spec - Local Sector 7 web page

Scan MacrosThe following sections summarize the usage of the standard scans in spec. This discussionis followed by a description of macros to customize the scan output sent to theprinter and data file. Refer to page154 for a detailed discussion of a single-motorscan.All the scans use the same basic invocation syntax. For example, the single motor,absolute-position scan is invoked asascan motor start finish intervals timeThe range of a scan is specified by the starting position start ,the final position finishand the number of intervals intervals of the scanned parameters. Thusascan tth 26 28 20 60would start with the tth motor at 26°, and move the motor to 28°, using 20 intervalsof 0.1°. The total number of points scanned is one more than the number of intervals,in this case, 21 points. The time per point time ,ifapositive number, indicatescounting to seconds. In the above example, each point takes 60 seconds. Using anegative time indicates counting to monitor counts.Scan Miscellanyresumesetscans# Restart an aborted scan# Set scan-mode optionsIf a scan is halted by typing the interrupt character (ˆC ), or because of some othererror such as hitting a motor limit, you can normally restart the scan by typingresume . You must not have changed the value of any of the internal scan variablesin the meantime. If you use resume to continue a relative position scan, such as lupor dscan ,the scanned motors will not be returned to the center point when the scanends, as they otherwise would be.Youalso have the option to control how the scan data is displayed on the screen as itis taken. An option to the setscans macro allows the motor positions and scalerscontents to be displayed while they are changing during a scan. The rate of updatesis set by the UPDATE global variable, just as with the umv and uct macros. An optionto the setplot macro, presented earlier, allows real-time plots of the data points tobe displayed as they are measured.Another option selected in the setscans macro lets you choose whether to do prescanmotor limit checks with reciprocal space scans. The purpose of these checks is toavoid running into a software motor limit in the middle of a scan. For regular motorINTERIM WORK-IN-PROGRESS (8/16/01) NOT FOR GENERAL DISTRIBUTION STANDARD MACRO GUIDE 145