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Chapter

4 Theory

of

Operation

SCXI-1125 User Manual

4-4

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Theory of Parallel Hardware Operation

In parallel mode, the CH0 signal on the rear signal connector is configured
as the output of the SCXI-1125 analog input channel 0. The rear signal
connector carries each of the analog outputs of the SCXI-1125 to the
connected DAQ device. You can use an SCXI-1180 feedthrough connector
to make each of the outputs available at the front of the chassis; which is
useful for cascading these signals to other modules for additional signal
conditioning purposes. Parallel mode allows you to bypass scanning and
you are not limited by the settling time required by the multiplexer of
SCXI-1125. You can scan the channels more accurately at a faster rate,
depending on which E/M Series DAQ device you connect to the module.

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Summary of Contents for Module SCXI-1125

Page 1: ...SCXI TM SCXI 1125 User Manual SCXI 1125 User Manual April 2008 372425B 01 ...

Page 2: ...anon 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 Thailand 662 ...

Page 3: ...ing 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 softw...

Page 4: ...n a product it denotes a component that may be hot Touching this component may result in bodily injury 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 introduction to a key concept Italic text also denotes text that is a p...

Page 5: ...ed Scanning 1 4 Connecting the SCXI 1125 to a n E M Series DAQ Device for Parallel Scanning 1 5 Verifying the SCXI 1125 Installation in Software 1 5 Installing SCXI Using NI DAQmx in Software 1 5 Manually Adding Modules in NI DAQmx 1 6 Installing SCXI Using Traditional NI DAQ Legacy in Software 1 6 Manually Adding Modules in Traditional NI DAQ Legacy 1 6 Verifying and Self Testing the Installation...

Page 6: ... Virtual Channel 3 6 Verifying the Signal 3 6 Verifying the Signal in NI DAQmx Using a Task or Global Channel 3 6 Verifying the Signal in Traditional NI DAQ Legacy 3 7 Verifying the Signal Using Channel Strings 3 7 Verifying the Signal Using Virtual Channel 3 8 Chapter 4 Theory of Operation Gain 4 1 Filter Bandwidth and Cutoff Frequency 4 2 Operating in Multiplexed Mode 4 2 Multiplexed Hardware Op...

Page 7: ... Display Using Traditional NI DAQ Legacy in LabVIEW 5 20 Traditional NI DAQ Legacy in Text Based ADEs 5 21 Configuring System Settings Using Traditional NI DAQ Legacy C API 5 21 Configure Module Settings Using Traditional NI DAQ Legacy C API 5 22 Perform Offset Null Compensation Using Traditional NI DAQ Legacy C API 5 23 Perform Acquisition Using Traditional NI DAQ Legacy C API 5 23 Perform Scalin...

Page 8: ...l 2 3 Figure 2 3 Connecting a Floating AC Coupled Signal 2 4 Figure 2 4 Connecting a Ground Referenced AC Coupled Signal 2 4 Figure 4 1 SCXI 1125 Block Diagram 4 1 Figure 5 1 Typical Program Flowchart 5 6 Figure 5 2 LabVIEW Channel Property Node with Lowpass Frequency Set at 10 kHz on Channel SC1Mod1 ai0 5 12 Figure 5 3 Typical SCXI 1125 Program Flow with Traditional NI DAQ Legacy 5 17 Figure 5 4 ...

Page 9: ...perties 5 8 Table 5 4 Programming a Task in LabVIEW 5 10 Table 5 5 NI DAQmx Properties 5 15 Table 5 6 Settings for Configuring the SCXI 1125 Through the AI Parameter 5 18 Table 5 7 Configuration Functions 5 22 Table 5 8 NI DAQ Functions Used to Configure SCXI 1125 5 23 Table 5 9 Gain Values and Input Limits 5 31 Table A 1 Input Signal Range Versus Gain A 1 Table A 2 Terminal Block Maximum Voltages...

Page 10: ... inputs that you can use for offset calibration An onboard EEPROM provides nonvolatile storage of software correction constants for both gain and offset The SCXI 1125 provides up to 300 Vrms working isolation per channel and has an input range of up to 1000 VDC when using an appropriate attenuator terminal block The SCXI 1125 supports both multiplexed and parallel output modes and includes a cold ...

Page 11: ...afety and Radio Frequency Interference DAQ Getting Started Guide SCXI Quick Start Guide SCXI 1125 User Manual Documentation for your hardware Documentation for your software National Instruments Documentation The SCXI 1125 User Manual is one piece of the documentation set for data acquisition DAQ systems You could have any of several types of manuals depending on the hardware and software in the s...

Page 12: ...ter Use this documentation for hardware installation and configuration instructions specification information about the E M Series DAQ device and application hints Software documentation You may have both application software and NI DAQ software documentation National Instruments NI application software includes LabVIEW LabWindows CVI and Measurement Studio After you set up the hardware system use...

