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Chapter 3

Signal Conditioning

©

National Instruments Corporation

3-5

BNC-2090A User Manual

Table 3-2 lists population options for passive signal conditioning
components.

Building Lowpass Filters

You can install simple, RC lowpass filters on any input channel of the
BNC-2090A. The filters are useful for accurate measurement and noise
rejection. By substituting resistance and capacitance values into
Equation 3-1, you can calculate a simple, one-pole RC filter to have a
–3 dB cutoff frequency (

f

c

):

(3-1)

The frequency response rolls off at a rate of –20 dB per decade of increase
thereafter. Figure 3-3 shows a Bode plot of the amplitude versus
normalized frequency.

Table 3-2.

Signal Conditioning Component Population Options

Configuration

Normal

Attenuator

Lowpass

Filter

Highpass

Filter

AC Couple

Termination

Single-
Ended

A

Open

Open

Open

Open

Open

Resistor

B

Open

Open

Open

Open

Open

Resistor

C

*

0

Ω

Jumper

Resistor

Resistor

Capacitor

Capacitor

0

Ω

Jumper

D

*

0

Ω

Jumper

Resistor

Resistor

Capacitor

Capacitor

0

Ω

Jumper

E

Open

Open

Open

Open

Open

Open

F

Open

Resistor

Capacitor

Resistor

Open

Open

G

Open

Resistor

Capacitor

Resistor

Open

Open

Differential

A

Open

Open

Open

Open

Open

Resistor

B

Open

Open

Open

Open

Open

Resistor

C

*

0

Ω

Jumper

Resistor

Resistor

Capacitor

Capacitor

0

Ω

Jumper

D

*

0

Ω

Jumper

Resistor

Resistor

Capacitor

Capacitor

0

Ω

Jumper

E

Open

Resistor

Capacitor

Resistor

Open

Open

F

Open

Open

Open

Open

Open

Open

G

Open

Open

Open

Open

Open

Open

*

Factory-installed 0

Ω

resistor.

f

c

1

2

π

RC

(

)

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

=

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Summary of Contents for BNC-2090A

Page 1: ...DAQ BNC 2090A User Manual Rack Mount Connector Accessory for E M Series DAQ Devices BNC 2090A User Manual January 2007 372101A 01 ...

Page 2: ...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 Russia 7 495 783 6851 Singapore 1800 226 5886 Slovenia 386 3 425 42 00 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 2005151 Taiwan 886 02 2377 2222 Thail...

Page 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 respects the intellectual property of others and we ask our users to do the same NI software is protected by copyright and other intellectual property laws Where NI software may be used to reproduce soft...

Page 4: ...nt of Communications DOC Changes or modifications not expressly approved by NI could void the user s authority to operate the equipment under the FCC Rules Class A Federal Communications Commission This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC Rules These limits are designed to provide reasonable protection against ha...

Page 5: ...arked on a product refer to the Read Me First Safety and Radio Frequency Interference document available on ni com manuals for information about precautions to take bold Bold text denotes items that you must select or click in the software such as menu items and dialog box options Bold text also denotes parameter names italic Italic text denotes variables emphasis a cross reference or an introduct...

Page 6: ...Input Signals 2 3 Measuring Floating Signals in Single Ended Input Mode 2 4 Measuring Ground Referenced Signals in Single Ended Input Mode 2 5 Connecting AO APFI 0 and PFI 0 Signals 2 5 Connecting Digital Signals 2 6 Using the USER 1 and USER 2 BNC Connectors 2 7 Chapter 3 Signal Conditioning Analog Input Signal Conditioning 3 1 Building Lowpass Filters 3 5 Example 3 6 Building Highpass Filters 3 ...

Page 7: ...Contents BNC 2090A User Manual viii ni com Appendix A Specifications Appendix B Frequently Asked Questions Appendix C Technical Support and Professional Services Index ...

Page 8: ...AO BNC connectors Two user defined BNC connectors One APFI BNC connector One PFI BNC connector Spring terminal block for digital input output DIO and Programmable Function Interface PFI connections Silkscreened component locations for resistors and capacitors for building single pole highpass and lowpass filters and voltage dividers Two 68 pin input output I O connectors for DAQ device connection ...

