Signal-conditioning amplifier recorders (SCAmpRs) have been proposed as a means of simplifying and upgrading the Kennedy Space Center (KSC) Ground Measurement System (GMS), which is a versatile data-acquisition system that gathers and records a variety of measurement data before and during the launch of a space shuttle. In the present version of the GMS system, signal conditioning amplifiers digitize and transmit data to a VME chassis that multiplexes up to 416 channels. The data is transmitted via a high-speed data bus to a second VME chassis where it is available for snapshots. The data is passed from the second VME chassis to a high-speed data recorder. This process is duplicated for installations at two launch pads and the Vehicle Assembly Building (VAB). Since any failure of equipment in the data path results in loss of data, much of the system is redundant. The architecture of the existing GMS limits expansion or any modification to the system to meet changing requirements because of the cost and time required. A SCAmpR-based system is much more flexible.
The basis of the simplification, flexibility, and reliability is the shifting of the recording function to the individual amplifier channels. Each SCAmpR is a self-contained single channel data acquisition system, which in its current implementation, has a data storage capacity of up to 30 minutes when operating at the fastest data sampling rates. The SCAmpR channels are self-configuring and self-calibrating. Multiple SCAmpR channels are ganged on printed circuit boards and
mounted in a chassis that provides power, a network hub, and Inter-Range Instrument Group (IRIG) time signals. The SCAmpR channels share nothing except physical mounting on a circuit board. All circuitry is electrically separate for each channel. All that is necessary to complete the data acquisition system is a single master computer tied to the SCAmpR channels by standard network equipment. The size of the data acquisition system dictates the requirements for the specific network equipment.
The computer polls each channel for health status and data snapshots. The bandwidth of the network dictates the extent of the data snapshots. It is likely that in most applications the health status/data snapshot frame can be obtained often enough to pass all data in real time to the master computer. Data is time tagged and stored safely in non-volatile memory at the SCAmpR where it remains for retrieval regardless of the status of the communication network. Once a SCAmpR is commanded to record, no further communication is necessary to successfully complete a measurement. Even the loss of the IRIG time input will not cause a disruption because each SCAmpR channel will automatically revert to generating time if the input is interrupted.
A SCAmpR can record data in any of a variety of ways upon command. For example:
- A SCAmpR can be configured to record and time-stamp data only when a predefined minimum change occurs, for example during a long fueling operation where flows and pressures would normally remain constant.
- A SCAmpR can be commanded to start recording at a future time, for a given duration, so that in the event of a failure of communication at a critical time, data would still be recorded as originally intended. As long as communication continued, the commanded starting time could be adjusted (as would be needed to accommodate a hold in the launch countdown).
- A SCAmpR can be commanded to record data samples at a specified rate or to sample at different specified rates at specified times in the future.
Inexpensive commercial-off-the-shelf (COTS) hubs integrate the SCAmpR chassis into a communications network. Transfer of data and other communications, such as commands and health status, will be performed by a standard method of network communication. The current implementation is a polling form of TCP/IP. Any number of computers can be connected to the network for viewing or rebroadcasting of data snapshots in addition to commanding and monitoring health status of the SCAmpR channels.
The GMS is intended to be a quick response system. A SCAmpR chassis can be installed for special situation measurements with minimal infrastructure requirements. Also, it has become a recurring requirement for the GMS to support measurements during rollout of the mobile launch platform. The SCAmpR architecture will provide the capability for quick implementation of a very reliable and easily reconfigurable data acquisition system.
This work was done by Pedro J. Medelius and John Taylor of Dynacs, Inc., for Kennedy Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Computers/Electronics category. This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Technology Programs and Commercialization Office, Kennedy Space Center, (321) 867-8130. Refer to KSC-12296.
This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Technology Programs and Commercialization Office, Kennedy Space Center, (321) 867-8130. Refer to KSC-12296.