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Chapter 3

Using the NI PXI-4204

©

 National Instruments Corporation

3-5

NI PXI-4204 User Manual

Input Impedance

Figure 3-2 illustrates the input impedance of an NI PXI-4204 and its effect 
on the measurement of a circuit under test. If you know the source 
impedance of the circuit under test, you can correct for the attenuation 
caused by the NI PXI-4204 in software. Since R

IN

 is relatively large, 

1 M

Ω

, it requires a large source impedance, 

R

S

, to cause a significant 

change in the measured voltage, 

V

MEAS

. In general, a source impedance of 

less than 200

Ω

 does not interfere with the accuracy of the measurement. 

For example, a 200

Ω

 source impedance results in a 0.02% gain error.

Figure 3-2.  

Effect of Input Impedance on Signal Measurements

Common-Mode Rejection Ratio

The ability of a measurement device to reject voltages that are common to 
both input terminals is referred to as the common-mode rejection ratio 
(CMRR) and is usually stated in decibels at a given frequency or over a 
given frequency band of interest. Common-mode signals can arise from a 
variety of sources and can be induced through conductive or radiated 
means. One of the most common sources of common-mode interference is 
due to 50 or 60 Hz powerline noise.

The minimum NI PXI-4204 CMRR is 60 dB. This results in a reduction of 
CMV by a factor of 1000. The measured signal source impedance can 
reduce the NI PXI-4204 CMR. Specifically, if the signal source has an 
imbalanced source impedance like the one in Figure 3-2, then an imbalance 
is introduced into the NI PXI-4204 front-end. This imbalance causes a 
reduction in the CMRR. The reduction in CMRR due to source impedance 

V

MEAS

V

SIG

R

IN

R

S

R

IN

+

---------------------

=

V

SIG

+

–

+

–

Measured

Voltage

V

MEAS

Input

Impedance

Source

Impedance

R

IN

R

S

Signal Source

Содержание PXI-4204

Страница 1: ...PXI NI PXI 4204 User Manual NI PXI 4204 User Manual June 2007 373529C 01...

Страница 2: ...1 3400 Lebanon 961 0 1 33 28 28 Malaysia 1800 887710 Mexico 01 800 010 0793 Netherlands 31 0 348 433 466 New Zealand 0800 553 322 Norway 47 0 66 90 76 60 Poland 48 22 3390150 Portugal 351 210 311 210...

Страница 3: ...ding photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation National Instruments res...

Страница 4: ...bout precautions to take When symbol is marked on a product it denotes a warning advising you to take precautions to avoid electrical shock When symbol is marked on a product it denotes a component th...

Страница 5: ...ing Signal Source Connection Recommended 2 7 Ground Referenced Signal Connection 2 8 Shielded Ground Referenced Signal Connection Recommended 2 9 Alternative Shielded Ground Referenced Connection 2 10...

Страница 6: ...ng the NI PXI 4204 3 19 Synchronizing the NI PXI 4204 Using LabVIEW 3 21 Other Application Documentation and Material 3 22 Calibrating the NI PXI 4204 3 23 Loading Calibration Constants 3 23 Self Cali...

Страница 7: ...1 NI PXI 4204 Dimensions A 6 Figure B 1 Typical Posttriggered Sequence B 2 Figure B 2 Typical Pretriggered Sequence B 2 Figure B 3 AI START TRIG Input Signal Timing B 3 Figure B 4 AI START TRIG Output...

Страница 8: ...l gain settings The NI PXI 4204 is an eight channel device for measuring voltages up to 100 volts The NI PXI 4204 has the following features Eight differential analog input AI channels 16 bit resoluti...

Страница 9: ...dio Frequency Interference DAQ Getting Started Guide PXI or PXI SCXI combination chassis user manual Documentation for your software Tools 1 8 in flathead screwdriver You can download NI documents fro...

Страница 10: ...your application software documentation or the NI DAQmx documentation to help you write your application If you have a large complicated system it is worthwhile to look through the software documenta...

Страница 11: ...llowing LEDs on the NI PXI 4204 front panel confirm the system is functioning properly The ACCESS LED is normally green and blinks yellow for a minimum of 100 ms during the NI PXI 4204 configuration T...

Страница 12: ...cting Signals to the NI PXI 4204 After you have verified that the NI PXI 4204 is installed correctly and self tested the device refer to the following sections to connect signals to the device Caution...

Страница 13: ...tion Refer to the Read Me First Safety and Radio Frequency Interference document before removing equipment covers or connecting disconnecting any signal wires 1 PXI Chassis 2 PXI System Controller 3 N...

Страница 14: ...Remove power from the signal lines If this is not possible complete the following steps while referring to Figures 2 2 and 2 3 a Remove the COMBICON connector from the NI PXI 4204 b Attach the signal...