Page 9: ...ce with one or two I O connectors 68 pin E Series device 100 pin E Series device 68 position1 or 100 position cable s The E Series User Manual or the M Series User Manual BNC cables 20 AWG wire or smaller Wire strippers 1 BNC Connectors 2 68 Position Connectors 3 Spring Terminal Block 4 5V LED 5 SE DIFF Switches 6 RSE NRSE Switch 1 Two connector M Series devices can be cabled to two BNC 2090A acce...

Page 10: ...vice refer to Figure 1 2 as you complete the following steps Consult your computer user manual or technical reference manual for specific instructions and warnings Note If you have not already installed your DAQ device refer to the DAQ Getting Started Guide for instructions Figure 1 2 Connecting the BNC 2090A to Your DAQ Device 1 Verify that the SE DIFF switches and RSE NRSE switch are set correct...

Page 11: ...er to the Adding Signal Conditioning Components section of Chapter 3 Signal Conditioning for more information 4 Place the BNC 2090A near the host computer or mount the BNC 2090A into a 19 inch rack If you do not rack mount the accessory attach the four adhesive rubber feet included in the BNC 2090A kit to the bottom of the accessory Caution Do not connect the BNC 2090A to any device other than a N...

Page 12: ...8 Position VHDCI Connector 68 Position Connector 68 Position Connector 68 Position Connector SHC68 68 EPM or RC68 68 Cable Two 68 Pin Connector M Series DAQ Device BNC 2090A 68 Position VHDCI Connector 68 Position Connector SHC68 68 EPM or RC68 68 Cable BNC 2090A 68 Position VHDCI Connector SHC68 68 EPM or RC68 68 Cable 68 Position Connector Two 68 Pin Connector M Series USB Mass Termination DAQ D...

Page 13: ...ector and the rear connector of the BNC 2090A to create a pass through Caution Do not connect input voltages greater than 42 4 Vpk 60 VDC to the BNC 2090A The BNC 2090A is not designed for any input voltages greater than 42 4 Vpk 60 VDC even if a user installed voltage divider reduces the voltage to within the input range of the DAQ device Input voltages greater than 42 4 Vpk 60 VDC can damage the...

Page 14: ...mplete the following steps while referring to Figure 1 5 Table 1 1 Shield Ground Jumper Settings Setting Description 100 Ω to Digital Ground Use this setting to reduce any potential ground loop current thereby improving the system noise performance When the BNC 2090A is rack mounted it is connected to a different ground This is the factory default setting Digital Ground Use this setting when the B...

Page 15: ...the top and bottom screws and two front panel screws 3 Hold the front panel and slide the unit out of the metal case 4 Set the shield ground jumper labeled W1 on the PCB as needed 5 Reassemble the BNC 2090A in reverse order 1 Front Panel Screws 2 Shield Ground Jumper W1 3 Side Panel Screw 4 Rear Panel Screws 5 Top Screw 6 Bottom Screw NATIONAL INSTRUMENTS 5 4 6 2 3 1 BNC 2090A ...

Page 16: ...e 2 1 shows an overview of the BNC 2090A circuitry Figure 2 1 BNC 2090A Circuitry Overview Connecting Analog Input Signals The BNC 2090A can be configured in three analog input modes Differential factory default setting Referenced single ended Nonreferenced single ended For more information about choosing an analog input mode refer to E Series User Manual or the M Series User Manual Front 68 Pin S...

Page 17: ...our software to measure this channel differentially Figure 2 2 shows how differential AI signals are routed to the DAQ device Figure 2 2 Analog Input Differential Mode The BNC 2090A is configured for differential mode by default Measuring Floating Signals in Differential Input Mode A floating signal source is a signal source that is not connected in any way to the building ground system but has an...

Page 18: ...ged into the same power system The non isolated outputs of instruments and devices that plug into the building power system fall into this category If the DAQ device is configured for differential inputs ground referenced signal sources connected to the BNC 2090A need no special components added to the BNC 2090A You can leave the inputs of the BNC 2090A in the factory default configuration with th...

Page 19: ...g ground system but has an isolated ground reference point If an instrument or device has an isolated output that instrument or device falls into the floating signal source category Some examples of floating signal sources are thermocouples transformers battery powered devices optical isolators and isolation amplifiers The ground reference of a floating source must be tied to the ground of the DAQ...

