Miniaturized Thermocouple Scanner

The AEDC Engine Test Facility (ETF) has more than 20 test cells that can be used for testing prototype propulsion systems and components.  The testing of propulsion systems requires significant data acquisition capabilities, with one test utilizing more than 4200 channels of instrumentation, including 700 thermocouples.  In response to the sheer set-up challenge, AEDC has developed the concept of Snap-In/Snap-Out sensors in which each sensor is close-coupled to electronics sufficient to control the sensor and convert analog output to digital data that is transmitted over a network for recording and processing.  This concept closely mirrors that of smart transducers described in IEEE standard 1451 that defines the Smart Transducer Interface Module that interacts with a sensor, contains a Transducer Electronic Data Sheet with information required to convert raw output into engineering units, and communicates with a Network Capable Application Processor that transmits collected data over a conventional network.  This project will focus on demonstrating the feasibility of developing a smart thermocouple that will provide plug-and-play functionality, enable thermocouples to be mounted on an engine prior to shipping to AEDC, and significantly reduce the amount of wiring required in the test cell with attendant reductions in test preparation time. BENEFITS: A search of the literature indicates that there are numerous papers and articles discussing the potential of the IEEE 1451 smart transducer standard to revolutionize the design and installation of data acquisition systems.  The reality, however, is that the buzz far outstrips the reality.  A recent survey of people involved in the design of temperature control systems indicated that only about 20% were even aware of the IEEE 1451 standard.  Of these, only 11% were using smart sensors (2% of the overall pool of respondents).  An interesting finding was that 20% of respondents familiar with IEEE 1451 have no intention of using smart sensors in the foreseeable future.  The reason for this is that the vast majority of data acquisition systems are installed once, verified to be operational, and then operated for years with only routine maintenance.  The additional labor involved in installing conventional instrumentation and initial troubleshooting that would be avoided by using networked smart sensors is offset by the added cost of smart sensors this means that for many applications there is not a significant cost savings that could be realized by adopting the new smart sensor technology.  To a great extent, the market reflects the fact that there are not clear and significant cost savings to be gained by adopting smart sensors.  There are a handful of companies marketing smart temperature and pressure transducers, and NCAPs.  The selection of other types of transducers is even more limited.  AEDC''''s engine testing application, however, is atypical.  It involves the use of many sensors that are installed in the test cell for a short period of time.  The set-up time for installing and wiring these sensors directly impacts test schedules.  Additionally, current practice involves manually tracking the locations of thermocouples using spreadsheets that are prone to error and that may create problems downstream during data analysis.  The use of smart transducers will alleviate both of these problems.  The installation of smart thermocouples will make test set-up easier by minimizing the amount of wiring that is installed and run in the test cell.  Proper use of the TEDS will enable transducer location data to be stored along with other parameters.  The location information can then be carried along with the recorded data to ease the interpretation of test results.