Automated AC DC Calibration Systems and Software

1 Page 1 Operation and Reference Manual for the NIST Automated AC-DC Calibration Systems and Software Thomas E. Lipe NIST Special Publication 250-61 Open at page → 2 Page 2 NIST Special Publication 250-61 Operation and Reference Manual for the NIST AC-DC Calibration Systems and Software Thomas E. Lipe Fundamental Electrical Measurements Group Quantum Electrical Metrology Division May 2004 U... Open at page → 3 Page 3 Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or... Open at page → 4 Page 4 Table of Contents - 1 Table of Contents Introduction 1. Scope Introduction – 1 2. Introduction Introduction – 1 3. The NIST Automated Systems for Thermal Transfer Standard Calibrations Introduction – 3 4. Software Design... Open at page → 5 Page 5 Table of Contents - 2 11. The Measurement Sequence Running the Voltage VI – 9 12. The Two-Channel N-test VI Running the Voltage VI – 11 13. Using the Note Utility Running the Voltage VI – 13 14. Measuring a Check Standar... Open at page → 6 Page 6 Table of Contents - 3 The N-Test VI 1. Introduction Running the N-Test VI – 1 2. Running the N-Test VI Running the N-Test VI – 2 3. The GPIB Status Cluster Running the N-Test VI – 3 4. Starting the N-Test Software Runnin... Open at page → 7 Page 7 Table of Contents - 4 13. Parse Standard A–19 14. Printer Utility A–20 15. Read DVM A–25 16. Read Temperature A–27 17. Relay Control A–28 18. Set ac voltage A–29 19. Set dc voltage A–31 20. Set Frequency A–32 21. Standar... Open at page → 8 Page 8 Table of Contents - 5 Appendix D: Data Files 1. Introduction D–1 2. The Calibration Data File D–1 3. The Temperature Data File D–3 Appendix E: Instruments 1. Introduction E–1 2. Adding Instrument Definitions E–1 3. GPIB... Open at page → 9 Page 9 Introduction - 1 Introduction Scope This document supersedes the previous operations manual for the NIST Automated Thermal Transfer Standard Calibration Systems [1]. It provides information regarding the arrangement of t... Open at page → 10 Page 10 Introduction - 2 scale input, and respond in a roughly square-law manner to changes in the input signal. These are found in a wide range of commercial instruments and are useful from about 10 Hz to several hundred megahe... Open at page → 11 Page 11 Introduction - 3 a glass form. In either case, for higher voltages, the resistor makes the dominant contribution to both the ac-dc difference and the uncertainty of a TVC [16,17]. The NIST Automated Systems for Thermal T... Open at page → 12 Page 12 Introduction - 4 little structure and convoluted program flow. These features made the software extremely difficult to understand and maintain, and its monolithic structure precluded modifications necessary to calibrate... Open at page → 13 Page 13 Introduction - 5 Future Directions The LabVIEW-based software is presently in routine operation in the Ac-dc Difference Calibration Service at NIST and no major revision is anticipated. However, as is the case in all inf... Open at page → 14 Page 14 Introduction - 6 Table 1. Components of Automated System II as shown in Figure 1. instrument Function Instrument Function 1 Dc voltage monitor voltmeter 6 Oscilloscope 2 Temperature monitor voltmeter 7 Ac voltage monitor... Open at page → 15 Page 15 System Requirements - 1 NIST Ac-dc Difference Calibration Software System Requirements The software for controlling the NIST Ac-dc Difference calibration systems is written in LabVIEW, a graphically-oriented programming... Open at page → 16 Page 16 System Requirements - 2 • National Instruments GPIB-ENET adapter on Macintosh computers running MacOS 10.2 and higher. Note that even though the Ac-dc Difference Calibration software is platform independent, the user wil... Open at page → 17 Page 17 Running the Voltage VI - 1 Running the Voltage System VI Loading the Voltage System Program To load the software for the voltage calibration system, double-click the Voltage System Startup.vi icon on the desktop. After l... Open at page → 18 Page 18 Running the Voltage VI - 2 (DVMs) used to monitor the outputs of the thermal converters. • GPIB Bus Status: A cluster of enumerated lists, which defines the instruments available on the GPIB (IEEE-488) interface bus. • S... Open at page → 19 Page 19 Running the Voltage VI - 3 Getting Help You may get help at any time by clicking the box with the question mark at the right side of the title banner. Clicking this button launches Adobe Acrobat Reader, and displays the... Open at page → 20 Page 20 Running the Voltage VI - 4 Table 1. Descriptions of the fields on the Voltage System VI front panel. The number indicates the order in which the fields are entered using the TAB key. 10 Mt The value of M for the UUT. 11... Open at page → 21 Page 21 Running the Voltage VI - 5 Entering the Response Characteristics for the Converters To calculate the ac-dc