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DAQ M Series NI USB-621 x User Manual Bus-Powered M Series USB Devices NI USB-621 x User Manual August 2006 371931A-01.
Support Worldwide Technical Support and Product Info rmation ni.com National Instruments Corporate Headquarters 11500 North Mopac Expressway Aust in, Texas 78759-3504 USA Tel: 512 683 0100 Worldwide O.
Important Information Warranty The USB-6210, USB -6211, USB-6215, an d USB-6218 devices are warrant ed against defects in mat erials and workmanshi p for a period of three years from the date of shipment, as evidenced by receipts or other document ation.
NATIONAL INSTRUMENTS PRODUCTS ARE IN CORPORATED IN A SYSTEM OR APPLICATION, INC LUDING, WITHOUT LIMITATION, THE APPROPRIATE DESIGN, PROC ESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLI CATION.
© National Instruments Corpor ation v NI USB-621x User Manual Contents About This Manual Conventions ............ .............. .............. .............. .............. .............. ............... .............. .... x iii Related Documentation .
Contents NI USB-621x User Manual vi ni.com Chapter 4 Analog Input Analog Input Circuitry ............. .............. .............. .............. .............. ............... .............. 4-1 Analog Input Range ............ .............. ......
Contents © National Instruments Corporat ion vii NI USB-621x User Manual AI Pause Trigger Signal .......... .............. .............. .............. .............. ................ 4-23 Using a Digital Source ......... .............. ............
Contents NI USB-621x User Manual viii ni.com Chapter 7 Analog Output Analog Output Circuitry ......................... .............. .............. .............. ................. ............ 7-1 AO Range ................... .............. ........
Contents © National Instruments Corpor ation ix NI USB-621x User Manual Pulse-Width Measurement ............ .............. .............. .............. ................. ....... 9-5 Single Pulse-Width Measurement .................... ..............
Contents NI USB-621x User Manual x ni.com Counter n A, Counter n B, and Counter n Z Signals .... .............. .............. ...... 9-28 Routing Signals to A, B, and Z Count er Inputs ............ .............. ...... 9-28 Counter n Up_Down Signal .
Contents © National Instruments Corpor ation xi NI USB-621x User Manual Chapter 11 Isolation and Di gital Isolators Digital Isolation ................. .............. .............. .............. ............... .............. .............. .......
Contents NI USB-621x User Manual xii ni.com Appendix B Troubleshooting Appendix C Technical Support and Professional Services Glossary Index Device Pinouts Figure A-1. USB-6210 Pinout ........ ..........................................................
© National Instruments Corporat ion xiii NI USB-621x User Manual About This Manual The NI 621x User Manual contains information abou t using the National Instrument s USB-621 x data acquisition (DA Q) devices with NI-D A Qmx 8.
About This Manual NI USB-621x User Manual xiv ni.com Related Documentation Each application software package an d driv er includes inform ation about writing applications for taking measur ements and controlling measurement devices. The follo wing references to documents assume you have NI-D A Q 8.
About This Manual © National Instruments Corpor ation xv NI USB-621x User Manual tools. Refer to the following locations on the Contents tab of the LabVIEW Help for info rmation about NI-DA Qmx: • .
About This Manual NI USB-621x User Manual xvi ni.com .NET Languages without NI Application Software The NI Measurement Studio Help contains function reference and measurement concepts for using th e Measurement Studio NI-D A Qmx .NET and V isual C++ class libraries.
© National Instruments Corporat ion 1-1 NI USB-621x User Manual 1 Getting Started Figure 1-1. USB-6210/6211.
Chapter 1 Getting Started NI USB-621x User Manual 1-2 ni.com Figure 1-2. USB-6215/6218 NI 621 x devices feature up to 32 analog input (AI) channels, up to two analog output (A O) channels, 8 lines of digital inp ut (DI), 8 lines of digital output (DO), and two counters.
Chapter 1 Getting Started © National Instruments Corporat ion 1-3 NI USB-621x User Manual Installing the Hardware The NI-D A Qmx for USB Devices Getting Started Guide contains non-software-specif ic information ab out ho w to install USB devices. Device Pinouts Refer to Appendix A , Device-Specific Information , for NI 621 x device pinouts.
© National Instruments Corporat ion 2-1 NI USB-621x User Manual 2 DAQ System Over view Figure 2-1 sho ws a typical D A Q sy stem, which i ncludes sensors, transducers, signal condition ing devi ces, cables that connect the v arious device s to the accessories, the M Serie s device, programming software, and PC.
Chapter 2 DAQ System Over view NI USB-621x User Manual 2-2 ni.com Figure 2-2. USB-621 x Block Diagram DAQ-STC2 The D A Q-STC2 implemen ts a high-performance digital engine for M Series data acquisition hardware.
Chapter 2 DAQ System Overview © National Instruments Corporat ion 2-3 NI USB-621x User Manual Factory-calibration constants are permanently stored in an onboard EEPR OM and cannot be mod ified. When you self-calibrate th e device, software stores new constants in a us er -modifiable section of the EEPR OM.
Chapter 2 DAQ System Over view NI USB-621x User Manual 2-4 ni.com Programming Devices in Software National Instruments measurement de vices are packaged with NI-D A Q dri ver software, an e xtensiv e .
© National Instruments Corporat ion 3-1 NI USB-621x User Manual 3 Connector Information The I/O Connector Si gnal Descriptions and +5 V Power sections contain information about NI 621 x connectors. Refer to Appen dix A, Device-Specific Information , for device I/O connector pinouts.