Страница 15: ...2 Connecting Signals NI PXI 4204 User Manual 2 4 ni com Figure 2 2 NI PXI 4204 Screw Terminals AI5 AI4 AI3 AI7 AI6 AI6 AI4 AI2 AI2 AI1 AI1 AI0 AI0 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 AI3 AI5 AI7 PF...

Страница 16: ...al diagrams showing the signal source and connections Whenever possible use shielded twisted pair field wiring to reduce the effects of unwanted noise sources In the electrical diagrams two different...

Страница 17: ...SIG is connected to the channel reference AIX The lack of shielding on the field wiring can cause this configuration to be susceptible to electrically coupled noise This configuration has only one gro...

Страница 18: ...onnection shown in Figure 2 4 by using a shielded cable to connect the signal source to the instrument as shown in Figure 2 5 This is the recommended shielding configuration for floating signal source...

Страница 19: ...VSIG is connected to the channel reference AIX The signal ground reference VSIG Ground Reference is referenced to the NI PXI 4204 chassis ground reference inherently through some conductive path that...

Страница 20: ...l source in Figure 2 7 is identical to the signal source in Figure 2 6 The shielding is grounded at only one point to the signal source ground VSIG Ground Reference Connect the signal VSIG to the NI P...

Страница 21: ...ucing electrically induced noise in a ground referenced measurement However if connecting the shielding to the signal source ground is cumbersome or inconvenient use the connection shown in Figure 2 8...

Страница 22: ...e between the signal source reference and the NI PXI 4204 chassis ground reference To connect a signal source with high CMV to the NI PXI 4204 connect the signal VSIG to the NI PXI 4204 channel AIX Co...

Страница 23: ...XI 4204 channel AIX Connect the signal reference VSIG to the channel reference AIX The shielding is grounded at only one point to the NI PXI 4204 chassis ground reference This shielding scheme is effe...

Страница 24: ...2 10 Shielded High CMV Connection For more information about the function of the NI PXI 4204 and other measurement considerations refer to Chapter 3 Using the NI PXI 4204 Shielding Twisted Pair Wirin...

Страница 25: ...scribes the theory of operation measurement considerations timing information programming creating program applications in LabVIEW and calibration Theory of Operation Figure 3 1 illustrates the key fu...

Страница 26: ...lug and Play 82C55 DIO Control Configuration Memory MINI MITE Generic Bus Interface PCI Bus Interface EEPROM EEPROM ADC FIFO A D Converter AI Control IRQ DMA NI PGA Analog Mode Multiplexer Voltage Ref...

Страница 27: ...a balanced divide by ten attenuator The attenuation is provided by a resistor divider network that provides 1 M input impedance The balanced attenuator followed by an instrumentation amplifier provid...

Страница 28: ...s of 6 Hz or 10 kHz The 6 Hz filter setting attenuates differentially connected 60 Hz signals by 40 dB T H Circuitry You can enable the NI PXI 4204 track and hold circuitry to enable SS H This allows...

Страница 29: ...of a measurement device to reject voltages that are common to both input terminals is referred to as the common mode rejection ratio CMRR and is usually stated in decibels at a given frequency or ove...

Страница 30: ...rmal mode rejection ratio NMRR specification which specifies the capability of the NI PXI 4204 to reject a differentially applied unwanted 60 Hz signal In the case of the NI PXI 4204 this specificatio...

Страница 31: ...ral measurement functions to a common trigger or timing event The PXI trigger bus is connected through the rear signal connector to the PXI chassis backplane The DAQ STC provides a flexible interface...

Страница 32: ...tion Inputs PFI0 is connected to the front SMB connector of the NI PXI 4204 Software can select PFI0 as the external source for a given timing signal Any timing signal can use the PFI0 pin as an input...

Страница 33: ...another device programmed to receive this timebase signal This clock source whether local or from the PXI trigger bus is used directly by the device as the primary frequency source The default configu...

Страница 34: ...ity on PFI0 SMB Availabilityon PXI Trigger Bus AI START TRIG Input Output This is the source for the analog input digital start trigger the trigger that begins an acquisition This sends out the actual...

Страница 35: ...DAQmx For more information about how to create tasks and channels refer to the example programs AI SAMP CLK Input Output This clock controls the time interval between samples Each time the sample cloc...

Страница 36: ...s Create a Task Programmatically Create Task in DAQ Assistant or MAX No Hardware Timing Triggering Create Task Using DAQ Assistant No Yes No Yes Configure Channels Further Configure Channels Start Mea...

Страница 37: ...ease of use when using a sensor that requires complex scaling or when many properties differ between channels in the same task If you are using an ADE other than an NI ADE or if you want to explicitly...

