5698 Users Guide.vp
Contents
1. at least six inches This error is due to heat lost or gained by the sensing ele ment through the thermometer stem In addition heat losses occur due to radia tion losses from the sensing element to the housing The sand blasted finish on the fused silica sheath is designed to mimimize losses due to radiation piping Convection prevention discs also provide multiple radiation shields along the lead wires Convection discs and the quartz insulation on lead wires cause some shunt resistance at very high temperatures However the effect of the shunt re sistance is insignificant Full immersion is recommended in a furnace or freeze point cell The immersion depth for primary standards is dependent on several factors in cluding accuracy requirements and type of liquid Therefore we recommend an 8 inch minimum immersion depth The exact immersion depth required can be determined by performing a gradi ent test taking measurements approximately every 1 2 inch 1 27 cm until there is a significant difference in readings Allow the thermometer to stabilize at each new depth Plot the results to see the stem effect Thermal EMF Two factors contribute to thermal EMF chemical consistency and physical con sistency Variations in chemical structure due to impurities and discrepancies in crystal structure can contribute to thermal EMF These factors are minimized by annealing the full length of wire before construction of the SPRT Likewise connec2. that you label the crate as extremely fragile Whether the SPRT is returned for repair or warranty please include a letter containing the following information e Description of the faulty operation and circumstances of failure e Complete shipping instructions for the return of the thermometer to the customer Hart Scientific 5698 3 1 3 2 3 Specifications Specifications Specifications Temperature Range 200 to 661 C Nominal 2550 0 5Q Current 1 0 mA Resistance Ratios W 234 315K lt 0 844235 W 302 9146K gt 1 11807 Sensitivity 0 10 C Drift Rate lt 0 006 C 100 hours at max temperature typically lt 0 003 C Diameter of Pt Sensor Wire 0 003 0 07 mm Protective Sheath Fused Silica Glass Diameter 0 28 7 mm Length 19 1 485 mm Lead Wires Four sensor wires Construction Construction of the 5698 is shown in Figure 2 and explained below The 5698 covers the range from 200 C to 661 C The 25 5Q sensor element is 3 Specifications crafted using high purity platinum wire wound strain free design a fused silica cross frame The 5698 has a sensitivity of 0 10 C 3 5 19 1 99 485 Protecting Tube Strain Relief Terminal Box Fused Silica 7 5 1 Terminal Gold Plated Lead Wire 85 2159 Figure 2 Standard Dimensions 3 3 Electrical Circuit The SP
3. Specifications upon examination by Hart to be defective If Hart determines that the defect or malfunction has been caused by misuse alteration abuse or abnormal condi tions or operation or handling Hart will repair the product and bill the pur chaser for the reasonable cost of repair To exercise this warranty the purchaser must forward the product after calling or writing a Hart Scientific Authorized Service Center for authorization see Section 1 4 The Service Center assumes NO risk for in transit damage THE FOREGOING WARRANTY IS PURCHASER S SOLE AND EXCLU SIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTIES EX PRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OR MERCHANTABILITY OR FITNESS FOR ANY PARTIC ULAR PURPOSE OR USE HART SHALL NOT BE LIABLE FOR ANY SPECIAL INDIRECT INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS WHETHER IN CONTRACT TORT OR OTHERWISE 5698 4 1 4 2 4 3 4 Installation Installation Environmental Issues Primary standard equipment should be used in a calibration laboratory or other facility specifically designed for this purpose Environmental requirements include e Stable temperature and humidity e Clean draft free area e Low noise level low radio frequency magnetic or electrical interference e Low vibration levels Mounting Most often temperature standards primary and secondary are used to calibrate other temperature sensitive equipment Three repre