Chapter 3 Connector Information NI USB-621x User Manual 3-2 ni.com +5 V Power The +5 V terminals on the I/O connector can be use as either an output or an input.
Chapter 3 Connector Information © National Instruments Corporat ion 3-3 NI USB-621x User Manual +5 V Power as an Input If you hav e high current loads for the digital outp uts to dri ve, you can exceed the 50 mA internal limit b y connecting an external +5 V power source to the +5 V terminals.
© National Instruments Corporat ion 4-1 NI USB-621x User Manual 4 Analog Input Figure 4-1 shows the analog in put circuitry of NI 621 x devices. Figure 4-1. M Series Analog Input Circuitry Analog Input Circuitr y I/O Connector Y ou can connect analog i nput signals to the M Series device through the I/O connector .
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-2 ni.com Ground-Reference Settings The analog input ground-reference settings circu itry selects between differential, referenced s ingle-ended, and non-referenced single-ended input modes. Each AI channel can use a different mode.
Chapter 4 Analog Input © National Instruments Corporat ion 4-3 NI USB-621x User Manual calibration method im prov es absolute accuracy , bu t it increases the nominal resolution of input ranges by about 5% over what the formula sho wn abov e would indicate.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-4 ni.com The AI gr o und-r efer ence setting determines how you should connect y our AI signals to the NI 621 x de vice. Refer to Chapter 5, Connecting AI Signals on the USB-6210/ 6211 Devices , section for mor e informatio n.
Chapter 4 Analog Input © National Instruments Corporat ion 4-5 NI USB-621x User Manual pairs that form dif ferential input channels, refer to the I/O Connector Si gnal Descriptions section of Chapter 3, Connector Information .
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-6 ni.com Multichannel Scanning Considerations M Series de vices can scan multiple chan nels at high rate s and digitize the signals accurately . Howe v er , you should consider sev eral issues when designing your measurement system to ensure the high accuracy of your measurements.
Chapter 4 Analog Input © National Instruments Corporat ion 4-7 NI USB-621x User Manual If your source impedance is high, you can decrease the scan rate to allow the NI-PGIA mo re time to settle. A nother option is to use a voltage follo wer circuit external to your D A Q device to decrease the impedance seen b y the D A Q device.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-8 ni.com Y ou can connect channel 2 to AI GND (o r you can use the internal ground signal; refer to Internal Ch annels in the NI-DA Qmx Help ) . Set the input range of channel 2 to –200 mV to 200 m V to match channel 1.
Chapter 4 Analog Input © National Instruments Corporat ion 4-9 NI USB-621x User Manual Example 2 If the time relationship between channe ls is not critical, you can sample from the same c hannel multip le times and scan l ess frequently .
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-10 ni.com Buffered In a buf fered acquisition, data is mov ed from the D A Q device’ s onboard F I F O m e m o r y t o a P C bu f f e r u s i n g USB signal streams or progr ammed I/O before it is transferred to appli cation memory .
Chapter 4 Analog Input © National Instruments Corporat ion 4-11 NI U SB-621x User Manual A digital trigger can initiate these acti ons. All NI 621 x devices support digital triggering.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-12 ni.com Figure 4-4. Analog Input T iming Options M Series de vices use ai/SampleClock and ai/Conv ertClock to perform interval sampling. As Figure 4-5 sh ows, ai/SampleClock controls the sample period, which is determined by the following equation: 1/Sample Period = Sample Rate Figure 4-5.
Chapter 4 Analog Input © National Instruments Corporat ion 4-13 NI U SB-621x User Manual NI-D A Qmx chooses the default con vert rate to allo w for the maximum settling time between con versions. T yp ically , this rate is the sampling rate for the task multiplied by the number of channels in the task.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-14 ni.com Figure 4-7. Pretriggered Data Ac quisition Example If an ai/ReferenceT rigger pulse occurs before the specified number of pretrigger samples are acquired, the trigger pulse is ignored.
Chapter 4 Analog Input © National Instruments Corporat ion 4-15 NI U SB-621x User Manual Using an Inte rnal Source One of the follo wing internal signals can dri ve ai/SampleClock.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-16 ni.com to AI Con vert Clock Signal for more information abou t the timing requirements between ai/Con v e rtClock and ai/SampleClock. Figure 4-8 shows the relationship of ai/SampleClock to ai/StartTrigger .
Chapter 4 Analog Input © National Instruments Corporat ion 4-17 NI U SB-621x User Manual channel to allow for adequate settling time. This scheme enables the channels to approximate simultaneous samp ling and still allow for adequate settling time.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-18 ni.com Figure 4-9 shows the relationship of ai/SampleClock to ai/Con vertClock. Figure 4-9. ai/SampleCl ock and ai/ConvertCloc k Other Timing Requi.
Chapter 4 Analog Input © National Instruments Corporat ion 4-19 NI U SB-621x User Manual Figure 4-10. ai/SampleClo ck T oo Fast Figure 4-11. ai/ConvertClock T oo Fast Figure 4-12.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-20 ni.com Figure 4-13. ai/SampleClock and ai/C onvertClock Properly Matched It is also possible to use a single external signal to driv e both ai/SampleClock and ai/Con v ertClock at the same time. In this mode, each tick of the external clock will cause a con version on the ADC.
Chapter 4 Analog Input © National Instruments Corporat ion 4-21 NI U SB-621x User Manual AI Hold Complete Event Signal The AI Hold Complete Event (ai/HoldCompleteEvent) signal generates a pulse after each A/D con version begins. Y ou can route ai/HoldCompleteEvent out to any PFI <4.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-22 ni.com The device also uses ai/StartT rig ger to initiate pretriggered D A Q operations. In most p retriggered applications, a software trigger generates ai/StartT rigger .