difference of the thermal converters, the system needs to know how the output of the converters changes in respon... Open at page → 22 Page 22 Running the Voltage VI - 6 shutdown, set this slider to OFF. After the measurement cycle finishes, the software is reset, but the GPIB bus is not, so that will still be supplied to the TVCs. Warning: A potential safety h... Open at page → 23 Page 23 Running the Voltage VI - 7 • Add Note (OFF): Occasionally you may wish to describe the measurement conditions in more detail than the Test Information field has room for. Clicking on this slider opens a window, where you... Open at page → 24 Page 24 Running the Voltage VI - 8 choosing the instruments for the calibration system, as you can change instruments without changing the source code. You may need to modify the GPIB bus definitions. To change the defined instr... Open at page → 25 Page 25 Running the Voltage VI - 9 If you have chosen the automatic warm-up option, the software will calculate a warm-up period based on the applied voltage. The time until the start of data collection is displayed in the Syste... Open at page → 26 Page 26 Running the Voltage VI - 10 If the ac-dc difference of the standard channel is less than 50 × 10 -6 , then the ac and dc sources are balanced well enough so that the imbalance in the sources will have a negligible effect... Open at page → 27 Page 27 Running the Voltage VI - 11 sends it to the print queue. Because LabVIEW has the dominant priority for system resources in order to keep the measurement timing consistent, the hardcopy will be printed only after all N me... Open at page → 28 Page 28 Running the Voltage VI - 12 Figure 3. The two-channel n-test front panel. The N- TEST subVI is called and executed automatically with no intervention on your part. At the end of the n-test measurement, the ns of both the... Open at page → 29 Page 29 Running the Voltage VI - 13 Using the Note Utility Occasionally, you might need to preserve more information about a measurement than the Test Information field allows. To create a note, click on the ADD NOTE slider in t... Open at page → 30 Page 30 Running the Voltage VI - 14 When you are finished entering the check standard information, click on the OK button. A third window pops up to let you select the data file to which to save the check standard data. Select a... Open at page → 31 Page 31 Running the Current VI - 1 Running the Current System VI Loading the Current System Program To load the software for the current calibration system, double-click the Current System Startup.vi icon on the desktop. After l... Open at page → 32 Page 32 Running the Current VI - 2 • Amplifier Type: This section lets you define a particular type of transconductance amplifier (or no amplifier at all), and sets its transconductance. • GPIB Bus Status: A cluster of enumerate... Open at page → 33 Page 33 Running the Current VI - 3 Getting Help You may get help at any time by clicking the box with the question mark at the right side of the title banner. Clicking this button launches Adobe Acrobat Reader, and displays the... Open at page → 34 Page 34 Running the Current VI - 4 Table 1. Descriptions of the fields on the Current System VI front panel. The number indicates the order in which the fields are entered using the TAB key. 13 Filter Delay (s) The time delay be... Open at page → 35 Page 35 Running the Current VI - 5 column by pressing the RETURN key. The other columns in the table are for data collected during the measurement sequence, and you need not enter information into these columns. Similarly, the A... Open at page → 36 Page 36 Running the Current VI - 6 Warning: A potential safety hazard may exist if you deselect the automatic shutdown feature. You should be aware that current will still be supplied to the TCCs after the program has stopped, a... Open at page → 37 Page 37 Running the Current VI - 7 • Chk. Standard (OFF): Click on this slider to measure a check standard simultaneously with the UUT. After you click this slider to ON, LabVIEW opens a window into which you enter information a... Open at page → 38 Page 38 Running the Current VI - 8 either pressing the TAB key until it appears, or by pressing the COMMAND () key while simultaneously depressing the mouse button. Once you select this tool, you can see a list of the defined i... Open at page → 39 Page 39 Running the Current VI - 9 √ Note: To ensure that the ac-dc differences are calculated properly, the software automatically takes the absolute value of the output emfs shown on the nanovoltmeters. The signs of the therma... Open at page → 40 Page 40 Running the Current VI - 10 calculated (uncorrected) ac-dc difference of UUT is displayed as a yellow point on the graph displayed in the Results section. If the ac-dc difference of the standard channel is less than 150... Open at page → 41 Page 41 Running the