4. and Handling Guidelines 5 DO anneal the SPRT at a temperature slightly higher than the maxi mum temperature at which the thermometer will be used when it has been subjected to mechanical or temperature shock The SPRT should also be annealed before calibration The SPRT should be annealed at 675 6 DO use the protective case provided or other protection when the ther mometer is not in use 7 DON T subject the thermometer to any physical shock or vibration 8 DON T subject the thermometer to temperatures above the highest specified operating temperature 9 DON T expose the thermometer s handle or cables to extreme tempera tures 10 DON T submerge the handle or cable in liquids 5 3 Metal lon Contamination of SPRTs Since the acceptance of ITS 90 information has been accumulating about con tamination of SPRTs ITS 90 extended the range of the SPRT as an interpola tion device and new problems manifested themselves Metal 1 contamination is one of the new problems and can start at approximately 700 C At high temperatures the lattice structure of most metals becomes open This allows energetic metal ions to come off the surface analogous to steam rising from hot water Since the molecular activity increases with temperature so does the amount of ion loss and the risk of contamination Ion transfer occurs at dif ferent temperatures for different metals Copper nickel iron and manganese are metals that hav
5. e Warning identifies conditions and actions that may pose hazards to the user e Caution identifies conditions and actions that may damage the instru ment being used 1 2 1 Warnings To avoid personal injury follow these guidelines General DONOT use this instrument for any application other than calibration work Use of the instrument outside the designed use may subject the user to unknown hazards DONOT use this instrument in environments other than those listed in the user s guide Use of the instrument in inappropriate environments may subject the user to unknown hazards or damage the instrument e Follow all safety guidelines listed in the user s guide e Calibration Equipment should only be used by Trained Personnel Electric Shock DONOT use this instrument to measure the temperature of any hazard ous live component Electric shock may occur 2 Hart Scientific 5698 1 2 2 1 3 1 Before You Start Burn Hazard Use of this instrument at high temperatures for extended periods of time can cause the handle to become hot A Cautions DO NOT remove the label from the handle The delicate nature of the in strument is described on the label Read Section 5 entitled Care and Handling Guidelines before remov ing the SPRT from the shipping box or case Incorrect handling can dam age the SPRT and void the warranty If the SPRT has been calibrated follow the procedure out
6. kept extremely clean and free of contamination devitrification occurs only at high temperatures The process oc curs more rapidly and at lower temperatures when the glass is contaminated by alkaline metals Na K Mg and Ca The alkalis found in normal tap water can trigger the process Note There is conflicting opinion among the experts as to whether the process can be stopped Some say that once the process starts it does not stop Others indicate that once the alkali is removed the process of devitrification stops Removal of the devitrification is not practical as it requires drastic measures and is potentially dangerous to the instrument and or the user Devitrification starts with a dulling or opacity of the fused silica sheath It de velops into a rough and crumbling surface Devitrification ultimately weakens the fused silica until it breaks or is otherwise no longer useful The best cure for contamination and devitrification is prevention Being aware of the causes and signs of contamination can help the user take the steps neces sary to control contamination of the SPRT Keep your SPRT clean and avoid contact with metals at temperatures above 700 C 5698 6 1 6 2 6 3 6 Operation Operation General For best results be familiar with the operation of the calibration bath or furnace and the readout instrument Be sure to follow the manufacturer s instructions for the readout instrument and the calibration bath
7. m HART SCIENTIFIC A Fluke Company 5698 Working Standard Platinum Resistance Thermometer User s Guide Rev 272301 Copyright 2002 All rights reserved Hart Scientific Inc 799 E Utah Valley Drive American Fork Utah 84003 9775 Telephone 801 763 1600 Fax 801 763 1010 Internet http www hartscientific com E Mail support hartscientific com Table of Contents Before You SII dec d ARES ORDA 1 1 1 SymbosUsed 2 RR RR 1 1 2 5 2 TL 2 E22 carp 3 1 3 Verifying 3 14 Hart Scientific Authorized Service 4 Introduction gt oo Oa RO a ew VOR RC E 7 2i Genil 5 gt gt gt 52 7 22 ApplicGhOns 25252252 Ba 7 23 Calibration ans 8 231 aeneae ace RE ee 8 24 8 25 Return Procedure 8 Specifications kh SRR KS 9 3 1 Specifications 9 222 GCONSHTUCHON osos 3 6 85 ne SHAD ede eis sse bod oo p ae 9 3 3 Electrical Circuit ccce GOS RS
