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Chapter 4

Signal Conditioning

©

National Instruments Corporation

4-7

AMUX-64T User Manual

Connecting Ground-Referenced Signal Sources

A grounded signal source is connected in some way to the building system
ground; therefore, the signal source is already connected to a common
ground point with respect to the DAQ board (assuming the host computer
is plugged into the same power system). Nonisolated outputs of
instruments and devices that plug into the building power system fall into
this category.

Differential Inputs

If the MIO DAQ board is configured for differential inputs,
ground-referenced signal sources connected to the AMUX-64T board need
no special components added to the AMUX-64T board. You can leave the
inputs of the AMUX-64T board in the factory-original condition, that is,
with only jumpers in the two series positions, E and F (see Table 4-1).
You can build signal conditioning circuitry, such as filters and attenuators
(described in

Building Lowpass Filters

Building Highpass Filters

, and

Building Attenuators (Voltage Dividers)

later in this chapter), in the open

component positions.

Single-Ended Inputs

When measuring ground-referenced signals, the external signal supplies
its own reference ground point and the MIO board should not supply one.
Therefore, you should configure the MIO board for nonreferenced
single-ended input mode. In this configuration, you should tie all of the
signal grounds to AISENSE, which connects to the negative input of the
instrumentation amplifier on the MIO board. You can leave the inputs of
the AMUX-64T board in the factory-default condition, that is, with
jumpers in the series position (E or F, depending on the channel). You
should not use the open positions that connect the input to AIGND, B and
D (see Table 4-1 and Figure 4-1) in this configuration. Therefore, you
should not build signal conditioning circuitry requiring a ground reference
in the open component positions. Referencing the signal to AIGND can
cause inaccurate measurements resulting from an incorrect ground
reference.

Caution

N

EVER

connect a signal to screw terminals CH0–CH63 that violates their

overvoltage protection limits. When the AMUX-64T is powered on, the screw
terminals CH0–CH63 overvoltage protection is ±35 V; when the AMUX-64T is
powered off, overvoltage protection is ±20 V.

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Содержание AMUX-64T

Страница 1: ...DAQ AMUX 64T User Manual Analog Multiplexer with Temperature Sensor AMUX 64T User Manual January 1999 Edition Part Number 320253C 01...

Страница 2: ...36 Canada Ontario 905 785 0085 Canada Qu bec 514 694 8521 Denmark 45 76 26 00 Finland 09 725 725 11 France 01 48 14 24 24 Germany 089 741 31 30 Hong Kong 2645 3186 Israel 03 6120092 Italy 02 413091 Ja...

Страница 3: ...NSEQUENTIAL DAMAGES EVEN IF ADVISED OF THE POSSIBILITY THEREOF This limitation of the liability of National Instruments will apply regardless of the form of action whether in contract or tort includin...

Страница 4: ...ication Software 1 3 NI DAQ Driver Software 1 3 Register Level Programming 1 6 Optional Equipment 1 7 Chapter 2 Configuration and Installation Board Configuration 2 1 Power Temperature Sensor and Shie...

Страница 5: ...4 Channel Configurations 4 5 Connecting Nonreferenced or Floating Signal Sources 4 5 Differential Inputs 4 5 Single Ended Inputs 4 6 Connecting Ground Referenced Signal Sources 4 7 Differential Inputs...

Страница 6: ...el 1 4 6 Figure 4 3 Normalized Frequency Response of Lowpass Filter 4 8 Figure 4 4 Lowpass Filter on Differential Channel 1 4 9 Figure 4 5 Normalized Frequency Response of Highpass Filter 4 10 Figure...

Страница 7: ...Settings for Four Board Configuration 2 10 Table 3 1 Pin Mapping for I O Connectors J1 J2 and J42 3 2 Table 3 2 Thermocouple Voltage Output Extremes mV 3 6 Table 3 3 NIST Polynomial Coefficients 3 8...

Страница 8: ...need to get started with your AMUX 64T describes the software programming choices and optional equipment and explains how to unpack your AMUX 64T Chapter 2 Configuration and Installation describes the...

Страница 9: ...data loss or a system crash This icon to the left of bold italicized text denotes a warning which advises you of precautions to take to avoid being electrically shocked bold italic Bold italic text d...

Страница 10: ...tion to help you write your application If you have a large and complicated system it is worthwhile to look through the software documentation before you configure your hardware Accessory installation...

