement Parameters

This measurement is affected by the following settings (choose Measure > Thresholds...):

• Thresholds tab

To measure

1. Click the toolbar's Time tab.
2. Click the toolbar's More buttons to locate the Frequency button.
3. Click the button.
4. Select the Region in which to make the measurement:
   • Displayed Waveform — is what you see in the waveform window (which can be a zoomed-in view of the complete waveform).
   • Entire Waveform — specifies the complete waveform.
   • Region N — If regions are enabled for the selected signal, you can select one of those regions.
5. Select the number of Occurrences to measure per acquisition:
   • Measure One — makes one measurement per acquisition using edges closest to the timebase reference.
   • Measure All — makes as many measurements per acquisition as possible using all edges in the acquisition. In this case, the measurement closest to the timebase reference is the "current" measurement (and is the one with annotations).
6. Specify the Edge Direction as Rising or Falling. The measurement is made from rising edge to rising edge or falling edge to falling edge.

SCPI Command

:MEASure:HORizontal:FREQuency