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Appendix C

Common Questions

©

 National Instruments Corporation

C-5

SCXI-1581 User Manual

Can I use an SCXI-1303 terminal block as an accessory for the 
SCXI-1581?

This is not recommended. The SCXI-1303 is optimized for temperature 
measurement using thermocouples. It will work with the SCXI-1581, but 
only if you remove all resistor packs. Refer to the 

SCXI-1303 32-Channel 

Isothermal Terminal Block Installation Guide

 for more information. As 

with the SCXI-1300 and BNC-2095, you cannot measure the CJC sensor.

Can I configure the SCXI-1581 in MAX for use in a chassis controlled 
by an SCXI-1200?

Yes. However, remember that you cannot auto-detect modules in a chassis 
controlled by an SCXI-1200.

Summary of Contents for SCXI-1581

Page 1: ...SCXI TM SCXI 1581 User Manual SCXI 1581 User Manual March 2003 Edition Part Number 323074B 01...

Page 2: ...any 49 0 89 741 31 30 Greece 30 2 10 42 96 427 India 91 80 51190000 Israel 972 0 3 6393737 Italy 39 02 413091 Japan 81 3 5472 2970 Korea 82 02 3451 3400 Malaysia 603 9131 0918 Mexico 001 800 010 0793...

Page 3: ...ation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of third parties or other events ou...

Page 4: ...with the product for 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 it...

Page 5: ...I Using Traditional NI DAQ 1 7 Manually Adding and Configuring Modules in Traditional NI DAQ 1 9 Verifying and Self Testing the Configuration 1 9 Configuring SCXI Using NI DAQmx 1 10 Manually Adding a...

Page 6: ...pendix C Common Questions Glossary Index Figures Figure 1 1 Installing the SCXI 1581 Module 1 4 Figure 1 2 Connecting an SCXI Chassis to an E Series DAQ Device 1 6 Figure 1 3 Removing the SCXI 1581 1...

Page 7: ...nstruments Corporation vii SCXI 1581 User Manual Tables Table 2 1 Front Signal Pin Assignments 2 2 Table 2 2 Signal Descriptions 2 3 Table B 1 Callendar Van Dusen Coefficients B 3 Table C 1 SCXI 1581...

Page 8: ......

Page 9: ...s 100 A fixed current excitation The SCXI 1581 is configured using Measurement Automation Explorer MAX What You Need to Get Started To set up and use the SCXI 1581 you need the following items SCXI 15...

Page 10: ...oad or you can contact a National Instruments sales representative to request it on a CD Installing the SCXI 1581 The following section describes how to install the SCXI 1581 for use with SCXI chassis...

Page 11: ...the SCXI 1581 module into the SCXI chassis complete the following steps while referring to Figure 1 1 1 Power off the computer that contains the E Series DAQ device or disconnect it from the SCXI cha...

Page 12: ...anning in an SCXI Chassis In this configuration you can multiplex the input channels of the analog input SCXI modules into a single channel of the E Series DAQ device You need the following items for...

Page 13: ...multaneous sampling capability you will get an error message each time you run your application Note The SCXI 1581 is not an analog input module To connect the chassis to an E Series DAQ device for mu...

Page 14: ...eries DAQ Device for Multiplexed Scanning in a PXI Combination Chassis In this configuration you can multiplex the input channels of the SCXI analog input modules into a single channel of the E Series...

Page 15: ...described in the Connecting the SCXI 1581 to an E Series DAQ Device for Multiplexed Scanning in an SCXI Chassis section 2 Power on the SCXI portion of the PXI combination chassis You should have alrea...

Page 16: ...sing multiple chassis or one or more of the chassis address DIP switches is not in the OFF position refer to the SCXI Chassis User Manual for more information c If you are using a PXI 1010 or PXI 1011...

Page 17: ...een instructions to complete the configuration When you have clicked Finish the module configuration is complete 7 Repeat steps 2 through 6 until you have added all the modules The SCXI chassis and SC...

Page 18: ...ssis go to the Manually Adding and Configuring Modules in NI DAQmx section 3 Add a new chassis to the configured devices and interfaces by holding down the right mouse button on NI DAQmx Devices and s...

Page 19: ...he Cabling tab 4 When you have finished click OK 5 When you have completed configuring the module click OK The SCXI chassis and SCXI module s should now be configured properly If you need to change th...

Page 20: ...connected to device x If you get the message Failed to find followed by the module codes and the message Unable to communicate with chassis 1 Make sure the SCXI chassis is powered on 2 Make sure the...

Page 21: ...section and retest the SCXI chassis If these measures do not successfully configure the SCXI system refer to Appendix C Common Questions for more information Removing the SCXI 1581 This section provi...