Page 13: ...pment covers or connecting or disconnecting any signal wires Installing the SCXI 1125 Module into the SCXI Chassis Refer to the SCXI Quick Start Guide to install your SCXI 1125 module Connecting the SCXI 1125 in an SCXI Chassis to an E M Series DAQ Device for Multiplexed Scanning Refer to the SCXI Quick Start Guide to install the cable adapter and connect the SCXI modules to the DAQ device If you ...

Page 14: ...essed in parallel mode by the E M Series DAQ device Refer to the installation guide for the cable assembly for more information 3 Connect the cable to the back of the cable adapter ensuring that the cable fits securely 4 Connect the other end of the cable to the E M Series DAQ device that you want to use to access the SCXI 1125 in parallel mode 5 Connect additional SCXI 1125 modules intended for p...

Page 15: ...t auto detect the SCXI modules you must manually add each of the modules Refer to the SCXI Quick Start Guide to manually add modules Note NI recommends auto detecting modules for the first time configuration of the chassis Verifying and Self Testing the Installation The verification procedure for the SCXI chassis is the same for both NI DAQmx and Traditional NI DAQ Legacy To test the successful in...

Page 16: ...spect the cable connectors for bent pins Make sure you are using the correct NI cable assembly Test the E M Series DAQ device to verify it is working properly Refer to the E M Series DAQ device help file for more information If you get a Verify SCXI Chassis message box showing the SCXI chassis model number Chassis ID x and the message Slot Number x Configuration has module SCXI XXXX or 1125 hardwa...

Page 17: ...e following the steps listed in the SCXI Quick Start Guide Click OK Ensure that you have the highest priority SCXI module cabled to the E M Series DAQ device Refer to the SCXI Quick Start Guide to find out which SCXI module in the chassis should be cabled to the E M Series DAQ device After checking the preceding items return to the Troubleshooting the Self Test Verification section and retest the ...

Page 18: ...ode voltage into a single ended signal with respect to the SCXI 1125 chassis ground With this conversion you can extract the analog input signal from a high common mode voltage before sampling by the E M Series DAQ device Second the isolation amplifier amplifies and filters an input signal resulting in increased measurement resolution and accuracy The following sections explain how to make signal ...

Page 19: ... Referenced Signal When the negative input signal line is connected either directly or indirectly to earth ground usually at the transducer end connect this line to the negative input terminal as shown in Figure 2 1 No ground connection is made at the SCXI 1125 This situation includes cases where a floating source can be riding on a high common mode voltage that is ground referenced Figure 2 1 Con...

Page 20: ...he negative input line to chassis ground in the terminal block as shown in Figure 2 2 This eliminates noise that can ride on the floating signal If the floating signal is not configured like Figure 2 2 the noise can couple to the chassis ground through the amplifier and exhibit a differential mode signal that can be amplified by the amplifier Connecting the signal to chassis ground breaks the isol...

Page 21: ...e channel to DC reference the input stage of the SCXI 1125 You do not need to use a bias resistor with any high voltage terminal blocks since the terminal blocks already have a resistor between the input terminals or with the SCXI 1305 BNC connectivity terminal block since this terminal block already has an AC coupling option built in Figure 2 3 Connecting a Floating AC Coupled Signal Caution Conn...

Page 22: ...an damage the SCXI 1125 module Pin Assignments The front signal connector is a special 32 pin DIN C male front connector used for connecting analog input signals including the CJC to the analog circuitry of the SCXI 1125 This connection allows access to the eight differential analog input signals The positive terminal is AIx and the negative terminal AIx A missing pin exists between two consecutiv...

Page 23: ...means no connection means no pin 32 AI 0 AI 0 31 30 AI 1 AI 1 29 28 NC NC 27 26 AI 2 AI 2 25 24 AI 3 AI 3 23 22 NC NC 21 20 AI 4 AI 4 19 18 AI 5 AI 5 17 16 NC NC 15 14 AI 6 AI 6 13 12 AI 7 AI 7 11 10 NC NC 9 8 RSVD RSVD 7 6 RSVD RSVD 5 4 5 V CJ TEMP 3 2 CHS GND RSVD 1 Column A B C 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 ...

Page 24: ...ies DAQ device In multiplexed mode the CH 0 signal pair is used for sending all eight channels of the SCXI 1125 and other analog signals from other modules to the connected E M Series DAQ device If the module is directly connected to the E M Series DAQ device the other analog channels of the E M Series DAQ device are still unavailable for general purpose analog input because they are still connect...

