Standard Platinum Resistance Thermometer Calibrations

1 Page 1 Standard Platinum Resistance Thermometer Calibrations from the Ar TP to the Ag FP G. F. Strouse NIST Special Publication 250-81 Open at page → 2 Page 2 ii NIST Special Publication 250-81 Standard Platinum Resistance Thermometer Calibrations from the Ar TP to the Ag FP G. F. Strouse Chemical Science and Technology Laboratory Process Measurements Division Thermometry Grou... Open at page → 3 Page 3 iii 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 recommendatio... Open at page → 4 Page 4 iv 1 Introduction ............................................................................................................................. 1 2 ITS-90 Overview (Ar TP to Ag FP) .......................................... Open at page → 5 Page 5 v 6.1.3 Constant cell pressure parameter .......................................................................... 41 6.1.4 Cell corrections parameter ....................................................................... Open at page → 6 Page 6 1 1 Introduction The National Institute of Standards and Technology (NIST) is in charge of realizing, maintaining, and disseminating the International Scale of 1990 (ITS-90) [1-5]. The Standard Platinum Resistance Thermo... Open at page → 7 Page 7 2 2.1 ITS-90 equations For the temperature range of the SPRT Laboratory, the ITS-90 uses the two reference functions and eight deviation functions to cover eight temperature subranges. Table 2 shows the eight temperature... Open at page → 8 Page 8 3 where the ITS-90 defined reference function coefficients A0 and Ai are given in Table 3. The approximate inverse function is specified as:    K273.16x35.065.0– 15 1 61 090          i i riWBBT where th... Open at page → 9 Page 9 4 2.2 ITS-90 thermometer specifications The ITS-90 gives specifications on the purity of the platinum (Pt) used for the sensor element for an ITS-90 defining PRT. Note that the ITS-90 does not use the word “standard” to... Open at page → 10 Page 10 5 Table 4. ITS-90 temperature range suitable for NIST calibration of an SPRT, for each combination of nominal resistance at the TPW, sheath material, and sensor support material. Nominal R(TPW), Ω Sheath Material Sensor... Open at page → 11 Page 11 6 Table 5. NIST calibration schedule for SPRT calibrations from the Ar TP to the Ag FP. Service ID No. SPRT Type ITS-90 coefficients ITS-90 Fixed Points Range of Use, °C 33065S Capsule SPRT a4, b4 Ar TP, Hg TP, TPW –200... Open at page → 12 Page 12 7 The cost of a calibration changes yearly, occurring normally in February. The current calibration costs may be found within the NIST Technology Services webpages http://ts.nist.gov/MeasurementServices/Calibrations/resi... Open at page → 13 Page 13 8 The shipped SPRT should be packed in a suitable container, such that the SPRT should be softly supported within a case but not be free to rattle. This necessitates the use of packing material that does not become compa... Open at page → 14 Page 14 9 3.9 Special Tests / Requests Arrangements for special tests or requests outside of the calibration services listed in Table 5 should be made with the NIST technical contact. Special tests include, but are not limited t... Open at page → 15 Page 15 10 external wire leads and connectors, and measurement of the insulation resistance for metal sheathed SPRTs). During the login process, a unique 4-digit code (NIST ID) is assigned to the SPRT that is used to identify th... Open at page → 16 Page 16 11 Figure 3. Simplified flowchart of the stabilization procedure for the Stabilize SPRT step. Third, an SPRT is calibrated from the highest to lowest required fixed-point temperature. Figure 4 shows a simplified flowchar... Open at page → 17 Page 17 12 Figure 4. Simplified flowchart showing the SPRT calibration measurement pattern used during the Calibrate SPRT step. Table 6. The maximum allowable change in the check SPRT values [W2(SPRTcheck) – W1(SPRTcheck)] / (dW... Open at page → 18 Page 18 13 Fourth, the calibration results