Chapter 4 Analog Input © National Instruments Corporat ion 4-23 NI U SB-621x User Manual Using a Digital Source T o use ai/ReferenceT rigger with a di gital source, specify a source and an edge. The source can be the PFI <0..3> or PFI <8..11> signals.
Chapter 4 Analog Inpu t NI USB-621x User Manual 4-24 ni.com Getting Started with AI Applications in Software Y ou can use the M Series de vice in the following analog input applications.
© National Instruments Corporat ion 5-1 NI USB-621x User Manual 5 Connecting AI Signals on the USB-6210/6211 Devices T able 5-1 summarizes the recommen ded input configuration for both types of signal sources on NI 6210/6211 devices.
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-2 ni.com Table 5-1. Analog Input Configuration AI Ground-Refer ence Setting * Floating Signal Sources (Not Conne.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-3 NI USB-621x User Manual Connecting Floating Signal Sources What Are Floating Signal Sources? A floating signal sour ce is not connected to t he building ground system, but has an isolated ground-reference point.
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-4 ni.com In the single-ended modes, more elect rostatic and magnetic noise couples into the signal connections than in D IFF configurations. The coupling is the result of differences in the signal path.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-5 NI USB-621x User Manual Using Differential Connections for Floating Signal Sources It is important to connect the negati ve lead of a floating source to AI GND (either directly or th rough a bias resistor).
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-6 ni.com Figure 5-2. Differential Connections for Floating Signal Source s with Single Bias Resistor Y ou can fu.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-7 NI USB-621x User Manual Figure 5-3. Differential Connections for Floating Signal Sour ce s with Balanced Bias Resistors Both inputs of the NI-PGIA require a DC path to ground in order for the NI-PGIA to work.
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-8 ni.com inputs; be aware that there is some ga in error from loading down the source, as sho wn in Figure 5-4.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-9 NI USB-621x User Manual connection is shared with all channels rather than being cabled in a twisted pair with the AI+ signal. Using the D A Q Assistant, you can conf igure the channels for RSE or NRSE input modes.
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-10 ni.com The dif ference in ground potenti al be tween two instruments connected to the same building po wer system is typically between 1 and 100 mV , but the diff erence can be much higher if po we r distribution circuits are improperly connected.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-11 NI U SB-621x User Manual In the single-ended modes, more elect rostatic and magnetic noise couples into the signal connections than in D IFF configurations.
Chapter 5 Connecti ng AI Signals on the USB-6210/6211 Devices NI USB-621x User Manual 5-12 ni.com Using Differential Connections for Ground-Referenced Signal Sources Figure 5-7 shows ho w to connect a ground-referenced signal source to the USB-6210/6211 device configured in DIFF mode.
Chapter 5 Connecting AI Signal s on the USB-6210/6211 Devices © National Instruments Corporat ion 5-13 NI U SB-621x User Manual Using Non-Referenced Single-E nded (NRSE) Connections for Ground-Referenced Signal Sources Figure 5-8 shows ho w to connect ground-reference signal sources to th e USB-6210/6211 device in NRSE mode.
© National Instruments Corporat ion 6-1 NI USB-621x User Manual 6 Connecting AI Signals on the USB-6215/6218 Devices Y ou can connect the USB-6215/6218 directly to a v ariety of devices and other signal sources. Make sure the devices you connect to the USB-6215/6218 are compatib le with the input specifications of the module.
Chapter 6 Connecti ng AI Signals on the USB-6215/6218 Devices NI USB-621x User Manual 6-2 ni.com Refer to Figure 6-1 for an illustr a tion of a dif feren tial connection configuration.
Chapter 6 Connecting AI Signal s on the USB-6215/6218 Devices © National Instruments Corporat ion 6-3 NI USB-621x User Manual The dif ferential connection configuration allows the common-mode noise voltage, V cm , to be rejected duri ng the measurement of V 1 .
Chapter 6 Connecti ng AI Signals on the USB-6215/6218 Devices NI USB-621x User Manual 6-4 ni.com Non-Referenced Single-Ended (NRSE) Measurements T o reach a compromise between RSE and differential measurements, you can use an NRSE measurem ent configuration.
© National Instruments Corporat ion 7-1 NI USB-621x User Manual 7 Analog Output Many M Series de vices have analog output functionalit y . NI 621 x devices that support analog output have tw o A O chan nels controlled by a single clock and capable of wav eform generation.
Chapter 7 Analog Output NI USB-621x User Manual 7-2 ni.com D A Cs. It allows you to do wnload the points of a wav eform to your M Series device without host computer interaction. AO Sample Clock The A O Sample Clock signal reads a sample from the D A C FIFO and generates the A O voltage.
Chapter 7 Analog Output © National Instruments Corporat ion 7-3 NI USB-621x User Manual Hardware-timed generations ha ve se veral adv antages ov er software-timed acquisitions: • The time between samples can be m uch shorter . • The timing between samples can b e deterministic.
Chapter 7 Analog Output NI USB-621x User Manual 7-4 ni.com the buf fer at a f ast enough rate to k e ep up with the generation, the buffer will underflo w and cause an error .
Chapter 7 Analog Output © National Instruments Corporat ion 7-5 NI USB-621x User Manual Analog Output T iming Signals Figure 7-3 summarizes all of the timi ng options provided by the analog output timing eng ine. Figure 7-3. Analog Output T iming Options USB M Series devices feature the follo wing A O (waveform generation) timing signals.