Page 25: ... 3 CH 4 11 12 CH 4 CH 5 13 14 CH 5 CH 6 15 16 CH 6 CH 7 17 18 CH 7 OUT REF 19 20 NC NC 21 22 NC NC 23 24 D GND SER DAT IN 25 26 SER DAT OUT DAQ D A 27 28 NC SLOT 0 SEL 29 30 NC NC 31 32 NC D GND 33 34 NC NC 35 36 AI HOLD COMP AI HOLD SER CLK 37 38 NC NC 39 40 NC NC 41 42 NC NC 43 44 NC NC 45 46 SYNC NC 47 48 NC NC 49 50 NC 49 50 47 48 45 46 43 44 41 42 39 40 37 38 35 36 33 34 31 32 29 30 27 28 25 ...

Page 26: ... and how to verify the signal using both NI DAQmx and Traditional NI DAQ Legacy Common Software Configurable Settings This section describes the most frequently used software configurable settings for the SCXI 1125 Refer to Chapter 4 Theory of Operation for a complete list of software configurable settings Filter Bandwidth Filter bandwidth is a software configurable setting that allows you to sele...

Page 27: ... configure the SCXI 1125 module s Configurable Settings in MAX Note If you are not using an NI ADE using an NI ADE prior to version 7 0 or are using an unlicensed copy of an NI ADE additional dialog boxes from the NI License Manager appear allowing you to create a task or global channel in unlicensed mode These messages continue to appear until you install version 7 0 or later of an NI ADE This se...

Page 28: ... you set the minimum and maximum range of NI DAQmx Task or NI DAQmx Global Channel the driver selects the best gain for the measurement You also can set it through your application Modes of operation configure only using chassis installation in software Refer to Chapter 1 About the SCXI 1125 for more information on chassis installation The default setting in NI DAQmx is multiplexed Terminal block ...

Page 29: ...apter 3 Configuring and Testing for more information 10 Click the Device tab and select the autozero mode and lowpass filter cutoff frequency 11 If you are creating a task and want to set timing or triggering controls enter the values in the Task Timing and Task Triggering tabs Traditional NI DAQ Legacy In Traditional NI DAQ Legacy you can configure software settings such as configuration voltage ...

Page 30: ...d to an E Series DAQ device select that device by using Connected to If you want this E Series DAQ device to control the chassis confirm there is a check in the This device will control the chassis checkbox If the module you are configuring is not connected to an E Series DAQ device select None 3 Click the Channel tab Select the appropriate gain and filter for each channel If you want to configure...

Page 31: ...dware from the drop down list b Which analog input mode will be used from the drop down list 11 Click Finish Verifying the Signal This section describes how to take measurements using test panels in order to verify signal and configuring and installing a system in NI DAQmx and Traditional NI DAQ Legacy Verifying the Signal in NI DAQmx Using a Task or Global Channel You can verify the signals on th...

Page 32: ...ls Verifying the Signal Using Channel Strings The format of the channel string is as follows obx scy mdz channel where obx is the onboard E Series DAQ device channel with x representing a particular channel where the multiplexed channels are sent This value is 0 for E Series DAQ device channel 0 in a single chassis system In a multichassis or remote chassis system the E Series DAQ device channel x...

Page 33: ... the input limits 7 Select the Data Mode 8 Select the Y Scale Mode Refer to the LabVIEW Measurements Manual for more information and for proper formatting of channel strings for different uses Verifying the Signal Using Virtual Channel If you have already created a virtual channel complete the following steps to verify the signal 1 Right click the virtual channel you want to verify and select Test...

Page 34: ...2 different gain settings from 1 to 2000 enabling signal ranges 5 V to 2 5 mV When the SCXI 1125 is used with a terminal block that provides attenuation the input range expands up to 1000 V Refer to Appendix A Specifications for a full list of input ranges Gain Select Rear Signal Connector AI 0 AI 0 AI 7 AI 0 AI 7 AI 7 AI 0 AI 7 Gain Select MTEMP Lowpass Filter Lowpass Filter Lowpass Filter Lowpas...

Page 35: ...of LabVIEW LabWindows CVI or Measurement Studio By combining hardware anti aliasing with digital filtering you can choose any cutoff frequency The Advanced Analysis functions are only available in LabVIEW Full or Professional Development Systems and LabWindows CVI Base or Full Development Systems Refer to the Configurable Settings in MAX section of Chapter 3 Configuring and Testing for more inform...

Page 36: ...If the module is cabled to an E M Series DAQ device in multiplexed mode the differential inputs 1 through 7 on the E M Series DAQ device cannot be used for general purpose analog input Refer to Appendix D Common Questions for more information on available pins on the rear signal connector Multiplexed mode is typically used for performing scanning operations with the SCXI 1125 Immediately prior to ...

Page 37: ...125 to the connected DAQ device You can use an SCXI 1180 feedthrough connector to make each of the outputs available at the front of the chassis which is useful for cascading these signals to other modules for additional signal conditioning purposes Parallel mode allows you to bypass scanning and you are not limited by the settling time required by the multiplexer of SCXI 1125 You can scan the cha...

