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National Instruments NI 435 Series Скачать руководство пользователя страница 6

Contents

NI 435x User Manual

viii

ni.com

Optimizing Measurements .............................................................................. 2-8

Auto-Zero ......................................................................................... 2-9
Programmable Ground-Referencing................................................. 2-9
Programmable Open-Thermocouple Detection................................ 2-9
AC Noise Effects .............................................................................. 2-10
Thermal EMF ................................................................................... 2-10

Measuring DC Voltage.................................................................................................. 2-11

Connecting the DC Voltage Signal ................................................................. 2-11
Input Ranges ................................................................................................... 2-11
Optimizing Measurements .............................................................................. 2-11

Auto-Zero ......................................................................................... 2-12
Programmable Ground-Referencing................................................. 2-12
Programmable Open-Thermocouple Detection................................ 2-12
Source Impedance............................................................................. 2-12
AC Noise Effects .............................................................................. 2-13
Thermal EMF ................................................................................... 2-13

Measuring Temperature with RTDs and Thermistors and Measuring Resistance........ 2-13

Introduction to RTDs ...................................................................................... 2-14

Relationship of Resistance and Temperature in RTDs..................... 2-14

Connecting the RTD ....................................................................................... 2-16
Introduction to Thermistors ............................................................................ 2-18

Resistance-Temperature Characteristic of Thermistors.................... 2-20

Connecting the Thermistor.............................................................................. 2-20
Connecting the Resistor .................................................................................. 2-21
Input Ranges ................................................................................................... 2-23
Optimizing Measurements .............................................................................. 2-24

Auto-Zero ......................................................................................... 2-24
Programmable Ground-Referencing................................................. 2-25
Programmable Open-Thermocouple Detection................................ 2-25
Connecting to External Circuits ....................................................... 2-25
2-Wire, 3-Wire, and 4-Wire Measurements ..................................... 2-25
Self-Heating...................................................................................... 2-26
AC Noise Effects .............................................................................. 2-26
Thermal EMF ................................................................................... 2-27

Using the Current Source .............................................................................................. 2-27
Using Digital Inputs and Outputs .................................................................................. 2-27

Connecting the Digital Input and Output ........................................................ 2-28

Appendix A
Specifications

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Содержание NI 435 Series

Страница 1: ...DAQ NI 435x User Manual High Precision Temperature and Voltage Meters NI 435x User Manual September 2003 Edition Part Number 370841A 01...

Страница 2: ...Germany 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...

Страница 3: ...rvice failures caused by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent act...

Страница 4: ...ent 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 T...

Страница 5: ...1 4 What Is the MAX Create New Channel Wizard 1 6 Installing the Software and Hardware 1 6 LED Patterns 1 6 Optional Equipment 1 8 Power Considerations for the NI USB 4350 1 8 Safety Information 1 9...

Страница 6: ...istors and Measuring Resistance 2 13 Introduction to RTDs 2 14 Relationship of Resistance and Temperature in RTDs 2 14 Connecting the RTD 2 16 Introduction to Thermistors 2 18 Resistance Temperature C...

Страница 7: ...Contents National Instruments Corporation ix NI 435x User Manual Appendix B Signal Connections Appendix C Technical Support and Professional Services Glossary Index...

Страница 8: ...enotes a note which alerts you to important information This icon denotes a caution which advises you of precautions to take to avoid injury data loss or a system crash When this symbol is marked on t...

Страница 9: ...software and NI DAQ software documentation National Instruments application software includes LabVIEW LabWindows CVI and VirtualBench Logger After you set up the hardware system use either the applic...

Страница 10: ...ith standard benchtop instruments such as data loggers and digital multimeters DMMs The NI 435x contains a 24 bit sigma delta analog to digital converter ADC with differential analog inputs The low le...

Страница 11: ...urements Detailed specifications for the NI 435x DAQ devices are in Appendix A Specifications Using PXI with CompactPCI Using PXI compatible products with standard CompactPCI products is an important...

Страница 12: ...rformance easy to use virtual instruments application program for use with the NI 435x devices Yes Use the NI DAQ instrument driver Use virtual channels with the MAX Create New Channel Wizard Configur...

Страница 13: ...enhances traditional programming languages The LabWindows CVI Data Acquisition Library a series of functions for using LabWindows CVI with National Instruments DAQ hardware is included with the NI DAQ...