Chapter 7 Analog Output NI USB-621x User Manual 7-6 ni.com The source also can be one of several internal signals on your D A Q device. Refer to Device Routing in MAX in the NI-D AQmx Help or the LabVIEW 8.
Chapter 7 Analog Output © National Instruments Corporat ion 7-7 NI USB-621x User Manual The source also can be one of sev eral other internal signals on your DA Q device. Refer to Device Routing in MAX in the NI-D A Qmx Help or the LabVIEW 8.x Help for mor e informatio n.
Chapter 7 Analog Output NI USB-621x User Manual 7-8 ni.com Figure 7-5 shows the relationship of ao/SampleClock to ao/StartTrigger . Figure 7-5. ao/SampleC lock an d ao/StartT rigger AO Sample Clock T imebase Signal The A O Sample Clo ck T imebase (ao/SampleClockTimebase) signal is di vided down to pro vide a source for ao/SampleClock.
Chapter 7 Analog Output © National Instruments Corporat ion 7-9 NI USB-621x User Manual Getting Started with AO Applications in Software Y ou can use an NI 62 1 x device in the following an alog ou tput appli cations.
© National Instruments Corporat ion 8-1 NI USB-621x User Manual 8 Digital I/O NI 621 x devices ha v e eight static digital inpu t lines, P0.<0..7>. These lines also can be used as PFI inputs. NI 621 x devices hav e eight static digital output l ines, P1.
Chapter 8 Digital I/O NI USB-621x User Manual 8-2 ni.com The voltage input and output lev els and the current driv e le vels of the DIO lines are listed in the sp ecifications of your device. Static DIO Y ou can use static DI and DO lines to monitor or cont rol digital signals.
Chapter 8 Digital I/O © National Instruments Corporat ion 8-3 NI USB-621x User Manual Connecting Digital I/O Signals The DI and DO signals, P0.<0..7> and P1.<0..7> are referenced to D GND. Digital input applications include receiving TTL signals and sensing external de vice states, such as the st ate of the switch sho wn in the figure.
Chapter 8 Digital I/O NI USB-621x User Manual 8-4 ni.com Getting Started with DIO Applications in Software Y ou can use the M Series de vice in the follo wing digital I/ O applications: • Static dig.
© National Instruments Corporat ion 9-1 NI USB-621x User Manual 9 Counters M Series devices hav e two general-purpose 32-b it counter/timers and one frequency generator , as sho wn in Figure 9-1. The general-purpose counter/timers can be used for many measurement and pulse generation applications.
Chapter 9 Counters NI USB-621x User Manual 9-2 ni.com The counters have se ven input signals, although in most applications only a fe w inputs are used. For information about connecting counter signals, refer to the Default Counter/Timer Pinouts section.
Chapter 9 Counters © National Instruments Corporat ion 9-3 NI USB-621x User Manual Figure 9-3. Single Point (On-Demand) Edge Counting with Pause T rigger Buffered (Sample Cl ock) Edge Counting W ith b uffered edge counting (edge counting using a sample clock), the counter counts the nu mber of edges on the Source input after the counter is armed.
Chapter 9 Counters NI USB-621x User Manual 9-4 ni.com Non-Cumulative Buffe red Edge Counting Non-cumulativ e edge counting is similar to buf fered (sample clock) edge counting. Ho wev er , the counter resets after each acti v e edge of the Sample Clock.
Chapter 9 Counters © National Instruments Corporat ion 9-5 NI USB-621x User Manual Pulse-Width Measurement In pulse-width measuremen ts, the counter measures the width of a pulse on its Gate input signal. Y ou can configur e the counter to measure the width of high pulses or low pulses on the Gate signal.
Chapter 9 Counters NI USB-621x User Manual 9-6 ni.com The counter counts the number of edges o n the Source input whi le the Gate input remains acti ve. On each trailing ed ge of the Gate signal, the counter stores the count in a hardware sa ve re gister .
Chapter 9 Counters © National Instruments Corporat ion 9-7 NI USB-621x User Manual Single Period Measurement W ith single period measurement, the counter counts the number of rising (or falling) edges on the Source inp ut occurring between two active edges of the Gate input.
Chapter 9 Counters NI USB-621x User Manual 9-8 ni.com Figure 9-9. Buffered Period Measu rement Note that if you are using an external signal as the Source, at least one Source pulse should occu r between each acti ve edge of the Gate signal. This condition ensures that correct v alues are returned b y th e counter .
Chapter 9 Counters © National Instruments Corporat ion 9-9 NI USB-621x User Manual Semi-Period Measurement In semi-period measuremen ts, the counter measures a semi-peri od on its Gate input signal after the counter is arme d. A semi-period is the time between any tw o consecuti ve e dges on the Gate input.
Chapter 9 Counters NI USB-621x User Manual 9-10 ni.com This condition ensures that correct v alues are returned b y th e counter . If this condition is not met, the count er returns a zero. Refer to the Duplicate Count Prevention section for more information.
Chapter 9 Counters © National Instruments Corporat ion 9-11 NI U SB-621x User Manual Method 1b—Measure Low Frequency with One Counter (Averaged) In this method, you measure sev eral periods of your signal using a known timebase. This method is good for low to medium freq uency signals.
Chapter 9 Counters NI USB-621x User Manual 9-12 ni.com generate the pulse externally and connect it to a PFI terminal. Y ou only need to use one counter if you generate the pulse externally . Route the signal to measure (F1) to the Source of the co unter .
