MTS9000 - vxitech.com

1 Online at 955 189419 Technology VX IOverviewWind Tunnel Jet Aircraft engine Test CellsRocket engine TestingAutomotive Powertrain TestingAutomotive Safety Testing Shock/Vibration TestingLimit TestingSampling rates, channel counts, signal conditioning and datastorage are key factors in most data acquisition sampling rates and channel counts logically affect theamount of data that is collected. How long the data must besampled and whether or not all the data collected must belogged to disk for immediate or post processing coulddetermine the type of acquisition hardware that best fits theapplication requirements. VTI focuses on all types of data acquisition in functional test these applications are eithertransient in nature (single shot measurements go/no-go), orthe need for high-speed constant monitoring of multiplechannels is required, but storage of data is only necessarywhen any one of the channels falls outside a specified windowof tolerance.

2 In these applications a snapshot of the data maybe all that is necessary, thereby conserving hard drive these examples, pre-trigger data is also frequently ofinterest, which allows analysis of the events that led up to theout-of-tolerance condition. VTI offers two modules, theVM2616 (16 channel, 16-bit digitizer), and the VM4016 (16channel analog comparator card) that when used togethersatisfy these requirements for functional test. See Figure MTS9000 family of subsystems, however, is focused athigh-channel count data acquisition applications that gobeyond simple go-no/go or limit testing. These applicationstypically require all the key fundamentals of true dataacquisition:Desirable if the parameters being measured or monitored arephysical in nature such as strain, pressure or in these parameters result in very small changes involtages, and a data acquisition system that provides signalconditioning hardware to adequately amplify these voltageswill result in accurate test data.

3 We offer an extensive productlisting geared toward the most demanding requirements facedwhen measuring physical phenomena. These include VXIbusmodules such as the V246 bridge signal conditioner, V25 Xgain/analog filters, V241 and V243 multiplexers, and V710,V765, V768 and V792 external termination panels for very highchannel count signal offers 2 types of A/D solutions multiplexed and non-multiplexed:The multiplexed systems utilize one A/D converter with an n channel multiplexer in front of it. The effective sampling ratemust then be scaled down depending on how many channelsare enabled during the acquisition as it takes time to switchfrom one channel to the next on the multiplexer.

4 There aremany benefits when using multiplexed systems. Most evidentis cost/channel. It is much less expensive to add switches toan A/D board and multiplex, than it is to dedicate an individualA/D per channel. Further, parameters such as strain, pressureand temperature do not change very fast, and slower samplingrates across a large number of channels are usually Acquisition SubsystemsSignal ConditioningAnalog-to-Digital Converters (A/D Modules)Online at 955 1894 VTI offers the V207 and V208 scanning ADC and the VM2716 Ascanning dvm(A/D) multiplexed A/D a non-multiplexed A/D system, each channel has anassociated A/D converter dedicated to it. Each converter ispulsed by the same clock, therefore, there is no time skewbetween sampling of data.

5 More importantly, the sampling rateof one channel is equal to that of the overall sampling ratespecified for the system. In other words, the sampling rate ofany channel is independent of the number of channels enabledduring the acquisition. These types of systems are useful forvery high-speed sampling requirements over a large numberof channels. VTI offers the VM2608/VM2616 16-bit digitizer andV200 Sigma-Delta ADC non-multiplexed lot of applications require the acquisition of data over anextended period of time. For example, in road testing ofvehicles, vibration sensors are mounted to various pointsalong the body of the vehicle. Each sensor converts thevibration to analog voltage data that is fed to the A/Dacquisition unit.

6 Data on all channels is continuously sampled,typically at >5khz/channel. Automobile manufacturers areinterested in the frequency response of the body while thevehicle travels around the test track. Minutes of data must beacquired, and all of it is saved for post-test analysis. Thisamounts to a great deal of data, much more than is typicallypresent on the data acquisition device itself. This mandates the ability of the acquisition device to streamdata to the hard disk. Incoming voltages are digitized andwritten to a FIFO buffer. A background process empties the20 Technology VX IMTS9000 Data Acquisition SubsystemsFIFO and writes the retrieved data to a file stored on the harddrive of the host computer, or onto large memory modulessomewhere else in the data acquisition system.

7 Fasteracquisitions and/or high channel counts require fasterinteractions between the host controller and the on-boardFIFO. If the rate of data being collected is faster than the host sability to offload it, data will be lost as the FIFO is overwrittenwith new data. This is a challenge that continuous samplingand storage applications must overcome. If data must beprocessed and displayed on a graphical user interface, anadditional burden is placed on the host controller and theeffective sampling rate might further be reduced. VTI offers several processors for real-time data capture thatinclude embedded Pentium, Power PC or 68040 computers,and DSP modules with up to GFLOP processing power.

8 Tosupport large memory applications we offer the V110 (up to128 megabyte) memory acquisition applications offer up a variety of challenges tothe test systems designer. Different approaches must beinvestigated to come up with the ideal solution for theapplication at hand. Multiplexed systems typically offer agreat deal of flexibility in channel counts, signal conditioningand data storage while keeping cost/channel to a systems allow the designer to utilize multiplechannel acquisitions at very high sampling rates. Further, theVXIbus provides a platform for incredible density in a verysmall footprint (up to 1056 channels in a 13-slot chassis), andthe speed of the bus allows for fast retrieval of data.

9 Thebreadth of products offered by VXI Technology Inc. can satisfyeven the most challenging data acquisition requirements.> DataPost-Trigger DataTrigger PointDigitized DataComparatorDigitizerExt. Trigger InputConclusionFigure 1 Processing and Data Storag