When you choose the Measurement Type and the Cal Port, the Vector Network Analyzer compares these measurement settings with the current calibration. If a match is found, then the current calibration is applied to the measured data, and the Cal info box on the display (refer to Figure: Continuous Wave Menu – MS20xxC VNA Master) shows “CAL: ON (OK)”. If no match is found (for example, the calibration was for S11, but the Cal Port is set to Port 2), then the display shows “CAL: --”. Adjusting the setting (the Measurement Type or the Cal Port) to match the calibration automatically applies the correction. The calibration correction can also be turned off manually under the Calibration menu by toggling the Cal Correction soft key from On to Off. In that case, the display shows “CAL: OFF”.
Note that “CAL: OFF” means that a calibration correction has been created, but it is not currently being used. This is different from “CAL: --”, which means that no valid calibration correction is available for the current setting.
Another status information display that you may see is “CAL: ON (?T)” which indicates that the instrument temperature has deviated by more than a set amount since the time the calibration was conducted. The calibration is most likely still valid, but a new calibration is recommended. If you see “CAL: ON (X)” on the display, this indicates that the instrument temperature has deviated (since the time that the calibration was conducted) by an amount that has more than likely rendered the calibration invalid. When this occurs, a new calibration is highly recommended before further measurements are conducted.
Only one calibration is available at one time. Performing a new calibration overwrites any existing calibration. You can, however, store a measurement setup, which also stores the calibration. You can therefore have multiple calibrations available (as long as the calibration settings and conditions continue to apply).
Calibration Status Display
Cal Status
Description
CAL: ON (OK)
current calibration is applied to the measured data
CAL: ON (?T)
instrument temperature has deviated by more than a set amount since the time the calibration was conducted
CAL: ON (X)
instrument temperature has deviated (since the time that the calibration was conducted) by an amount that has probably rendered the calibration invalid
CAL: OFF
a calibration correction has been created, but is not currently being used
CAL: --
no valid calibration correction is available for the current setting
Figure: 2‑Port Calibration, using MS2028C shows an optional adapter for the Through connection. If you are using test port cables, and if you have sufficient calibration components, then using male OSL standards on one port and female OSL standards on the other port allows you to connect the cable ends together without the adapter. This becomes more important at higher frequencies.
Continuous Wave Menu – MS20xxC VNA Master
Note
The Cal Port soft key is available only on the MS20xxC VNA Master. The MS20xxB VNA Master and the S412E LMR Master calibrate only on Port 1, so they do not use this soft key.