Chapter 9 Counters © National Instruments Corporat ion 9-13 NI U SB-621x User Manual Figure 9-14. Method 3 Then route the Counter 0 Internal Output signal to the Gate input of Counter 1. Y ou can route a signal of kno wn freq uenc y (F2) to the Counte r 1 Source input.
Chapter 9 Counters NI USB-621x User Manual 9-14 ni.com 80 MHz T imebase. Y our measurement may return 1600 ± 1 cycles depending on the phase of the signal with respect to the timebase. As your frequency becomes larger , this error of ±1 cycle becomes more significant; T ab le 9-2 illustrates this point.
Chapter 9 Counters © National Instruments Corporat ion 9-15 NI U SB-621x User Manual T able 9-3 summarizes some of the di f ferences in methods of measuring frequency . For information about connecting counter signals, refer to the Default Counter/Timer Pinouts section.
Chapter 9 Counters NI USB-621x User Manual 9-16 ni.com Figure 9-15 shows a quadrature c ycle and the resulting increments and decrements for X1 encoding. When channel A leads channel B, the increment occurs on the rising edge of channel A. When channel B leads channel A, the decrement occurs on the f alling edge of channel A.
Chapter 9 Counters © National Instruments Corporat ion 9-17 NI U SB-621x User Manual Channel Z Behavior Some quadrature encoders hav e a thir d channel, channel Z, which is also referred to as the index channe l. A high lev el on channel Z causes the counter to b e reloaded w ith a specifi ed value in a specif ied phase of the quadrature cycle.
Chapter 9 Counters NI USB-621x User Manual 9-18 ni.com The counter increments on each rising edge of channel A. The counter decrements on each rising edge of channel B, as shown in Figure 9-19. Figure 9-19. Measurements Using T wo Pulse Encoders For information about connecting counter signals, refer to the Default Counter/Timer Pinouts section.
Chapter 9 Counters © National Instruments Corporat ion 9-19 NI U SB-621x User Manual Figure 9-20 shows an example of a si ngle two-signal edge-separation measurement.
Chapter 9 Counters NI USB-621x User Manual 9-20 ni.com Counter Output Applications Simple Pulse Generation Single Pulse Generation The counter can output a single pulse. The pulse appears on the Counter n Internal Output sign al of the counter . Y ou can specify a delay from when the counter is armed to the beginning of the pulse.
Chapter 9 Counters © National Instruments Corporat ion 9-21 NI U SB-621x User Manual Figure 9-23 shows a generation of a pulse with a pulse del ay of four and a pulse width of three (using the rising edge of Source).
Chapter 9 Counters NI USB-621x User Manual 9-22 ni.com Pulse T rain Generation Continuous Pulse T rain Generation This function generates a train of pul ses with programmab le frequency and duty cycle. The pulses appear on the Counter n Internal Outp ut signal of the counter .
Chapter 9 Counters © National Instruments Corporat ion 9-23 NI U SB-621x User Manual Frequency Generation Y ou can generate a frequency b y using a counter in pulse train generation mode or by using the frequency generator circuit. Using the Frequency Generator The frequency generator can output a square wav e at many dif ferent frequencies.
Chapter 9 Counters NI USB-621x User Manual 9-24 ni.com Frequency Output can be routed out to any PFI <4..7> or PFI <12..15> terminal. All PFI terminals are set to high-impedance at startup. The FREQ OUT signal also can be routed to DO Sample Clock and DI Sample Clock.
Chapter 9 Counters © National Instruments Corporat ion 9-25 NI U SB-621x User Manual frequency of the system. Figure 9-28 sho ws an e xample of pulse generation for ETS; the delay from the trigger to the pulse increases after each subsequent Gate activ e edge.
Chapter 9 Counters NI USB-621x User Manual 9-26 ni.com Counter n Source Signal The selected edge of the Counter n Source signal increments and decrements the counter v alue dependin g on the application the counter is performing. T able 9-4 lists how this terminal is used in various applications.
Chapter 9 Counters © National Instruments Corporat ion 9-27 NI U SB-621x User Manual Counter n Gate Signal The Counter n Gate signal can perform many dif ferent operations depending on the application includi ng starting and stopping the counter, and saving the counter contents.
Chapter 9 Counters NI USB-621x User Manual 9-28 ni.com Output, Counter 0 Gate, Counter 0 Source, or Co unter 1 Gate can be routed to Counter 1 Aux. Some of these options may not be av ailable in some driv er software. Counter n A, Counter n B, and Counter n Z Signals Counter n B can control the direction of counting in edge counting applications.
Chapter 9 Counters © National Instruments Corporat ion 9-29 NI U SB-621x User Manual Some of these options may not be av ailable in some driv er software. Counter n Internal Output and Counter n TC Signals Counter n TC is an internal signal that asserts when the counter value is 0.
Chapter 9 Counters NI USB-621x User Manual 9-30 ni.com CTR 0 B 2 (PFI 1) CTR 1 SRC 4 (PFI 3) CTR 1 GA TE 3 (PFI 2) CTR 1 A UX 4 (PFI 3) CTR 1 OUT 7 (PFI 5) CTR 1 A 4 (PFI 3) CTR 1 Z 2 (PFI 1) CTR 1 B 3 (PFI 2) FREQ OUT 8 (PFI 6) Table 9-6.
Chapter 9 Counters © National Instruments Corporat ion 9-31 NI U SB-621x User Manual Y ou can use these defaults or select other sources and destinations for the counter/timer si gnals in NI-DA Qmx. Refer to Con necting Counter Signals in the NI-D A Qmx Help or the LabVIEW 8.