8. or furnace Comparison Calibration of Other Instruments The uniformity and stability of the bath and the degree of accuracy required de termine the number of temperature measurements necessary However to fol low good practice procedures always measure the triple point of water Rtp after each temperature measurement This provides the most accurate measure ment of the ratio R R Measuring Current The 5698 SPRT has a specified drive current The recommended current is listed in the specifications and below Suggested Drive Current Model Resistance Drive Current 5698 250 Errors caused by self heating of the element need to be minimized Allowing sufficient time for the SPRT to stabilize and the heat to be dispersed into the surrounding medium will provide the most accurate results The Report of Calibration provided with the SPRT represent data that has been extrapolated For example on 5698 measurements are made at 1 mA and 1 4 mA These measurements are then extrapolated to zero current This can be done graphically by plotting 2 vs and extrapolating to zero power or by us ing the following equation R R i R R 2 2 i i where Zero current resistance R Resistance measured at current i 6 Operation 6 4 6 5 6 6 R Resistance measured at current i Immersion Requirements Stem effect can cause measurement errors for SPRTs not immersed in the fluid
9. with Long Stem SPRTs Figure Liquid Bath Installation a Hart Scientific 5698 Precooling Access Hole N Figure 4 Water Triple Point Cell in Ice Bath Dewar 4 Installation Lid Thermometer Guide Tube Water Vapor Dewar Flask i Borosilicate Glass Reentrant Thermometer Well Water from Ice Bath or Alcohol Water Solid Ice Water Liquid Metal Bushing Soft Pad Ice Bath or Maintenance Bath Cushion Outer Canister 4 Installation SPRT Equilibration Top Zone Heater SPRT Thermal Guard Assembly Main Controller PRT Sensor SET DOWN UP EXIT Zone Controller SET DOWN UP EXT Differential TCs Differential TCs Bottom Zone Controller V lt TOP END ZONE Main Heater Freeze Point WWW AAA YAY Bottom Zone Heater Figure 5 Hart 9114 Metrology Furnace with SPRT in Fixed Point Cell Cell lt PRIMARY ZONE Cell Support Container Thermal Block 3 zone subdivision lt BOTTOM END ZONE Water Cooling Coils Supercooling Gas Supply Argon Hart Scientific 5698 4 Installation measurement the readout device should
10. A A ta tn soos 10 34 Warranty i Rat e DEN ER ER ESOS E REN S 10 Installation uu dace cic c t ERR ace MCCC Rp n SR e 13 4 Environmental 13 42 Mounting 13 43 Lead Wire 13 Care and Handling 19 SPRING ore uct oc eng pee bane ne cea LE 19 52 SPRT Handling 19 5 3 Metal lon Contamination of SPRTs llle 20 54 Devitrification of Fused Silica 01065 2 Operation a seos aea 23 23 62 Comparison Calibration of Other 23 63 Measuring 23 64 Immersion 24 65 Thermal 24 6 6 Cooling Rates at High 24 555959555555 EA OPE XR AEG AR KE 27 Pl WSC T PD Pc 2 12 SPRI Termination hor dane ee 27 8 Troubleshooting 4 999 RR EO 29 81 Troubleshooting 29 Figures Figure Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 5698 Working Standard Platinum Resistance 7 Standard Dimensions 10 Liquid Bath
11. Centers to coordinate service on your Hart product Hart Scientific Inc 799 E Utah Valley Drive American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 E mail support hartscientific com Fluke Nederland B V Customer Support Services Science Park Eindhoven 5108 5692 EC Son Hart Scientific 1 Before You Start NETHERLANDS Phone 31 402 675300 Telefax 31 402 675321 E mail ServiceDesk fluke nl Fluke Int l Corporation Service Center Instrimpex Room 2301 Sciteck Tower 22 Jianguomenwai Dajie Chao Yang District Beijing 100004 PRC CHINA Phone 86 10 6 5 12 3436 Telefax 86 10 6 512 3437 E mail xingye han fluke com cn Fluke South East Asia Pte Ltd Fluke ASEAN Regional Office Service Center 83 Clemenceau Avenue 15 15 06 Ue Square 239920 SINGAPORE Phone 65 737 2922 Telefax 65 737 5155 E mail antng singa fluke com When contacting these Service Centers for support please have the following information available e Model Number e Serial Number e Complete description of the problem 5698 5 5698 2 1 2 2 2 Introduction Introduction General The Hart Standard Platinum Resistance Thermometer SPRT is designed to be the best primary standard interpolating instrument converting resistance to temperature With full calibration options ITS 90 coefficients can be used with your 1590 1560 or 1529 Hart thermometer readout With drift rate typically