from Step 3, using the required W(t90) values for the calibration range, are used to calculate the ITS-90 deviation function coefficients. Figure 5 shows a simplified flowchart of the a... Open at page → 19 Page 19 14 4.2 Fixed point cells All NIST-fabricated fixed-point cells contain appropriate substances of the highest available purity (>99.9999 % pure) [5,19,20]. A minimum of three reference cells for each fixed-point is availa... Open at page → 20 Page 20 15 to increase the duration of the Hg TP plateau. The cell contains 2.5 kg of Hg (99.999 999 wt% pure) which provides an SPRT immersion depth of 18 cm. Following assembly of a Hg TP contained in a stainless-steel cell, t... Open at page → 21 Page 21 16 As shown in Figure 10, the NIST-fabricated Ga TP cell uses virgin Teflon for the crucible and cap, and a glass thermometer well and outer enclosure [8,28]. The Ga TP cell is evacuated during the preparation of the Ga... Open at page → 22 Page 22 17 Figure 11. NIST In FP, Sn FP, and Zn FP cells. Graphite crucible cutaway (enlarged view on left) shows the inside of the fixed-point cell. Figure 12 shows a graphite crucible, lid and thermometer well assembly for con... Open at page → 23 Page 23 18 Figure 12. NIST Al FP and Ag FP cells. Only one is shown as there is no visual difference between the three fixed-point cells. 4.2.2 ITS-90 fixed-point cell corrections The assigned ITS-90 temperatures for the various... Open at page → 24 Page 24 19 The correction for immersion depth is calculated by determining the depth of immersion of an SPRT in the fixed-point cell and multiplying that value by the ITS-90 assigned hydrostatic-head pressure correction for the... Open at page → 25 Page 25 20 4.3 Fixed-point cell maintenance systems The maintenance systems used to realize the ITS-90 fixed-point temperatures from the Ar TP to the Ag FP are either constructed at NIST or acquired commercially and are designed... Open at page → 26 Page 26 21 used for the preparation of the outer liquid-solid interface of the Ga TP cell. In this furnace, the triple-point plateau will last approximately 13 h. With the other two furnace, which operate at 29.9 °C, the triple-... Open at page → 27 Page 27 22 shown in Table 9, the vertical temperature differences over the length of the re-entrant well of the fixed-point cells in the maintenance baths, single-zone Ga TP furnace, three-zone furnace and the sodium heat pipe f... Open at page → 28 Page 28 23 The ability of SPRTs of various manufacturer models to exhibit proper immersion in the NIST fixed-point cells was investigated. For the SPRT to be considered properly immersed (no stem conduction effect influencing th... Open at page → 29 Page 29 24 4.4 SPRT measurement system A semi-automated system controlled by a LabView program governs and performs the SPRT measurements (See section 4.5). The commercially-available ac resistance-ratio bridge (ASL F900) operat... Open at page → 30 Page 30 25 and appear as electrical noise on the ASL bridge. Using a NIST-calibrated thermistor, the LabView program reads the oil bath temperature every three seconds. If the oil bath temperature exceeds the allowable maintenan... Open at page → 31 Page 31 26 HTSPRTs used above 700 °C require protection against metal ion contamination. Inside the two HTSPRT annealing furnace re-entrant wells are concentric fused silica, Pt, and fused silica test tubes. The Pt test tube (66... Open at page → 32 Page 32 27 5.2 Calibration by fixed points We describe below each NIST realization method of each ITS-90 fixed-point cell. The setpoint temperatures and duration of fused-silica rods in the thermometer re-entrant well are design... Open at page → 33 Page 33 28 2.0 1.5 1.0 0.5 0.0 0.5 0 2 4 6 8 Distance from bottom of well, cm Deviation from temperature at full immersion, mK NIST Ag 92-1 hydrostatic head Figure 15. Heat-flux (immersion) test results during realization of... Open at page → 34 Page 34 29 0.8 0.6 0.4 0.2 0.0 0.2 0 2 4 6 8 10 Distance from bottom of well, cm Deviation from temperature at