National Instruments Data Acquisition Device NI USB-621x User Manual - Important Information

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Manual is about: DAQ M Series Bus-Powered M Series USB Devices

Summary of Data Acquisition Device NI USB-621x

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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.

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    Support worldwide technical support and product information ni.Com national instruments corporate headquarters 11500 north mopac expressway austin, texas 78759-3504 usa tel: 512 683 0100 worldwide offices australia 1800 300 800, austria 43 0 662 45 79 90 0, belgium 32 0 2 757 00 20, brazil 55 11 326...

  • Page 3: Important Information

    Important information warranty the usb-6210, usb-6211, usb-6215, and usb-6218 devices are warranted against defects in materials and workmanship for a period of three years from the date of shipment, as evidenced by receipts or other documentation. National instruments will, at its option, repair or...

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    National instruments products are incorporated in a system or application, including, without limitation, the appropriate design, process and safety level of such system or application..

  • Page 5: Contents

    © national instruments corporation v ni usb-621x user manual contents about this manual conventions ...................................................................................................................Xiii related documentation..............................................................

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    Contents ni usb-621x user manual vi ni.Com chapter 4 analog input analog input circuitry .................................................................................................. 4-1 analog input range.............................................................................................

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    Contents © national instruments corporation vii ni usb-621x user manual ai pause trigger signal ..................................................................................4-23 using a digital source ......................................................................4-23 getting started wit...

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    Contents ni usb-621x user manual viii ni.Com chapter 7 analog output analog output circuitry................................................................................................ 7-1 ao range .....................................................................................................

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    Contents © national instruments corporation ix ni usb-621x user manual pulse-width measurement ..............................................................................9-5 single pulse-width measurement.....................................................9-5 buffered pulse-width measurement.......

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    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 counter inputs................................ 9-28 counter n up_down signal ...........................................................

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    Contents © national instruments corporation xi ni usb-621x user manual chapter 11 isolation and digital isolators digital isolation .............................................................................................................11-2 benefits of an isolated daq device ......................

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    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 .................................................................................. A-2 figure a-2. Usb-6211/6215 pin...

  • Page 13: About This Manual

    © national instruments corporation xiii ni usb-621x user manual about this manual the ni 621x user manual contains information about using the national instruments usb-621 x data acquisition (daq) devices with ni-daqmx 8.3 and later. Ni 621 x devices feature up to 32 analog input (ai) channels, up t...

  • Page 14: Related Documentation

    About this manual ni usb-621x user manual xiv ni.Com related documentation each application software package and driver includes information about writing applications for taking measurements and controlling measurement devices. The following references to documents assume you have ni-daq 8.3 or lat...

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    About this manual © national instruments corporation xv ni usb-621x user manual tools. Refer to the following locations on the contents tab of the labview help for information about ni-daqmx: • getting started»getting started with daq —includes overview information and a tutorial to learn how to tak...

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    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 the measurement studio ni-daqmx .Net and visual c++ class libraries. This help collection is integrated in...

  • Page 17: Getting Started

    © national instruments corporation 1-1 ni usb-621x user manual 1 getting started figure 1-1. Usb-6210/6211.

  • Page 18: Installing Ni-Daqmx

    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 (ao) channels, 8 lines of digital input (di), 8 lines of digital output (do), and two counters. If you have not already install...

  • Page 19: Installing The Hardware

    Chapter 1 getting started © national instruments corporation 1-3 ni usb-621x user manual installing the hardware the ni-daqmx for usb devices getting started guide contains non-software-specific information about how to install usb devices. Device pinouts refer to appendix a, device-specific informa...

  • Page 20: Daq System Overview

    © national instruments corporation 2-1 ni usb-621x user manual 2 daq system overview figure 2-1 shows a typical daq system, which includes sensors, transducers, signal conditioning devices, cables that connect the various devices to the accessories, the m series device, programming software, and pc....

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    Chapter 2 daq system overview ni usb-621x user manual 2-2 ni.Com figure 2-2. Usb-621 x block diagram daq-stc2 the daq-stc2 implements a high-performance digital engine for m series data acquisition hardware. Some key features of this engine include the following: • flexible ai and ao sample and conv...

  • Page 22: Signal Conditioning

    Chapter 2 daq system overview © national instruments corporation 2-3 ni usb-621x user manual factory-calibration constants are permanently stored in an onboard eeprom and cannot be modified. When you self-calibrate the device, software stores new constants in a user-modifiable section of the eeprom....

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    Chapter 2 daq system overview ni usb-621x user manual 2-4 ni.Com programming devices in software national instruments measurement devices are packaged with ni-daq driver software, an extensive library of functions and vis you can call from your application software, such as labview or labwindows/cvi...

  • Page 24: Connector Information

    © national instruments corporation 3-1 ni usb-621x user manual 3 connector information the i/o connector signal descriptions and +5 v power sections contain information about ni 621 x connectors. Refer to appendix a, device-specific information , for device i/o connector pinouts. I/o connector signa...

  • Page 25: +5 V Power

    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. Both terminals are internally connected on the usb-621 x . +5 v power as an output because the usb-621 x devices are bus powered, there is...

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    Chapter 3 connector information © national instruments corporation 3-3 ni usb-621x user manual +5 v power as an input if you have high current loads for the digital outputs to drive, you can exceed the 50 ma internal limit by connecting an external +5 v power source to the +5 v terminals. These term...

  • Page 27: Analog Input

    © national instruments corporation 4-1 ni usb-621x user manual 4 analog input figure 4-1 shows the analog input circuitry of ni 621 x devices. Figure 4-1. M series analog input circuitry analog input circuitry i/o connector you can connect analog input signals to the m series device through the i/o ...

