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1. u ba e a e a 2 Vdd E Oi Ot Poise a YUTA xsvicksevele 7 1o Dl lL Measurement vimlesvanos 100 Ns Orset Tron Scan etare vine s P tiks a VUE e ee ale a aa Size or Cic aaa Re a EAE oe cil a MO a a HcJe values bee RELIABLE DATA FIRST TIME EVERY TIME technical Stiruicw 4 VUES ype e eis 3s Bray Si4e OF Tee seem lt VUES Cy cCaCOUNIESE dl olla a Or ecu Dro ADe ead iigce I CIC LCOUIES Screw eZ Ca CKS mete sa ticles 1Zem On we Crm CWS 7 Ve UI tiGe Casi CKSaVal 5 ale baited ar Nes tane v hissed Sets TrOm Scan Stare vine P IC E lt Sweuien 4 VUiee Mies ene ys seldieck See ton ie e S e a Sail CSc Ss e bese tO eden eciominie la I CC COMES rU VUT e ie E Wee T See ere AU elKS vaunt o aE re ibe Sa ci ING ie CIO Sir silos CIOs aS tO ar Servs 1P Ol o can Stot time 7 een me he ecee siren VUES 2 a e Vel eairdy a i2e com a il lence ba Vise iii GS vice a a 4 bts 1 Or a ema nine le 7 Pmt Note that there is only a single two part timestamp and one devid per scan page of data associated with up to 48 channels data per scan The time stamp indicates when the scan started If a timestamp for each measurement is desired the x_ticks member can also be exposed DeleteDatapage lThis function can be used to remove a page of data from the Server FIFO without reading it This can be useful if a previous scan is interrupted and unread data is left in the Server FIFO You may want2. FIRST TIME EVERY TIME technical 5 Initiate Acquisition This state advances the trigger model from Idle layer to the Arm layer Since the arming configuration is set to immediate by default it then proceeds directly to the Trig Layer In this example the decimated timer signal causes a Trig Event which causes a single scan to run on every tick set by the sample rate After Acquisition is initiated the system time is recorded in order to keep track of how long the acquisition has been running 6 Acquire This is the state which polls for and displays any data on the Streaming server FIFO This state loops continuously until one final reading is made after the acquisition time should have elapsed or until the user decides to stop the scan via the front panel button iiss O iii Server Fifo Count Haz Actui Data Count Trigger Countr ftSample Rater wy Required Time for Scan Wait The Get FIFO Count VI queries the number of samples remaining on the box waiting for the LXI interface to send it to the PC Another VI queries the FIFO on the Streaming server The wait control should be set to some time sufficient enough to execute the loop completely 100ms is generally enough time for even the maximum scan rate RELIABLE DATA FIRST TIME EVERY TIME technical 7 Stop This state simply shuts off the streaming server after the acquisition has been stopped Figure 6 displays the front panel
3. a dedicated process which handles the incoming streamed data For this example there are no parameters used Successful memory allocation returns O GetBufferCount A simple query which returns the number of data pages currently in the Server s FIFO This basic query does not check the content of any of the data collected ReadStreamingData Tlhis is the main accessor function for the Streaming Server s FIFO data In this example we are only extracting the timestamp components ss_secs ss_nsecs and sample values x members of the EX10xxA data structure The other members of the data structure are shown below and further detailed in the EX10xxA User s Manual where it documents the EX10xxA_enable_streaming_data function of the Plug amp Play driver We also return an integer called devid which can be uniquely assigned to each EX10xxA box which is streaming data in order to identify which instrument the data is coming from Struc Wdtarade EX1O0xxA_SampleData data ine Che vel Ge Is Struct EXIOxxA_SampleData VIUINES2 SSeSeeS Calta Sample tite stamp lt 7 VIVES 29sSunsecs 77s Traction Dari sOn tine Silane i sidihioeseronds microseconds in legacy mode sir riet 4 ViUiMts2 lt clenis apredy Size 01 davad samples 77 Vireda o2 xava li Tdi array Ol Cava salples 1 x spun VUT sce aeon eke sol lays 1 Ze Or ADL Ton o Vilitts2 gt SeOUuniSavdl lt cdiedtta ool cO Ute DC MP eddindsa 27 x counte
4. processes that data as needed Contrast the previous figure with the streaming method shown in Figure 2 More data is available at the host PC per unit time Find out more about how the RELIABLE DATA FIRST TIME EVERY TIME technical p 6660 E een ai f SD o o e E o a o Host PC EX1016A 16 Channel Precision Thermocouple TIME TIME SOFTWARE REQUIRED e Microsoft Visual Studio C 2010 VTI Instrument EX10xxA Plug amp Play Driver e Labview 2011 or later STREAMING SERVER Streaming requires a multi thread approach in which two processes are essentially running at once Modern operating systems can take advantage of multiple core processors by simultaneously dedicating process flow to different cores One such process in this application runs in the background and handles all data received from the instrument by copying it over to a FIFO on the host PC so thot it can later be collected and processed by the main API The actual example source code for both the streaming server and the Labview API should accompany this document and you should refer back to it while reading RELIABLE DATA FIRST TIME EVERY TIME technical The following exposed functions are basic necessities for creating the simple streaming server application provided in this example StartServer lInitializes a Critical Section Object for the callback and allocates memory for the data pages sent by the EX10xxA This initialization creates