full immersion, mK NIST Al 96-1 hydrostatic head Figure 16. Heat-flux (immersion) test results during realization... Open at page → 35 Page 35 30 or an “induced freeze”. A heat flux test is needed to validate the realization method (e.g the proper creation of the inner freeze). Figure 17 gives an example of a heat-flux test for two SPRTs of different manufactur... Open at page → 36 Page 36 31 The successive insertions of the fused-silica rod insure formation of a solid mantle of tin on the outside of the graphite re-entrant well. The recalesence occurs on the inner surface of the graphite crucible. The cre... Open at page → 37 Page 37 32 a small-diameter metal-sheathed SPRT, an aluminum bushing is used to improve thermal contact with the inner solid-liquid interface. The successive insertions of the fused-silica rod insure formation of a solid mantle... Open at page → 38 Page 38 33 The re-entrant well is filled with mineral oil to improve the thermal contact of the SPRT with the Ga TP inner liquid-solid interface. In the case of a small-diameter metal-sheathed SPRT, an aluminum bushing is used t... Open at page → 39 Page 39 34 o Fill the re-entrant well with crushed solid CO2 to the same level as that of the liquid water in the TPW cell. o For approximately 17 min, continue filling the re-entrant well to maintain the level of crushed solid... Open at page → 40 Page 40 35 5.2.8 Hg TP The Hg TP in a melting mode is achieved by following these steps: o Check that the re-entrant well is filled with ethanol. o The Hg TP cell is placed in the maintenance bath which is then set at –45 °C to... Open at page → 41 Page 41 36 5.2.9 Ar TP The Ar TP in a melting mode is achieved over three days by following these steps: o Check that the argon sample reservoir valve is closed o Turn on He supply to re-entrant wells o Remove surrogate SPRTs (e... Open at page → 42 Page 42 37 0.2 0.1 0.0 0.1 0.2 0 2 4 6 Distance from bottom of well, cm Deviation from temperature at full immersion, mK Hart 5681 Rosemount 162CE hydrostatic head Figure 23. Heat-flux (immersion) test results during realizati... Open at page → 43 Page 43 38 thermal and physical shock that the SPRT incurs over time. At this time, the NIST viewpoint on determining the re-calibration interval of an SPRT is twofold. First, using an SPRT does not allow for a set re-calibratio... Open at page → 44 Page 44 39 This IMAP encompasses six interactive elements for the realization of the ITS-90 fixed-point cells and the subsequent calibration of SPRTs. As shown in Table 12, the six elements are the Fixed-Point Cells, Furnace/Mai... Open at page → 45 Page 45 40 material assay of the sample gives the type and amount of impurities.As an overview, Table 13 gives four methods in order of priority. A detailed description with examples of four different samples of indium for each... Open at page → 46 Page 46 41 is not sufficient. Using the freezing-curve slope is inadequate by itself, but we see this method as very valuable in verifying that the cell construction did not add appreciable impurities. Direct comparisons of cell... Open at page → 47 Page 47 42 Temperature Stability of the NIST Fixed-Point Cell Furnaces measurements made over at least 15 hours -10 -8 -6 -4 -2 0 2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 fraction of measurement time  T / mK Ag, ±9 mK Al, ±8 mK Zn, ±... Open at page → 48 Page 48 43 was reached. After changing the immersion depth of the SPRT, the SPRT was allowed to re-equilibrate at each step prior to measurement. The immersion depth of the SPRT was calculated from the sensor midpoint to the hei... Open at page → 49 Page 49 44 6.3.5 Wetness parameter The Wetness parameter tests for moisture within the sheath of an SPRT. The first test is to measure the R(TPW) of the SPRT at currents of 1 mA, 1.41 mA, and 1 mA. The two 1 mA values of SPRT re... Open at page → 50 Page 50 45 6.4 Measurement system element 6.4.1 Repeatability parameter The Repeatability parameter of the Measurement System Element is statistically determined from