  • Page 28: Analog Input Range

    Chapter 4 analog input ni usb-621x user manual 4-2 ni.Com ground-reference settings the analog input ground-reference settings circuitry selects between differential, referenced single-ended, and non-referenced single-ended input modes. Each ai channel can use a different mode. Instrumentation ampli...

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    Chapter 4 analog input © national instruments corporation 4-3 ni usb-621x user manual calibration method improves absolute accuracy, but it increases the nominal resolution of input ranges by about 5% over what the formula shown above would indicate. Choose an input range that matches the expected i...

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    Chapter 4 analog input ni usb-621x user manual 4-4 ni.Com the ai ground-reference setting determines how you should connect your ai signals to the ni 621 x device. Refer to chapter 5, connecting ai signals on the usb-6210/6211 devices , section for more information. Ground-reference settings are pro...

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    Chapter 4 analog input © national instruments corporation 4-5 ni usb-621x user manual pairs that form differential input channels, refer to the i/o connector signal descriptions section of chapter 3, connector information . Caution the maximum input voltages rating of ai signals with respect to ai g...

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    Chapter 4 analog input ni usb-621x user manual 4-6 ni.Com multichannel scanning considerations m series devices can scan multiple channels at high rates and digitize the signals accurately. However, you should consider several issues when designing your measurement system to ensure the high accuracy...

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    Chapter 4 analog input © national instruments corporation 4-7 ni usb-621x user manual if your source impedance is high, you can decrease the scan rate to allow the ni-pgia more time to settle. Another option is to use a voltage follower circuit external to your daq device to decrease the impedance s...

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    Chapter 4 analog input ni usb-621x user manual 4-8 ni.Com you can connect channel 2 to ai gnd (or you can use the internal ground signal; refer to internal channels in the ni-daqmx help ). Set the input range of channel 2 to –200 mv to 200 mv to match channel 1. Then scan channels in the order: 0, 2...

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    Chapter 4 analog input © national instruments corporation 4-9 ni usb-621x user manual example 2 if the time relationship between channels is not critical, you can sample from the same channel multiple times and scan less frequently. For example, suppose an application requires averaging 100 points f...

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    Chapter 4 analog input ni usb-621x user manual 4-10 ni.Com buffered in a buffered acquisition, data is moved from the daq device’s onboard fifo memory to a pc buffer using usb signal streams or programmed i/o before it is transferred to application memory. Buffered acquisitions typically allow for m...

  • Page 37: Field Wiring Considerations

    Chapter 4 analog input © national instruments corporation 4-11 ni usb-621x user manual a digital trigger can initiate these actions. All ni 621 x devices support digital triggering. Ni 621 x devices do not support analog triggering. Field wiring considerations environmental noise can seriously affec...

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    Chapter 4 analog input ni usb-621x user manual 4-12 ni.Com figure 4-4. Analog input timing options m series devices use ai/sampleclock and ai/convertclock to perform interval sampling. As figure 4-5 shows, ai/sampleclock controls the sample period, which is determined by the following equation: 1/sa...

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    Chapter 4 analog input © national instruments corporation 4-13 ni usb-621x user manual ni-daqmx chooses the default convert rate to allow for the maximum settling time between conversions. Typically, this rate is the sampling rate for the task multiplied by the number of channels in the task. Note t...

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    Chapter 4 analog input ni usb-621x user manual 4-14 ni.Com figure 4-7. Pretriggered data acquisition example if an ai/referencetrigger pulse occurs before the specified number of pretrigger samples are acquired, the trigger pulse is ignored. Otherwise, when the ai/referencetrigger pulse occurs, the ...

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    Chapter 4 analog input © national instruments corporation 4-15 ni usb-621x user manual using an internal source one of the following internal signals can drive ai/sampleclock. • counter n internal output • ai sample clock timebase (divided down) • a software pulse a programmable internal counter div...

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    Chapter 4 analog input ni usb-621x user manual 4-16 ni.Com to ai convert clock signal for more information about the timing requirements between ai/convertclock and ai/sampleclock. Figure 4-8 shows the relationship of ai/sampleclock to ai/starttrigger. Figure 4-8. Ai/sampleclock and ai/starttrigger ...

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    Chapter 4 analog input © national instruments corporation 4-17 ni usb-621x user manual channel to allow for adequate settling time. This scheme enables the channels to approximate simultaneous sampling and still allow for adequate settling time. If the ai sample clock rate is too fast to allow for t...

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    Chapter 4 analog input ni usb-621x user manual 4-18 ni.Com figure 4-9 shows the relationship of ai/sampleclock to ai/convertclock. Figure 4-9. Ai/sampleclock and ai/convertclock other timing requirements the sample and conversion level timing of m series devices work such that clock signals are gate...

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    Chapter 4 analog input © national instruments corporation 4-19 ni usb-621x user manual figure 4-10. Ai/sampleclock too fast figure 4-11. Ai/convertclock too fast figure 4-12. Ai/sampleclock and ai/convertclock improperly matched • sample clock too fast for convert clock ai/sampleclock ai/convertcloc...

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    Chapter 4 analog input ni usb-621x user manual 4-20 ni.Com figure 4-13. Ai/sampleclock and ai/convertclock properly matched it is also possible to use a single external signal to drive both ai/sampleclock and ai/convertclock at the same time. In this mode, each tick of the external clock will cause ...

