Measurement Fundamentals Rajesh Vaidya DAQ Software Engineer Wed 10:15a, 12:45p, and 3:30p Colorado (6A) Rajesh Vaidya DAQ Software Engineer Wed 10:15a, 12:45p, and 3:30p Colorado (6A)
Presentation Outline Design considerations Hardware and software selection Demo of sample measurement systems Factors affecting accuracy Parting thoughts Design considerations Hardware and software selection Demo of sample measurement systems Factors affecting accuracy Parting thoughts
Design Considerations Define system requirements Classify application based on signal types (AI/AO/DIO/CTR or combination) Number of I/O channels Speed/accuracy Signal conditioning requirements Portability Scalability Backward compatibility with existing systems Define system requirements Classify application based on signal types (AI/AO/DIO/CTR or combination) Number of I/O channels Speed/accuracy Signal conditioning requirements Portability Scalability Backward compatibility with existing systems
Measurement System Components Physical phenomena (Temperature, pressure, etc.) Transducer Voltage current, resistance Signal conditioning PC with data acquisition Device + Measurement software wiring
Signal Types and Conditioning Requirements
Defining Requirements (cont’d.) Number of I/O channels Low – DAQ board Medium –Higher channel DAQ board –Multiple DAQ boards High –SCXI-based system Number of I/O channels Low – DAQ board Medium –Higher channel DAQ board –Multiple DAQ boards High –SCXI-based system
Requirements (cont’d.) PC-4350 PCI-603x PC-611x PCI-5112 Speed vs. Accuracy
Additional Considerations Multifunction DAQ board vs. computer-based instrument Does your system need portability? PCMCIA, PCI, AT, PXI, USB, FireWire, serial, parallel Multifunction DAQ board vs. computer-based instrument Does your system need portability? PCMCIA, PCI, AT, PXI, USB, FireWire, serial, parallel
Software/Programming Interface Interactive interface (ready to run) VirtualBench Programmatic interface LabVIEW LabWindows/CVI C++/Visual Basic/Delphi ActiveX controls Interactive interface (ready to run) VirtualBench Programmatic interface LabVIEW LabWindows/CVI C++/Visual Basic/Delphi ActiveX controls
DAQ Designer 99 Online system configuration tool Online system configuration tool
Demo VirtualBench and LabVIEW Interface
Making Accurate Measurements Signal resolution Grounding issues Line noise Environmental factors Calibration Source impedance Signal resolution Grounding issues Line noise Environmental factors Calibration Source impedance
Accuracy Issues (cont’d.) Signal resolution Type of A/D Converter – 12-bit vs. 16-bit Gain setting Grounding issues Differential Reference single ended Non-Referenced single ended Signal resolution Type of A/D Converter – 12-bit vs. 16-bit Gain setting Grounding issues Differential Reference single ended Non-Referenced single ended
Accuracy Issues (cont’d.) Line noise Use filtering to eliminate Hz line noise Environmental factors Use shielded cables Distance system from noise sources Calibration Perform regular calibration Source impedance High impedance sources can cause problems Line noise Use filtering to eliminate Hz line noise Environmental factors Use shielded cables Distance system from noise sources Calibration Perform regular calibration Source impedance High impedance sources can cause problems
Demo – Temperature Measurement
Demo – Frequency Measurement
Deploy the System Stand-alone systems “Executable” versions for clients Part of networked DAQ system DataSocket RDA VI Server Stand-alone systems “Executable” versions for clients Part of networked DAQ system DataSocket RDA VI Server
Measure Anything / Automate Everything PC-based measurement systems offer: Superior performance Lower cost Better integration Faster development cycles Distributed measurement capabilities PC-based measurement systems offer: Superior performance Lower cost Better integration Faster development cycles Distributed measurement capabilities