NI PXI-6653 and NI PXI-6652 Calibration Procedure
Contents
1. A CALIBRATION PROCEDURE NI PXI 6653 and NI PXI 6652 This document contains information and step by step instructions for calibrating the 10 MHz oscillator frequency of the NI PXI 6653 and NI PXI 6652 timing and synchronization modules Contents What Is Calibration iis scscs scessuves ce sassesiseceveesodvsdesaesdestgesreodsan EREE Ea 1 Why Should You Calibrate seseeeseeeseesseesesrsresreresresesrssrsresreerse 2 How Often Should You Calibrate oe eee seeeseeeeeeseeneeeeeens 2 Equipment and Other Test Requirement 0 0 eee eeeeeeseeeeeeeeeeeeees 2 Test EGUIPMEN E spss eener eae ERE EEEE OR 2 Software and Documentation sesessssessestssesreresrerrsresrsresreeesresrrees 2 DOLEW ALC eenean aa dete E EE a aeaa E EE 3 Documentation sss cescesessindes seces levstevexspasedtees Gisieves daytsegysaeaeei esis 3 Test CONGUONS yscscoesssesetsee sess etsssedtes estes cevssndeseseseeestes ean iaoee 3 Verifying the Oscillator Frequency of the NI PXI 6653 OF NEP XIEGO5 2 ssanie rer sevewseises ud r E E R E 3 Connecting the Clock Source seessssesssesssesreersrsrsresreresresresesreresee 4 Measuring the Frequency esceescccsceceseeeseeeeeeceeeeeeeeaeeeeeeeeeeeaees 4 Comparing the Measured Frequency to the Device Specifications eee ceeesececeseeseeseeseeeseeseeeaeeseeseeeeaes 5 Adjusting the Frequency of the 10 MHz Oscillator eee 5 Updating the Oscillator Frequency Calibration Value in the Calibration EEPROM cece2. N Sync User Manual for more information about how to program the NI PXI 6653 or NI PXI 6652 using NI Sync source terminal roperty Node AE misye Use PLL PXI_CIk10_In destination terminal Figure 1 Replacing Clk10 From an External Frequency Source Using Nl Sync Measuring the Frequency Connect an SMB to SMB cable from ClkOut to PFIO on the NI PXI 6653 or NI PXI 6652 Then use NI Sync to program the board to connect its onboard oscillator to CIkOut with the ClkOut high gain setting enabled Once the board has made this connection use the NI Sync Measure Frequency function to measure the frequency of the onboard oscillator For the NI PXI 6652 the frequency of the onboard oscillator should be measured to an accuracy of 200 ppb To achieve this accuracy in the measurement the Measure Frequency function should be programmed to measure for 0 5 seconds For the NI PXI 6653 the frequency of the onboard oscillator should be measured to an accuracy of ppb To achieve this accuracy in the measurement the Measure Frequency function should be programmed to measure for 100 seconds Figure 2 shows a sample LabVIEW program that uses NI Sync to measure the 10 MHz oscillator frequency for 0 5 seconds source terminal resource name p Pinisi j Aee Re nisy BE ae g f Ks z PckOut Gain Enable Lod as aen imal Pi destination terminal Figure 2 Measuring t
3. XI 665x to complete the calibration NI Sync provides a calibration API for writing a new calibration value to the Calibration EEPROM on the board Note that the value obtained earlier must be scaled to a voltage before passing it into the NI Syne Calibration VI which writes the oscillator frequency value to the EEPROM The values from 0x0000 to OxFFFF represent a range of voltages from 0 000 V to 4 095 V Figure 4 shows the calculation necessary to convert the 16 bit value obtained in the steps above into the calibrated oscillator voltage that can be written to the board EEPROM using NI Sync PXI1 15 INSTR niSync Close External Calibration vi niSync Adjust Oscillator Voltage vi niSync Initialize External Calibration vi Calibration Value Calibrated Oscillator Voltage Figure 4 Writing the 10 MHz Oscillator Calibration Value Using NI Sync Note NI Sync uses the new calibration value when the computer is rebooted 3 Note NI is the default user password If you have changed the calibration password use your user selected calibration password in place of NI CVI LabVIEW National Instruments NI ni com and NI VISA are trademarks of National Instruments Corporation Product and company names mentioned herein are trademarks or trade names of their respective companies For patents covering National Instruments products refer to the appropriate location Help Patent
4. he 10 MHz Oscillator Frequency Using NI Sync NI PXI 6653 and NI PXI 6652 Calibration Procedure a ni com Comparing the Measured Frequency to the Device Specifications You need to compute the oscillator accuracy from the measured frequency obtained using the test described above This accuracy can be compared to the specified accuracy in the appropriate section of the NJ PXI 665x User Manual For the NI PXI 6653 the oscillator specifications are listed in the OCXO Characteristics section of Appendix A Specifications For the NI PXI 6652 the oscillator specifications are listed in the TCXO Characteristics section of Appendix A Specifications To determine the measured accuracy subtract the nominal frequency 10 MHz from the measured frequency and divide by the nominal frequency 10 MHz Note that you must multiply the result by 1 000 000 000 to get units of parts per billion ppb and by 1 000 000 to get units of parts per million ppm The device is considered to be in calibration if the accuracy in units of ppb or ppm is within the range specified in the NJ PXI 665x User Manual Adjusting the Frequency of the 10 MHz Oscillator If the accuracy of the 10 MHz oscillator is outside the specified range for the product the device is out of calibration A programmable voltage controls the oscillator frequency By varying this voltage and precisely measuring the frequency you can find a voltage that gives a frequency as close a