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    Chapter 4 analog input © national instruments corporation 4-21 ni usb-621x user manual ai hold complete event signal the ai hold complete event (ai/holdcompleteevent) signal generates a pulse after each a/d conversion begins. You can route ai/holdcompleteevent out to any pfi or pfi terminal. The pol...

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    Chapter 4 analog input ni usb-621x user manual 4-22 ni.Com the device also uses ai/starttrigger to initiate pretriggered daq operations. In most pretriggered applications, a software trigger generates ai/starttrigger. Refer to the ai reference trigger signal section for a complete description of the...

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    Chapter 4 analog input © national instruments corporation 4-23 ni usb-621x user manual using a digital source to use ai/referencetrigger with a digital source, specify a source and an edge. The source can be the pfi or pfi signals. The source also can be one of several internal signals on your daq d...

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    Chapter 4 analog input ni usb-621x user manual 4-24 ni.Com getting started with ai applications in software you can use the m series device in the following analog input applications. • single-point analog input • finite analog input • continuous analog input you can perform these applications throu...

  • Page 51: Connecting Ai Signals On The

    © national instruments corporation 5-1 ni usb-621x user manual 5 connecting ai signals on the usb-6210/6211 devices table 5-1 summarizes the recommended input configuration for both types of signal sources on ni 6210/6211 devices..

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    Chapter 5 connecting 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-reference setting * floating signal sources (not connected to building ground) ground-referenced signal sources ** examples: • ungrounded thermocouples • si...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 5-3 ni usb-621x user manual connecting floating signal sources what are floating signal sources? A floating signal source is not connected to the building ground system, but has an isolated ground-referen...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices ni usb-621x user manual 5-4 ni.Com in the single-ended modes, more electrostatic and magnetic noise couples into the signal connections than in diff configurations. The coupling is the result of differences in the signal path. Magnetic cou...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 5-5 ni usb-621x user manual using differential connections for floating signal sources it is important to connect the negative lead of a floating source to ai gnd (either directly or through a bias resist...

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    Chapter 5 connecting 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 sources with single bias resistor you can fully balance the signal path by connecting another resistor of the same value between the positive input...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 5-7 ni usb-621x user manual figure 5-3. Differential connections for floating signal sources with balanced bias resistors both inputs of the ni-pgia require a dc path to ground in order for the ni-pgia to...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices ni usb-621x user manual 5-8 ni.Com inputs; be aware that there is some gain error from loading down the source, as shown in figure 5-4. Figure 5-4. Differential connections for ac coupled floating sources with balanced bias resistors using...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 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 daq assistant, you can configure the channels for rse or nrse i...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices ni usb-621x user manual 5-10 ni.Com the difference in ground potential between two instruments connected to the same building power system is typically between 1 and 100 mv, but the difference can be much higher if power distribution circu...

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    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 5-11 ni usb-621x user manual in the single-ended modes, more electrostatic and magnetic noise couples into the signal connections than in diff configurations. The coupling is the result of differences in ...

  • Page 62

    Chapter 5 connecting 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 how to connect a ground-referenced signal source to the usb-6210/6211 device configured in diff mode. Figure 5-7. Diff...

  • Page 63

    Chapter 5 connecting ai signals on the usb-6210/6211 devices © national instruments corporation 5-13 ni usb-621x user manual using non-referenced single-ended (nrse) connections for ground-referenced signal sources figure 5-8 shows how to connect ground-reference signal sources to the usb-6210/6211 ...

  • Page 64: Connecting Ai Signals On The

    © national instruments corporation 6-1 ni usb-621x user manual 6 connecting ai signals on the usb-6215/6218 devices you can connect the usb-6215/6218 directly to a variety of devices and other signal sources. Make sure the devices you connect to the usb-6215/6218 are compatible with the input specif...

  • Page 65

    Chapter 6 connecting ai signals on the usb-6215/6218 devices ni usb-621x user manual 6-2 ni.Com refer to figure 6-1 for an illustration of a differential connection configuration. Figure 6-1. Connecting a device to a usb-6215/6218 using differential connections 3 a i3 ai 11 4 a i4 ai 12 5 a i5 ai 13...

  • Page 66

    Chapter 6 connecting ai signals on the usb-6215/6218 devices © national instruments corporation 6-3 ni usb-621x user manual the differential connection configuration allows the common-mode noise voltage, v cm , to be rejected during the measurement of v 1 . You must connect the negative lead of your...

  • Page 67

    Chapter 6 connecting ai signals on the usb-6215/6218 devices ni usb-621x user manual 6-4 ni.Com non-referenced single-ended (nrse) measurements to reach a compromise between rse and differential measurements, you can use an nrse measurement configuration. This configuration allows for a remote sense...

  • Page 68: Analog Output

    © national instruments corporation 7-1 ni usb-621x user manual 7 analog output many m series devices have analog output functionality. Ni 621 x devices that support analog output have two ao channels controlled by a single clock and capable of waveform generation. Refer to appendix a, device-specifi...

  • Page 69: Ao Range

    Chapter 7 analog output ni usb-621x user manual 7-2 ni.Com dacs. It allows you to download the points of a waveform to your m series device without host computer interaction. Ao sample clock the ao sample clock signal reads a sample from the dac fifo and generates the ao voltage. Ao range the ao ran...

  • Page 70

    Chapter 7 analog output © national instruments corporation 7-3 ni usb-621x user manual hardware-timed generations have several advantages over software-timed acquisitions: • the time between samples can be much shorter. • the timing between samples can be deterministic. • hardware-timed acquisitions...