Page 38: ...ng This design reduces the CJC errors which might reduce the accuracy of your temperature measurement Most SCXI terminal blocks available for the SCXI 1125 contain a cold junction temperature sensor which is used for measuring ambient temperature This sensor connects to a special channel on the SCXI 1125 inside the terminal block close to where the thermocouple connects to the screw terminals Note...

Page 39: ...emperature reading from the thermocouple junction National Instruments software ADEs have useful conversion functions for CJC In LabVIEW virtual channels with the CJC channel invoked or the Convert Thermocouple Reading VI are used In C use the NI DAQ function Thermocouple_Convert In C you might also need to use the function Thermistor_Convert if your terminal block uses a thermistor to perform CJC...

Page 40: ... 3 times this or 300 nVpk because of the 4 Hz filter In this example you might or might not be able to average out the noise The total error is 1 73 µV at the full scale temperature range which gives a preliminary accuracy of 0 04 C 1 73 µV divided by 41 0 µV C 3 Next consider the accuracy of the cold junction sensor you are using For example using the SCXI 1328 which at about room temperature wit...

Page 41: ... a cold junction sensor so you can combine thermocouple measurements with high voltage measurements When making signal connections or when working with high voltage signals refer to the terminal block installation guide If you are using the SCXI 1125 to measure signals with attenuation on the terminal block an external bias resistor is not needed because a bias resistor is already used for achievi...

Page 42: ...nnel in unlicensed mode These dialog boxes continue to appear until you install version 7 0 or later of an NI ADE This section describes how to configure and use NI DAQmx to control the SCXI 1125 in LabVIEW LabWindows CVI and Measurement Studio These ADEs provide greater flexibility and access to more settings than MAX but you can use ADEs in conjunction with MAX to quickly create a customized app...

Page 43: ...ask Programmatically Create Task in DAQ Assistant or MAX No Hardware Timing Triggering Create Task Using DAQ Assistant No Y es No Yes Configure Channels Further Configure Channels Start Measurement Read Measurement Clear Task Continue Sampling Stop Measurement Yes No Analyze Data Display Data No No Process Data Graphical Display Tools Yes Yes Create Another Channel No Yes ...

Page 44: ...you are using an ADE other than an NI ADE or if you want to explicitly create and configure a task for a certain type of acquisition you can programmatically create the task from your ADE using functions or VIs If you create a task using the DAQ Assistant you can still further configure the individual properties of the task programmatically with functions or property nodes in your ADE NI recommend...

Page 45: ...igure the module for your application For a complete list of NI DAQmx properties refer to your ADE help file Note You cannot adjust some properties while a task is running For these properties you must stop the task make the adjustment and re start the application Figure 5 1 assumes all properties are configured before the task is started Note This is not a complete list of NI DAQmx properties and...

Page 46: ...lide controls and gauge indicators NI ADEs have tools that allow you to easily save the data to files such as spread sheets for easy viewing ASCII files for universality or binary files for smaller file sizes Completing the Application After you have completed the measurement analysis and presentation of the data it is important to stop and clear the task This releases any memory used by the task ...

Page 47: ... the DAQ Assistant They are only available for the present session of the task in LabVIEW Adjust Timing Settings optional DAQmx Timing vi Sample Clock by default This VI is optional if you created and configured your task using the DAQ Assistant Any timing settings modified with this VI are not saved in the DAQ Assistant They are only available for the present session Configure Channels optional D...

Page 48: ...annels the properties are set on all of the channels in the task 6 Right click ActiveChans and select Add Element Left click the new ActiveChans box Navigate through the menus and select the property you wish to define Display Data You can use graphical tools such as charts gauges and graphs to display your data Some display tools are located on the Controls All Controls Numeric Numeric Indicators...

Page 49: ...ew property left click it and select the property you wish to define Note Refer to the LabVIEW Help for information about property nodes and specific NI DAQmx properties Specifying Channel Strings in NI DAQmx Use the channel input of DAQmx Create Channel to specify the SCXI 1125 channels The input control constant has a pull down menu showing all available external channels The strings take one of...

Page 50: ... with different properties separate the lists of properties with another ActiveChans box and assign the appropriate channel to each list of properties 6 Right click ActiveChan and select Add Element Left click the new ActiveChan box Navigate through the menus and select the property you wish to define 7 You must change the property to read or write to either get the property or write a new value R...

Page 51: ...meters you define in MAX and the device defaults To change a property of the channel programmatically use the DAQmxSetChanAttribute function Note Refer to the NI LabWindows CVI Help for more information on creating NI DAQmx tasks in LabWindows CVI and NI DAQmx property information Measurement Studio Visual Basic NET and C When creating a task in Visual Basic NET and C follow the general programmin...

