WORLD METEOROLOGICAL ORGANIZATION INSTRUMENTS AND OBSERVING METHODS REPORT No. 45 I WMOTDNo310 I 1989 W0 R L D MET E 0 R 0 LOG I CAL 0 R G A NIZ A T ION INSTRUMENTS AND OBSERVING METHODS REPORT No. 45 ANALYSIS OF INSTRUMENT CALIBRATION METHODS USED BY MEMBERS by H. DOERING 1989 @ 1989, World Meteorological Organization NOTE The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat o[ thc World Meteorological Organization concerning the legal stalus o[ any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. EdilorilJl not~: This report has [or lhc grcater part been produced without cditorial rc',ision by the WMO Sccrelarial. It is not an official publication and its distribution in this form does not imply endorsement by the Organization of the ideas expressed. INTRODUCTION The ninth session of CIMO in 1985 decided to survey and analyze calibration techniques and methods used in different countries. The analysis should serve as a first step for promoting the standardization of calibration methods of Members. CIMO-IX allocated this task to the Working Group on Surface Measurements. A Questionnaire on the Calibration of Meteorological Surface Instruments was prepared in 1987 for the variables: temperature, humidity, pressure, wind speed and direction. The Questionnaire was distributed by WMO and replies were received from 76 Members of which 52 calibrate their meteorological instruments, 24 do no calibration, 17 intend to establish calibration facilities and 12 wish to send instruments for calibration to a suitable center in their region. The preliminary analysis showed that there are significant differences in the ranges of calibration, the number of calibration points used and the calibration accurancy. Other differences in calibration methodology amongst Members are for example: For field tests with a reference instrument. a large number of measurements are carried out under ambient conditions over a period of 2 to 4 days. The reference instrument used was usually a relatively new example of the same type calibrated by its supplier, but often with unknown accuracy. For field test with a travelling standard the same procedure is used in conjunction with a calibrated travelling instrument. Members which have laboratory calibration facilities at their disposal often use such field tests as an additional calibration method. Field instruments are checked at a few points only. For calibrations performed in the laboratory the atmospheric conditions are usually simulated over a range which does not necessarily fully cover the total measuring range of the instrument under test. In order to improve instrument performance worldwide, it is recommended that those Members which do not have calibration facilities should introduce travelling standards. Suitable travelling standards for comparison checks are: .precision thermometer for thermometers and thermographs; .precision psychrometer (e.g. Assmann type) for hygrometers; .precision barometer for barometers and barographs; -hand-held anemometer for anemometers and ~compass for wind vanes. All these instruments should be stored in. rugged cases suitable for transportation by air and under poor road conditions. The establishment of instrument centers as proposed in Rec. 19 (elMO-IX) especially in those areas where many Members at present either do not or are unable to calibrate their instruments would make a significant improvement of meteorological instruments. The Working Group expresses the gratitude to its mernber r Mr. H. Doering, Federal Republic of Germany, for the valuable work he has done in compiling the analysis and preparing this publication. TYPE OF IHSIRUiERI: !L.ECIRlCAL IHERIIOIEIERS caUlmy IAIfUFACIURER/1I0DEL. PRINCIPLE OF IEJ,SUREIEII LIllIS OF CALIBRAnOK RAISE OF KUIBER OF TYPE OF 'ORKIR6 SIUDARD OPERAnOI RAII6E ERROR IIIIERYAL CALIBRATION CAL.POHITS Australia Rosemount Platinum -20 ..