Page 22: ...al instructions and cautions To remove the SCXI 1581 module from an SCXI chassis complete the following steps while referring to Figure 1 3 1 Power off the SCXI chassis Do not remove the SCXI 1581 mod...

Page 23: ...s by expanding Devices and Interfaces a If the module is installed in a Traditional NI DAQ chassis click the next to the Traditional NI DAQ Devices icon b If the module is installed in a NI DAQmx chas...

Page 24: ...on information for these modules is also lost 4 You are presented with a confirmation window Click Yes to continue deleting the module or chassis or No to cancel this action The SCXI chassis and or SC...

Page 25: ...accurate to within 0 05 of the specified value with a temperature drift of no more than 5 ppm C The high accuracy and stability of these current sources makes them especially well suited to measuring...

Page 26: ...EX9 EX9 22 NC EX10 EX10 21 NC EX11 EX11 20 RSVD EX12 EX12 19 RSVD EX13 EX13 18 NC EX14 EX14 17 NC EX15 EX15 16 NC EX16 EX16 15 NC EX17 EX17 14 NC EX18 EX18 13 NC EX19 EX19 12 NC EX20 EX20 11 NC EX21 E...

Page 27: ...eries DAQ device and the SCXI system are SERDATIN SERDATOUT DAQD A SLOT0SEL SERCLK and SCANCLK The digital ground DIGGND on pins 24 and 33 provides a separate ground reference for the communication si...

Page 28: ...signals from other SCXI modules to the E Series DAQ device The SCXI 1581 routes multiplexed signals from other SCXI modules to the E Series DAQ device even though the SCXI 1581 does not have any anal...

Page 29: ...XI 1581 does not have any input channels to scan multiplexed scanning is the only scanning mode that is possible when the SCXI 1581 is the cabled module If the module you are scanning is directly cabl...

Page 30: ......

Page 31: ...herwise noted Stability Recommended warm up time 10 minutes Excitation Channels 32 single ended outputs Current output 100 A Accuracy 0 05 Temperature drift 5 ppm C Output voltage compliance 10 V Maxi...

Page 32: ...e requirements of the following standards for safety and electrical equipment for measurement control and laboratory use IEC 61010 1 EN 61010 1 UL 3111 1 UL 61010B 1 CAN CSA C22 2 No 1010 1 Note For U...

Page 33: ...European Directives as amended for CE marking as follows Low Voltage Directive safety 73 23 EEC Electromagnetic Compatibility Directive EMC 89 336 EEC Note Refer to the Declaration of Conformity DoC f...

Page 34: ......

Page 35: ...al RTDs drift less than 0 1 C year and some models are stable to within 0 0025 C year RTDs are sometimes difficult to measure because they have relatively low nominal resistance commonly 100 that chan...

Page 36: ...nt called alpha differs between RTD curves Although various manufacturers specify alpha differently alpha is most commonly defined as the change in RTD resistance from 0 to 100 C divided by the resist...

Page 37: ...r Van Dusen equation is commonly used to approximate the RTD curve where RT is the resistance of the RTD at temperature T R0 is the resistance of the RTD at 0 C A B and C are the Callendar Van Dusen c...

Page 38: ...raditional NI DAQ section or the Creating an RTD Virtual Channel Using NI DAQmx section depending on the version of NI DAQ you are using Creating an RTD Virtual Channel Using Traditional NI DAQ To cre...

Page 39: ...I DAQ Virtual Channels Creating an RTD Virtual Channel Using NI DAQmx To create an RTD virtual channel using traditional NI DAQ complete the following steps 1 Launch MAX 2 Right click Data Neighborhoo...

Page 40: ...measurement system that also supplies a constant current IEX to excite the RTD As shown in Figure B 2 the voltage drop across the lead resistances labeled RL adds an error voltage to the measured volt...

Page 41: ...A main advantage of thermistors for temperature measurement is their extremely high sensitivity For example a 2 252 thermistor has a sensitivity of 100 C at room temperature Higher resistance thermis...

Page 42: ...e is typically limited to around 300 C Figure B 3 shows the resistance temperature curve for a 2 252 thermistor The curve of a 100 RTD is also shown for comparison Figure B 3 Resistance Temperature Cu...

Page 43: ...or calculated from the resistance versus temperature curve Creating a Thermistor Virtual Channel Using NI DAQmx To creat an RTD virtual channel using NI DAQmx complete the following steps 1 Launch MAX...

Page 44: ...nique is to use a constant current source and measure the voltage developed across the thermistor As shown in Figure B 4 the measured voltage V0 equals RT IEX Figure B 4 Thermistor Measurement with Co...

Page 45: ...ion constant minimize the level of the excitation current to minimize self heating errors Connecting Resistive Devices to the SCXI 1581 You can connect resistive devices to the SCXI signal conditionin...

Page 46: ...pair of wires to sense the voltage across the resistive sensor Because of the high input impedance of the differential amplifier negligible current flows through the sense wires This results in a very...