Page 52: ...on 7 0 or later of an NI ADE This section describes how to configure and use Traditional NI DAQ Legacy to control the SCXI 1125 in LabVIEW LabWindows CVI Measurement Studio and other text based ADEs These NI ADEs provide greater flexibility and access to more settings than MAX but you can use ADEs in conjunction with MAX to quickly create a customized application Table 5 5 NI DAQmx Properties Prop...

Page 53: ...mends using the virtual channel for ease of use Refer to Appendix B Using SCXI Channel Strings with Traditional NI DAQ Legacy 7 0 or Later for more information on how to create a virtual channel The SCXI channel string allows you to combine large numbers of channels into fewer scan list entries to measure the signal voltage level directly for custom scaling and to dynamically perform an offset nul...

Page 54: ... design your application using a typical program flow such as the one shown in Figure 5 3 Figure 5 3 Typical SCXI 1125 Program Flow with Traditional NI DAQ Legacy Virtual Channel Create Virtual Channel in MAX Use Virtual Channel or SCXI Channel String SCXI Channel String Configure Acquisition Settings Configure Mode Properties Yes No Start Acquisition Take Measurements Continue Sampling Scale Anal...

Page 55: ... is called The AI parameter VI merely changes the configuration in the driver memory When called the AI Start VI reads the configuration settings in the driver memory and then sends the actual control information to the SCXI 1125 module A setting established through AI Parameter VI is only valid for the LabVIEW session and does not change the setting in MAX You can use the AI Parameter VI to confi...

Page 56: ...u can use the intermediate analog input functions AI Config VI AI Start VI AI Read VI and AI Clear VI to create your data acquisition application You can find the intermediate data acquisition Traditional NI DAQ Legacy functions in the function subpalettes Data Acquisition Analog Input NI recommends using the intermediate analog input functions for most SCXI 1125 applications For more information ...

Page 57: ...VIEW User Manual You also can use the LabVIEW Help for more detailed information about how to use these nodes to perform mathematical calculations such as scaling conversions Analyze and Display Using Traditional NI DAQ Legacy in LabVIEW In LabVIEW you can easily analyze SCXI 1125 measurements with a variety of powerful analysis functions that you can find in the function subpalettes Analyze Wavef...

Page 58: ... in the Traditional NI DAQ Legacy C API Refer to the ADE user documentation for more information about how to use the high level data acquisition tools that are provided in your NI ADE For more advanced SCXI 1125 applications or if you are using an ADE other than an NI ADE you can use the Traditional NI DAQ Legacy C API to call functions from the DAQ driver dynamically linked library dll Configuri...

Page 59: ...e to its default state You also can use SCXI_Reset to reset the SCXI chassis Slot 0 scanning circuitry or reset the entire chassis The SCXI 1125 default conditions are Gain set at 1000 0 4 Hz lowpass filter SCXI_Load_Config Loads the SCXI chassis configuration information you established in MAX Sets the software states of the chassis and the modules present to their default states This function ma...

Page 60: ...e several NI DAQ functions you can use to take measurements Usually in SCXI the preference is to take multiple samples from multiple channels using the SCAN_Op function SCAN_Op performs a synchronous multiple channel scanned data acquisition operation SCAN_Op does not return until Traditional NI DAQ Legacy acquires all the data or an acquisition error occurs MIO AI and DSA devices only For this re...

Page 61: ...ation regarding SCXI_Scale refer to the Traditional NI DAQ Legacy Function Reference Help installed by default in Start Programs National Instruments NI DAQ After you have adjusted the measurement by the appropriate calibration constants using SCXI_Scale you can use a function from the NI conversion library convert h to convert a voltage or voltage buffer from a voltage to units of temperature or ...

Page 62: ... scan list When the application program runs the channel string is used for programming the channel information into the SCXI system The format of the channel string is as follows obx scy mdz channels where obx is the onboard E Series DAQ device channel with x representing a particular channel where the multiplexed channels are sent This value is 0 for DAQ channel 0 in a single chassis system In a...

Page 63: ... temperature drifts in the analog circuitry You can subtract these offsets from subsequent input readings to correct for temperature drift Refer to Appendix A Specifications for determining how temperature drift can affect your measurement accuracy Note Repeating channels or having channels out of sequence in a scan list is not supported on all SCXI modules Please refer to the manual of each modul...

Page 64: ...CJC automatically Note Virtual analog input channels can be randomly scanned therefore virtual channels can be entered in any order or repeated in the channel string Performing a Multiplexed Scan To perform a multiplexed scan in your application perform the following steps 1 Open an analog input example in your ADE 2 Enter the appropriate SCXI channel string or virtual channel string into the chan...