12. Installation 14 Water Triple Point Cell an Ice Bath 15 Hart 9114 Metrology Furnace with SPRT in Fixed Point 16 SPRT Circuit 9 17 Tables Table 1 International Electrical Symbols 5698 1 Before You Start Before You Start Symbols Used Table 1 lists the International Electrical Symbols Some or all of these symbols may be used on the instrument or in this manual Table 1 International Electrical Symbols Symbol Description AC Alternating Current AS Battery O gt gt i eH Double Insulated Electric Shock Fuse PE Ground Hot Surface Burn Hazard Read the User s Manual Important Information Off On 1 Before You Start Symbol Description e Canadian Standards Association OVERVOLTAGE Installation CATEGORY II Pollution Degree 2 per IEC1010 1 refers CATA the level of Impulse Withstand Voltage protection provided Equipment of OVERVOLTAGE CATEGORY II is energy consuming equipment to be supplied from the fixed installation Examples include household office and laboratory appliances 1 2 Safety Information Use this instrument only as specified in this manual Otherwise the protection provided by the instrument may be impaired The following definitions apply to the terms Warning and Caution
13. RT is provided with a terminal box handle The eight foot cable has four Teflon coated wires enclosed in a silicon rubber jacket with a stainless steel spring strain relief Gold plated spade lugs terminate the wires 3 4 Warranty Hart Scientific Inc Hart warrants this product to be free from defects in ma terial and workmanship under normal use and service for a period as stated in our current product catalog from the date of shipment If your SPRT was cali brated by Hart Hart also warrants the validity of the data on the certificate of calibration accompanying your probe However because probes are subject to change from mishandling vibration and other forms of mechanical shock Hart does not warrant the behavior of your probe once it has left Hart s control See Section 1 3 Verifying Probe Accuracy for procedures for initially checking your probe upon receipt at your facility This warranty extends only to the orig inal purchaser and shall not apply to any product which in Hart s sole opinion has been subject to misuse alteration abuse or abnormal conditions of opera tion or handling Software is warranted to operate in accordance with its programmed instruc tions on appropriate Hart products It is not warranted to be error free Hart s obligation under this warranty is limited to repair or replacement of a product which is returned to Hart within the warranty period and is determined 10 Hart Scientific 5698 3
14. around 3 mK this SPRT gets you from 200 C up to 661 C The 5698 is hand constructed at Hart by experts with years of SPRT manufac turing experience Each SPRT is carefully annealed at the appropriate tempera tures and precisely tested for stability Convection prevention discs are used to reduce stem errors caused by thermal radiation The sensing element is fabracated using high purity platinum wire wound in a strain free design on a fused silica cross frame A fused silica sheath is pressure sealed with a special argon oxygen mixed gas and fitted with a terminal box handle with a strain re lieved connection to the four wire cable Gold plated spade lugs terminate the wires Application The 5698 SPRT is a working standard A working standard is defined in terms of transfer of the ITS 90 from a standards laboratory to a customer s laboratory Working standards are calibrated in a standards lab using known intrinsic values AN d Figure 1 5698 Working Standard Platinum Resistance Thermometer 2 Introduction 2 3 2 3 1 2 4 2 5 Calibration In order for any instrument to be used as a standard it must be calibrated The SPRT may be purchased calibrated or non calibrated Hart Scientific has the ca pability of performing fixed point calibrations traceable to NIST The 5698 can be economically calibrated using the comparison method or any one of several fixed point calibrations matching ITS 90 subranges Calibrati
15. be equipped to handle four terminal resistors The lead wire colors are red black white and blue Lead wire pairs attached to each end of the sensor are identified by heat shrink tubing Red and black wires have red heat shrink tubing Blue and white wires have black heat shrink tubing see Figure 6 for details The circuit is connected in true four terminal configuration Therefore there is no distinction between voltage sense and current source leads Figure 6 SPRT Circuit Schematic 5698 541 5 2 5 Care and Handling Guidelines Care and Handling Guidelines A Caution Read before removing the SPRT from the case SPRT Care The 5698 Standard Platinum Resistance Thermometer SPRT is an extremely delicate instrument Great care must be taken in handling the SPRT to maintain calibration accuracy Vibration or shock may cause the resistance to increase A slight tap to the SPRT tip as it is removed from an instrument can cause a change in as high as 1 mK At high temperatures SPRT may become contaminated if inserted into metal blocks This contamination can effect the condition of the sensor if the contamination invades the sensor degrading the purity of the platinum wire The fused silica sheath is very fragile and also sus ceptible to contamination Once a SPRT is contaminated it can contaminate other standards equipment Copper contamination shows as red smudged on the sheath Any contamination can ca