Current VI - 11 point at the new frequency. The results of the measurements at the just-completed frequency are passed to the subVI PRINTER UTILITY, which puts the information in a presentable format, and sen... Open at page → 42 Page 42 Running the Current VI - 12 Figure 3. The two-channel n-test front panel. The N- TEST subVI is called and executed automatically with no intervention on your part. At the end of the n-test measurement, the ns of both the... Open at page → 43 Page 43 Running the Current VI - 13 Using the Note Utility Occasionally, you might need to preserve more information about a measurement than the Test Information field allows. To create a note, click on the ADD NOTE slider in t... Open at page → 44 Page 44 Running the N-Test VI - 1 The N-test VI Introduction Changes in the output emf of a thermal converter are related to changes in the input signal by the relation EkI n = (1) where E is the output emf, k is a constant, I i... Open at page → 45 Page 45 Running the N-Test VI - 2 practice is to measure n at several input levels and use a linear regression analysis to fit a line to the resulting data. Then, using the slope and intercept of this line, you can determine n a... Open at page → 46 Page 46 Running the N-Test VI - 3 The GPIB Bus Status Cluster Rather than explicitly define the types and addresses of each instrument on the GPIB bus in the program code, this information is disseminated throughout the program... Open at page → 47 Page 47 Running the N-Test VI - 4 After you click on the RUN button, the Previous Data arrays, and Present Data arrays are cleared, as are the test information fields, and the current date and time displayed in the System Status... Open at page → 48 Page 48 Running the N-Test VI - 5 Table 1. Description of the fields in the Test Information section of the n-test VI front panel, along with the panel order for the TAB key. 6 Voltage Step (V) The step between applied voltages.... Open at page → 49 Page 49 Running the N-Test VI - 6 average n and standard deviation of the five determinations are calculated and displayed along with the baseline voltage and output emf in the Previous Data section of the display. The baseline... Open at page → 50 Page 50 Running the N-Test VI - 7 Table 2. Objects on the N-Test Report front panel and on the archival hardcopy. Test Information The information you entered into the TEST INFORMATION field. N-test Data The data from the n-test... Open at page → 51 Page 51 A - 1 Appendix A: The SubVIs Introduction to Appendix A This appendix presents an alphabetical list of the subVIs used by the voltage and current calibration software. The listing for each subVI includes a brief descript... Open at page → 52 Page 52 A - 2 Calculate Uncertainties CALCULATE UNCERTAINTIES calculates the root-sum-square (RSS) uncertainties from the standard deviation of the data collected from the measurement sequence and the (already-measured) Type B c... Open at page → 53 Page 53 A - 3 CH8100 CH8100 is used to control a Clarke-Hess Model 8100A transconductance amplifier, and returns the compliance voltage delivered by the amplifier. Connector Pane Front Panel Amplifier Type: Label: Amplifier Type... Open at page → 54 Page 54 A - 4 Chauvenet CHAUVENET checks the data collected from a calibration against a normal distribution and discards points which are outside the 95 % confidence interval of the distribution. The maximum number of discarded... Open at page → 55 Page 55 A - 5 Check Std. Info This subroutine lets the user specify a check standard to be measured simultaneously with the UUT. The subVI opens an appropriate data file to write the measurement information to, and returns the c... Open at page → 56 Page 56 A - 6 Open at page → 57 Page 57 A - 7 Clear System CLEAR SYSTEM resets the defined GPIB-based instruments to their power-on state, places the ac-dc relay in its normally closed position, and halts execution of the ac-dc difference program. Connector Pa... Open at page → 58 Page 58 A - 8 Date and Time Returns the present system date and time. Connector Pane Front Panel Date and Time: Label: Date and Time Type: String indicator Direction: Outbound Visible on front panel: No Returns the present syste... Open at page → 59 Page 59 A - 9 Initialize System INITIALIZE SYSTEM does the following: > Sets the IEEE-488 instruments defined in GPIB BUS STATUS to their power-on state > Sets the output voltage on the supplies and puts them in their operate mo... Open at page → 60 Page 60 A - 10 N-Test This VI measures the n of a thermal converter at applied voltages defined by the user. The VI then fits a straight line to the data, to calculate the M (intercept on the n – axis) and N (slope of n versus o... Open at page → 61 Page 61 A - 11 Scram Label: Stop and Clear System Type: Boolean control Direction: Internal Visible on front panel: Yes Clicking on this button