Страница 11: ...mments on our products and manuals We are interested in the applications you develop with our products and we want to help if you have problems with them To make it easy for you to contact us this man...

Страница 12: ...for low cost thermocouple cold junction compensation Cold junction compensation is achieved by adding the temperature reading of the sensor to the temperature readings of thermocouples at the remainin...

Страница 13: ...metal part of your computer chassis before removing the device from the package Remove the device from the package and inspect the device for loose components or any other sign of damage Notify Natio...

Страница 14: ...LabWindows for DOS is for use on PCs running DOS and LabWindows CVI is for use on PCs running Windows and for Sun SPARCstations LabWindows CVI features interactive graphics a state of the art user in...

Страница 15: ...DIO 24 can transfer data using interrupts or software polling With the NI DAQ Resource Manager you can simultaneously use several functions and several DAQ devices The Resource Manager prevents multip...

Страница 16: ...C for Windows and Microsoft Visual C for Windows NT You can use your AMUX 64T together with other PC AT MC EISA DAQCard and DAQPad Series DAQ and SCXI hardware with NI DAQ software for PC compatibles...

Страница 17: ...lways consider using NI DAQ LabVIEW or LabWindows to program your National Instruments DAQ hardware Using the NI DAQ LabVIEW or LabWindows software is easier than and as flexible as register level pro...

Страница 18: ...0 5 or 1 0 m cable SH6868 shielded cable assembly with 1 2 5 or 10 m cable SH6850 shielded cable assembly with 1 2 5 or 10 m cable R6868 1 m ribbon cable assembly R6850 1 m ribbon cable assembly Rack...

Страница 19: ...ch at U12 configures the AMUX 64T for single board or multiple board operation Switch SW1 selects either the internal 5 V power from the MIO board or an external 5 V power source for the AMUX 64T Jump...

Страница 20: ...64T User Manual 2 2 National Instruments Corporation Figure 2 1 AMUX 64T Parts Locator Diagram 1 Serial Number 2 J1 3 W1 4 J2 5 J42 6 Temperature Sensor 7 Product Name and Assembly Number 8 U12 9 W2 1...

Страница 21: ...ion Use this setting to draw 5 V power from an external supply connected to connector J41 Table 2 2 Temperature Sensor Selection Jumper Description Configuration CH0 and CH32 position Use this setting...

Страница 22: ...lection Jumper Description Configuration No Connect position Use this setting to disconnect the AMUX 64T analog ground from the shield of a rack mounted chassis factory setting AIGND position Use this...

Страница 23: ...Semiconductor LM 35CZ that provides a voltage output of 10 m V C with an accuracy of 1 C The sensor is jumper selected on differential input channel 0 Table 2 4 MIO Board Power Budget Board Power Allo...

Страница 24: ...isolated from the rack Jumper W3 connects the shield of the 68 position connector to the rack mount kit Setting this jumper to the CABLE SHLD position connects the shield of the 68 position connector...

Страница 25: ...s to different AMUX 64T boards Table 2 5 lists the description and configuration of the switches Note In all of the following dual in line package DIP switch illustrations the dark shaded end of the s...

Страница 26: ...rmined by the configuration of switch U12 The switch settings for each board configuration are given in the following sections Table 2 6 Channel Ranges for Multiple AMUX 64T Boards Number of External...

Страница 27: ...board has a different switch setting You assign the first board channel addresses from 0 to 63 the second board channel addresses from 64 to 127 the third board channel addresses from 128 to 191 and...

Страница 28: ...ard I O connector to J42 on the AMUX 64T If you use more than one AMUX 64T you can daisy chain the boards by connecting J1 or J2 on one AMUX 64T to J1 or J2 on another AMUX 64T and so on see Figure 2...

Страница 29: ...sitioning for the AMUX 64T Power On Sequence If the AMUX 64T is powered by an external power source you must turn on power to the AMUX 64T before turning on the computer Similarly you must turn off po...

Страница 30: ...any way If it is damaged disconnect power and do not use the board until service trained personnel can check its safety If necessary return the board to National Instruments for service and repair to...

Страница 31: ...pping for I O Connectors J1 J2 and J42 50 Pin Connector J1 and J2 Pin Numbers 68 Pin Connector J42 Pin Numbers 1 2 24 27 29 32 56 59 64 67 3 68 4 34 5 33 6 66 7 65 8 31 9 30 10 63 11 28 12 61 13 60 14...

