Real-Time Auxiliary Display Devices Enhance the Performance of Thermal Array Chart Recorders
AuthorGaskill, David M.
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Collection InformationProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection.
AbstractChart recorders are needed both for producing a permanent record for post-mission analysis and for providing real-time information during a test. Immediate feedback is important when test conditions may require mid-course warnings or corrections. In the traditional galvanometer based chart recorder, the operator can look directly at the pens moving on the paper and quickly judge speed and amplitude. When using a thermal array recorder, there is a small delay between the time of printing and the time when the trace is visible. This is due to the construction of the thermal array itself. Individual printing elements are deposited on a ceramic substrate which eliminates all motion from the printing process and physically blocks the operator’s view of the printhead so that for a short time there are no visual clues as to the exact waveform position. At higher chart speed this gap only represents milliseconds of elapsed time, well below human reaction time, and therefore of no real importance. At trending speeds, however, the delay could be half a second or even more and could be a problem in some situations. The first solution offered by manufacturers of thermal array recorders was a row of LED’s that stretched across the recorder directly over the printheads and reflected printing activity in real-time and indicated the actual position of the individual waveform traces. This was found to be a satisfactory solution by most telemetrists who wanted to change to the new technology in order to take advantage of the thermal array recorder’s higher frequency response and flexible formats. While the LED array satisfies basic real-time response requirements, there are many other applications for auxiliary displays which include variable chart labeling and graphic display of waveforms.
SponsorsInternational Foundation for Telemetering