Inaccurate or non-repeatable measurements may be the result of:
The cable should be held in the same position during measurement as during calibration. Hold the probe and cable with the mounting bracket and probe stand.
The flatness of the probe is crucial for accurate measurements. Visually inspect the measurement surface of the probe, especially the center portion. Look for nicks, dents, discoloration, and other sign of stress. If measuring solid materials, they must also be flat.
If using ECal for Electronic Refresh, make sure it is connected correctly. See Setup with ECal An ECal module that is not switching at all or not switching repeatably will cause severe problems. There is also a ECal Module Check utility in the help menu to help you troubleshoot. When in doubt, remove ECal from the system and try calibration and measurement again.
Temperature should be constant for best measurement results. Avoid thermal shock. Allow one-half hour for the probe to achieve temperature equalization if it has been subjected to temperature variations. When deionized water is used as a calibration standard, it is important to enter the correct temperature and maintain that temperature during calibration and measurements.
A bad calibration can be caused by the following:
Make sure you select the correct probe under Configure Cal in the Calibration menu
Connecting the calibration short requires practice to make good repeatable measurements. Also, any damage to the short or probe will cause non repeatable measurements. See Check Calibration Short utility under the Help menu.
Visually inspect the shorting surface, especially the center portion. On the Performance probe short and High Temperature probe short, look for nicks, dents, discoloration, and other sign of stress. The Performance probe short will have a slight circular dent the size of the outer diameter of the probe which is not a defect. Inspect the Slim Form probe short for damage to the conductive elastomer pad. flat.
Tiny air bubbles can cling to the probe tip when measuring the calibration water or liquid samples, which can cause inaccurate and non repeatable measurement results. This is most common with the Slim Form Probe. A glass beaker is recommended so air bubbles can be seen. If they are present, remove them by gently tapping the probe tip on the bottom of the beaker, or lowering the beaker away from the probe. then re-imersing the probe.
Deionized water of known temperature should be used for best measurement results. Distilled water can be a substitute if deionized water is not available. Impurities n the water will cause measurement error mostly at the lower frequencies
Refer to the network analyzer manual for help determining if your network analyzer is operating correctly.