Страница 14: ...LabVIEW NI DAQ provides support for all NI 435x functions Whether you are using the NI 435x instrument driver VirtualBench Logger LabVIEW LabWindows CVI or Visual Basic the application uses NI DAQ as...

Страница 15: ...e also known as a virtual channel is then referenced throughout the application with all of the conversion processes performed transparently Notes Using virtual channels and NI DAQ you can completely...

Страница 16: ...is recognized but not configured 2 blinks Addressed state The host computer detects the NI USB 4350 but cannot configure it because NI DAQ is improperly installed or system resources are unavailable C...

Страница 17: ...the USB power supply internal protection circuitry turns off most of the circuitry in the NI USB 4350 to protect the USB supply This over current condition makes the LED blink in the power supply ove...

Страница 18: ...Corporation 1 9 NI 435x User Manual Safety Information For safety information that is relevant to the NI 435x devices refer to the Read Me First Safety and Radio Frequency Interference document that s...

Страница 19: ...artup before taking measurements To maximize the relative accuracy of measurements take all measurements after the NI 435x device warms up for about 30 minutes Choosing a Measurement Mode Each analog...

Страница 20: ...tualBench Logger or the MAX Create New Channel Wizard you can specify the range based on the sensor type in engineering units appropriate to the sensor This sensor range is used to automatically set t...

Страница 21: ...the NI 435x devices to fully charge or discharge To optimize measurement accuracy and minimize the noise level choose the 10 Hz notch filter setting In practice most of the noise encountered in measur...

Страница 22: ...or exposed junctions connected to grounded test points The outputs of plug in devices with nonisolated outputs Voltage across RTDs thermistors or resistors that you may be measuring using the built in...

Страница 23: ...and CH rises rapidly above 100 mV if the thermocouple breaks open All thermocouples functioning under normal conditions generate a voltage of less than 100 mV even at very high temperatures which make...

Страница 24: ...tromotive force EMF However just measuring this voltage is not sufficient because connecting the thermocouple to the NI 435x accessory creates the reference junction or cold junction shown in Figure 2...

Страница 25: ...bVIEW and MAX virtual channels the software includes examples that perform these temperature to voltage and voltage to temperature conversions for the cold junction thermistor and various types of the...

Страница 26: ...DC when the NI 435x is powered on and 17 VDC when the NI 435x is powered off The NI 435x analog inputs are protected against damage from voltages within 42 VDC in all ranges when powered on and 17 VDC...

Страница 27: ...s floating switch on ground referencing on that channel Otherwise the thermocouple inputs may float out of the input common mode limits of the NI 435x device On all the NI 435x accessories used with t...

Страница 28: ...f the thermocouple or gauge of the wire use a wire of larger diameter Alternatively you can switch off the open thermocouple detection to eliminate the current injected into the thermocouple AC Noise...

Страница 29: ...r exceed 42 VDC when the NI 435x is powered on and 17 VDC when the NI 435x is powered off Input Ranges The NI 435x has six bipolar input ranges available for measuring DC voltage These ranges are 625...

Страница 30: ...ble Ground Referencing If you determine that the signal source is ground referenced switch off ground referencing on that channel If you determine that the signal source is floating switch on ground r...

Страница 31: ...signal can introduce errors in measurements that change with variations in temperature To minimize thermal EMFs use copper wires to connect the signal to the NI 435x accessory Avoid using dissimilar m...

Страница 32: ...an be difficult to measure because they have relatively low resistance 100 that changes only slightly with temperature less than 0 4 C To accurately measure these small changes in resistance you may n...

Страница 33: ...D in at 0 C A B and C are the Callendar Van Dusen coefficients shown in Table 2 4 and TRTD is the temperature in C For temperatures above 0 C coefficient C equals 0 Therefore for temperatures above 0...

Страница 34: ...435x accessory that also supplies a constant current source IEX to excite the RTD As shown in Figure 2 4 the voltage drop across the lead resistance RL adds to the measured voltage Figure 2 4 2 Wire R...

Страница 35: ...sistance error of RL2 and RL3 is negligible Figure 2 5 illustrates this configuration Figure 2 5 4 Wire RTD Measurement Alternatively you can use a 3 wire RTD Figure 2 6 shows a 3 wire RTD configurati...

Страница 36: ...details Introduction to Thermistors A thermistor is a piece of semiconductor made from metal oxides pressed into a small bead disk wafer or other shape which is sintered at high temperatures and final...

