There are many different parameters that need to be monitored and recorded as part of automotive testing. One group of these relate to the emissions given off by the engine and/or its fuel. These readings are typically not required for the entire length of test and sample readings may simply be required every few hours or number of test cycles. This allows for sharing of the emissions reading equipment between several test beds.

An application was developed in Microsoft C to respond to digital inputs either from push button displays or from Digalog Test bed controllers. The PC based program would detect which test bed was requesting an emissions reading and set digital outputs to select the appropriate valves for the hot exhaust line.

After a configurable passage of time to allow enough exhaust gases to travel the hot lines to the Horiba Mexa 9100 Gas Analyser the application would request sample readings and finally an averaging reading. The physical connection between the analyser and the PC was via an IEEE-488 channel. Once the readings had been taken the valves would be shut, the lines purged of gases to prevent contamination of future samples, and provide the data readings to the remote displays via an RS-423 line.

As a result of my work in completing the project performing corrective work, error handling and optimisations the performance of this application went from failing several times a day to never failing.

A fully working protocol was later developed by myself which simplified the design of the system whilst enhancing its features. This version was written to run under Microsoft Windows and take advantage of the NetAPI inherent in the operating system to use standard PCs rather the Horiba Remote Displays. With the ever increasing number of PCs required at each test bed this was considered excellent use of existing resources. The other advantage of running under Windows was that the application was written to see NetDDE and so emissions sampling and monitoring could be achieved from any PC available to the network whether on the shop floor or the engineers desk.