making two similar measurements. The first method is to measu... Open at page → 51 Page 51 46 reference-resistor uncertainty component is calculated from the determination of the effect of the two parts of the Ohm parameter. During measurements, the software checks the second part of the Ohm parameter for stab... Open at page → 52 Page 52 47 The ratio error uncertainty component (Type A) is the result obtained using the RBC, verified by the results from the ASL RTU for the ac bridges and the two-way ratio complements check. Figure 29 gives an example of t... Open at page → 53 Page 53 48 The RTU allows the user to verify four parameters that check the operational compliance of the ac resistance ratio bridge with the manufacturer’s specifications. The checks ensure: 1) that the correct number of turns... Open at page → 54 Page 54 49 calibrated to within the stated calibration uncertainties. The external parameter verifies that the NIST realization temperatures of the fixed-point cells and assigned uncertainties are consistent with other National... Open at page → 55 Page 55 50 6.6.3 SPRT calibration results parameter Within the SPRT Calibration Results parameter, the calibrated SPRT must meet several ITS-90 and NIST criteria in order to be designated as an ITS-90 defining standard with the... Open at page → 56 Page 56 51 The uncertainties given in this document do not contain estimates for: 1) any effects introduced by transportation of the SPRT between NIST and the end user’s facility, 2) drift of the SPRT from use by the end user, 3... Open at page → 57 Page 57 52 Table 14. NIST SPRT Calibration Laboratory ITS-90 fixed-point cell realization uncertainties. Values are in millikelvins. Unc. Type Ag FP Al FP Zn FP Sn FP In FP Ga TP TPW Hg TP Ar TP Bridge Repeatability A 0.003 0.00... Open at page → 58 Page 58 53 7.2 Propagated fixed-point uncertainty for each ITS-90 temperature subrange The total calibration uncertainty at any given temperature within an ITS-90 temperature subrange is determined from the combined individual u... Open at page → 59 Page 59 54 0.5 0.0 0.5 1.0 0 200 400 600 Temperature, °C Propagated uncertainty ( k =2), mK Al: U (0.79 mK) Zn: U (0.51 mK) Sn: U (0.28 mK) Total Expanded Uncertainty Figure 31. Propagated fixed-point uncertainty for the temper... Open at page → 60 Page 60 55 0.2 0.0 0.2 0.4 0 100 200 Temperature, °C Propagated uncertainty ( k =2), mK Sn: U (0.28 mK) In: U (0.18 mK) Total Expanded Uncertainty Figure 33. Propagated fixed-point uncertainty for the temperature subrange 0 °C... Open at page → 61 Page 61 56 0.02 0.00 0.02 0.04 0.06 0.08 0 15 30 Temperature, °C Propagated uncertainty ( k =2), mK Ga: U (0.07 mK) and Total Expanded Uncertainty Figure 35. Propagated fixed-point uncertainty for the temperature subrange 0 °C... Open at page → 62 Page 62 57 0.1 0.0 0.1 0.2 0.3 0.4 200 150 100 50 0 Temperature, °C Propagated uncertainty ( k =2), mK Ar: U (0.14 mK) Hg: (0.15 mK) Total Expanded Uncertainty Figure 37. Propagated fixed-point uncertainty for the temperatu... Open at page → 63 Page 63 58 7.3 ITS-90 non-uniqueness uncertainty contribution to SPRT calibration uncertainties The ITS-90 contains three types of non-uniqueness labeled non-uniqueness I, II, and III [10- 12,58]. Only non-uniqueness Types I and... Open at page → 64 Page 64 59 Table 16. Maximum SPRT calibration uncertainty for each ITS-90 temperature subrange. ITS-90 Temperature Subrange Maximum Uncertainty (k=2), mK Ar TP to 0.01 °C 0.40 Hg TP to Ga MP 0.23 0 °C to Ga MP 0.07 0 °C to In FP... Open at page → 65 Page 65 60 7.6 Temperature measurement uncertainty of a calibrated SPRT To calculate the total uncertainty (where k=2) of a temperature measurement with a calibrated SPRT, first determine the expanded uncertainty of the resistan... Open at page → 66 Page 66 61 9 References 1. Preston-Thomas H., The International Temperature Scale of 1990 (ITS-90), Metrologia 27, 3-10, 1990; ibid. p 107. 