Страница 37: ...or example while RTD measurements typically require 4 wire or 3 wire connections to reduce errors caused by lead wire resistances 2 wire connections to thermistors are usually adequate The major trade...

Страница 38: ...15 and Rt is the resistance of the thermistor The coefficients a b and c can be provided by the thermistor manufacturer or calculated from the resistance versus temperature curve Software packages su...

Страница 39: ...details Connecting the Resistor You can use signal connection techniques described in the Connecting the RTD section and the Connecting the Thermistor section for any resistor as well The NI 435x acc...

Страница 40: ...IEX0 Internal to the NI 435x 2 5 V Ground Referencing Off Open Thermocouple Detection Off Ground Referencing Off Open Thermocouple Detection On Ground Referencing On Open Thermocouple Detection On Gr...

Страница 41: ...es for resistance measurements These ranges are 25 k 50 k 100 k 150 k 300 k and 600 k with the 25 A current source These ranges correspond to the six input ranges available for measuring DC voltages d...

Страница 42: ...ange The input common mode limits are 2 5 V and 15 V for the lower three and higher three input ranges respectively For resistance higher than 25 k a settling time of over 1 s may be required when cha...

Страница 43: ...that use the current source Connecting to External Circuits Refer to Figures 2 10 and 2 11 for examples of how different transducers connect to analog channels in the same measurement setup To measur...

Страница 44: ...onstants range anywhere from less than 0 5 mW C for still air to 10 mW C or higher for a thermistor immersed in water A 5 000 thermistor powered by a 25 A excitation current dissipates as follows I2R...

Страница 45: ...onnections Also keep out temperature gradients in the space enclosing the signal source the NI 435x and its accessories Using the Current Source The NI 435x features a precision current source which s...

Страница 46: ...tting the trigger start the analog acquisition Connecting the Digital Input and Output All NI 435x accessories are designed to be used for DIO Refer to the accessory installation guide for instruction...

Страница 47: ...above these levels to these signals Note If the number of digital input lines is not adequate for the application you can use the analog input channels to measure the voltage of the digital signal you...

Страница 48: ...Operating the NI 435x Device NI 435x User Manual 2 30 ni com Table 2 6 Logic Family Thresholds Logic Family Low High CMOS 0 8 V 2 0 V TTL 0 8 V 2 0 V Note Check the logic family data sheets for any v...

Страница 49: ...ions Thermocouple Accuracy1 1 Thermocouple measurement specifications include cold junction compensation error with sensor between 15 C and 35 C isothermal accuracy and system noise The specifications...

Страница 50: ...82 1 16 1 65 0 06 0 12 1 000 0 72 0 99 1 37 1 767 0 91 1 19 1 60 S 250 0 91 1 28 1 83 0 07 0 13 1 000 0 77 1 05 1 47 1 767 0 96 1 27 1 72 B 600 1 08 1 64 2 47 0 11 0 00 1 000 0 76 1 14 1 69 1 820 0 74...

Страница 51: ...C 15 C 35 C 55 C Filter Setting Temperature Coefficient C C RTD C 10 Hz 50 Hz 60 Hz Pt 100 200 1 00 1 33 1 81 0 01 0 1 14 1 49 2 00 100 1 22 1 58 2 10 300 1 38 1 76 2 32 600 1 66 2 08 2 69 2 RTD spec...

Страница 52: ...Filter Setting 10 Hz 50 Hz 60 Hz Temperature Coefficient 0 C 15 C 35 C 55 C Thermistor C C C C 5 000 0 50 0 03 0 001 2 Voltage specifications do not include errors resulting from common mode voltages...

Страница 53: ...24 21 24 57 0 0013 100 000 0 0355 0 0384 0 0414 0 51 1 00 1 28 1 26 1 60 1 80 0 0013 50 000 0 0361 0 0390 0 0420 0 45 0 80 1 02 1 21 1 46 1 62 0 0013 25 000 0 0373 0 0402 0 0432 0 41 0 54 0 74 1 18 1...

Страница 54: ...C filter setting of 10 Hz accuracy is 0 73 C as a result of 0 42 C 38 C 35 C 0 02 0 25 C Measurement of 1 V using 1 25 V range filter setting of 60 Hz at 28 C ambient temperature after 90 days of cali...

Страница 55: ...ics Input impedance Normal powered on 1 G in parallel with 0 39 F Powered off 10 k Overload 10 k Open thermocouple detection 10 M between CH and 2 5 V software selectable Ground referencing 10 M betwe...