Page 65: ...er of channels programmed in step 2 You are now ready to acquire the channel data with the E Series DAQ device If you are using a multifunction E Series DAQ device you can use SCAN_OP to perform the scanning operation After scanning convert the binary data to voltage data using SCXI_Scale Refer to the NI DAQ User Manual for additional information on scanning with DAQ devices Using Software for Par...

Page 66: ...I_Scale Refer to the NI DAQ User Manual for additional information on parallel scanning of SCXI modules Other Application Documentation and Material Refer to the ADE manual and the DAQ analog input examples that come with your application software for more detailed information on programming the SCXI modules for scanning in multiplexed mode Traditional NI DAQ Legacy CVI Examples Many example progr...

Page 67: ...etails about the analog stability of your SCXI 1125 module Calibration Procedures You can calibrate the offset on the SCXI 1125 using National Instruments software When calibrating the offset on the SCXI 1125 make sure the DAQ device you are using has been calibrated recently or you will invalidate the offset calibration on the SCXI 1125 The SCXI 1125 provides input switching that allows you to pr...

Page 68: ...at a time b Select internal calibration as the calibration operation you are going to perform c Select the Default EEPROM load area as the area you want to update d The offset varies with the selected gain value Therefore enter the high and low limits that correspond to the gain value for which you are calibrating offset Refer to Table 5 9 for a list of the gain values and the corresponding input ...

Page 69: ... Since offset varies with gain enter the gain setting for which you are calibrating offset e Enter 1 for the terminal block gain since it is not used f Enter 0 0 as the input reference voltage 3 Repeat step 2 for calibrating additional channels The SCXI 1125 may take a few seconds to perform the calibration After completion your module will have new calibration constants stored for the channels an...

Page 70: ...5 1 and 5 2 for extended range using the SCXI 1313A SCXI 1327 and TBX 1316 Table A 1 Input Signal Range Versus Gain Overall Gain Overall Voltage Range SCXI 1125 Gain 1 5 Vpeak or VDC 1 2 2 5 Vpeak or VDC 2 5 1 Vpeak or VDC 5 10 500 mVpeak or VDC 10 20 250 mVpeak or VDC 20 50 100 mVpeak or VDC 50 100 50 mVpeak or VDC 100 200 25 mVpeak or VDC 200 250 20 mVpeak or VDC 250 500 10 mVpeak or VDC 500 100...

Page 71: ...ix A Specifications SCXI 1125 User Manual A 2 ni com Overvoltage protection Isolated connector pins Powered on and off 300 V Inputs protected CH0 CH7 Non isolated connector pins Powered on and off 5 5V 0 5 V ...

Page 72: ... 65 25 mV 3 mV 48 mV 641 μ V 11 mV 0 0029 4 4 mV 200mV 10 V 4 0 5 0 2548 0 65 10 mV 1 mV 19 1 mV 238 μ V 4 1 mV 0 0029 2 2 mV 80 0mV 5 V 1 0 07 0 52 5 0 mV 530 μ V 8 6 mV 122 μ V 2 1 mV 0 0027 251 μ V 33 0mV 2 5 V 2 0 07 0 52 2 5 mV 254 μ V 4 3 mV 60 μ V 1 1 mV 0 0027 126 μ V 16 5mV 1 V 5 0 07 0 52 1 0 mV 110 μ V 1 7 mV 24 μ V 403 μ V 0 0027 51 μ V 6 6mV 500 mV 10 0 07 0 52 500 μ V 69 μ V 882 μ V ...

Page 73: ...V 0 0027 0 6 μ V 31 μ V 1 Absolute accuracy 15 to 35 ºC To calculate the absolute accuracy for the SCXI 1125 visit ni com accuracy 2 V rms refers to sinusoidal waveform V refers to DC or AC peak 3 With TBX 1316 high voltage terminal block 4 With SCXI 1327 high voltage terminal block Nominal Range Overall Gain of Reading Offset System Noise peak 3 sigma Temperature Drift Absolute Accuracy at Full S...

Page 74: ...h TBX 1316 40 M Input bias current 100 pA typical 1 nA max Filter type 3 pole Butterworth filter response Bandwidth 3dB cut off frequency 4 Hz filter 4 Hz 5 10 kHz filter 10 kHz 5 Full power bandwidth 7 kHz 5 With SCXI 1327 or SCXI 1313A high voltage terminal blocks 2 6 kHz 5 With TBX 1316 high voltage terminal block 500 Hz 5 Slew rate Typical 0 15 V μs Minimum 0 1 V μs Scan interval accuracy 0 01...

Page 75: ...r TBX 1329 AC or DC Power Consumption 18 5 V 140 mA max 18 5 V 140 mA max 5 V 10 mA max Output Characteristics Output range 5 0 V Output impedance Multiplexed output mode 100 Ω Parallel output mode 330 Ω Transfer Characteristics Nonlinearity All ranges 0 02 of full scale range Stability Recommended warm up time 15 minutes Offset drift 0 42 250 gain μV C Gain drift 20 ppm C typical Calibration Exte...