Page 20: ...building power system fall into this category When measuring ground referenced signals the external signal supplies its own reference ground point and the DAQ device should not supply one Therefore configure the DAQ device for the nonreferenced single ended NRSE mode in which all of the signal grounds are tied to AI SENSE which connects to the negative input of the instrumentation amplifier on the...

Page 21: ...conditioning circuitry Connecting Digital Signals Use the BNC 2090A spring terminal block on the front panel to connect digital signals to your DAQ device Refer to the E Series User Manual or the M Series User Manual for information about the use of these signals When connecting signals to the spring terminal blocks you can use up to 20 AWG wire with the insulation stripped to 0 5 in AO 0 DAQ Devi...

Page 22: ...e 2 5 Figure 2 5 USER 1 2 BNC Connections Figure 2 6 shows an example of how to use the USER 1 2 BNCs To access the PFI 5 signal from a BNC connect USER1 on the spring terminal block to PFI 5 with a wire Figure 2 6 Connecting PFI 5 to USER 1 BNC USER 1 BNC USER 2 BNC Screw Terminal Block D GND D GND USER2 5 6 7 8 9 10 11 12 13 14 15 DGND 6 7 5V DGND 1 2 4 3 USER1 DGND 0 1 2 3 4 5 P0 PFI Internal C...

Page 23: ...th your DAQ device Analog Input Signal Conditioning Each analog input signal has several open positions for passive signal conditioning components The factory default positions for the 0 Ω jumpers are the C and D positions of the input network as shown in Figure 3 1 You can remove these 0 Ω jumpers to build analog input signal conditioning circuits You can also add passive analog input signal cond...

Page 24: ...e onboard components for differential mode Figure 3 1 Channel 0 Differential Mode Onboard Components COMMON AI 8 BNC AI 8 AI 0 AI 0 R31 R32 B E A AI GND BNC SE SW9 DIFF D C Factory Installed 0 Ω Jumpers To Input Multiplexer of DAQ Device C10 R33 R30 R50 R51 G F AI GND Do Not Connect ...

Page 25: ... onboard components for single ended mode Figure 3 2 Channel 0 and Channel 8 Single Ended Mode Onboard Components COMMON AI 8 BNC AI 0 R31 R32 B A AI GND BNC RSE NRSE AI GND AI SENSE SE SW9 SW1 DIFF Factory Installed 0 Ω Jumpers AI 8 AI 0 E D C To Input Multiplexer of DAQ Device C10 R33 R30 R50 R51 G F AI GND ...

Page 26: ...hannel Position in Figures 3 1 and 3 2 Differential Single Ended A B C D E F G 0 0 8 R32 R31 R33 R30 C10 R51 R50 1 1 9 R28 R27 R29 R26 C9 R49 R48 2 2 10 R24 R23 R25 R22 C8 R47 R46 3 3 11 R20 R19 R21 R18 C7 R45 R44 4 4 12 R16 R15 R17 R14 C6 R43 R42 5 5 13 R12 R11 R13 R10 C5 R41 R40 6 6 14 R8 R7 R9 R6 C4 R39 R38 7 7 15 R4 R3 R5 R2 C3 R37 R36 Factory installed 0 Ω jumpers ...

Page 27: ... frequency Table 3 2 Signal Conditioning Component Population Options Configuration Normal Attenuator Lowpass Filter Highpass Filter AC Couple Termination Single Ended A Open Open Open Open Open Resistor B Open Open Open Open Open Resistor C 0 Ω Jumper Resistor Resistor Capacitor Capacitor 0 Ω Jumper D 0 Ω Jumper Resistor Resistor Capacitor Capacitor 0 Ω Jumper E Open Open Open Open Open Open F Op...

Page 28: ...d is preferable because more standard resistor values are available If a capacitance of 1μF is available the resistance is by substitution into Equation 3 1 about 39 8 kΩ This resistance must be split evenly between each input of a differential channel Therefore in this example each input channel has a 19 89 kΩ resistor or the closest standard value in its series positions C and D NI recommends us...