Страница 56: ...8 Compatibility TTL DIO 0 3 7 0 001 3 0 0004 7 Parameter IEX or IEX0 IEX1 Level 25 A 1 mA1 Maximum Load Resistance 600 k 15 k Temperature Coefficient 15 ppm C 15 ppm C 1 The 1 mA excitation level is...

Страница 57: ...mA at 5 V Power available at I O connector 4 6 V to 5 2 V 1 A PXI PCI 4 6 V to 5 2 V 50 mA USB Physical Dimensions USB 14 6 21 3 3 8 cm 5 8 8 4 1 5 in PXI 16 10 cm 6 3 3 9 in PCI PCI half size I O co...

Страница 58: ...uipment 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 UL and other safety certifications refer to the product label or visit...

Страница 59: ...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 for this product for any additio...

Страница 60: ...with it Table B 1 shows how the screw terminals on the TBX 68 connector block and the SH6868 cable and the R6868 cables correspond to the signal names on the NI 435x USB PXI PCI Table B 1 Using the NI...

Страница 61: ...H8 57 CH8 23 CH9 22 CH9 55 CH10 54 CH10 21 CH11 19 CH11 53 CH12 52 CH12 18 CH13 17 CH13 50 CH14 49 CH14 15 CH15 13 CH15 46 IEX IEX0 NI 4351 12 IEX IEX0 NI 4351 45 Table B 1 Using the NI 435x USB PXI P...

Страница 62: ...38 39 40 41 42 AGND 9 10 11 14 16 20 24 27 32 43 44 47 48 51 56 59 64 67 1 Screw terminals 10 and 44 are AGND on the NI 4350 only and are not labeled AGND on revision C or later of the TBX 68T 2 The c...

Страница 63: ...ct NI engineers and other measurement and automation professionals by visiting ni com support Our online system helps you define your question and connects you to the experts by phone discussion forum...

Страница 64: ...ou 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 als...

Страница 65: ...y 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 degree negative of or minus ohm per percent plus or minus positive o...

Страница 66: ...1 B byte eight related bits of data an eight bit binary number Also used to denote the amount of memory required to store one byte of data bandwidth the range of frequencies present in a signal or the...

Страница 67: ...d measuring electrical 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...

Страница 68: ...le read only memory ROM that can be erased with an electrical signal and reprogrammed EMF electromotive force event the condition or state of an analog or digital signal F filters digital or analog ci...

Страница 69: ...designated activity ITS International Temperature Scale K K 1 kelvin 2 kilo the prefix for 1 024 or 210 used with B in quantifying data or computer memory kbytes s a unit for data transfer that means...

Страница 70: ...isplays computers electrical storms welders radio transmitters and internal sources such as semiconductors resistors and capacitors Noise corrupts signals you are trying to send or receive NPN type of...

Страница 71: ...ch sample is updated resolution the smallest signal increment that can be detected by a measurement system Resolution can be expressed in bits in proportions or in percent of full scale For example a...

Страница 72: ...r of channels in the output group update rate the rate at which the measurement data is updated USB Universal Serial Bus V V the basic unit of electromotive force or electric pressure that causes elec...

Страница 73: ...9 C calibration certificate NI resources C 2 Callendar Van Dusen coefficients table 2 16 cold junction compensation methods 2 7 effect of figure 2 7 CompactPCI using with PXI 1 2 current source 2 27 D...

Страница 74: ...edgeBase C 1 L LEDs for NI 4350 USB patterns table 1 7 M measurement mode choosing 2 1 N National Instruments support and services C 1 NI 4350 USB LEDs patterns table 1 7 NI 435x instruments See also...

Страница 75: ...rce impedance 2 12 thermal EMF 2 13 RTDs thermistors and resistors AC noise effects 2 26 auto zero method 2 24 connecting to external circuits 2 25 guidelines for resistance measurement table 2 25 pro...

Страница 76: ...four wire RTD measurement figure 2 17 three wire RTD measurement figure 2 17 two wire RTD measurement figure 2 16 definition 2 14 measuring temperature 2 14 optimizing measurements 2 24 relationship o...

Страница 77: ...ocouples 2 10 thermistors accuracy specifications table A 4 advantages and disadvantages 2 18 connecting 2 20 optimizing measurements 2 24 resistance temperature characteristics 2 20 resistance temper...

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