Page 76: ...Appendix A Specifications National Instruments Corporation A 7 SCXI 1125 User Manual Physical Figure A 1 SCXI 1125 Dimensions Weight 641 g 22 6 oz 3 0 cm 1 2 in 17 2 cm 6 8 in 18 8 cm 7 4 in ...

Page 77: ...dous voltages 42 4 Vpk 60 VDC are present on any channel all channels are considered hazardous Ensure that external wiring or any circuits connected to the device are properly insulated from human contact Environmental Operating temperature 0 to 50 C Storage temperature 20 to 70 C Humidity 10 to 90 RH noncondensing Maximum altitude 2 000 meters Pollution Degree indoor use only 2 Table A 2 Terminal...

Page 78: ...quipment for measurement control and laboratory use EN 61326 EMC requirements Minimum Immunity EN 55011 Emissions Group 1 Class A CE C Tick ICES and FCC Part 15 Emissions Class A Notes For EMC compliance operate this device according to product documentation For EMC compliance operate this device with shielded cabling CE Compliance This product meets the essential requirements of applicable Europe...

Page 79: ...is page contains the environmental regulations and directives with which NI complies as well as any other environmental information not included in this document Waste Electrical and Electronic Equipment WEEE EU Customers At the end of their life cycle all products must be sent to a WEEE recycling center For more information about WEEE recycling centers and National Instruments WEEE initiatives vi...

Page 80: ...es configures multiple modules for scanning When the application program runs the channel string is used for programming the channel information into the SCXI system The format of the channel string is as follows obx scy mdz channels where obx is the onboard E M Series DAQ device channel with x representing a particular channel where the multiplexed channels are sent This value is 0 for E M Series...

Page 81: ...ed in the channel list Notes Using parenthesis surrounding multiple channels in a channel string is important for correct scanning operation of the SCXI channels In a single chassis system the obx specifier is optional and causes the gains on the module and E M Series DAQ device to be automatically set to fit the input limits parameter When this specifier is omitted the default gain on the E M Ser...

Page 82: ...y the installed modules 4 Right click the module or chassis you want to delete and click Delete 5 You are presented with a confirmation window Click Yes to continue deleting the module or chassis or No to cancel this action Note Deleting the SCXI chassis deletes all modules in the chassis All configuration information for these modules is also deleted The SCXI chassis and or SCXI module s should n...

Page 83: ...s that secure the SCXI 1125 to the chassis counterclockwise until they are loose but do not completely remove the thumbscrews 5 Remove the SCXI 1125 by pulling steadily on both thumbscrews until the module slides completely out Figure C 1 Removing the SCXI 1125 1 Cable 2 SCXI Module Thumbscrews 3 SCXI 1125 4 Sensor 5 Terminal Block 6 SCXI Chassis Power Switch 7 SCXI Chassis MA INF RA ME SCXI 3 2 5...

Page 84: ...ith TBX 1316 Isolation 250 Vrms 300 Vrms Gains 1 2 5 10 20 50 100 200 250 500 1000 and 2000 jumper selectable 1 2 5 10 20 50 100 200 250 500 1000 and 2000 software selectable Filters 4 Hz or 10 kHz jumper selectable 4 Hz or 10 kHz software selectable Autozero Not supported Software configurable and scannable Calibration Manually rotateable potentiometers for one point offset calibration Software i...

Page 85: ...uesting technical support by phone have your system near at hand so that you can try these measures immediately Can I use the unused analog input channels of the E M Series DAQ device if I am directly cabled to the SCXI 1125 It depends The SCXI 1125 always outputs channels 1 through 7 to the rear signal connector to permit parallel mode scanning If you are using a 16 channel 8 differential inputs ...

Page 86: ...l channels work with parallel mode operation on the SCXI 1125 The E M Series DAQ device must be directly connected to the module in parallel mode operation Also virtual channels that use built in CJC are disabled and cannot be used in parallel mode In LabVIEW can I use the calgnd channel string when the SCXI 1125 is in parallel mode Yes you can autozero the SCXI 1125 in LabVIEW when using the modu...

Page 87: ... NI DAQ Legacy there is no VI available to do this You must use the configuration utility in MAX to configure the filter setting of each channel In C can I randomly scan the SCXI 1125 using low level Traditional NI DAQ Legacy function calls No using C you can scan only consecutive channels using traditional SCXI channel programming Refer to the NI DAQ function reference manual for more details on ...

Page 88: ...l Glossary Symbol Prefix Value p pico 10 12 n nano 10 9 μ micro 10 6 m milli 10 3 k kilo 103 M mega 106 G giga 109 T tera 1012 Numbers Symbol Degrees Greater than or equal to Less than or equal to Ω Ohms Per Percent Plus or minus 5 V signal 5 VDC source signal ...

