Display Cal Data and the Real-Time Calibration Display
When calibrating in an on-wafer or fixtured environment (and sometimes even in connectorized environments), it is sometimes difficult to tell if one has made good contact with the standard. Rather than completing the entire calibration and then seeing if the result was acceptable, it may be useful to get a quick indication of what is being measured, in a quasi-corrected sense, before moving on to the next standard.
The Display Cal Data function is accessible from the CAL OPTIONS menu.
Display Cal Data in CAL OPTIONS Menu
When turned on (default is on), Display Cal Data enables the use of a previous calibration to provide a real-time quasi-corrected view of the current standard being measured. After one clicks the standard button (during which the real data for the new calibration is collected), the display reverts to one where the swept data is corrected by the previous calibration in the system. Assuming the previous calibration was good, a load standard should then appear to have high return loss if connected properly, a thru should have low insertion loss and high return loss, etc. Some things to keep in mind:
• The display correction will only be applied if the previous calibration is of the same type as the current calibration (e.g., full 2-port…) and consists of the same frequency list or a superset of the current frequency list. If both of these statements are not true, then the data displayed will only be corrected by a factory RF calibration (should it exist).
• The previous calibration correction is not applied to the data being acquired for the new calibration directly. That is, this is not a second tier calibration; it is the newly acquired raw data that is fed into the calibration algorithm when Done is selected.
• If the previous calibration was poor (e.g., a standard was not connected at some point), the displayed values during the current calibration may appear erroneous. The Display Cal Data should be turned off if the previous calibration is known to be bad. If Display Cal Data is left on in this case, however, it will not affect the result of the new calibration. Only the appearance of the value during the current calibration will be affected.