2. CCT Working Group 1, "Supplementary Information for the International Temperature Sca... Open at page → 67 Page 67 62 14. Strouse, G.F., NIST Certification of ITS-90 Fixed-Point Cells from 83.8058 K TO 1234.93 K: Methods and Uncertainties”, in Proc. TEMPMEKO 2004, p. 879-884, 2005. 15. Moiseeva, N.P., Pokhodun, A.I., Mangum, B.W., St... Open at page → 68 Page 68 63 27. Strouse, G.F., Furukawa, G.T., and Mangum, B.W., “Preliminary Results of a Comparison of Water Triple-Point Cells Prepared by Different Methods,” CCT/93-24, 1993. 28. Strouse, G.F., “NIST Realization of the Galliu... Open at page → 69 Page 69 64 40. ISO/IEC 17025:2005(E), “General requirements for the competence of testing and calibration laboratories”, 2005. 41. http://ts.nist.gov/QualitySystem/ 42. Strouse, G.F., “NIST methods of estimating the impurity unc... Open at page → 70 Page 70 65 55. Stock M., Solve S., del Campo D., Chimenti V., Méndez-Lango E., Liedber H., Steur P.P.M., Marcarino P., Dematteis R., Filipe E., Lobo I., Kang K.H., Gam K.S., Kim Y.-G., Renaot E., Bonnier G., Valin M., White R.,... Open at page → 71 Page 71 66 10 Appendix Appendix A. Report of Calibration for an SPRT calibrated from the Al FP to the Ar TP. Open at page → 72 Page 72 67 REPORT OF CALIBRATION International Temperature Scale of 1990 Standard Platinum Resistance Thermometer Rosemount Model 162CE Serial Number 4415 Submitted by: NIST Thermometry Group Gaithersburg, Maryland 20899 USA Thi... Open at page → 73 Page 73 68 Tables: The table given in this Report of Calibration was calculated from the 1 mA coefficients for your SPRT. The first column of the table lists values of temperature. Unless otherwise requested, the second column l... Open at page → 74 Page 74 69 ITS-90 Uncertainty Propagation 83.8058 K to 273.16 K 0.1 0.0 0.1 0.2 0.3 75 125 175 225 275 Temperature, K Propagated uncertainty ( k =2), mK Ar: U (0.14 mK) Hg: U (0.15 mK) Total Expanded Uncertainty ITS-90 Uncertai... Open at page → 75 Page 75 70 R(273.16 K) ITS-90 Uncertainty Propagation in W(T 90) 13.8033 K to 1234.93 K 0.0 0.2 0.4 0.6 0 200 400 600 800 1000 1200 Temperature, K Propagated uncertainty, mK For a 0.1 mK uncertainty at 273.16 K Zn Al Ag Sn In Ga... Open at page → 76 Page 76 71 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) -200 0.16987204 -150 0.38537815 -199 0.17417541 232.3761 -149 0.38962614 235.4056 -198 0.17848559 232.0087 -148 0.39387... Open at page → 77 Page 77 72 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) -100 0.59459407 -50 0.79901192 -99 0.59872259 242.2175 -49 0.80306243 246.8829 -98 0.60284928 242.3250 -48 0.80711157 2... Open at page → 78 Page 78 73 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 0 0.99996012 50 1.19783766 1 1.00394739 250.7978 51 1.20176442 254.6629 2 1.00793345 250.8746 52 1.20568997 254.7409 3... Open at page → 79 Page 79 74 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 100 1.39270697 150 1.58459633 101 1.39657388 258.6047 151 1.58840390 262.6348 102 1.40043959 258.6844 152 1.59221029 26... Open at page → 80 Page 80 75 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 200 1.77353177 250 1.95953989 201 1.77728054 266.7546 251 1.96323037 270.9678 202 1.78102813 266.8380 252 1.96691968 27... Open at page → 81 Page 81 76 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 300 2.14264395 350 2.32285790 301 2.14627653 275.2867 351 2.32643273 279.7340 302 2.14990795 275.3743 352 2.33000639 27... Open at page → 82 Page 82 77 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 400 2.50018147 450 2.67459807 401 2.50369838 284.3411 451 2.67805656 289.1439 402 2.50721412 284.4351 452 2.68151387 28... Open at page → 83 Page 83 78 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 500 2.84607611 550 3.01457360 501 2.84947542 294.1773 551 3.01791283 299.4699 502 2.85287354 294.2806 552 3.02125085 29... Open at page → 84 Page 84 79 September 14, 2007 ITS-90 Table for SPRT S/N 4415 at 1 mA t(°C) W(t) dt/dW(t) t(°C) W(t) dt/dW(t) 600 3.18004510 650 3.34244986 601 3.18332337 305.0390 651 3.34566645 310.8880 602 3.18660041 305.1533 652 3.34888180 31... 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