Distributed data

Aircraft gas turbine engines and generators, which require testing under conditions that simulate the pressures and temperatures found in flight.

Develop a data-acquisition system that records temperature, pressure, and flow from more than 2000 channels. The system must control test parameters as well as distribute data to a control room and store every data point.

• Exact Flow: flow meters and flow computers. www.exactflow.com.
• National Instruments: two PXI chassis; multifunction data-acquisition cards; digital I/O cards; and a signal-conditioning chassis with current and voltage signal conditioners, thermocouple signal conditioners, isolated analog-input modules, isolated frequency-input modules, and relay modules. www.ni.com.
• Scanivalve: Ethernet-based pressure and temperature data-acquisition systems. www.scanivalve.com.
• Sorensen: power supplies. www.elgar.com/products/sorensen.
• VMIC (now GE Fanuc): reflective-memory cards. www.geindustrial.com/cwc/gefanuc.

A distributed data-acquisition system measures parameters from an aircraft engine component and distributes more than 2000 channels of data to remote computers.

Honeywell specified that the system use distributed architecture to perform real-time control of the test parameters for the unit under test. And the system had to let engineers, analysts, and technicians monitor the tests from six locations.

The distributed system consists of five computers, two of which are embedded PXI controllers. One handles the data acquisition of temperature, flow, and pressure; the other, called the facility-control computer, performs real-time control of the test bed.

To keep the data flowing, all five computers use a reflective memory architecture that updates all computers' memory over a fiber-optic ring network. As the data-acquisition chassis collects data, the data is instantly copied into the memory of the other four computers on the ring. The three host computers make data available to six display clients, a data-archive computer, and another remote computer. All data from the host computers travels over a Gigabit Ethernet network. Test engineers, analysts, and technicians look at the data during and after a test to see how different flight parameters affect the component under test.

The data-acquisition PXI chassis collects temperature, pressure, and flow data from sensors connected to a local signal-conditioning chassis. A frequency-input module collects data from flow meters, while pressure sensors send 0-V to 10-V and 4-mA to 20-mA signals to other signal-conditioning cards. Thermocouples connect to thermocouple-input modules that boost the signals and send them to the data-acquisition card in the PXI chassis. The facility-control PXI chassis uses PXI cards with 0-V to 10-V analog outputs and 24-V digital outputs to control valves, pumps, and heaters.

Multiple remote data-acquisition modules collect additional absolute and relative pressure, temperature, and flow data. Both units connect to the data-acquisition chassis through an Ethernet port. Honeywell chose these systems to reduce the amount of wiring in the system and to distribute the acquisition channels around the test facility.

Prior to using this system, engineers used various data-acquisition systems, all of which incorporated numerous PC platforms. All of these systems could acquire and display a limited number of parameters. The new system has the capability of collecting and storing many more parameters and provides additional features, such as multiple viewing stations and simultaneous real-time and historical data analysis.