halts the n-test routine and calls C LEAR SYSTEM to reset the measurement system. Pr... Open at page → 62 Page 62 A - 12 Open at page → 63 Page 63 A - 13 N-test Report Captures the data from a one-channel n-test, displays it on the front panel, and then prints the panel. It then returns the processing to the calling VI. Connector Pane Front Panel Min: Label: Min Ty... Open at page → 64 Page 64 A - 14 Open at page → 65 Page 65 A - 15 N-Test (2 channel) This subVI measures the n of both TVCs simultaneously at the present applied voltage. Connector Pane: Front Panel: Test ID: Label: Test ID Type: String control Direction: Inbound Visible on fron... Open at page → 66 Page 66 A - 16 Standard Channel: Label: Standard Channel Type: Two-dimensional real array Direction: To display Visible on front panel: Yes Displays the data for the standard channel. “Ei” and “Ef” are the initial and final read... Open at page → 67 Page 67 A - 17 Filter: Label: Filter Type: Integer indicator Direction: To display Visible on front panel: Yes Displays the time between the activation of the filters and the start of data collection. Open at page → 68 Page 68 A - 18 Note Utility NOTE UTILITY lets the operator append a note to the calibration data sheet. The note is appended below the graph on the data sheet. Commands are provided to accept the note or reset the text. The note... Open at page → 69 Page 69 A - 19 Parse Standard PARSE STANDARD is used to let the operator select the appropriate standard for a measurement. It selects a set of possible standards based on the applied voltage, and presents this set of standards... Open at page → 70 Page 70 A - 20 Printer Utility This VI is called by AC-DC DIFFERENCE and displays the calibration data for a unit under test. The VI then prints the panel as a permanent record of the calibration. Connector Pane Front Panel Data... Open at page → 71 Page 71 A - 21 Standard: Label: Standard Type: Real vector Direction: Inbound Visible on front panel: No The measurement information for the standard thermal converter, specifically the output emf and K s. Test: Label: Test Type... Open at page → 72 Page 72 A - 22 ∆: Label: ∆ Type: Real vector Direction: To display Visible on front panel: Yes Column vector containing the corrected ac-dc differences of the unit under test. Rs: Label: Rs Type: Real vector Direction: To displa... Open at page → 73 Page 73 A - 23 Test Range (V): Label: Test Range (V) Type: Real indicator Direction: To display Visible on front panel: Yes The range of the unit under test. Voltage Drop of Series Resistor (V): Label: Voltage Drop of Series Res... Open at page → 74 Page 74 A - 24 Rt (µV/V): Label: Rt (µV/V): Type: Real indicator Direction: To display Visible on front panel: Yes The dc reversal error of the test TVC. D graph Label: D graph Type: XY graph Direction: To display Visible on fro... Open at page → 75 Page 75 A - 25 Read DVM READ DVM reads the voltmeters used as detectors for the thermal converters. The user can set the delay between filter activation and triggering, as well as the number of reading per trigger. As of this re... Open at page → 76 Page 76 A - 26 Open at page → 77 Page 77 A - 27 Read Temperature Gets the temperature from an external DVM with temperature probe. Connector Pane Front Panel GPIB Bus Status: Label: GPIB Bus Status Type: Cluster of enumerated lists. Direction: Inbound Visible o... Open at page → 78 Page 78 A - 28 Relay Control RELAY CONTROL operates the appropriate relay to switch the output voltage from ac to dc or vice-versa. The subVI will recognize both internal and external relay types, and multiple controller types.... Open at page → 79 Page 79 A - 29 Set ac voltage SET AC VOLTAGE calculates the amount of offset to be introduced in the ac signal so that the output from the ac source will match that of the dc source, and sets the ac source to that value. If the... Open at page → 80 Page 80 A - 30 Open at page → 81 Page 81 A - 31 Set dc voltage Sets the dc source to the proper voltage. Connector Pane Front Panel GPIB Bus Status: Label: GPIB Bus Status Type: Cluster of enumerated lists. Direction: Inbound Visible on front panel: Yes The Ins... Open at page → 82 Page 82 A - 32 Set Frequency Fluke 5200A ac sources may have large frequency offsets at frequencies above about 1 kHz. This may cause significant errors when measuring instruments with large frequency coefficients of ac-dc diffe... Open at page → 83 Page 83 A - 33 Standard Correction Given the NIST standard and frequency for a measurement, this subVI uses a LabVIEW table to look up and return the standard correction. Connector Pane Front Panel Standard Corrections: Label: S... Open at page → 84 Page 84 A - 34 Std Corr Fit This subVI calculates standard corrections for non-cardinal frequencies. For frequencies < 1 kHz, and for frequencies > 100 kHz, the corrections are found from square-law