  • Page 71

    Chapter 7 analog output ni usb-621x user manual 7-4 ni.Com the buffer at a fast enough rate to keep up with the generation, the buffer will underflow and cause an error. Analog output digital triggering analog output supports two different triggering actions: • start trigger • pause trigger a digita...

  • Page 72: Analog Output Timing Signals

    Chapter 7 analog output © national instruments corporation 7-5 ni usb-621x user manual analog output timing signals figure 7-3 summarizes all of the timing options provided by the analog output timing engine. Figure 7-3. Analog output timing options usb m series devices feature the following ao (wav...

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    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 daq device. Refer to device routing in max in the ni-daqmx help or the labview 8.X help for more information. You also can specify whether the waveform generation begins on the r...

  • Page 74

    Chapter 7 analog output © national instruments corporation 7-7 ni usb-621x user manual the source also can be one of several other internal signals on your daq device. Refer to device routing in max in the ni-daqmx help or the labview 8.X help for more information. You also can specify whether the s...

  • Page 75

    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/sampleclock and ao/starttrigger ao sample clock timebase signal the ao sample clock timebase (ao/sampleclocktimebase) signal is divided down to provide a ...

  • Page 76

    Chapter 7 analog output © national instruments corporation 7-9 ni usb-621x user manual getting started with ao applications in software you can use an ni 621 x device in the following analog output applications. • single-point (on-demand) generation • finite generation • continuous generation • wave...

  • Page 77: Digital I/o

    © national instruments corporation 8-1 ni usb-621x user manual 8 digital i/o ni 621 x devices have eight static digital input lines, p0.. These lines also can be used as pfi inputs. Ni 621 x devices have eight static digital output lines, p1..These lines also can be used as pfi output. By default th...

  • Page 78: Static Dio

    Chapter 8 digital i/o ni usb-621x user manual 8-2 ni.Com the voltage input and output levels and the current drive levels of the dio lines are listed in the specifications of your device. Static dio you can use static di and do lines to monitor or control digital signals. All samples of static di li...

  • Page 79

    Chapter 8 digital i/o © national instruments corporation 8-3 ni usb-621x user manual connecting digital i/o signals the di and do signals, p0. And p1. Are referenced to d gnd. Digital input applications include receiving ttl signals and sensing external device states, such as the state of the switch...

  • Page 80

    Chapter 8 digital i/o ni usb-621x user manual 8-4 ni.Com getting started with dio applications in software you can use the m series device in the following digital i/o applications: • static digital input • static digital output • digital waveform generation • digital waveform acquisition • di chang...

  • Page 81: Counters

    © national instruments corporation 9-1 ni usb-621x user manual 9 counters m series devices have two general-purpose 32-bit counter/timers and one frequency generator, as shown in figure 9-1. The general-purpose counter/timers can be used for many measurement and pulse generation applications. Figure...

  • Page 82: Counter Input Applications

    Chapter 9 counters ni usb-621x user manual 9-2 ni.Com the counters have seven input signals, although in most applications only a few inputs are used. For information about connecting counter signals, refer to the default counter/timer pinouts section. Counter input applications counting edges in ed...

  • Page 83

    Chapter 9 counters © national instruments corporation 9-3 ni usb-621x user manual figure 9-3. Single point (on-demand) edge counting with pause trigger buffered (sample clock) edge counting with buffered edge counting (edge counting using a sample clock), the counter counts the number of edges on th...

  • Page 84

    Chapter 9 counters ni usb-621x user manual 9-4 ni.Com non-cumulative buffered edge counting non-cumulative edge counting is similar to buffered (sample clock) edge counting. However, the counter resets after each active edge of the sample clock. You can route the sample clock to the gate input of th...

  • Page 85

    Chapter 9 counters © national instruments corporation 9-5 ni usb-621x user manual pulse-width measurement in pulse-width measurements, the counter measures the width of a pulse on its gate input signal. You can configure the counter to measure the width of high pulses or low pulses on the gate signa...

  • Page 86

    Chapter 9 counters ni usb-621x user manual 9-6 ni.Com the counter counts the number of edges on the source input while the gate input remains active. On each trailing edge of the gate signal, the counter stores the count in a hardware save register. A usb signal stream transfers the stored values to...

  • Page 87

    Chapter 9 counters © national instruments corporation 9-7 ni usb-621x user manual single period measurement with single period measurement, the counter counts the number of rising (or falling) edges on the source input occurring between two active edges of the gate input. On the second active edge o...

  • Page 88

    Chapter 9 counters ni usb-621x user manual 9-8 ni.Com figure 9-9. Buffered period measurement note that if you are using an external signal as the source, at least one source pulse should occur between each active edge of the gate signal. This condition ensures that correct values are returned by th...

  • Page 89

    Chapter 9 counters © national instruments corporation 9-9 ni usb-621x user manual semi-period measurement in semi-period measurements, the counter measures a semi-period on its gate input signal after the counter is armed. A semi-period is the time between any two consecutive edges on the gate input...

  • Page 90

    Chapter 9 counters ni usb-621x user manual 9-10 ni.Com this condition ensures that correct values are returned by the counter. If this condition is not met, the counter returns a zero. Refer to the duplicate count prevention section for more information. For information about connecting counter sign...

  • Page 91

    Chapter 9 counters © national instruments corporation 9-11 ni usb-621x user manual method 1b—measure low frequency with one counter (averaged) in this method, you measure several periods of your signal using a known timebase. This method is good for low to medium frequency signals. You can route the...

  • Page 92

    Chapter 9 counters ni usb-621x user manual 9-12 ni.Com generate the pulse externally and connect it to a pfi terminal. You only need to use one counter if you generate the pulse externally. Route the signal to measure (f1) to the source of the counter. Configure the counter for a single pulse-width ...