5. to clear out this data to begin with an empty FIFO In that case this function should be looped for each page of data found remaining in the FIFO before a new scan is initiated StopServer This function is necessary to delete and close out the Critical Section Process Two unexposed functions are also used ServerCallback is a function which handles the synchronous callback executed whenever data is received by the host PC from the box Itis best to optimize this function as much as possible so thot it is ready to handle the next block of data it receives as soon as possible To accomplish this it must allocate memory for storing the streamed data and put it on the Server FIFO CopyDatapage handles the copying of the various data structures that the callback requires RELIABLE DATA FIRST TIME EVERY TIME technical LABVIEW API The state machine Labview model was used in this example to break up the various parts of the application re cn rans enn nats m Ac q u ire v M E F Use All Channels i f Boolean E d Tab Control r LJ LJ i Total Scans f gt a i Here is an overview of the states that are used 1 Init This default state initializes the card and resets all measurement parameters to the default state 2 Setup Channels This state generates the scan list as well as the EU Conversion and Filter frequency for those same channels Alternatively a user could have a
6. controls Total Scans Elapsed Time s 0 0 Device Setup Server Info Debug Info Hours Minutes Seconds Nano Seconds Data Device ID Jo fewn fo fo yo fo Je fo VISA resource name 16 00 00 fo J bo o io o TCPIPO 10 1 4 182 inst0 INSTR g Trigger Count Sample Rate 41000 4 J 100 Sa s Device ID J Use Specified Channels ry J123 zJ 0 f j e s Wait 4 lt 100 ms Scanlist i EU COnversion J Type K STOP CONCLUSION By using Asynchronous Streaming we overcome the limitations and inefficiencies associated with the instrument polling method of data collection Data is streamed to the host machine as soon as it is available and collected into a FIFO on the host PC The main User API then polls this data from the FIFO on the host PC in a much more efficient manner This allows the User to access the highest sampling rates available on the device without a risk of overflowing the EX10xxA memory It also represents about half as much network traffic as the polling method would require FIRST TIME EVERY TIME RELIABLE DATA
7. esent the instrument still needs to receive the request for data and send a response to indicate that no data is present It is important to note that LXI is not a strictly deterministic interface and polling at some regular rate does not guarantee that you will receive the same amount of data every time Figure 1 shows the flow of a typical FIFO polling setup VTI Instruments AMETEK ADVANCED MEASUREMENT TECHNOLOGY RELIABLE DATA FIRST TIME EVERY TIME technical DID YOU KNOW The EX1000A family implements IEEE 1588 precision time stamp protocol and the LXI wired trigger bus to precisely synchronize data and allow for distributed high channel count systems E 2 bey Jm ns O mes EX1016A 16 Channel Precision Thermocouple X ite ee Find out more about the EX10XXA Series Host PC EX1048A 48 Channel Precision Thermocouple Measurement Instrument TIME TIME The second method Asynchronous Data Streaming allows data to be sent as soon as it becomes available and the LXI interface allows without having to send queries Bere ae to the instrument after setup This overcomes the problems with the polling method It mission critical LXI DAQ system requires two threads to be running simultaneously A Streaming Server which collects pages of data sent to it asynchronously from the instrument and an API which sets up the instrument then polls for data from the Streaming Server thread and
8. subset list of channels with a variety of different settings depending on what they are trying to measure This state also sets the trigger count which is the number of triggers received after initiating measurement before the unit returns to the idle state Alternatively a Set Trigger Infinite Enabled VI could be used to enable continuous acquisition This would override any trigger count setting 3 Setup Triggering This state sets up the various aspects of triggering This simple example uses the default immediate arm setting and the trigger is some decimation of the timer internal EX10xxA oscillator This is a simple way to set a uniform scan rate on a box If multiple boxes are used some Vls for synchronous arming are recommended here RELIABLE DATA FIRST TIME EVERY TIME technical IDLE LAYER INIT LAYER Soare Am Wait for ARM Event ARM a e Dacemet ARR COUNT te Sota Trager Wait for irae TRIS Event Tr canem a TRIG LAYER Aa recast 5 Ho Yes DEVICE SC LAYER RUN SCAN LIST 4 Enable Streaming lThis state uses a VI built around the streaming server to begin waiting for data streamed from the acquisition system It then enables streaming on the box The device ID is an input to the Enable Streaming VI and can be any value However if multiple boxes are running you should use a unique value for each one so that you can identify where a given page of data is coming from RELIABLE DATA
9. technical Maximizing Data Throughput on the EX 0XXA series INTRODUCTION The EX10xxA is a family of high performance signal conditioning and data acquisition products which may include thermocouple and or voltage measurement channels on a single instrument It is an LXI instrument which means that all communication is through a common LAN Ethernet interface The family of products provides a high level of measurement integrity and channel independence which far exceeds alternative methods which generally involve separate elements for the terminal blocks signal conditioning and digitization There are two basic methods available to gather data from the EX10xxA besides using the embedded web page to collect data One method is simply to poll the memory of the instrument at some regular rate While this method is simple to implement there are several major problems that users may experience depending on test conditions One is that it is not possible to collect data fast enough by polling to prevent a memory overflow at higher sampling rates Such an overflow will result in a loss of data as soon as the 14 MB memory on the EX10xxA is filled This is unacceptable in many test applications especially over longer testing periods A second problem is that constant polling is inefficient for the processor as well as the LAN interface where the normal implementation is to poll as quickly as possible For example even when there is no data pr
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