(Setting the Backend and Determine the Total-Power-Counter Offsets)

There exists an addendum to the OBS_E - manual, where all parameters of the new 8192-channel AC are described.

The new autocorrelator is backend number 3 and with the "show be3" command one gets displayed in OBS_INP the parameters oft that backend. They are comparable to the parameters of the old 1024-channel AC.

As all backends are served by the same process one has to specify which line backend shall be active. That is done by the OBS_E - adverb BACKEND_L . That switches for line observations (PSWITCH etc...) between the old 1024-channel and the new 8192-channel autocorrelator.

• set backend_l <type> or l_mode /backend <type>
• 1024-AC: <type> = ak
• 8192-AC: <type> = new

The OBS_E - verb AUTOCORREL sets the parameters for the old 1024-channel AC, the new OBS_E - verb KORREL8192 sets the parameters for the new 8192-channel AC. The parameters or adverbs for the new AC are very similar to the old ones. They are prefixed with the character "N", for example instead of SPLIT for the old NSPLIT for the new AC. Determining the Offsets of the Total-Power-Counters The new 8192-channel AC can subtract the offsets of the TP counters from the delivered data. To do that the user first must make an offset observation. By that measurement the offsets will be determined and afterwards subtracted from the data. These values are active until a new offset observation is made or the AC will be reset. Such an observation can be made by setting a special adverb and using OBS_E - verbs. After such an observation has begun, the adverb is reset, so that the next observation runs in normal mode. Such a measurement can be made at every time, there is no need for an IF-signal or the telescope driving. It can be made by a short PSWITCH or FSWITCH observation in the same configuration as the following real observations. The OBS_E - parameter, which will be reset after that measurement, is:

• SET NAC_OPTIONS <special> [ * * ]
• <special>: has to be a character string beginning with "O" (e.g. offset)

Forced setting of all parameters of the Autocorrelator Before making a new measurement the program checks whether an input parameter for the AC has changed. If not, there will be sent no setting commands to the AC assuming that the AC is in the same state as in the observation before. That can be in conflict, if the AC has been manually reset or a parameter has been manually typed in. That is not known to the program running in the control computer. To force the program to send all input commands to the AC in any way, one cane use the above parameter. It must be a character string beginning with "S" (e.g. setak). After that measurement the parameter will automatically be reset.

• SET NAC_OPTIONS <special> [ * * ]
• <special>: has to be a character string beginning with "S" (e.g. setak)

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