  • Page 93

    Chapter 9 counters © national instruments corporation 9-13 ni usb-621x user manual figure 9-14. Method 3 then route the counter 0 internal output signal to the gate input of counter 1. You can route a signal of known frequency (f2) to the counter 1 source input. F2 can be 80mhztimebase. For signals ...

  • Page 94

    Chapter 9 counters ni usb-621x user manual 9-14 ni.Com 80 mhz timebase. Your 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; table 9-2 illustrates this point. ...

  • Page 95

    Chapter 9 counters © national instruments corporation 9-15 ni usb-621x user manual table 9-3 summarizes some of the differences in methods of measuring frequency. For information about connecting counter signals, refer to the default counter/timer pinouts section. Position measurement you can use th...

  • Page 96

    Chapter 9 counters ni usb-621x user manual 9-16 ni.Com figure 9-15 shows a quadrature cycle 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...

  • Page 97

    Chapter 9 counters © national instruments corporation 9-17 ni usb-621x user manual channel z behavior some quadrature encoders have a third channel, channel z, which is also referred to as the index channel. A high level on channel z causes the counter to be reloaded with a specified value in a spec...

  • Page 98

    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 two pulse encoders for information about connecting counter signals, refer...

  • Page 99

    Chapter 9 counters © national instruments corporation 9-19 ni usb-621x user manual figure 9-20 shows an example of a single two-signal edge-separation measurement. Figure 9-20. Single two-signal edge-separation measurement buffered two-signal edge-separation measurement buffered and single two-signa...

  • Page 100: Counter Output Applications

    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 signal of the counter. You can specify a delay from when the counter is armed t...

  • Page 101

    Chapter 9 counters © national instruments corporation 9-21 ni usb-621x user manual figure 9-23 shows a generation of a pulse with a pulse delay of four and a pulse width of three (using the rising edge of source). Figure 9-23. Single pulse generation with start trigger retriggerable single pulse gen...

  • Page 102

    Chapter 9 counters ni usb-621x user manual 9-22 ni.Com pulse train generation continuous pulse train generation this function generates a train of pulses with programmable frequency and duty cycle. The pulses appear on the counter n internal output signal of the counter. You can specify a delay from...

  • Page 103

    Chapter 9 counters © national instruments corporation 9-23 ni usb-621x user manual frequency generation you can generate a frequency by 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 squar...

  • Page 104

    Chapter 9 counters ni usb-621x user manual 9-24 ni.Com frequency output can be routed out to any pfi or pfi 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. In software, program the frequency generator as...

  • Page 105: Counter Timing Signals

    Chapter 9 counters © national instruments corporation 9-25 ni usb-621x user manual frequency of the system. Figure 9-28 shows an example of pulse generation for ets; the delay from the trigger to the pulse increases after each subsequent gate active edge. Figure 9-28. Pulse generation for ets for in...

  • Page 106

    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 value depending on the application the counter is performing. Table 9-4 lists how this terminal is used in various applications. Routi...

  • Page 107

    Chapter 9 counters © national instruments corporation 9-27 ni usb-621x user manual counter n gate signal the counter n gate signal can perform many different operations depending on the application including starting and stopping the counter, and saving the counter contents. Routing a signal to coun...

  • Page 108

    Chapter 9 counters ni usb-621x user manual 9-28 ni.Com output, counter 0 gate, counter 0 source, or counter 1 gate can be routed to counter 1 aux. Some of these options may not be available in some driver software. Counter n a, counter n b, and counter n z signals counter n b can control the directi...

  • Page 109

    Chapter 9 counters © national instruments corporation 9-29 ni usb-621x user manual some of these options may not be available in some driver 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. The counter n interna...

  • Page 110

    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 gate 3 (pfi 2) ctr 1 aux 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. Default ni-daqmx counter/timer pins for usb-6218 devices count...

  • Page 111: Counter Triggering

    Chapter 9 counters © national instruments corporation 9-31 ni usb-621x user manual you can use these defaults or select other sources and destinations for the counter/timer signals in ni-daqmx. Refer to connecting counter signals in the ni-daqmx help or the labview 8.X help for more information abou...

  • Page 112: Other Counter Features

    Chapter 9 counters ni usb-621x user manual 9-32 ni.Com the signal goes high or vice versa. For continuous pulse generations, the counter stops generating pulses while the external trigger signal is low and resumes when the signal goes high or vice versa. When using a pause trigger, the pause trigger...

  • Page 113

    Chapter 9 counters © national instruments corporation 9-33 ni usb-621x user manual cascading counters you can internally route the counter n internal output and counter n tc signals of each counter to gate inputs of the other counter. By cascading two counters together, you can effectively create a ...

  • Page 114

    Chapter 9 counters ni usb-621x user manual 9-34 ni.Com the filter setting for each input can be configured independently. On power up, the filters are disabled. Figure 9-30 shows an example of a low to high transition on an input that has its filter set to 125 ns (n = 5). Figure 9-30. Filter example...

  • Page 115

    Chapter 9 counters © national instruments corporation 9-35 ni usb-621x user manual figure 9-31. Prescaling prescaling is intended to be used for frequency measurement where the measurement is made on a continuous, repetitive signal. The prescaling counter cannot be read; therefore, you cannot determ...

  • Page 116

    Chapter 9 counters ni usb-621x user manual 9-36 ni.Com example application that works correctly (no duplicate counting) figure 9-32 shows an external buffered signal as the period measurement source. Figure 9-32. Duplicate count prevention example on the first rising edge of gate, the current count ...