Страница 32: ...al 25 52 26 19 27 17 28 51 29 49 30 16 31 47 32 48 34 35 8 14 36 46 37 45 38 11 39 10 40 43 41 42 42 41 43 40 44 6 45 5 46 38 47 37 48 3 49 2 50 1 Table 3 1 Pin Mapping for I O Connectors J1 J2 and J4...

Страница 33: ...E pin and that AIGND on the AMUX 64T is connected to the AIGND signal of the MIO board Figure 3 1 AMUX 64T Signal Routing AMUX 64T Input Signals Signals Sent to MIO Board CH0 CH1 CH2 CH3 CH4 CH5 CH6 C...

Страница 34: ...either differential or single ended configurations Differential connection tends to yield the best results but single ended connection allows twice as many thermocouples to be used on each AMUX 64T T...

Страница 35: ...r memory usage The polynomials are in the following form where x is the thermocouple voltage in volts T is the temperature difference between the measuring end and the AMUX 64T screw terminals in degr...

Страница 36: ...written several extra multiplications will be performed to raise x to the various powers If the polynomial is instead written as follows and evaluated this way no powers are computed and execution pro...

Страница 37: ...31 1 2668171E 24 c8 1 1564890E 29 1 0629823E 35 8 3823321E 29 c9 3 2447087E 41 R R S S K K 50 C to 250 C 0 02 C 250 C to 1 200 C 0 005 C 50 C to 250 C 0 02 C 250 C to 1 200 C 0 01 C 200 C to 0 C 0 04...

Страница 38: ...Check with the vendor to determine the output polarity of any particular thermocouple Since thermocouples are floating signal sources you must attach a bias return resistor between the negative chann...

Страница 39: ...be either 1 or 10 10 for the best resolution Multiply the voltage by 100 to get the AMUX 64T temperature in degrees Celsius For example if the reading is 0 25 V the AMUX 64T is at 25 C 2 Translate the...

Страница 40: ...on temperature from step 1 to the temperature obtained in the previous step This result is the temperature at the measuring end of the thermocouple For the example given the temperature is 175 C 25 C...

Страница 41: ...Sources of Error There are several major sources of error when making thermocouple measurements with the AMUX 64T and an MIO board These sources of error are compensation linearization measurement an...

Страница 42: ...n on thermocouple wire errors and more specific data see Application Note 043 Measuring Temperature with Thermocouples Thermocouple Measurement Accuracies Table 3 4 lists the expected thermocouple acc...

Страница 43: ...uments Corporation Other Connection Considerations Refer to the sections titled Analog Input Signal Connections and Cabling and Field Wiring in the Signal Connections chapter of the user manual that c...

Страница 44: ...designated as resistors and one is designated as a capacitor The board is shipped with jumpers in two positions for each input The equivalent circuit of one input is shown in Figure 4 1 You can use th...

Страница 45: ...ble 4 1 Component Positions in Each Channel Channel Positions in Figure 4 1 Differential Single Channel A B C D E F G 0 0 32 R1 R2 R3 R4 R65 R66 C3 1 1 33 R5 R6 R7 R8 R67 R68 C4 2 2 34 R9 R10 R11 R12...

Страница 46: ...17 17 49 R133 R134 R135 R136 R99 R100 C38 18 18 50 R137 R138 R139 R140 R101 R102 C39 19 19 51 R141 R142 R143 R144 R103 R104 C40 20 20 52 R145 R146 R147 R148 R105 R106 C41 21 21 53 R149 R150 R151 R152...

Страница 47: ...lowing applications require you to make modifications to the printed circuit board usually in the form of removing jumpers and adding components The AMUX 64T board is shipped with wire jumpers in the...

Страница 48: ...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 outputs for the following thermoco...

Страница 49: ...ed to the analog ground Therefore you should use the AMUX 64T board in its factory configuration In the factory configuration jumpers are in the two series positions E and F see Table 4 1 In this conf...

Страница 50: ...n this chapter in the open component positions Single Ended Inputs When measuring ground referenced signals the external signal supplies its own reference ground point and the MIO board should not sup...

Страница 51: ...malized frequency is shown in Figure 4 3 Figure 4 3 Normalized Frequency Response of Lowpass Filter When measuring low frequency signals about 4 Hz if you have 400 Hz noise on your inputs you can add...