Страница 38: ...al routing of the clock source or select the active edge of the clock signal Configuring Channel Properties All of the different ADEs used to configure the NI PXI 4204 access an underlying set of NI D...

Страница 39: ...g background After you acquire the data and perform any required analysis it is useful to display the data in a graphical form or log it to a file NI ADEs provide easy to use tools for graphical displ...

Страница 40: ...O DAQmx Name Controls subpalette right click it and select New Task DAQ Assistant Create a Task Programmatically optional DAQmx Create Task vi This VI is optional if you created and configured your ta...

Страница 41: ...level checking Some data analysis tools are located on the Functions Signal Analysis subpalette and on the Functions All Functions Analyze subpalette Display Data You can use graphical tools such as c...

Страница 42: ...roperties Navigate through the menus and select the property you wish to define 7 To either get the property or write a new value you must change the property to read or write Right click the property...

Страница 43: ...all of the synchronized devices is called the master The master NI PXI 4204 exports the shared timing signals through the PXI bus to the slave devices Each NI PXI 4204 contains a DAQ STC chip and is c...

Страница 44: ...Master Timing Create a Slave Task Optional Create Slave AI Voltage Channels Set Slave to Use Timebase from Master Start Slave Measurement s Start Master Measurement Configure Master Channel Continue...

Страница 45: ...o the Using a DAQmx Channel Property Node in LabVIEW section for more information Configure Master Timing DAQmx Timing vi Sample Clock by default Get Master Timebase Source and Rate from Master Task U...

Страница 46: ...vailable at ni com Go to ni com info and enter the info code rdfwn3 Configure Slave Triggering DAQmx Trigger vi Start Digital Edge use MasterDevice ai StartTrigger as the source substituting the maste...

Страница 47: ...e values that were written to the CalDACs to achieve calibration in the factory and the remaining signal conditioning error are stored in the onboard nonvolatile flash memory The digitizer calibration...

Страница 48: ...bration reference for the DAQ circuitry and the signal conditioning circuitry to ensure the accuracy of self calibration The specifications are listed in Appendix A Specifications The reference voltag...

Страница 49: ...Input range 100 V Resolution 16 bits Maximum sampling rate 200 kS s aggregate multichannel Input coupling DC Bandwidth 6 Hz or 10 kHz 2 pole lowpass Butterworth filter response Differential input impe...

Страница 50: ...erature coefficient 32 ppm C Remaining gain error temperature coefficient after self calibration 25 ppm C CMRR DC to 60 Hz 60 dB 100 Hz to 10 kHz 40 dB Normal mode 60 Hz rejection 6 Hz filter setting...

Страница 51: ...ng and averaging of 100 single channel readings Measurement accuracies are listed for operational temperatures within 1 C of internal calibration temperature and 10 C of external or factory calibratio...

Страница 52: ...calibration interval 1 year Onboard calibration reference Level 5 000 V 1 mV actual value stored in EEPROM TC 5 ppm C Long term stability 15 ppm Pre calibration Errors1 Pre calibration offset error r...

Страница 53: ...and stop trigger gate clock Source PFI0 AI START TRIG front SMB connector PXI_Trig 0 5 to PXI Star PXI trigger bus Compatibility 5 V TTL Response Rising or falling edge Pulse width 10 ns min Impedance...

Страница 54: ...signal connector 16x1 miniature COMBICON 3 81 mm pitch Analog input signal mating connector 16x1 miniature COMBICON screw terminal connector 3 81 mm pitch 28 16 AWG signal wires 2 0 cm 0 79 in 21 3 c...

Страница 55: ...00 V This device can withstand up to 500 V impulse voltage without creating a safety hazard Do not use this device for connection to signals or for measurements within Categories II III or IV Do not c...

Страница 56: ...roup 1 Class A CE C Tick ICES and FCC Part 15 Emissions Class A Note For EMC compliance operate this device according to product documentation CE Compliance This product meets the essential requiremen...

Страница 57: ...ysical wiring to the device I O connector for applications requiring alternative wiring Note The NI PXI 4204 cannot output the PXI Star trigger line As an input each PFI signal can be individually con...

Страница 58: ...e B 1 Typical Posttriggered Sequence Pretriggered DAQ allows you to view data that is acquired before the trigger of interest in addition to data acquired after the trigger Figure B 2 shows a typical...

Страница 59: ...sition is externally triggered by another PFI The output is an active high pulse with a pulse width of 50 to 100 ns This output is set to high impedance at startup Figures B 3 and B 4 show the input a...

Страница 60: ...ded with the number of posttrigger scans to acquire while the acquisition continues The device ignores AI REF TRIG if it is asserted prior to the SC decrementing to zero After the selected edge of AI...