Page 29: ...Highpass Filters You can install simple RC highpass filters on any input channel of the BNC 2090A The filters are useful for accurate high frequency measurement and low frequency noise rejection By substituting resistance and capacitance values into Equation 3 1 you can calculate a simple one pole RC filter to have a 3 dB cutoff frequency fc The frequency response rolls off at a rate of 20 dB per ...

Page 30: ...equired is preferable because more standard resistor values are available The filter circuit has one series capacitor on each input signal of the differential channel Because the two capacitors are in series the capacitance value that must be substituted into Equation 3 1 is the series capacitance of the two capacitors For two capacitors in series the net capacitance is the reciprocal of the sum o...

Page 31: ...l 1 If the input signal source is floating you must place a bias return resistor in positions A and or B position R28 and R27 respectively Refer to the Installing Bias Resistors section for information about installing bias resistors Figure 3 7 Highpass Filter on Differential Channel 1 Figure 3 8 shows both the schematic and the component placement for a 50 kHz highpass filter placed on single end...

Page 32: ...vice Input voltages greater than 42 4 Vpk 60 VDC can damage the BNC 2090A all devices connected to it and the host computer Overvoltage can also cause an electric shock hazard for the operator National Instruments is not liable for damage or injury resulting from such misuse The gain in differential mode GDIFF of this attenuator is given by the Equation 3 2 3 2 The gain in single ended mode GSE of...

Page 33: ...ors on the open component positions for channel 1 Figure 3 10 Attenuator for Use with Single Ended Inputs Using the values in Figure 3 9 3 5 or Figure 3 10 3 6 Therefore in either case 3 7 When the DAQ device is configured for 10 V input signals the device can acquire 30 V signals with this attenuator circuit R29 C 10 kΩ R26 D 10 kΩ C9 E 10 kΩ To DAQ Device J10 AI 1 R29 C 20 kΩ J10 AI 1 R49 F 10 k...

Page 34: ...signal source to avoid signal loading errors Analog Output Signal Conditioning Each analog output has two open component positions for passive signal conditioning components One is designated as a resistor and one is designated as a capacitor Factory default positions for the 0 Ω jumpers are R34 and R1 as shown in Figure 3 11 Figure 3 11 AO 0 and AO 1 You can remove and or install components in th...

Page 35: ...bout lowpass filters and how to calculate values for lowpass filters Refer to Figure 3 14 for component locations Figure 3 12 shows a 4 Hz lowpass filter for AO 0 Figure 3 12 Lowpass Filter on AO 0 Building Highpass Filters Building highpass filters for analog output is the same as for analog input Refer to the Analog Input Signal Conditioning section for more detailed information about highpass f...

Page 36: ... examples using a specific channel If you want to install the circuit in a different channel consult Table 3 1 to determine the equivalent component positions for the other channels Complete the following steps to add signal conditioning components to the BNC 2090A as shown in Figure 3 14 Figure 3 14 Disassembly of the BNC 2090A 1 Remove the two rear panel screws the side panel screw the top screw...

Page 37: ...adding components The BNC 2090A is shipped with 0 Ω jumpers in the C and D positions as listed in Table 3 1 and shown in Figure 3 1 Note This product is RoHS compliant If you require that the product remain RoHS compliant ensure that you use RoHS compliant solder and components Visit ni com rohs for more information Installing Bias Resistors You can install bias resistors in positions A and B on t...

Page 38: ...in DIFF Mode Figure 3 16 shows both the schematic and the component placement for an optional user installed bias resistor R35 between AI SENSE and AI GND Figure 3 16 User Installed Bias Resistor between AI SENSE and AI GND R29 C R28 A C9 E To DAQ Device R26 D J10 AI GND R27 B 100 kΩ AI 1 2 AI SENSE R35 AI GND 1 User Installed Bias Resistor ...

Page 39: ...ectors Signal conditioning 7 component positions per differential channel Analog Output Channels 2 single ended Field connections 2 BNC connectors for AO 1 BNC connector for APFI 0 input Signal conditioning 2 component positions per output channel Digital Input and Output Channels 8 digital I O 16 PFI Field connections 1 BNC connector for PFI 0 2 BNC connectors for user defined spring terminals fo...