  • Page 117

    Chapter 9 counters © national instruments corporation 9-37 ni usb-621x user manual example application that works incorrectly (duplicate counting) in figure 9-33, after the first rising edge of gate, no source pulses occur, so the counter does not write the correct data to the buffer. Figure 9-33. D...

  • Page 118

    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 counter value and counter n internal output signals change synchronously to the source signal. With duplicate count prevention, the counter...

  • Page 119: Pfi

    © national instruments corporation 10-1 ni usb-621x user manual 10 pfi ni 621 x devices have up to eight input and eight output programmable function interface (pfi) signals, which also can be used as static digital input or static digital output signals. Each input pfi can be individually configure...

  • Page 120

    Chapter 10 pfi ni usb-621x user manual 10-2 ni.Com figure 10-2. Ni 621 x pfi output circuitry when a terminal is used as a timing 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. X or p1. X . On the i/o connector, each termina...

  • Page 121: Connecting Pfi Input Signals

    Chapter 10 pfi © national instruments corporation 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 level sensitive. Exporting timing output signals using pfi terminals you can route any of the following timing signals to a...

  • Page 122: Pfi Filters

    Chapter 10 pfi ni usb-621x user manual 10-4 ni.Com figure 10-3. Pfi input signals connections pfi filters you can enable a programmable debouncing filter on each pfi signal. When the filters are enabled, your device samples the input on each rising edge of a filter clock. M series devices use an onb...

  • Page 123

    Chapter 10 pfi © national instruments corporation 10-5 ni usb-621x user manual the filter setting for each input can be configured independently. On power up, the filters are disabled. Figure 10-4 shows an example of a low to high transition on an input that has its filter set to 125 ns (n = 5). Fig...

  • Page 124: I/o Protection

    Chapter 10 pfi ni usb-621x user manual 10-6 ni.Com i/o protection each di, do, and pfi signal is protected against overvoltage, undervoltage, and overcurrent conditions as well as esd events. However, you should avoid these fault conditions by following these guidelines. • do not connect a do or pfi...

  • Page 125

    © national instruments corporation 11-1 ni usb-621x user manual 11 isolation and digital isolators usb-6215/6218 devices are isolated data acquisition devices. As shown in figure 11-1, the analog input, analog output, counters, pfi/static di, and pfi/static do circuitry, and digital routing and cloc...

  • Page 126: Digital Isolation

    Chapter 11 isolation and digital isolators ni usb-621x user manual 11-2 ni.Com the isolated ground is an input to the usb-6215/6218 device. The user must connect this ground to the ground of system being measured or controlled. Refer to chapter 5, connecting ai signals on the usb-6210/6211 devices ,...

  • Page 127

    Chapter 11 isolation and digital isolators © national instruments corporation 11-3 ni usb-621x user manual switching voltages through the transformer cause charging and discharging of the parasitic capacitances and inductances in the switching power supplies that occur on every switch cycle, resulti...

  • Page 128

    Chapter 11 isolation and digital isolators ni usb-621x user manual 11-4 ni.Com add an ac return path from the device isolated ground to earth ground. For non-isolated systems, an ac return path is only needed for high or source impedances. An ac return path can be created by connecting a capacitor b...

  • Page 129: Digital Routing and Clock

    © national instruments corporation 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 between the bus interface and the acquisition/generation sub-systems (analog input, analog output, digita...

  • Page 130: 100 Khz Timebase

    Chapter 12 digital routing and clock generation ni usb-621x user manual 12-2 ni.Com 100 khz timebase the 100 khz timebase can be used to generate many of the ai and ao timing signals. The 100 khz timebase also can be used as the source input to the 32-bit general-purpose counter/timers. The 100 khz ...

  • Page 131: Bus Interface

    © national instruments corporation 13-1 ni usb-621x user manual 13 bus interface the bus interface circuitry of m series devices efficiently moves data between host memory and the measurement and acquisition circuits. All m series devices are jumperless for complete plug-and-play operation. The oper...

  • Page 132

    Chapter 13 bus interface ni usb-621x user manual 13-2 ni.Com programmed i/o programmed i/o is a data transfer mechanism where the user’s program is responsible for transferring data. Each read or write call in the program initiates the transfer of data. Programmed i/o is typically used in software-t...

  • Page 133: Triggering

    © national instruments corporation 14-1 ni usb-621x user manual 14 triggering a trigger is a signal that causes 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 you want the trigger to ca...

  • Page 134

    Chapter 14 triggering ni usb-621x user manual 14-2 ni.Com you also can program your daq device to perform an action in response to a trigger from a digital source. The action can affect the following: • analog input acquisition • analog output generation • counter behavior.

  • Page 135: Device-Specific Information

    © national instruments corporation a-1 ni usb-621x user manual a device-specific information this appendix contains device pinouts, specifications, cable and accessory choices, and other information for the following usb m series devices. • usb-6210 • usb-6211/6215 • usb 6218 to obtain documentation...

  • Page 136

    Appendix a device-specific information ni usb-621x user manual a-2 ni.Com figure a-1. Usb-6210 pinout table a-1. Default ni-daqmx counter/timer pins counter/timer signal default terminal number (name) ctr 0 src 1 (pfi 0) ctr 0 gate 2 (pfi 1) ctr 0 aux 1 (pfi 0) ctr 0 out 6 (pfi 4) ctr 0 a 1 (pfi 0) ...

  • Page 137

    Appendix a device-specific information © national instruments corporation a-3 ni usb-621x user manual note for more information about default ni-daqmx counter inputs, refer to connecting counter signals in the ni-daqmx help or the labview 8.X help . Usb-6210 specifications refer to the ni 621x speci...