16. ccessories Case The SPRTS are shipped in a protective case The SPRT should be stored in this case when not in use The SPRT should be shipped in this case when returning see Section 2 5 Return Procedure SPRT Termination The 5698 SPRTs are terminated with gold plated lugs 8 Troubleshooting 8 Troubleshooting 8 1 Troubleshooting In the event that the SPRT appears to function abnormally this section may help to find and solve the problem Several possible problem conditions are de scribed along with likely causes and solutions If a problem arises read this section carefully and attempt to understand and solve the problem If the SPRT seems faulty or the problem cannot otherwise be solved contact a Hart Scien tific Authorized Service Center for assistance see Section 1 4 Problem Solution Data changes Slight mechanical shock can cause temperature errors as much as 2mkK If this is observed first measure and record the R Next anneal the SPRT at 675 C overnight 12 hours Measure the R again The annealing should decrease the Repeat the annealing R measurement cycle sev eral times If the Ry returns the proper value the SPRT may be returned to service If the SPRT does not returen to the proper value but is stable return for recalibration When the is stable recalibrate the SPRT If the does not stabilize contact a Hart Scientific Authorized Service Center for assistance se
17. e Section 1 4 Severe mechanical shock can permanently damage the SPRT If an nealing the SPRT does not resolve the data change contact a Hart Scientific Authorized Service Center for assistance see Section 1 4 Oxidation of the platinum sensor may occur after prolonged use be tween 200 and 450 C R will show an increase To reduce the effects of oxidation anneal the SPRT at the appropriate temperature as described above Measure the again Repeat the annealing R measurement cycle several times This annealing process should return within calibration tolerances If R is within calibration tolerance the SPRT is usable If the R is not within calibration tolerance but it is stable recalibrate the SPRT Data unstable Connection may not be made If the data is unstable at the Triple Point of Water TPW check the connection first If this action does not fix the problem contact Hart Scientific Authorized Service Center for assistance see Section 1 4 The SPRT may be damaged and need repair Electrical noise in the system If the data is unstable at high tempera tures it may be due to electrical noise in the system Reduce the temperature and observe the data If it is stable electrical noise is interfering with the measurements at high temperatures Check the grounding of the readout de vice and the heat source A faulty ground on either device could interfere with high temperature measuremen
18. e been attributed to causing contamination In addition the fused silica lattice structure also becomes open at these high temperatures This allows the fused silica to become transparent to these metal ions permitting the transfer of these ions from adjacent metal surfaces to the pure platinum wire of the SPRT sensor The contaminated platinum behaves unpredictably resulting in a loss of stability and calibration Contamination can be spread by an infected SPRT to other primary standards analogous to a virus Therefore it is very important to avoid contamination as much as possible to ensure the longevity of the SPRT itself and to decrease the spread to other standards Isolation of sensitive materials can prevent contamination Pure platinum foil 18 being used by some experts to intercept the ions before they reach the SPRT Silicon carbide is also used by some experts to shield the SPRT because it 1s less expensive than platinum foil Information on contamination effects and prevention is still being gathered by experts in the field 20 Hart Scientific 5698 5 4 5 Care and Handling Guidelines Devitrification of Fused Silica Glass Devitrification is a natural process with quartz materials The fused silica is uti lized in a glass non crystalline state The most stable state for fused silica is crystalline Therefore devitrification is the tendency of the fused silica to return to its most stable state If the fused silica is