Chapter 9 Counters NI USB-621x User Manual 9-32 ni.com the signal goes high or vice versa. F or continuous pulse generati ons, the counter stops generating pulses while the external trigger signal is low and resumes when the signal goes high or vice versa.
Chapter 9 Counters © National Instruments Corporat ion 9-33 NI U SB-621x User Manual Cascading Counters Y ou can internally route th e Counter n Internal Output and Counter n TC signals of each counter to Gate input s of the other counter . By cascading two counters together , you can eff ecti vely create a 64-bit counter .
Chapter 9 Counters NI USB-621x User Manual 9-34 ni.com The filter setting for each input can be conf igured independently . On power up, the filters are dis abled. Figure 9- 30 shows an e xample of a low to high transition on an input that has its filter set to 125 ns (N = 5).
Chapter 9 Counters © National Instruments Corporat ion 9-35 NI U SB-621x User Manual Figure 9-31. Pres caling Prescaling is intended to be used for frequency measurement where the measurement is made on a continu ous, repetiti ve signal.
Chapter 9 Counters NI USB-621x User Manual 9-36 ni.com Example Application That W orks Correctly (No Duplicate Counting) Figure 9-32 shows an e xternal buf fered signal as the period measurement Source. Figure 9-32. Duplicate Count Pr evention Example On the first rising edge of Gate, the current count of 7 is stored.
Chapter 9 Counters © National Instruments Corporat ion 9-37 NI U SB-621x User Manual Example Application That W orks Incorrectly (Duplicate Counting) In Figure 9-33, after the first rising edge of Gate, no Source pulses occur , so the counter does not write th e correct data to the buf fer .
Chapter 9 Counters NI USB-621x User Manual 9-38 ni.com Even if the Source pulses are long, the counter increments only once for each Source pulse. Normally , the coun ter value and Counter n Internal Output signals change synchronously to the Source signal.
© National Instruments Corporat ion 10-1 NI USB-621x User Manual 10 PFI NI 621 x devices ha ve up to eight input and eight output Programmab le Function Interface (PFI) signals, which also can be used as static digital input or static digital ou tput signals.
Chapter 10 PFI NI USB-621x User Manual 10-2 ni.com Figure 10-2. NI 621 x PFI Output Cir cuitry When a terminal is used as a t iming input or output signal , it is called PFI x . When a terminal is used as a static digital input or output , it is called P0.
Chapter 10 PFI © National Instruments Corporat ion 10-3 NI USB-621x User Manual Most functions allow you to configure the polarity of PFI inputs and whether the input is edge or lev el sensitiv e. Exporting T iming Output Signals Using PFI T erminals Y ou can route any of the following timing signals to any PFI output terminal.
Chapter 10 PFI NI USB-621x User Manual 10-4 ni.com Figure 10-3. PFI Input Signals Connections PFI Filters Y ou can enable a programmable debouncing filter on each PFI signal. When the f ilters are enabled, your de vice samples the input on each ris ing edge of a filter clock.
Chapter 10 PFI © National Instruments Corporat ion 10-5 NI USB-621x User Manual The filter setting for each input can be conf igured independently . On power up, the filters are dis abled. Figure 10-4 shows an e xample of a lo w to high transition on an input that has its filter set to 125 ns (N = 5).
Chapter 10 PFI NI USB-621x User Manual 10-6 ni.com I/O Protection Each DI, DO, and PFI signal is protected against o verv oltage, undervoltage, and o vercurrent condition s as well as ES D e v ents. Ho wev er , you should avoid these fault conditions by following these guidelines.
© National Instruments Corporat ion 11-1 NI USB-621x User Manual 11 Isolation and Digital Isolators USB-6215/6218 devices are isolated data acquisition devices.
Chapter 11 Isolati on and Digital Isolators NI USB-621x User Manual 11-2 ni.com The isolated ground is an input to th e USB-6215/6218 device. The user must connect this g round to the grou nd of system being m easured or controlled.
Chapter 11 Isolation and Digi tal Isolators © National Instruments Corporat ion 11-3 NI USB-621x User Manual Switching voltages through the transformer cause charging and discharging of the parasitic.
Chapter 11 Isolati on and Digital Isolators NI USB-621x User Manual 11-4 ni.com Add an AC return path from the device isolated ground t o earth ground.
© National Instruments Corporat ion 12-1 NI USB-621x User Manual 12 Digital Routing and Clock Generation The digital routing circuitry has the following main functions. • Manages the flow of data be tween the bus interf ace and the acquisition/generat ion sub-systems (analog inpu t, analog output, digital I/O, and the counters).
Chapter 12 Digital Ro uting and Clock Generation NI USB-621x User Manual 12-2 ni.com 100 kHz T imebase The 100 kHz T imebase can be used to generate many of the AI and A O timing signals. The 100 kHz Timebase al so can be used as the Source input to the 32-bit general-pur pose counter/timers.
© National Instruments Corporat ion 13-1 NI USB-621x User Manual 13 Bus Interface The b us interface circuitry of M Serie s de vices ef f iciently mov es data between host memory and the measurement and acquisition circuits. All M Series de vices are jumperless fo r complete plug-and-play operation.
Chapter 13 Bus Interface NI USB-621x User Manual 13-2 ni.com Programmed I/O Programmed I/O is a data transfer m echanism where the user’ s program is responsible for transferring data. Each read or write call in the program initiates the transfer of data.