  • Page 138: Usb-6211/6215

    Appendix a device-specific 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 . Single...

  • Page 139

    Appendix a device-specific information © national instruments corporation a-5 ni usb-621x user manual figure a-2. Usb-6211/6215 pinout table a-3. Default ni-daqmx counter/timer pins counter/timer signal default terminal number (name) ctr 0 src 1 (pfi 0) ctr 0 gate 2 (pfi 1) ctr 0 aux 1 (pfi 0) ctr 0...

  • Page 140

    Appendix a device-specific information ni usb-621x user manual a-6 ni.Com note for more information about default ni-daqmx counter inputs, refer to connecting counter signals in the ni-daqmx help or the labview 8.X help . Usb-6211/6215 specifications refer to the ni 621x specifications for more deta...

  • Page 141: Usb 6218

    Appendix a device-specific information © national instruments corporation 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 informa...

  • Page 142

    Appendix a device-specific information ni usb-621x user manual a-8 ni.Com figure a-3. Usb 6218 pinout table a-5. Default ni-daqmx counter/timer pins counter/timer signal default terminal number (name) ctr 0 src 1 (pfi 0) ctr 0 gate 2 (pfi 1) ctr 0 aux 34 (pfi 9) ctr 0 out 6 (pfi 4) ctr 0 a 1 (pfi 0)...

  • Page 143

    Appendix a device-specific information © national instruments corporation a-9 ni usb-621x user manual note for more information about default ni-daqmx counter inputs, refer to connecting counter signals in the ni-daqmx help or the labview 8.X help . Usb 6218 specifications refer to the ni 621x speci...

  • Page 144

    Appendix a device-specific information ni usb-621x user manual a-10 ni.Com single-blink operating normally. Connected to usb hi-speed port. Refer to the ni 621x specifications for more information. Double-blink connected to usb full speed port. Device performance might be affected. Refer to the ni 6...

  • Page 145: Troubleshooting

    © national instruments corporation b-1 ni usb-621x user manual b troubleshooting this section contains common questions about m series devices. If your questions are not answered here, refer to the national instruments knowledgebase at ni.Com/kb . Analog input i am seeing crosstalk or ghost voltages...

  • Page 146

    Appendix b troubleshooting ni usb-621x user manual b-2 ni.Com are various methods of achieving this reference while maintaining 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 ...

  • Page 147: Analog Output

    Appendix b troubleshooting © national instruments corporation b-3 ni usb-621x user manual analog output i am seeing glitches on the output signal. How can i minimize it? When you use a dac to generate a waveform, you may observe glitches on the output signal. These glitches are normal; when a dac sw...

  • Page 148: Technical Support and

    © national instruments corporation c-1 ni usb-621x user manual c technical support and professional services visit the following sections of the national instruments web site at ni.Com for technical support and professional services: • support —online technical support resources at ni.Com/support in...

  • Page 149

    Appendix c technical support and professional services ni usb-621x user manual c-2 ni.Com • calibration certificate —if your product supports calibration, you can obtain the calibration certificate for your product at ni.Com/ calibration . If you searched ni.Com and could not find the answers you ne...

  • Page 150: Glossary

    © national instruments corporation g-1 ni usb-621x user manual glossary numbers/symbols % percent. + positive of, or plus. – negative of, or minus. ± plus or minus. Less than. > greater than. ≤ less than or equal to. ≥ greater than or equal to. / per. º degree. Ω ohm. A a amperes—the unit of electri...

  • Page 151

    Glossary ni usb-621x user manual g-2 ni.Com ai 1. Analog input. 2. Analog input channel signal. Ai gnd analog input ground signal. Ai sense analog input sense signal. Analog a signal whose amplitude can have a continuous range of values. Analog input signal an input signal that varies smoothly over ...

  • Page 152

    Glossary © national instruments corporation g-3 ni usb-621x user manual asic application-specific integrated circuit—a proprietary semiconductor component designed and manufactured to perform a set of specific functions for a specific customer. Asynchronous 1. Hardware—a property of an event that oc...

  • Page 153

    Glossary ni usb-621x user manual g-4 ni.Com cascading process of extending the counting range of a counter chip by 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 signal. Analog si...

  • Page 154

    Glossary © national instruments corporation g-5 ni usb-621x user manual counter/timer a circuit that counts external pulses or clock pulses (timing). D d gnd digital ground signal. D-sub connector a serial connector. Dac digital-to-analog converter—an electronic device, often an integrated circuit, ...

  • Page 155

    Glossary ni usb-621x user manual g-6 ni.Com 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 daq device whenever the cpu receives a softw...

  • Page 156

    Glossary © national instruments corporation g-7 ni usb-621x user manual digital trigger a ttl level signal having two discrete levels—a high and a low level. Dio digital input/output. Dma direct memory access—a method by which data can be transferred to/ from computer memory from/to a device or memo...

  • Page 157

    Glossary ni usb-621x user manual g-8 ni.Com f fifo first-in-first-out memory buffer—a data buffering technique that functions like a shift register where the oldest values (first in) come out first. Many daq products and instruments use fifos to buffer digital data from an a/d converter, or to buffe...

  • Page 158

    Glossary © national instruments corporation g-9 ni usb-621x user manual function 1. A built-in execution element, comparable to an operator, function, or statement in a conventional language. 2. A set of software instructions executed by a single line of code that may have input and/or output parame...

  • Page 159

    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 driver a set of high-level software functions that controls a specific gpib, vxi, or rs232 programmable ...