19. lined in Section 1 3 Verifying SPRT Accuracy or your quality procedure for verifying the accuracy of your SPRT before placing the instrument in service DO NOT subject the SPRT to mechanical shock Use of the SPRT at temperature greater than 500 C requires a specified minimum cooling rate in order to prevent damage to the SPRT Refer to Section 6 6 Cooling Rates at High Temperatures Keep the shipping container in case it is necessary to ship the SPRT In correct packaging of the SPRT for shipment can cause irreparable damage Verifying SPRT Accuracy A This section is applicable only if the SPRT has been calibrated Before using your SPRT verify that its behavior has not changed significantly from the most recent calibration as can sometimes occur from mechanical shock during shipping for example To verify your SPRT check the SPRT at the triple point of water 0 01 C or in a well constructed ice bath by following these steps 1 25 Connect the SPRT to a calibrated readout Properly prepare a triple point of water cell TPW or bath Ensure that the SPRT is pre chilled prior to measurement Contact a Hart Sci entific Authorized Customer Service Center if unsure how to do this A triple of water cell is preferred Ice baths should use distilled water and crushed ice made with distilled water in a Dewar flask or thermos 1 Before You Start 1 4 bottle The ratio of ice to water should be such that the mix
20. on Options In order for the SPRTs to make accurate temperature measurements they must be calibrated Calibration can be attained through any recognized primary stan dard laboratory performing temperature calibrations Hart Scientific can pro vide either comparison calibration or fixed point calibrations Recalibration The recalibration of the SPRTs should be scheduled according to the user s company Quality Assurance requirements Generally an SPRT is used over a specific range The SPRT should be calibrated over the range applicable to its use The SPRT should only be calibrated over its full temperature range if it is used over its full range For information on recalibrating your SPRT contact a Hart Scientific Authorized Customer Service Center see Section 1 4 Return Procedure Note Call a Hart Scientific Authorized Customer Service Center for a return authorization We recommend that a good TPW measurement be made before returning the SPRT to ensure stability Extreme care must be taken when shipping an SPRT Place the SPRT in the fac tory provided protective storage case Be sure the case is latched securely Place the protective case in the original manufacturer s wooden shipping crate or wooden crate with similar dimensions 44 4 in x 11 3 4 in x 11 3 4 in Place soft insulation on all sides of the crate to cushion the SPRT against mechanical shocks The cover of the crate should be attached with screws We recommend
21. sentative applications are shown in the following figures e Figure 3 Liquid Bath Installation e Figure 4 Water Triple Point Cell in an Ice Bath Dewar e Figure 5 Hart 9114 Metrology Furnace with SPRT in Fixed Point Cell The SPRT must be mounted carefully to avoid any damage to the sheath or sen sor If the fluid bath used does not have a lid designed for SPRT insertion clamps should be used to ensure the handle and cable are not immersed If metal comparison blocks are used in the bath maintain a close fit between the SPRT sheath and the well in the comparison block However allow for the ther mal expansion and contraction of the SPRT sheath and block when determining block well tolerances For applications where the fluid in the bath is not compatible with the SPRT e g salt the SPRT can be slid into a thin walled metal sheath for protection Ensure that the sheath is clean inside The gap between the protective sheath and the SPRT should not be any larger than 0 003 in 0 08 mm At high temperatures the SPRT is subject to metal ion contamination metal equilibration block is used in a furnace above 700 C protective shielding such as thin wall platinum tubing or high purity ceramic is advised Lead Wire Identification The SPRT is equipped with a four wire cable see Figure 6 Four lead wires are used to prevent measurement errors due to lead wire resistance For proper 13 4 Installation 24 7007 Tank