Страница 61: ...e selected edge of AI SAMP CLK initiates a scan The SI2 counter starts if you select an internally triggered AI CONV CLK As an output AI SAMP CLK reflects the actual start pulse that initiates a scan...

Страница 62: ...ulses are masked off until the device generates AI SAMP CLK If you use internally generated conversions the first AI CONV CLK appears when the onboard SI2 counter reaches zero If you select an externa...

Страница 63: ...I0 PXI_Trig 0 5 or PXI Star can externally input the AI CONV CLK signal which is also available as an output on PXI_Trig 0 5 Refer to Figures B 1 and B 2 for the relationship of AI CONV CLK to the seq...

Страница 64: ...ence Scans occurring within a sequence can be gated by either the hardware AI PAUSE TRIG signal or the software command register gate AI PAUSE TRIG Signal PFI0 PXI_Trig 0 5 or PXI Star can externally...

Страница 65: ...internal timebase generates AI SAMPLE CLK TIMEBASE unless you select an external source Figure B 11 shows the timing requirements for AI SAMPLE CLK TIMEBASE Figure B 11 AI SAMPLE CLK TIMEBASE Signal...

Страница 66: ...Appendix B Timing Signal Information NI PXI 4204 User Manual B 10 ni com Figure B 12 AI HOLD COMPLETE Signal Timing tw 400 to 500 ns td 50 to 100 ns AI CONV CLK AI HOLD COMPLETE td tw...

Страница 67: ...4204 device from a PXI chassis complete the following steps while referring to Figure C 1 1 Power off the PXI chassis Do not remove the NI PXI 4204 device from a chassis that is powered on 2 Rotate t...

Страница 68: ...pand Devices and Interfaces to display the list of installed devices and interfaces The NI PXI 4204 should have a red circle with a white X inside it next to the device to indicate it has been physica...

Страница 69: ...solated device No the NI PXI 4204 is not an isolated device and should not be used in applications with working voltages larger than 100 V The NI PXI 4204 has only resistive isolation which does not f...

Страница 70: ...ad approximately 0 0 V How do I program the NI PXI 4204 Refer to Chapter 3 Using the NI PXI 4204 for application programming information or your ADE help file There is no register level programming ma...

Страница 71: ...lo 103 M mega 106 G giga 109 Symbols percent positive of or plus negative of or minus per degree ohm A A amperes A D analog to digital AC alternating current ADC analog to digital converter an electro...

Страница 72: ...ors or dielectric materials See also working voltage bus the group of conductors that interconnect individual circuitry in a computer Typically a bus is the expansion vehicle to which I O or other dev...

Страница 73: ...cal signals from sensors transducers and test probes or fixtures and inputting them to a computer for processing 2 collecting and measuring the same kinds of electrical signals with A D and or DIO dev...

Страница 74: ...able programmable read only memory ROM that can be erased with an electrical signal and reprogrammed EMC electromagnetic compatibility EMI electromagnetic interference defines unwanted electromagnetic...

Страница 75: ...espect to ground is proportional to the difference between the voltages at its two high impedance inputs K k kilo the standard metric prefix for 1 000 or 103 used with units of measure such as volts h...

Страница 76: ...ical storms welders radio transmitters and internal sources such as semiconductors resistors and capacitors Noise corrupts signals you are trying to send or receive P PCI peripheral component intercon...

Страница 77: ...an analog signal sample counter the clock that counts the output of the channel clock in other words the number of samples taken On devices with SS H this counter counts the output of the scan clock a...

Страница 78: ...T TRIG trigger signal trigger any event that causes or starts some form of data capture TTL transistor transistor logic a digital circuit composed of bipolar transistors wired in a certain manner V V...

Страница 79: ...able 3 10 AI AutoZeroMode property table 3 15 AI Coupling property table 3 14 AI Lowpass CutoffFreq property table 3 14 AI SampAndHold Enable property table 3 15 alternative shielded ground referenced...

Страница 80: ...output signal timing figure B 8 overview table 3 11 AI HOLD COMPLETE description B 9 signal timing figure B 10 AI PAUSE TRIG description B 8 overview table 3 11 AI REF TRIG description B 4 input sign...

Страница 81: ...on application software 1 3 NI PXI 4204 1 3 Instrumentation Amplifier table 3 3 isolation D 1 L LabVIEW software application development 3 16 DAQmx channel property node 3 17 steps table 3 16 synchron...

Страница 82: ...ications A 6 posttriggered data acquisition B 2 power requirements specifications A 5 pretriggered acquisition B 2 programmable function inputs description B 1 overview 3 8 programming See application...

Страница 83: ...istics A 3 transfer characteristics A 4 SS H characteristics specifications A 3 Star Trigger controller 3 9 synchronization and triggering NI PXI 4204 3 19 overview 3 19 program flowchart figure 3 20...

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