  • Page 160

    Glossary © national instruments corporation g-11 ni usb-621x user manual l labview a graphical programming language. Led light-emitting diode—a semiconductor light source. Lowpass filter a filter that passes signals below a cutoff frequency while blocking signals above that frequency. Lsb least sign...

  • Page 161

    Glossary ni usb-621x user manual g-12 ni.Com monotonicity a characteristic of a dac in which the analog output always increases as the values of the digital code input to it increase. Multichannel pertaining to a radio-communication system that operates on more than one channel at the same time. The...

  • Page 162

    Glossary © national instruments corporation g-13 ni usb-621x user manual nrse non-referenced single-ended mode—all measurements are made with respect to a common (nrse) measurement system reference, but the voltage at this reference can vary with respect to the measurement system ground. O offset th...

  • Page 163

    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 devices port. 1. A communications connection on a computer or a remote controller; 2. A digital port, consisting of fou...

  • Page 164

    Glossary © national instruments corporation g-15 ni usb-621x user manual q quadrature encoder an encoding technique for a rotating device where two tracks of information are placed on the device, with the signals on the tracks offset by 90° from each other. This makes it possible to detect the direc...

  • Page 165

    Glossary ni usb-621x user manual g-16 ni.Com scan one or more analog or digital input samples. Typically, 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 clock produces one scan which acquires one new sample from every...

  • Page 166

    Glossary © national instruments corporation g-17 ni usb-621x user manual single-ended output a circuit whose output signal is present between one output terminal and ground. Software applications the programs that run on your computer and perform a specific user- oriented function, such as accountin...

  • Page 167

    Glossary ni usb-621x user manual g-18 ni.Com timebase the reference signals for controlling the basic accuracy of time or frequency-based measurements. For instruments, timebase refers to the accuracy of the internal clock. T out output delay time. Traditional ni-daq (legacy) an upgrade to the earli...

  • Page 168

    Glossary © national instruments corporation g-19 ni usb-621x user manual v g ground loop voltage. V ih volts, input high. V il volts, input low. V in volts in. V m measured voltage. V oh volts, output high. V ol volts, output low. V out volts out. V s signal source voltage. Virtual channel see chann...

  • Page 169: Index

    © national instruments corporation i-1 ni usb-621x user manual index symbols +5 v power input, 3-3 +5 v power output, 3-2 +5 v power source, 3-2 .Net languages documentation, xvi numerics 100 khz timebase, 12-2 20 mhz timebase, 12-1 80 mhz timebase, 12-1 a a/d converter, 4-2 ac return path, creating...

  • Page 170

    Index ni usb-621x user manual i-2 ni.Com ai sample clock timebase, 4-16 ai start trigger, 4-21 analog output, 7-1 circuitry, 7-1 connecting signals, 7-4 data generation methods, 7-2 fundamentals, 7-1 getting started with applications in software, 7-9 glitches on the output signal, 7-2 timing signals...

  • Page 171

    Index © national instruments corporation i-3 ni usb-621x user manual ground-referenced signal sources, 5-9 pfi input signals, 10-3 connections for floating signal sources, 5-9 single-ended for floating signal sources, 5-9 single-ended, rse configuration, 5-9 connector information, 3-1 usb-6210 pinou...

  • Page 172

    Index ni usb-621x user manual i-4 ni.Com declaration of conformity (ni resources), c-1 default counter terminals, 9-29 ni-daqmx counter/timer pins, 9-29 pins, 9-29 device information, a-1 pinouts, 1-3 specifications, 1-3, a-1 usb-6210, a-1 usb-6211, a-4 usb-6215, a-4 usb-6218, a-7 diagnostic tools (...

  • Page 173

    Index © national instruments corporation i-5 ni usb-621x user manual f features, counter, 9-32 field wiring considerations, 4-11 filters counter, 9-33 pfi, 10-4 floating signal sources connecting, 5-3 description, 5-3 using in differential mode, 5-5 using in nrse mode, 5-8 using in rse mode, 5-9 whe...

  • Page 174

    Index ni usb-621x user manual i-6 ni.Com instrumentation amplifier, 4-2 interface, bus, 13-1 isolated daq devices, 11-1 benefits, 11-2 common-mode noise, 11-2 isolators, 11-1 k knowledgebase, c-1 l labview documentation, xiv labwindows/cvi documentation, xv led usb-6210, a-3 usb-6211, a-6 usb-6215, ...

  • Page 175

    Index © national instruments corporation i-7 ni usb-621x user manual when to use with ground-referenced signal sources, 5-10 nrse connections using with floating signal sources, 5-8 using with ground-referenced signal sources, 5-13 when to use with floating signal sources, 5-4 when to use with groun...

  • Page 176

    Index ni usb-621x user manual i-8 ni.Com when to use with ground-referenced signal sources, 5-11 related documentation, xiv retriggerable single pulse generation, 9-21 routing digital, 12-1 rse configuration, 5-9 rse connections using with floating signal sources, 5-9 when to use with floating signa...

  • Page 177

    Index © national instruments corporation i-9 ni usb-621x user manual software configuring ai ground-reference settings, 4-5 programming devices, 2-4 software (ni resources), c-1 software-timed acquisitions, 4-9 generations, 7-2 specifications, a-1 device, 1-3 usb-6210, a-3 usb-6211, a-6 usb-6215, a-...

  • Page 178

    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 low impedance sources, 4-6 using pfi terminals as static digital i/os, 10-3 as timing input signals, 10-2 to export timing output signals, 10-3 w waveform generation signa...