Measurement Stability

There are several situations that can cause unstable measurements. To ensure that you are making repeatable measurements, you can use various methods to create a stable measurement environment.

• Frequency Drift

• Temperature Drift

• Inaccurate Measurement Calibrations

• Device Connections

Other topics about Optimizing Measurements

Frequency Drift

The analyzer frequency accuracy is based on an internal 10 MHz frequency oscillator. See Technical Specifications for stability and aging specifications.

If your measurement application requires better frequency accuracy and stability, you can override the internal frequency standard and provide your own high-stability external frequency source through the 10 MHz Reference Input connector on the rear panel.

Temperature Drift

Thermal expansion and contraction changes the electrical characteristics of the following components:

• Devices within the analyzer

• Calibration kit standards

• Test devices

• Cables

• Adapters

To reduce the effects of temperature drift on your measurements, do the following.

• Switch on the analyzer 1/2 hour before performing a measurement calibration or making a device measurement.

• One hour before you perform a measurement calibration, open the case of the calibration kit and take the standards out of the protective foam.

• Use a temperature-controlled environment. All specifications and characteristics apply over a 25 °C ±5 °C range (unless otherwise stated).

• Ensure the temperature stability of the calibration kit devices.

• Avoid handling the calibration kit devices unnecessarily during the calibration procedure.

• Ensure the ambient temperature is ±1°C of the measurement calibration temperature.

Inaccurate Measurement Calibrations

If a measurement calibration is inaccurate, you will not measure the true response of a device under test. To ensure that your calibration is accurate, you should consider the following practices:

• Perform a measurement calibration at the points where you connect the device under test, that is, the reference plane.

• If you insert any additional accessory (cable, adapter, attenuator) to the test setup after you have performed a measurement calibration, use the port extensions function to compensate for the added electrical length and delay.

• Use calibration standards that match the definitions used in the calibration process.

• Inspect, clean, and gage connectors. See Connector Care.

See Accurate Measurement Calibrations for more detailed information.

Device Connections

Good connections are necessary for repeatable measurements. To help make good connections, do the following:

• Inspect and clean the connectors for all of the components in the measurement setup.

• Use proper connection techniques.

• Avoid moving the cables during a measurement.