Trace-based Comparison and Calculation

Other topics about Setting Up the Display of Measurement Results

Traces 1 and 2 each provide two different trace types: data and memory. The data trace keeps track of the DUT's characteristics as it is being tested, while the memory trace captures the measurement data at a specific point in time and displays that data. With the data trace, you can perform a simple calculation on the measurement data and display the results. For example, you can display the differential between the measured data and the memory trace data or the result of subtracting your specified offset value from the measured data. Table below lists the trace types and their functions:

Trace Types

Function

Trace 1

Data trace (yellow1)

Displays measurement data/calculations (updated during measurement cycle)

Memory trace (green1)

Stores and displays previously measured data (captures data when Display > Data -> Memory is selected)

Trace 2

Data trace (blue1)

Displays measurement data/calculations (updated during measurement cycle)

Memory trace (brown1)

Stores and displays previously measured data (captures data when Display > Data -> Memory is selected)

1   Factory default settings.

These features add flexibility to your testing task; for example, on the same screen you can compare the data and memory traces with each other or simultaneously display the results of a calculation as shown by the data and memory traces.

Identifying Differences between Data and Memory Traces through Comparison or Calculation

  1. Activate the trace for which you want to perform calculation or comparison between the two trace types.

  2. Press the Display key to display the Display menu.

  3. Press Display > Data.

  4. Start testing the DUT so that the data trace displays the results.

  5. At this time, you may want to hold (stop) the sweep cycle for the data trace by pressing Trigger > Hold. Doing so ensures that you can create an exact snapshot of the measurement data when you later store the data into the memory trace.

  6. Press Data -> Memory to store the measurement data into the memory trace.

  1. The Keysight E4990A provides a number of options that allow you to control how each trace is displayed. Select one of the following display options by pressing the appropriate key:

Softkey

Function

Data

Displays only data trace on the screen

Mem

Displays only memory trace stored by Data -> Mem operation on the screen

Data & Mem

Displays data trace and memory trace on the screen. You can now easily compare the data trace and memory trace on the screen.

Off

Trace is not displayed

 

  1. Start testing the DUT to obtain the measurement data for comparison or calculation with the reference measurement data you stored into the memory trace (if the sweep cycle is in the hold state, you can restart the measurement by pressing Trigger).

Subtracting an Offset Value

You can specify an offset value to be subtracted from the measurement data, and the result of this operation is displayed by the data trace.

  1. Press Display > Data -> Mem to store the measured data in memory.

  2. Press Data Math Offset and input the desired offset value (the offset value defaults to zero in the preset state).

  3. Press Data Math.

  4. Select the data math operation to perform.

Softkey

Function

OFF

Turns off data math functions (Do not perform data math)

Data / Mem

Divides measured data by memory trace and stores result in data trace

Data * Mem

Multiplies data trace by memory trace and stores result in data trace

Data - Mem

Subtracts memory trace from data trace and stores result in data trace

Data + Mem

Adds data trace and memory trace and stores result in data trace

  1. Press Display.

  2. Select the type of data on display ON the screen.

  3. Send the trigger to make measurements.