Quality measurements for design validation and certification requirements sometimes call for hundreds or thousands of sensors and actuators. Maintaining such a complex system is difficult, especially over an extended time period and inevitable personnel changes. Many hours are spent tracking down sensor problems related to the sensor, associated cables, mounting hardware, or some part of the data acquisition system. These are expensive, labor-intensive hours that consume valuable technical resources.

Another aspect to maintaining a complex system is the ability to gather data on critical elements that have a finite life expectancy. An example of such an element is a control valve. The two materials that provide the seal in a typical valve are copper and cast iron. During normal use, the copper will wear and the valve seal will need to be replaced. As wear occurs, the fully closed position will change. By monitoring this position change, it is possible to predict when a valve should be taken out of service and rebuilt. Predicting when a valve needs to be rebuilt before a failure will decrease the chances of a much more costly shutdown during a test.

Because of these issues, many hours can be consumed adapting data from all these data-generating devices to a format that can be used (consumed) by an application. Custom hardware interfaces and custom software drivers are often required. Therefore, a need for easier integration of industrial devices from multiple manufacturers, as well as a need for devices to become more intelligent and provide information about their own condition, in addition to the function they are performing or the process they are controlling or monitoring, was required.

To meet this need, Lion Precision developed an intelligent sensor (a sensor that can process information on its own, and is capable of two-way communication and the associated communication protocols) to monitor various components on the test stands, and a protocol with defined structure and data items using the MTConnect standard. This standard is a communication protocol that operates over Ethernet; it is not an application program. MTConnect provides information in XML format, which can be accessed and understood by multiple application programs.

The MTConnect standard was developed to accommodate many different types of devices — from intelligent sensors, to actuators, to status indicators — by providing a protocol that adheres to a pre-defined data structure and reporting scheme. In this way, sensors communicate measurement data, pre-processed measurement data, diagnostic data, and sensor/system health via existing, accepted protocols that have not yet been completely utilized in sensor interfaces. This system is the first of its type to use the MTConnect standard.

The device software is made up of several subsystems that provide the overall system functionality. The following are key system interfaces:

  1. Web Services that provide a platform-independent means to communicate with the ECD device. These Web services host both ECD-specific services as well as the MTConnect interface.
  2. Device Services that are responsible for hosting the various system services that include Web server, watchdog, and main board communications interface.
  3. Data Access that provides general storage for both configuration and data acquisition of measurement and diagnostic data.
  4. Device Framework that provides the core functionality of the ECD device software.
  5. User Interface, which is a Web user interface hosted on the device for status and configuration.

By having an “open standard” that defines different types of devices without regard to the manufacturer, it is possible for third parties to write programs that consume this data. The system that was developed had both hardware and software that met the following objectives:

  • Collect data from 4 displacement sensors located on 2 hardware (ECD152) devices using the MTConnect protocol.
  • Collect diagnostic data from the system and provide feedback to the user as to the overall system health (valves, re: flow of LOX and LH2).
  • Record and store events for analysis and history of system operation.

This type of functionality opens up the “sensor world” to a broad range of software possibilities. For example, Web developers and database developers could easily access and display or store sensor data. When measurement data, processed data, TEDS (Transducer Electronic Data Sheet), and HEDS (Health/Diagnostic Electronic Data Sheet) data types are incorporated into the MTConnect standard, the incremental cost of providing this data by the sensor manufacturer and the incremental cost of accessing the data by the end user is very low because all the data is over a single Ethernet connection, and the data is in a usable and well established format: XML.

The overall goal was to develop sensors to communicate measurement data, pre-processed measurement data, diagnostic data, and sensor/system health using MTConnect, which has not yet been utilized in sensor interfaces. The power of data integration is evident, for example, in other fields such as the diagnostic capability of modern automobiles and other complex systems. The benefit to industry has the potential to be enormous if data integration from an “open system” consisted of devices from multiple devices from different manufacturers.

This work was done for NASA's Stennis Space Center by Don Martin, Mike Knowd, Ray Herbst, and Greg Knowd of Lion Precision for Stennis Space Center. Please direct all inquiries to Don Martin, 563 Shoreview Park Road, St. Paul, MN 55126 or This email address is being protected from spambots. You need JavaScript enabled to view it., or 651-484-6544. Refer to SSC-00398.


Sensor Technology Magazine

This article first appeared in the March, 2017 issue of Sensor Technology Magazine.

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