Page 40: ...tor Two 68 position male connectors BNC connectors 22 Spring terminal block 29 positions Environment The BNC 2090A is intended for indoor use only Operating temperature 0 to 70 C Storage temperature 55 to 125 C Relative humidity 5 to 90 RH noncondensing Pollution Degree indoor use only 2 Maximum Altitude 2 000 m Safety This product is designed to meet the requirements of the following standards of...

Page 41: ...ate this device according to product documentation CE Compliance This product meets the essential requirements of applicable European Directives as amended for CE marking as follows 73 23 EEC Low Voltage Directive safety 89 336 EEC Electromagnetic Compatibility Directive EMC Note Refer to the Declaration of Conformity DoC for this product for any additional regulatory compliance information To obt...

Page 42: ...ront panel Traditional NI DAQ Legacy naming conventions on front panel Extra spring terminal to access PFI 15 N A User installed signal conditioning components are easy to access N A More signal conditioning component options N A Attenuators voltage dividers can be used with the DAQ device in both single ended and differential modes Attenuators voltage dividers can be used with the DAQ device in d...

Page 43: ...o measure current Yes You can use a pair of channels to route current through the a sense resistor located in position E Refer to the Analog Input Signal Conditioning section of Chapter 3 Signal Conditioning for the exact location of this component Caution When adding custom signal conditioning do not exceed the components power dissipation ratings Limit current into the BNC 2090A to 100 mA Set th...

Page 44: ...truments Application Engineers make sure every question receives an answer For information about other technical support options in your area visit ni com services or contact your local office at ni com contact Training and Certification Visit ni com training for self paced training eLearning virtual classrooms interactive CDs and Certification program information You also can register for instruc...

Page 45: ...m calibration If you searched ni com and could not find the answers you need contact your local office or NI corporate headquarters Phone numbers for our worldwide offices are listed at the front of this manual You also can visit the Worldwide Offices section of ni com niglobal to access the branch office Web sites which provide up to date contact information support phone numbers email addresses ...

Page 46: ... 13 lowpass filters 3 13 signal conditioning 3 12 diagram 3 12 AO See analog output APFI diagram 2 6 signals 2 5 attenuators 3 10 for use with differential inputs 3 11 for use with single ended inputs 3 11 using SCXI resistor kit B 2 B bias resistors adding 3 14 for DC coupled floating source on channel 1 in differential mode 3 16 installing 3 15 between AI SENSE and AI GND 3 16 BNC connectors acc...

Page 47: ...5 APFI 0 signals 2 5 differential analog input signals 2 2 digital signals 2 6 digital timing signals to a BNC 2 7 PFI 0 signals 2 5 signals 2 1 single ended analog input signals 2 3 to E Series devices 1 6 to M Series devices 1 5 USER 1 2 2 7 connectors USER 1 2 BNC 2 7 conventions used in the manual v current measurement B 2 D Declaration of Conformity NI resources C 1 desoldering 3 15 diagnosti...

Page 48: ...ls 2 6 wire specifications 2 6 disconnecting the shield from the DAQ ground jumper setting 1 7 documentation conventions used in the manual v NI resources C 1 drivers NI resources C 1 E E Series device connections 1 6 diagram 1 6 enclosure back 1 2 examples NI resources C 1 F FAQs B 1 features 1 1 filters analog input lowpass 3 5 analog output lowpass 3 13 analog output highpass 3 13 highpass 3 7 ...

Page 49: ...erenced single ended mode measuring ground referenced signals 2 5 normalized frequency response of highpass filters 3 8 NRSE mode See non referenced single ended mode O overview 1 1 P PFI 2 5 connecting to USER 1 BNC 2 7 diagram 2 6 programming examples NI resources C 1 R referenced single ended mode measuring floating signals 2 4 resistors adding 3 14 bias 3 15 between AI SENSE and AI GND 3 16 lo...

Page 50: ...ut signal conditioning figure 3 3 attenuator use 3 11 diagram 2 4 measuring floating signals 2 4 measuring ground referenced signals 2 5 signals 2 3 software NI resources C 1 soldering 3 15 caution 3 15 specifications A 1 spring terminal block using the USER 1 2 pins 2 7 support technical C 1 T technical support C 1 training and certification NI resources C 1 troubleshooting NI resources C 1 U USE...

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