If you are building passenger rail cars, how do you know if the heating system is sufficient? This is especially true in Europe where rail travel is very popular and the winter climate can be extreme, especially in the mountain areas. The heating and ventilation system inside a rail car must be designed to provide maximum comfort while using minimal space and energy. Verifying performance under actual climatic extremes is an important part of the design process, and involves dozens of temperature sensors placed throughout the passenger compartment.

Climatic extremes can be created in a modern wind tunnel facility.  Recently, a consortium of European rail car companies built a new facility dedicated to the testing of rail cars.  The tunnel is large enough to accept a full-size rail car and  can simulate the wind velocity and temperatures during an alpine blizzard. 

The inside of the rail car is fitted with dozens of RTD sensors to measure the temperature profile during the test.  RTD sensors change resistance with temperature and they must be connected to a data acquisition system that can provide precision excitation and resolve very small voltage changes.  The temperature readings must be linearized by the data acquisition system and sent to a host computer for recording during the test.

The key to efficient use of an expensive facility such as a large wind tunnel is to minimize the time needed for test preparation.  The sensors and the data acquisition system are mounted inside the rail car prior to being placed in the wind tunnel.  This can be done off-site.