fits. For other frequencies,... Open at page → 85 Page 85 A - 35 Datron Local Datron and Wavetek/Datron calibrators cannot be placed in LOCAL mode from the front panel, unless you turn off the power switch. This routine takes the less radical approach of sending a GTL (Go To Lo... Open at page → 86 Page 86 A - 36 The Help Facility Although not really a subVI, the Help Facility does deserve its own mention. The Help Facility is activated by clicking on the box with the question mark to the right of the AC-DC logo in the tit... Open at page → 87 Page 87 B - 1 Appendix B: Setting up Thermal Voltage Converters for Calibration Introduction Thermal voltage converters (TVCs) are used to compare an unknown ac voltage to a known dc voltage. This appendix provides instruction o... Open at page → 88 Page 88 B - 2 Coaxial Thermal Voltage Converters As a class, coaxial thermal voltage converters consist of thermoelements mounted coaxially with range resistors to make a single voltage range. The TE and resistor may or may not... Open at page → 89 Page 89 B - 3 Figure B-1. Photograph of a coaxial thermal voltage converter connected to one of the NIST automated systems.
To calibrate a coaxial thermal voltage converter, follow these steps: i. Connect the UUT to one leg of... Open at page → 90 Page 90 B - 4 iv. Connect the detector cables to the thermoelements, making sure that the standard channel detector cable is connected to the NIST standard, and the test channel cable to the UUT. v. Connect the ground wires from... Open at page → 91 Page 91 B - 5 Fluke 792A Thermal Transfer Standards The Fluke 792A Thermal Transfer Standard is a multirange device consisting of a solid-state thermal sensor and a set of range resistors mounted on a rotary switch. A separate b... Open at page → 92 Page 92 B - 6 Figure B-2. Front view of a Fluke 792A connected to one of the NIST automated systems. Battery Pack Fluke 792A Thermal Transfer Standard Monitor TENIST Standard TVC Test Channel Detector Cable Open at page → 93 Page 93 B - 7 Figure B-3. Rear view of Fluke 792A and NIST standard TVC connected to one of the NIST automated systems.
To calibrate a Fluke 792A, follow these steps: i. Connect the power supply to the transfer standard using... Open at page → 94 Page 94 B - 8 iv. Ensure that both the Type-N to GR-874 adapter and the Type-N extension are firmly connected to the Fluke 792A. You may need to use pliers to ensure an adequate connection. v. Connect one leg of a GR-874 Tee to... Open at page → 95 Page 95 B - 9 Fluke 540B and Holt 6A Transfer Standards These instruments represent an earlier generation of multirange thermal transfer standards. The two instruments are generally similar; both contain a set of range resistors... Open at page → 96 Page 96 B - 10
To calibrate a Fluke 540B or Holt 6A, follow these steps: i. Ensure that the transfer standard is powered. For the Holt 6A, this involves connecting the instrument to the ac power mains and turning the toggle sw... Open at page → 97 Page 97 B - 11 Ballantine Models 1600A and 1605A Ballantine Laboratories produced these instruments, the Models 1600A and 1605A, in the 1970s and 1980s. Few examples were sold, especially of the Model 1605A, and the likelihood t... Open at page → 98 Page 98 B - 12 thermoelement. This module can be calibrated independently of the autobalancing module, and is generally sent to NIST without the rest of the instrument. The measurement module connects to the autobalancing module... Open at page → 99 Page 99 B - 13 v. Set the appropriate input voltage range using the rotary switch on the front panel. vi. Connect the test channel detector lead to the Ballantine 1600A output connector through a 3-pin to 2-pin adapter. The outp... Open at page → 100 Page 100 C - 1 Appendix C: Setting up Thermal Current Converters for Calibration Introduction Thermal Current Converters (TCCs) are used to compare an unknown ac current to a known dc current. These devices are used to compare th... Open at page → 101 Page 101 C-2 Fluke A40 and A40A Current Shunts The Fluke A40 (for currents up to 5 A) and A40A (10 A and 20 A) currents shunts are designed to plug into the banana sockets on the front panel of a Model 540B Thermal Transfer Stand... Open at page → 102 Page 102 C-3
To calibrate a Fluke A40, follow these steps: i. Select a suitable transconductance amplifier. A transconductance amplifier passes voltage from the sources in the automated systems through a resistor to generate a... Open at page → 103 Page 103 C-4
Note: Owing to the geometry of the resistance element in Fluke A40 shunts, the orientation of the leads at the face of the A40 effects the measurement results, often dramatically. It is NIST practice to bring the i... Open at page → 104 Page 104 C-5 Figure C-2. Fluke A40A current shunt with separate thermoelement connected to one of the NIST automated systems.
