Laser Control Software (Elsie – LC)

This is the control screen of LC, showing a message that a macro has completed without issues!

The client program (LC) runs on a second computer beside the Aerodyne QCL.  It uses two screen, with one screen as the control surface and the other as the data display surface.  The program is written in Free Pascal with Lazarus.  Free Pascal is a high level object-orientated Pascal that will run under a variety of operating systems, including Windows and Linux.  The executables produced by it will also run on a variety of operating systems.  As an example, GUS (our gas-mixing system) is programmed and runs on a Raspberry Pi.  Lazarus provides a graphic environment constructed using Drag-And-Drop, with a fully integrated editor and debugger etc.  This is essentially very similar to the commercial program Delphi, but free!  If you are considering learning to program I (HSW) would recommend either, although the freeness and openendedness of Lazarus is particularly attractive.  The LC program is still being developed and screenshots may be out of date.

The Aerodyne TDLWintel software provides a facility to export the “raw” data as text through the serial port.  This comes out in various forms but the one that we use exports the isotopologue concentrations in ppb.  These are in the normalised form discussed in paragraph 3 of the introduction to data corrections.  

Serial I/O is managed using the buttons at the top left of the control screen.  In typical RS-232 format they appear as lines of ASCII text terminated by CR/LF at the rate of one per second and are displayed as aquamarine text above the yellow outlined button at the upper left of the control screen.  Our client program (LC) offers the option of operating at that rate or summing records together and averaging from the circular buffer that they were pushed onto.  All these data can be saved to a log file.

Graphing on screen 2 is turned on and off using the large button at the top with a picture of a graph!

The panel with the yellow button controls the gas mixer.  This connects to GUS over an Ethernet cable, using Samba.  Command packets are sent to GUS if the remote is locked.  The command packet includes the current [CO2] so that GUS can reset itself to provide the requested concentrations of CO2 (from one of the two selected reference valves) and the selected flow and mix of N2, O2 and CO2.  The precision of setting [CO2] is user-controllable.

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