© National Instruments Corporat ion 14-1 NI USB-621x User Manual 14 T riggering A trigger is a signal that caus es an action, such as starting or stopping the acquisition of data. When you configure a trigger , you must decide how you want to produce the trigger and the action yo u want the trigger to cause.
Chapter 14 T riggering NI USB-621x User Manual 14-2 ni.com Y ou also can program your D A Q device to perform an action in response t o a trigger from a digital source.
© National Instruments Corporat ion A-1 NI USB-621x User Manual A Device-Specific Information This appendix contains device pinout s, specif ications, cable and accessory choices, and other information for the following USB M Series devices.
Appendix A Device-Speci fic Information NI USB-621x User Manual A-2 ni.com Figure A-1. USB-6210 Pinout Table A-1. Default NI-DAQmx Counter/T imer Pins Counter/Timer Signal Default T erminal Number (Na.
Appendix A Device-Specific Information © National Instruments Corporat ion A-3 NI USB-621x User Manual Note For more information abou t default NI-D A Qmx coun ter inputs, refer to Connecting Counter Signals in the NI-DA Qmx Help or the LabVIEW 8.x Help .
Appendix A Device-Speci fic Information NI USB-621x User Manual A-4 ni.com USB-6211/6215 USB-6211/6215 Pinout Figure A-2 shows the pinout of the NI 6211/6215. For a detailed description of each signal, refer to the I/O Connector Signal Descriptions section of Chapter 3, Connector Information .
Appendix A Device-Specific Information © National Instruments Corporat ion A-5 NI USB-621x User Manual Figure A-2. USB-6211/6215 Pinout Table A-3. Default NI-DAQmx Counter/T imer Pins Counter/Timer S.
Appendix A Device-Speci fic Information NI USB-621x User Manual A-6 ni.com Note For more information abou t default NI-D A Qmx coun ter inputs, refer to Connecting Counter Signals in the NI-DA Qmx Help or the LabVIEW 8.
Appendix A Device-Specific Information © National Instruments Corporat ion A-7 NI USB-621x User Manual USB 6218 USB 6218 Pinout Figure A-3 shows the pinout of the NI 6218. For a detailed description of each signal, refer to the I/O Connector Signal Descriptions section of Chapter 3, Connector Information .
Appendix A Device-Speci fic Information NI USB-621x User Manual A-8 ni.com Figure A-3. USB 6218 Pinout Table A-5. Default NI-DAQmx Counter/T imer Pins Counter/Timer Signal Default T erminal Number ( N.
Appendix A Device-Specific Information © National Instruments Corporat ion A-9 NI USB-621x User Manual Note For more information abou t default NI-D A Qmx coun ter inputs, refer to Connecting Counter Signals in the NI-DA Qmx Help or the LabVIEW 8.x Help .
Appendix A Device-Speci fic Information NI USB-621x User Manual A-10 ni.com Single-blink O perating normally . Connected to USB Hi-Speed port. Refer to the NI 621x Specifications for more informatio n. Double-blink Connected to USB full speed port. Device performance might be affected.
© National Instruments Corporat ion B-1 NI USB-621x User Manual B T roubleshooting This section contains common questi ons about M Series devices. If your questions are not answered here, refer to the Natio nal Instruments KnowledgeBase at ni.com/kb .
Appendix B T roubleshootin g NI USB-621x User Manual B-2 ni.com are various methods of achie ving this reference while maintai ning a high common-mode rejection ratio (CMRR ). These methods are outlined in Chapter 5, Connecting AI Signals on the USB-6210/6211 Devices and Chapter 6, Connecting AI Signals on the USB-6215/6218 Devices .
Appendix B T roubleshootin g © National Instruments Corporat ion B-3 NI USB-621x User Manual Analog Output I am seeing glitches on the outp ut signal. Ho w can I minimize it? When you use a D A C to generate a wa veform, you may observe glitches on the output signal.
© National Instruments Corporat ion C-1 NI USB-621x User Manual C T echnical Support and Professional Ser vices Visit the following sections of the National Instruments Web site at ni.com for technical support an d professional services: • Support —Online technical support resources at ni.
Appendix C T echnical Support and Professional Ser vices NI USB-621x User Manual C-2 ni.com • Calibration Certificate —If your product supports calibration, you can obtain t he calibration certificate for your product at ni.com/ calibration . If you searched ni.
© National Instruments Corporat ion G-1 NI USB-621x User Manual Glossar y Numbers/Symbols % Percent. + Positiv e of, or plus. – Neg ativ e of, or minus. ± Plus or minus. < Less than. > Greater than. ≤ Less than or equal to. ≥ Greater than or equal to.
Glossary NI USB-621x User Manual G-2 ni.co m AI 1. Analog input. 2. Anal og input channel signal. AI GND Analog input ground signal. AI SENSE Analog input sense signal.
Glossary © National Instruments Corporat ion G-3 NI USB-621x User Manual ASIC Application-specific integrated circuit—A proprietary semiconduct or component designed and manufactur ed to perform a set of specific functions for a specif ic customer .
Glossary NI USB-621x User Manual G-4 ni.co m cascading Process of extending the count ing ra nge of a counter chip b y connecting to the next higher counter . CE European emissions control standard. channel Pin or wire lead to which you apply or from which you read the analog or digital si gnal.
Glossary © National Instruments Corporat ion G-5 NI USB-621x User Manual counter/timer A circuit that counts external pulses or clock pulses (timing).
Glossary NI USB-621x User Manual G-6 ni.co m data transfer A technique for moving digital data from one system to another . Options for data transfer are DMA, interrupt, and programmed I/O. For programmed I/O transfers, the CPU in the PC reads data from the D A Q device whenev er the CPU recei ves a soft ware signal to ac quire a single data point.
