Using Amplitude Data

Measurement results are expressed in either parameter units or measurement units. A parameter unit is a standard scienti￿c unit such as Watts, decibels, seconds, hertz, amperes, and ohms. Measurement units are an internal representation of the data. Measurement units apply only to traces and trace elements. In its preset state, the analyzer returns all measurement results in parameter units.

The amplitude parameter units used are shown in the following table. Use the AUNITS command to change the active amplitude units shown in display annotation and returned by queries to the computer.

 

Amplitude Parameter Units

 

 

 

 

 

Units

 

 

 

Decibels

 

dB, dBm

Watts

 

W, mW, ￿W

 

 

 

For linear trace information, measurement units are de￿ned as 0 (zero) for the bottom of the display, and 10,000 for the top (reference level). For logarithmic trace information, a measurement unit is one hundredth of a dBm:

measurement unit = (value in dBm) (100)

Thus, a 010 dBm value is equal to 01000 measurement units: 01000 measurement units = 010 dBm (100)

The measurement-unit range is restricted to integers between +32,767 and 032,768. Since measurement units are restricted to integers, 010.115 dBm equals 01012 measurement units, not 01011.5 measurement units because decimal values are rounded to the nearest integer.

01012 measurement units = 010.115 dBm (100)

Use the AMPU command to convert measurement-unit values to parameter-unit values. The MEASU command converts parameter-unit values to measurement-unit values.

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