History - Computer control

A new feature of SHRIMP I was the fully integrated computer control for digital data acquisition. SHRIMP I was originally controlled by an HP workstation (21MX < http://www.hpmuseum.net/exhibit.php?class=3&cat=33>) with GPIB (General Purpose Interface Bus) interfaces to the data acquisition modules. The original code was in Fortran 4. Compilation of the programs was carried out on a separate HP1000E computer, compiled and then loaded by tapes in to the 21MX. A single change to the operating program would require of the order of two hours for the loading of the new version. This was improved with the acquisition of an HP1000M system that had its own hard drive to allow the programming to be carried out directly.

The HP computer was replaced by an Apple Macintosh II in 1989. The Mac II was the first open architecture computer produced by Apple and allowed the incorporation of control boards and the use of a graphical interface. The Mac programming was carried out in C. This computer stayed in operation until 2006 despite regular shutdowns from stray discharges from the ion probe.

SHRIMP II was the first instrument to be programmed in the National Instruments LabView graphical programming language. This was initially carried out on the Macintosh computers but following National Instrument’s adoption of the Windows operating system as its standard, both SHRIMP II and SHRIMP RG computer control was changed to PC/Windows. LabVIEW operations were a factor of 2 to 4 faster on the Windows platform compared to the Mac.

The ION network was developed at RSES Electronics to interface the computers to the instrument control systems. One of the characteristics of the GPIB was the copper wire that connected all points of the instrument. This was a ready pathway for arc discharges and caused numerous failures of a variety of boards and computers, whichever was the weakest link. The ION was based on optical fibre communications and so any discharge was maintained in the box in which it occurred. Furthermore, the ION communication speed was much higher than the GPIB, and much more robust.

Computer Control Schematic
The SHRIMP HP-1000M computer network of ca. 1986.

 

Updated:  24 October 2011/ Responsible Officer:  SHRIMP Group leader/ Page Contact:  WebAdmin