Dear Dennis...
EN-Genius Network's Dennis Feucht answers your design
queries in his new Circuit Design Clinic!
September, 2009
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EN-Genius Network presents a new, interactive
analog design service to readers! Send us your design questions (with
relevant data; schematics in JPEG or GIF, please) for some free
engineering advice from EN-Genius Network's circuit
consultant, Dennis Feucht, on how you might solve a design problem or
improve circuit performance. Submissions may be edited for clarity or
brevity, and submitters and their email addresses will remain anonymous
(unless otherwise indicated). Please send your questions to Dennis here.
Data Acquisition and Instrumentation
Sensor Circuits
by Dennis L Feucht
Acquisition of useful data from sensors is accomplished by electronic instrumentation called data acquisition (DAQ) systems (DASs). They are often combined with analog and digital output capabilities as data acquisition or instrumentation and control systems. This series of articles is a tutorial presentation of principles of instrumentation that is typically multi-channel, medium to high resolution (12 to 20 bits) and relatively slow – slower than oscilloscopes in sample rate. DAQ principles – mostly basic, with some subtleties and simplifying concepts – and sensors will be emphasized.
To give the presentation a concrete context, the application example will be a rocket test system as used to verify the performance of small rockets fired statically on test stands. Test firings must be sequenced by a controller and a DAS acquires the sensor data. The rocket test control system must be informed about what is going on in the rocket, and the instrumentation subsystem provides it. Sensors convert quantities of interest, such as pressure or acceleration, to electrical form. The data acquisition system converts these electrical quantities, in order, to a digital form compatible with the control computer, as its input. In all but very simple rockets, a separate instrumentation computer will process the sensor information into a useable form. This is the instrumentation system of the rocket test stand.
...download complete article here (235 KB PDF)
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