To calibrate a Fluke A40A, follow these steps: i. Select a suitable transconductance amplifier. A tra... Open at page → 105 Page 105 C-6 To protect the thermal converters, ALWAYS short the output connector of the amplifier before you switch the power on. The Clarke-Hess 8100 has a true standby state and is immune to this hazard. ii. Connect an RG8/U c... Open at page → 106 Page 106 C-7 Holt HCS-1 Current Shunts The Holt HCS-1 current shunts are of a coaxial design, the resistor being a web of wire arranged coaxially about the axis of the shunt. The input terminal is a female UHF connector at one en... Open at page → 107 Page 107 C-8
To calibrate a Holt HCS-1, follow these steps: i. Select a suitable transconductance amplifier. A transconductance amplifier passes voltage from the sources in the automated systems through a resistor to generate a... Open at page → 108 Page 108 C-9 vii. Connect the detector leads to the outputs of the NIST current standard and to the output of the UUT. viii. Ensure that the NIST standard is set to the appropriate current range. Also make sure that the UUT is se... Open at page → 109 Page 109 C-10 Precision Measurements 9000 Series Shunts This is a set of four current shunts intended to cover ranges of 10 A to 100 A. These shunts are coaxial in design, the resistance element being a circular array of small re... Open at page → 110 Page 110 C-11
To calibrate a Precision Measurements, Incorporated (PMI) shunt, follow these steps: i. PMI shunts are coaxial and may be used two terminally or three terminally. In the NIST measurement scheme, the UUT is always... Open at page → 111 Page 111 D - 1 Appendix D: Data Files Introduction The ac-dc difference calibration routine writes out a tab-delimited, plain-text data file at the completion of each frequency. The data file, named for the voltage or current ran... Open at page → 112 Page 112 D - 2 Column Heading Information XAn “x” in this column indicates that a particular point was excluded from the average ac-dc difference because it failed Chauvenet’s Criterion NThe determination number ds The ac-dc diff... Open at page → 113 Page 113 D - 3 Example 1: Macintosh file hierarchy The file hierarchy on an Apple Macintosh goes something like this: Data Disk:Calibration Files:Calibration Data:Test Folder:123456:10V.dat To direct the ac-dc software to use thi... Open at page → 114 Page 114 E - 1 Appendix E: Instrument Definitions Introduction to Appendix E As described in the sections pertaining to running the voltage and current VIs, the software supports the use of many different types of instruments in... Open at page → 115 Page 115 E - 2 GPIB Instrument Definitions The instrument definitions included in the present version of the automated system software are presented in the tables below. The addresses of the instrument may vary according to syste... Open at page → 116 Page 116 E - 3 Table E-1. Automated system instrument definitions. Instrument Type Instrument Description Fluke 5700/PA-25 3 Multifunction Calibrator and Power Amplifier. 0 V to 100 V rms, 10 Hz to 1 MHz. Fluke Models 5700 and 57... Open at page → 117 Page 117 F - 1 Appendix F: A Brief Explanation of Uncertainty Analysis The uncertainties quoted by the NIST Ac-dc Difference Calibration Service are calculated in accordance with NIST Technical Note 1297. The combined standard un... Open at page → 118 Page 118 References - 1 Appendix G: References [1]T. E. Lipe, “Operations manual for the NIST automated ac-dc difference calibration system,” 1994, unpublished. [2] B. D. Inglis, “Standards for ac-dc transfer,” Metrologia, 29, pp... Open at page → 119 Page 119 References - 2 [16] J. R. Kinard and T. E. Lipe, “Recharacterization of thermal voltage converters after thermoelement replacement,” IEEE Trans. Instrum. Meas., IM-38, No. 2, pp. 351-356, April 1989. [17] D. X. Huang, T.... Open at page →