5. mmends a rubidium frequency standard clock source e A cable for connecting a frequency source to the NI PXI 6653 or NI PXI 6652 most likely a BNC to SMB cable e An SMB to SMB cable for connecting two of the SMB terminals on the NI PXI 6653 or NI PXI 6652 Software and Documentation You need the following software and documentation to calibrate the NI PXI 6653 or NI PXI 6652 e NI Sync e NI Sync User Manual e NI VISA NI PXI 6653 and NI PXI 6652 Calibration Procedure 2 ni com Test Conditions Software This calibration procedure requires NI Sync and NI VISA NI Sync and NI VISA support a number of application development environments ADEs and programming languages including LabVIEW LabWindows CVI and Microsoft Visual C When you install the drivers you need to install support for only the ADE or programming language you are using The illustrations in this manual show the LabVIEW code for implementing calibration steps using NI Sync and NI VISA Documentation The NI Sync User Manual contains detailed information about using the NI Sync driver including information about installing NI Sync and creating applications that use the NI Sync driver These sources along with this document are your primary references for writing your calibration utility You may also refer to the documentation for the programming language or application development environment you are using For further information about the device yo
6. no io aeara eE S 6 What Is Calibration Calibration consists of two steps verifying the accuracy of a device and correcting any discrepancy in the device accuracy and specified performance Verification is measuring the device performance and comparing the results to the factory specifications If the device is not operating within its specifications use the second step of the calibration procedure to correct the error Qr NATIONAL p INSTRUMENTS Why Should You Calibrate The accuracy of timing components can drift with time and temperature which could cause the module to be less accurate than specified Calibration ensures that the device still meets National Instruments specifications How Often Should You Calibrate The measurement requirements of the application determine how often you should calibrate the device to ensure its accuracy National Instruments recommends that you calibrate the NI PXI 6653 and NI PXI 6652 yearly You may want to shorten this interval based on the application demands Equipment and Other Test Requirements This section describes the equipment software documentation and test conditions required for calibrating the NI PXI 6653 and NI PXI 6652 Test Equipment Calibrating the NI PXI 6653 or NI PXI 6652 requires the following equipment e A highly stable 10 MHz clock source that is accurate to within 0 75 parts per billion ppb for the NI PXI 6653 or 150 ppb for the NI PXI 6652 NI reco
7. s in your software the patents txt file on your CD or ea a imei v 371238A 01 May04 ni com patents 2004 National Instruments Corp All rights reserved
8. s possible to 10 MHz The oscillator control voltage is set by writing a value in the range 0x001C0000 to 0x001CFFFF to the register at offset 0x1C in the NI PXI 665x BAR1 memory space You can do this most easily with VISA The last 16 bits of the value determine the oscillator frequency setting 3 Note Although the value stored in the register is 16 bits the hardware uses only the upper 12 bits The lower four bits are ignored It is usually best to start with a value of 0x001C8000 which is in the middle of the range and increase or decrease the value from there You can measure the frequency each time the control voltage is changed as described in the Measuring the Frequency section Sy Note NI Sync changes the oscillator control voltage back to the calibrated value if the board is reset Once the ideal value for the control voltage is determined proceed to the next step in which the new calibration value is written to the Calibration EEPROM Figure 3 shows how to adjust the oscillator frequency using NI VISA National Instruments Corporation 5 NI PXI 6653 and NI PXI 6652 Calibration Procedure address space Figure 3 Adjusting the Frequency of the CIk10 Oscillator Using NI VISA Updating the Oscillator Frequency Calibration Value in the Calibration EEPROM Once the ideal 16 bit value for the oscillator frequency setting has been determined this value should be written to the Calibration EEPROM on the NI P
9. u are calibrating refer to the NI PXI 665x User Manual Follow these guidelines to optimize connections and test conditions during the calibration procedure e Install the NI PXI 6653 or NI PXI 6652 in Slot 2 of your PXI chassis The calibration procedure requires features of PXI that are accessible only in Slot 2 e Maintain a temperature of approximately 25 C e Keep relative humidity below 80 percent e Use shielded copper wire for all cable connections to the device e Allow a warm up time of at least 15 minutes for the NI PXI 6652 and three hours for the NI PXI 6653 to ensure the measurement circuitry is at a stable operating temperature Verifying the Oscillator Frequency of the NI PXI 6653 or NI PXI 6652 The following steps outline the procedure for measuring the 10 MHz oscillator frequency on the NI PXI 6653 and NI PXI 6652 and determining whether the device requires adjustment to meet the published specifications National Instruments Corporation 3 NI PXI 6653 and NI PXI 6652 Calibration Procedure Connecting the Clock Source The first step in determining the precise frequency of the onboard oscillator is to connect a highly accurate frequency source to the system Connect the accurate 10 MHz source to the ClkIn connector on the NI PXI 6653 or NI PXI 6652 Using NI Sync program the NI PXI 6653 or NI PXI 6652 to route the ClkIn signal to PXI_Clk10In without using its 10 MHz PLL Refer to Figure 1 and the
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