Страница 52: ...ds using 1 or better tolerance resistors in this application because differences between the resistor values degrade the common mode rejection ratio Figure 4 4 shows both the schematic and the compone...

Страница 53: ...ized frequency is shown in Figure 4 5 Figure 4 5 Normalized Frequency Response of Highpass Filter When measuring high frequency signals about 50 kHz if you have 50 Hz noise on your inputs you can add...

Страница 54: ...on 4 2 6 366 or about 6 4 k Therefore in this example the input channel has a 6 37 k resistor or closest standard value in its capacitor position G The closest standard 5 tolerance resistors are 6 2 k...

Страница 55: ...is outside the normal input range of the DAQ board 10 V max Warning The AMUX 64T board is not designed for any input voltages greater than 42 V even if a user installed voltage divider reduces the vol...

Страница 56: ...Channel 1 The gain G of this attenuator is given by the following equation 4 3 Therefore the input to the MIO board VMIO is where VSC is the voltage applied to the screw terminals of the AMUX 64T The...

Страница 57: ...anual 4 14 National Instruments Corporation Example Using the values in Figure 4 7 Therefore When the MIO board is configured for 10 V inputs the board can acquire 30 V signals with this attenuator ci...

Страница 58: ...contains register level programming information for the MIO board Note If you plan to use a software package such as LabWindows NI DAQ or LabVIEW with your MIO board you need not read this chapter Fu...

Страница 59: ...MUX 64T scanning counter The MIO signal SCANCLK which is active during scanned data acquisition switches the input channels automatically on the AMUX 64T after each A D conversion CH0 CH1 CH2 CH3 Jump...

Страница 60: ...ore an AMUX 64T channel can be selected digital I O port A must be enabled as a digital output port You can enable this port by setting the DOUTEN0 bit in the MIO Command Register 2 this bit has diffe...

Страница 61: ...Table 5 1 AMUX 64T Channel Selection Channel Number Mux Gain Register MA 3 0 Digital Port A Bits ADO 1 0 0 0000 00 1 0000 01 2 0000 10 3 0000 11 4 0001 00 5 0001 01 6 0001 10 7 0001 11 28 0111 00 29...

Страница 62: ...single channel This 8 bit address must be split and written to the Digital Output Register and the Mux Gain Register the Mux Mem Register in the AT MIO 16F 5 Figure 5 3 shows the mapping of the 8 bit...

Страница 63: ...to load the channel address into the AMUX 64T scanning counter 3 Write to the MA 3 0 bits in the Mux Gain Register to select the four to one multiplexer on the AMUX 64T you want to address Now follow...

Страница 64: ...nput in the sequence When the MIO board is used alone a single level multiplexer switches the 16 input channels to the analog to digital converter ADC A two level multiplexer must be controlled when a...

Страница 65: ...64T channels must be scanned for every MIO board input channel For example channels 0 through 3 on AMUX 64T board A and channels 64 through 67 on AMUX 64T board B are multiplexed together into MIO bo...

Страница 66: ...2 3 CH0 MIO Board Two Board Configuration Board B 4 5 6 7 CH0 CH1 CH2 CH3 Board A Scanning Order 0 1 2 3 CH0 MIO Board CH0 64 CH1 65 CH2 66 CH3 67 8 9 10 11 CH0 CH1 CH2 CH3 Board A Four Board Configur...

Страница 67: ...r for Each MIO Board Input Channel MIO Board AMUX 64T Channels One Board Two Boards Four Boards Board A Board A Board B Board A Board B Board C Board D 0 0 3 0 3 64 67 0 3 64 67 128 131 192 195 1 4 7...

Страница 68: ...iguration The scanning order becomes complex only when more than one AMUX 64T board is used During interval scanning the number of channels scanned during an interval is four times the channel scan se...

Страница 69: ...the Counter 1 mode value Write FF09 to the Am9513 Command Register to select the Counter 1 Load Register Write the divide down value to the Am9513 Data Register to load counter 4 The divide down valu...

Страница 70: ...umber of channels Single board 64 single ended or 32 differential Two boards 128 single ended or 64 differential Four boards connected 256 single ended or 128 differential Input signal ranges Differen...

