A Complex Multitasked Data Acquisition and Control System for Measuring Window Thermal Efficiency, or How TSX+ Saved Our Project When It Outgrew RT-11
The Mobile Window Thermal Test facility (MoWiTT) predicts the energy efficiency of windows by continuously measuring the net heat transfer into and out of two room-sized calorimeters. The system consists of a data acquisition/control unit which communicates through a General Purpose Interface bus (GPIB IEEE-488) with an LSI-11/23 computer. We wrote the software in FORTRAN 77 and run it under TSX+ using detached jobs, the message facility, and shared run time systems to execute nine 64KB jobs which simultaneously take data and store it on disk. We arbitrate the access to a single scanner on the GPIB by running a SERVER task which acts as a virtual machine to serialize the requests. We can control and monitor the system remotely and run a number of interactive jobs without interfering with the data collection tasks. We cover a description of the hardware; the software requirements, including the libraries to control the data collection and drive the hardware; the system architecture, including a block diagram; design considerations to meet real-world requirements; and the problems we discovered along the way and the solutions we found either to correct or to bypass them.