Page 89: ...lopment AI GND analog input ground AI HOLD COMP AI HOLD clock that triggers scanning amplification A type of signal conditioning that improves accuracy in the resulting digitized signal by increasing signal amplitude relative to noise autozero A procedure for eliminating offsets generated by an amplifier stage B bandwidth The range of frequencies present in a signal or the range of frequencies to ...

Page 90: ...al channels chassis The enclosure that houses powers and controls SCXI modules CJ TEMP cold junction temperature sensor signal CJC cold junction compensation CLK clock input signal CMRR common mode rejection ratio A measure of the capability of an instrument to reject a signal that is common to both input leads code width The smallest detectable change in an input voltage of a DAQ device cold junc...

Page 91: ...ure of the ratio of two signal levels dB 20 log10 V1 V2 for signals in volts DC direct current device A plug in data acquisition board module card or pad that can contain multiple channels and conversion devices differential input An input circuit that actively responds to the difference between two terminals rather than the difference between one terminal and ground DIN deutsche Industrie Norme D...

Page 92: ...in decibels gain accuracy A measure of deviation of the gain of an amplifier from the ideal gain gain error See gain accuracy GND ground H Hz hertz I I O input output The transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces in inch input bias current The current that flows into the inputs of a circuit...

Page 93: ... of terminal blocks increases thermocouple measurement accuracy K K kelvin L linearization A type of signal conditioning in which software linearizes the voltage levels from transducers so the voltages can be scaled to measure physical phenomena M m meters M 1 Mega the standard metric prefix for 1 million or 106 when used with units of measure such as volts and hertz 2 mega the prefix for 1 048 57...

Page 94: ...e motors generators transformers fluorescent lights soldering irons CRT displays computers electrical storms welders and radio transmitters and internal sources such as digital clocks microprocessors and switched mode power supplies Video system noise can take various forms including snow which is a random video noise It corrupts signals you are trying to send or receive O offset error A constant ...

Page 95: ...Material Authorization rms root mean square RSVD reserved bit signal RTI referred to input Calculates a specification relative to the input range S s seconds sample An instantaneous measurement of a signal normally using an analog to digital converter in an E Series DAQ device sample rate The number of samples a system takes over a given time period usually expressed in samples per second scan One...

Page 96: ...t sound pressure motion flow and so on and produces a corresponding electrical signal Primary characteristics of sensors are sensitivity frequency range and linearity settling time The time required for an amplifier relays or other circuits to reach a stable mode of operation shunt See autozero shunt calibration The method of calibrating the gain of strain gauge data acquisition channel by placing...

Page 97: ...IEW software module VI which consists of a front panel user interface and a block diagram program virtual channels Channel names that can be defined outside of the application and used without having to perform scaling operations Virtual channels are called custom channels in MAX 3 0 and later voltage excitation A source that supplies the voltage needed by a sensor for its proper operation Vrms vo...

Page 98: ...ration 5 32 channel string calgnd channel string D 3 SCXI 5 25 virtual 5 26 channels C language scanning D 4 questions about D 3 unused analog input channels on DAQ device D 2 common questions D 1 configuration troubleshooting self test verification 1 7 configuration settings filter bandwidth 3 1 4 2 gain 3 1 4 1 connecting SCXI 1125 to DAQ device See also DAQ devices for parallel scanning 1 5 con...

Page 99: ... voltage measurements 5 4 I input characteristics A 1 installation connecting SCXI 1125 to DAQ device for parallel scanning 1 5 connecting to DAQ device for multiplexed scanning in PXI combination chassis 1 4 3 2 in SCXI chassis 1 4 3 2 into SCXI chassis 1 4 removing SCXI 1125 from Measurement Automation Explorer C 1 from SCXI chassis C 1 L LabVIEW multiplexed scanning operations SCXI channel stri...

Page 100: ...or description 2 7 pin assignments figure 2 8 table 2 8 regulatory compliance specifications A 9 removing SCXI 1125 from Measurement Automation Explorer C 1 from SCXI chassis C 1 S safety specifications A 9 SCXI channel string 5 25 SCXI chassis connecting SCXI 1125 to DAQ device 1 4 3 2 SCXI 1125 calibration 5 30 common questions D 1 digital signals table D 3 multiplexed mode 4 2 parallel mode 4 3...

Page 101: ...m working voltage A 8 physical A 7 regulatory compliance A 9 safety A 9 stability A 6 transfer characteristics A 6 stability specifications A 6 T temperature measurements using thermocouples 5 1 accurate method for temperature determination 5 2 guide for calculating overall temperature error 5 3 overview 5 1 temperature sensor connection 2 7 thermocouples for temperature measurements See temperatu...

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