Page 47: ...esistances RL1 and RL2 If we assume equal lead resistances RL1 RL2 RL the magnitude of the error voltage is VE 2RL IEX This is the most commonly used configuration for connecting thermistors to a sign...

Page 48: ...rrent flows through RL3 and therefore RL1 is the only lead resistance that introduces an error into the measurement The resulting measurement error is VE RL1 IEX An advantage of this configuration is...

Page 49: ...gure B 8 Figure B 8 3 Wire Configuration Using Matched Current Sources In this configuration the lead resistance voltage drop across RL3 is converted into a common mode voltage that is rejected by the...

Page 50: ...he value of the excitation current In this example the voltage equates to 1 V Converting this voltage into a resistance by dividing by IEX yields a resistance of 0 01 If this error is associated with...

Page 51: ...pectively the expression for V1 becomes V1 VRL1 VRT The second measurement labeled V2 in Figure B 9 is equal to the voltage drop across the lead resistance RL2 denoted as VRL2 therefore V2 VRL2 If the...

Page 52: ......

Page 53: ...ystem Can I use the SCXI 1581 with a version of NI DAQ that works under the Macintosh Operating System Mac OS At the time this manual was published you cannot auto detect or list the SCXI 1581 as a co...

Page 54: ...ded The accuracy or stability of the resulting current output value is unpredictable Can I connect N current output channels in series to achieve a higher terminal voltage compliance limit No Each cur...

Page 55: ...ystem Yes E Series DAQ device channels 1 through 7 are available to measure unconditioned signals Use an SCXI 1180 or the 50 pin breakout connector on the SCXI 1346 or SCXI 1349 cable adapter to route...

Page 56: ...ss the current output and use a voltmeter to measure the voltage drop across it If the current output is working you should measure V 100 10 6 A R where R is given in How does the screw terminal label...

Page 57: ...ng thermocouples It will work with the SCXI 1581 but only if you remove all resistor packs Refer to the SCXI 1303 32 Channel Isothermal Terminal Block Installation Guide for more information As with t...

Page 58: ......

Page 59: ...Glossary Symbol Prefix Value p pico 10 12 n nano 10 9 micro 10 6 m milli 10 3 k kilo 103 M mega 106 G giga 109 T tera 1012 Numbers Symbols percent positive of or plus negative of or minus plus or min...

Page 60: ...on a type of signal conditioning that improves accuracy in the resulting digitized signal by increasing signal amplitude relative to noise AOGND analog output ground AOGND GUARD analog output ground A...

Page 61: ...alog D A Data Address DAQ data acquisition 1 collecting and measuring electrical signals from sensors transducers and test probes or fixtures and processing the measurement data using a computer 2 col...

Page 62: ...ver software software that controls a specific hardware device such as an E Series DAQ device E EMC electromagnetic compliance EMI electromagnetic interference EX positive excitation channel EX negati...

Page 63: ...that occurs when a signal passes on the SCXIbus from the scanned SCXI module to the cabled SCXI module input bias current the current that flows into the inputs of a circuit input impedance the measur...

Page 64: ...ignal MOSI master out slave in signal multiplex to route one of many input signals to a single output multiplexed mode an SCXI operating mode in which analog input channels are multiplexed into one mo...

Page 65: ...ents are made with respect to a common measurement system reference but the voltage at this reference can vary with respect to the measurement system ground O offset error the output of a system with...

Page 66: ...red to input calculates a specification relative to the input range RTO referred to output S s seconds S samples S s samples per second used to express the rate at which a E Series DAQ device samples...

Page 67: ...g time the amount of time required for a voltage to reach its final value within specified accuracy limits signal conditioning the manipulation of signals to prepare them for digitizing Slot 0 refers...

Page 68: ...ware module VI which consists of a front panel user interface and a block diagram program virtual channels channel names that can be defined outside the application and used without having to perform...

Page 69: ...iguration B 13 3 wire resistive sensor connected in 2 wire configuration B 14 4 wire configuration B 12 lead resistance compensation using 3 wire resistive sensor and two differential amplifiers B 16...

Page 70: ...ired C 1 O operation of current sources 2 1 P physical specifications A 2 pin assignments front connector table 2 2 rear signal connector figure 2 4 power requirements from SCXI backplane A 1 PXI comb...

Page 71: ...iance A 3 electromagnetic compatibility A 2 environment A 2 excitation A 1 physical A 2 power requirements from SCXI backplane A 1 safety A 2 stability A 1 stability specifications A 1 T temperature m...

Page 72: ...rcuits B 10 overview B 7 resistance temperature characteristics B 9 resistance temperature curve figure B 8 troubleshooting self test verification 1 12 U unpacking SCXI 1520 1 2 V verifying and self t...

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