Страница 71: ...O 16E 2 AT MIO 16E 10 NB MIO 16 FS 0 to FS FS 0 to FS FS 0 to FS 5 5 3 9 8 1 5 3 9 8 14 12 2 5 3 9 8 5 5 3 9 8 10 6 4 9 8 20 15 20 6 5 10 9 50 7 6 11 10 100 9 8 12 11 20 20 500 50 50 Two AMUX 64T Boar...

Страница 72: ...r external power 5 VDC 5 150 mA typ Physical Dimensions 12 75 by 3 80 in 32 43 by 9 65 cm I O connector Two 50 pin male ribbon cable connectors one 68 pin male shielded or ribbon cable connector 78 sc...

Страница 73: ...Appendix A Specifications AMUX 64T User Manual A 4 National Instruments Corporation Environment Operating temperature 0 to 70 C Storage temperature 55 to 150 C Relative humidity 5 to 90 noncondensing...

Страница 74: ...es not answer your questions we offer fax and telephone support through our technical support centers which are staffed by applications engineers Electronic Services Bulletin Board Support National In...

Страница 75: ...office in your country contact the source from which you purchased your software to obtain support Country Telephone Fax Australia 03 9879 5166 03 9879 6277 Austria 0662 45 79 90 0 0662 45 79 90 19 Be...

Страница 76: ...___ Instruments used _________________________________________________________________ _______________________________________________________________________________ National Instruments hardware pro...

Страница 77: ...________________________________________________________ National Instruments software ______________________________________________________ Other boards in system ___________________________________...

Страница 78: ..._______ _______________________________________________________________________________ _______________________________________________________________________________ ________________________________...

Страница 79: ...9 micro 10 6 m milli 10 3 k kilo 103 M mega 106 Numbers Symbols degrees greater than greater than or equal to less than negative of or minus ohms percent plus or minus positive of or plus 5 V 5 Volts...

Страница 80: ...s cm centimeters CMOS complementary metallic oxide semiconductor CNTINT Counter Interrupt signal D D A digital to analog D A Data Address signal DAC digital to analog converter DAC OUTPUT UPDATE DAC o...

Страница 81: ...ased programmable read only memory EPP Enhanced Parallel Port EXTCONV External Convert signal EXTTRIG External Trigger signal EXTUPDATE External Update signal F ft feet G GATB 0 2 Counter B0 B1 B2 Gat...

Страница 82: ...t significant bit N NRSE nonreferenced single ended O OBF Output Buffer Full signal OUTB0 OUTB1 Counter B0 B1 Output signals P PA PB PC 0 7 Port A B or C 0 through 7 signals POSTTRIG Posttrigger mode...

Страница 83: ...l SERDATOUT Serial Data Out signal SLOT0SEL Slot 0 Select signal SPICLK Serial Peripheral Interface Clock signal SS Slot select signal STB Strobe Input signal T TTL transistor transistor logic typ typ...

Страница 84: ...Glossary AMUX 64T User Manual G 6 National Instruments Corporation Vrms volts root mean square Vs signal source W W watts WRT Write signal...

Страница 85: ...ifications A 1 onboard equivalent circuit figure 4 2 attenuators voltage dividers building 4 12 to 4 14 attenuators for use with differential inputs figure 4 13 input voltage greater than 42 V warning...

Страница 86: ...on 2 6 single board configuration factory settings 2 9 jumper settings table 2 7 temperature sensor selection jumper settings table 2 3 supplementary information 2 5 to 2 6 two board configuration ins...

Страница 87: ...thermocouple data 3 6 to 3 9 lowpass filters building 4 8 to 4 9 lowpass filter on differential channel 1 figure 4 9 normalized frequency response figure 4 8 to 4 9 M manual See documentation MIO boa...

Страница 88: ...ch channel table 4 2 to 4 4 onboard equivalent circuit figure 4 2 application notes 4 4 to 4 14 building attenuators voltage dividers 4 12 to 4 14 attenuators for use with differential inputs figure 4...

Страница 89: ...or A 3 environment A 4 physical A 3 power requirement A 3 switch settings See configuration T technical support B 1 to B 2 telephone and fax support numbers B 2 temperature sensor selection jumper set...

Страница 90: ...T User Manual I 6 National Instruments Corporation thermocouple output extremes table 3 6 using more than one AMUX 64T 3 12 U unpacking the AMUX 64T 1 2 V voltage dividers See attenuators voltage divi...

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