Glossary © National Instruments Corporat ion G-7 NI USB-621x User Manual digital trigger A TTL level signal ha ving two discrete lev els—A high and a low le v el.
Glossary NI USB-621x User Manual G-8 ni.co m F FIFO First- In-First-Out mem ory buf fer—A data buf fering technique that functions like a shift register where the oldest values (f irst in) come out first.
Glossary © National Instruments Corporat ion G-9 NI USB-621x User Manual function 1. A built-in ex ecution element, co mparable to an operator , function, or statement in a con v entional language. 2. A set of so ftware instructions executed by a single line of code that may hav e input and/or output parameters and returns a value when ex ecuted.
Glossary NI USB-621x User Manual G-10 ni.com impedance 1. The electrical characteristic of a circuit expressed in ohms and/or capacitance/inductance. 2. Resistance. in. Inch or inches. instrument driv er A set of high-lev el software functions that controls a specif ic GPIB, VXI, or RS232 programmable instrument or a specific plug-in D A Q device.
Glossary © National Instruments Corporat ion G-11 NI U SB-621x User Manual L LabVIEW A graphical programming language. LED Light-Emitting Di ode—A semiconductor l ight source. lowpass filter A filter that passes signals below a cutof f frequency while blocking signals abov e that frequency .
Glossary NI USB-621x User Manual G-12 ni.com monotonicity A characteristic of a DA C in whic h the analog output always increases as the values of the digital code input to it increase. multichannel Pertaining to a radio-co mmunication system t hat operates on more than one channel at the same time.
Glossary © National Instruments Corporat ion G-13 NI U SB-621x User Manual NRSE Non-Referenced Single-Ended mo de—All measurements are made with respect to a common (NRSE) measur ement system reference, b ut the voltage at this reference can v ary w ith respect to the measurement system ground.
Glossary NI USB-621x User Manual G-14 ni.com Plug and Play devices Devices that do not require DIP switches or jumpers to configure resources on the devices. Also called switchless de vices port. 1. A com munications connection on a computer or a remote controller; 2.
Glossary © National Instruments Corporat ion G-15 NI U SB-621x User Manual Q quadrature encoder An encoding technique for a rotating device where two tracks of information are placed on the de vice, wi th the signals on the tracks of fset by 90° from each other .
Glossary NI USB-621x User Manual G-16 ni.com scan One or more analog or digital input samples. T ypically , the number of input samples in a scan is equal to the number of channels in the input group . For example, one pulse from the scan cl ock produces one scan which acquires one new sample from e very analog input channel in the group.
Glossary © National Instruments Corporat ion G-17 NI U SB-621x User Manual single-ended output A circu it whose output signal is present between one output terminal and ground.
Glossary NI USB-621x User Manual G-18 ni.com T imebase The reference signals for controlling the basic accuracy of time or frequency-based measurements. For inst ruments, timebase refe rs to the accuracy of the internal clock. t out Output delay time.
Glossary © National Instruments Corporat ion G-19 NI U SB-621x User Manual V g Ground loop voltage. V IH V olts, inp ut high. V IL V olts, inp ut lo w . V in V olts in . V m Measured voltage. V OH V olts, output hi gh. V OL V olts, output low . V out V olts out.
© National Instruments Corporat ion I-1 NI U SB-621x User Manual Index Symbols +5 V po wer input, 3-3 +5 V po wer output, 3-2 +5 V po wer source, 3-2 .
Index NI USB-621x User Manual I-2 ni.com AI Sample Clock Timebase, 4-16 AI Start T rigger, 4-21 analog output, 7-1 circuitry, 7-1 connecting signals, 7-4 data generation methods, 7-2 fundamentals, 7-1.
Index © National Instruments Corporat ion I-3 NI U SB-621x User Manual ground-referenced signal sources, 5-9 PFI input signals, 10-3 connections for floating si gnal sources, 5-9 single-ended for flo.
Index NI USB-621x User Manual I-4 ni.com Declaration of Conformity (NI resources), C-1 default counter terminals, 9-29 NI-D A Qmx co unter/timer pins, 9-29 pins, 9-29 device information, A-1 pinouts, .
Index © National Instruments Corporat ion I-5 NI U SB-621x User Manual F features, counter, 9-32 field wiring considerations, 4-11 fil t e rs counter, 9-33 PFI, 10-4 floating signal sources connectin.
Index NI USB-621x User Manual I-6 ni.com instrumentation amplifier, 4-2 interface, b us, 13-1 isolated D A Q de vices, 11-1 benefits, 11-2 common-mode noise, 11 -2 isolators, 11-1 K Kno wledgeBase, C-.
Index © National Instruments Corporat ion I-7 NI U SB-621x User Manual when to use with groun d-referenced signal sources, 5-10 NRSE connections using with floating signal sources, 5-8 using with gro.
Index NI USB-621x User Manual I-8 ni.com when to use with groun d-referenced signal sources, 5-11 related documentation, xiv retriggerable single pu lse generation, 9-21 routing digital, 12-1 RSE conf.
Index © National Instruments Corporat ion I-9 NI U SB-621x User Manual software configuring AI ground-reference settings, 4-5 programming devices, 2-4 software (NI resources), C-1 software-timed acqu.
Index NI USB-621x User Manual I-10 ni.com USB-6218, A-7 analog input signals, 6-1 LED, A-9 pinout, A-7 specifications, A-9 using lo w impedance sources, 4-6 using PFI termin als as static digital I/Os.
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