Waveform Annotation Control > Special Considerations

#### Special Considerations

A logical channel number corresponds to a channel number's appearance in a data file. The first channel acquired is the first in the file, the second is the second, etc. In all operating modes dealing with channel assignments (e.g., Variable Waveform Assignments), logical channels are always specified. However, during waveform recording you have the ability to acquire any number of channels, not necessarily in sequential order. For example, you may have recorded channels 2,5,7,9, and 14. These channel numbers are called physical channels — relating to the actual physical channel number that provided the waveform. Their logical channel numbers are 1,2,3,4, and 5. When acquisition assignments are active, L=P means logical channel number L is assigned to physical channel number P. You would see the following annotation for each displayed channel:

1=2; 2=5; 3=7; 4=9; 5=14

Acquisition assignments annotation provides a convenient method of determining, for any given waveform, which physical channel number provided the signal. Note also that a physical channel number displayed when acquisition assignments annotation is active will indicate whether the channel was acquired single-ended or differential. If physical channel 3, for example, was acquired single-ended and as logical channel number 2, then its assignments notation would be 2=3. If channel 3 was acquired differential, its assignment would be shown as 2=3D. Differential channel numbers always carry the channel number of the lowest channel input of the differential pair (e.g., a differential channel formed by channel pair 7 and 15, would carry a channel number of 7D).

Neither base line nor channel annotation is displayed while display formats 9 or 10 are active.