Specifications

Chapter 4 55

Preparing for Accurate Measurement

Running the Compensation Process

4. Preparing for Accurate

Measurement

The measurement data of the OPEN and SHORT standards used for calculating the

compensation coefficients for impedance measurement are stored in the calibration data

array (see “Compensation Data Arrays” on page 81). You can retrieve this data with the

following command:

• :DATA:CMD{1-2}? on page 261

This command returns RF measurement data without compensation, which require more

complex handling than R

values.To detect operational errors that may have occurred

while measuring the compensation data, it is best to use R

values instead.

Saving or recalling compensated state (retrieving or writing

compensation coefficients)

You can retrieve the compensation coefficients and save them to a file. Later, you can

retrieve the compensation coefficients from the file and load them into the 4287A to restore

the compensated state at the time you saved the file.

The compensation coefficients for impedance measurement are stored in the compensation

coefficient array (see “Compensation Coefficient Arrays” on page 81). To read or write the

compensation coefficient array, use the following command:

• :DATA:CMP{1-3} on page 262

To read or write the compensation coefficients for R

measurement, use the following

command:

• :DATA:RCMP{1-3} on page 266

NOTE When setting compensation coefficients, note these precautions:

• To ensure that the instrument will provide correct measurement results, you must

configure the instrument to use the same measurement points (point setup table

settings) as when you obtained measurement data for compensation and turn on the

calibration function before you set the coefficients.

• You must turn on the compensation function before setting the compensation

coefficients. To do so, follow the steps shown in “Measuring data for calculating

compensation coefficients” on page 52. This procedure includes only measuring

tentative data, and does not require you to connect the standard before issuing the data

measurement command.