22. tion to extension lead wires and readout instruments can be a source of thermal EMF The thermal EMF is caused by a difference in tempera ture between two connections If the two connections are the same temperature there will be little or no thermal EMF effects However if there is a substantial temperature difference between connections the thermal EMF effects will be significant Therefore cover or insulate any exposed bridge or galvanometer terminals to lessen the source of error The effects of thermal EMF can be reduced by using an AC bridge or a DC bridge with reversible current Cooling Rates at High Temperatures The equilibrium concentration of point defects in the pure platinum wire in crease exponentially to the increase in temperature If a high cooling rate 1 removing a SPRT from a high temperature and cooling it to room temperature in less than a minute occurs above 500 C some of the point defects in the plat inum wire become trapped in the crystalline structure causing a slight increase Hart Scientific 6 Operation in resistance This slight increase in resistance can be reversed by annealing the SPRT To avoid this problem slowly cool the SPRT at a rate of roughly 150 C hour above 500 C before removing to room temperature The SPRT can be safely removed from an instrument at 500 C or less and cooled to room temperature without concern for the cooling rate 5698 25 5698 7 1 7 2 7 Accessories A
23. ts 5698 25 29 8 Troubleshooting Problem Solution Temperature readout different than expected e g the heat source is set at 300 C the SPRT measures 275 C Measure the SPRT resistance at TPW If the resistance of the SPRT is less than the rated resistance there may be a short in the sensor If the resistance of the SPRT is only a few ohms there may be a short in the four lead wires If the SPRT is open the resistance will be Out of Limits or in the kilo ohm or mega ohm range Contact a Hart Scientific Authorized Service Center for as sistance see Section 1 4 Hart Scientific
24. ture is firm after preparation 3 Set your readout to read in ohms rather than temperature Place your pre chilled SPRT in the TPW or ice bath and allow it to stabilize Re member TPW is at 0 01 C and an ice bath is at 0 C 4 If using a TPW cell compare the resistance value on your readout with the resistance value at TPW given on the probe s certificate If using an ice bath compare the resistance value on your readout with the resis tance indicated on the certificate for 0 You may have to use the SPRT s temperature versus resistance table to get the SPRT s calibrated resistance value at 0 5 Considering SPRT s uncertainty specification and the uncertainty of the thermometer readout determine whether or not it is within toler ance as specified in your quality requirements of the data on its most recent Report of Calibration If it is it may be placed in service Hart recommends that an SPRT be periodically checked against a standard such as a triple point of water cell or well constructed bath if an ITS 90 fixed point standard 1 not available The verification interval depends on how the SPRT is handled how much it is used and your documented experience with it Your probe should also be checked any time you suspect it may have re ceived mechanical shock or whenever its accuracy appears suspect Hart Scientific Authorized Service Centers Please contact one of the following authorized Service
25. use devitrification of the sheath at high temperatures The fused silica sheath should not be handled with bare hands Cotton gloves or other suitable methods should be used in handling the SPRT The sheath should always be cleaned with 200 proof Ethyl Alcohol or other suitable solvent before exposure to high temperatures Correct handling of the SPRT will prolong the life expectancy When not in use the SPRT should be stored in its protective case SPRT Handling Guidelines 1 DO keep the SPRT as clean as possible Always remove any fluid from the sheath as soon as possible after taking the SPRT from a bath En sure that the fluid and SPRT have cooled sufficiently to prevent a safety hazard To remove any possible contaminants always wipe the sheath with ethyl alcohol or other solvent before submitting the SPRT to high temperatures 2 DO immerse the SPRT in the appropriate liquid for the temperature range If a dry block is used the well diameter should allow the SPRT to comfortably slip in and out without excess movement For best re sults immerse the SPRT as deep as possible to avoid stem effect the temperature error caused by the conduction of heat away from the sen sor Do not submerge the handles 3 allow sufficient time for the SPRT to stabilize before making mea surements This allows for the best accuracy 4 DO use the correct drive current with the SPRT to prevent error in tem perature or resistance 5 Care
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