+55'C .t 0.3 K Field checks annually -10 ... +50·C 7 l.eed & Northrup, Platinum, 1974 Austria NTC, Pt 100 -30 ...+40'C .t·0.1 I 1 year -30 .. , +40'C 15 Bossecker, Hg", Ti-thermometer, 1942 France Pt 100 Kot regularly -20 ... +50·C • Platinum 25, Datron Dill! German Demoer. VEB Thermometerwerk Geraberg Pt 100 -30 ...+40'C .t 0.2 K liot regularly -15 ...+40'( 3 Precision Hg-Thermometer and/or Renublie pt 100 Germany, Degussa, Heraeus Pt 100, DIIi 43760 -30 ...+50'C several years -30 ...+35"C typ 3 Thermo-Schneider Fed.Rep. of Pt 100, DIN 43760 -40 .. +4O'C typ .t 0.1 K Knt regularly cal ibr. -30 ...,t30·C typ 3 Heraeus Platinum Thermometer PH:Z 100-1, 1987 Japan llakaasa Instruments Platinum -40 ...+40'C .t 0.5 K 5 years O..+30·C 2 Glass thermometer, Yoshino Keiko (0 Ind. F-732 and others lIod.S-501 Netherlands Degussa, for soi 1 Temperature Pt 500 -30 ...+40'( ..!. 0.1 K 2 years o..+30·C Sensing Devices Ltd., lIod. , for Psychrometer Pt SOD -30 ...+40·C .t 0.1 K 2 years -20 ..+40'C 13• pt 100 S 351-100, 1987 ... New Zealand Yellow Springs Instrument Co. Thermistor -30 .. +lOO·C .t 0.15 K 2 years in lab . -5 ..+40'C 3 Sensor: Platinum, Leeds & Korthrup Mod.i'01 and 703X 1 year in field Readout 1nstr.: Datron Mod. 10£lA, 19B7 Phi lips Pt 100 -£0 ... +40'C DIN 43760,K1.B 2 years in lab. 0, .+40'( I year in field Republic of Ishikawa, lIod. lEH-8£p Platinum -50 ...+50'C :. 1.0 K 5 years -50 ..+50'( 21 Korea Snain Thies Pt 100 -30 ... +50·C :. 0.3 K a years -15 ..+35"C 3 fluke 2180. Pt 100, 1987 Schneider Hg. 1987 Sweden Heraeus Pt 100 -50 ...+50'C .t 0.2 K 1-2 years -50 ..+50'( 8 Heraeus Pt 10-0, 1974-198£ Hewlett-Packard DVI Switzerland Meteolabor AG Yearly field tests -80 ... +50'C step of 1 K Thermometry System, 1985 Vent i lated Thermometer YlIT-l Linear. thermistor -30 ...+50'C ,t 0.25 K Initial calibration Rosemount lIod. IS 104 HL Ventilated Thermohygrometer Linear. thermocouple -50 ...+50'C .t 0.2 I pt sensor United Kinll"dom Rosemount, lIod. l14a .!. 0.15 K initial calibration -10 ..+30·C 3 H. Tinsley & co Ltd .. lIod. 5187SA pt thermometer with ACbridl!e ASL lIod H7. 1980 TYPE OF IKSTROIEIlT: ELECTRICAL THERIOIETERS COmHY IA.KlIfACTURERIIODEL ACCURA(Y OF COISTANCY Of (lUBRATIOI CALIBRATIOI COIPARISON lITH CERTIfICATES DESCRIPTIOIf OF THE CALIBRATIOII PROCESS 'DRIllS STAIDARD COIIDIIIOIiS ACCURACY NATIONAL SIAIDARD OF CALIBRAIIOif Australia Rose.Gunt .±. 0.05 K .±. 0.01 K .±. 0.05 K Every 5 years No stirred tell(lerature bath Austria .±. 0.1 K -30 ...+5'(: t 0.1 K !. 0.1 K Not regularly Y" Oil-bath or antifreezing agenth-bath +10 ...+WC::±: 0.05 K France !. 0.05 K 1 !. ll.l K IHII: 6 months No Calibration in a bath Resistors: 2 years German DellOcr. VEB ThenOlleterwerk 6eraberg .t lLOI K .±. 0.01 K .±.U5 ..!.O.1 K Every 2 years '0 Calibration in an Precision cryostat- Republic temperature bath Germany, Degussa, Heraeus .t 0.05 K .±. 0.02 K !. 0.2 K Every 10 years No Calibration in a bath Fed.Rep.of above O'C: t 0.01 K !. 0.03 K above 0·C:.:!:.0.05 K Every 5 years y" Calibration in a fluor inert bath belo.. 1I"e: :t 0.2 • below O'e:.:!:.0.25 K Computer aided measuring and calculation Japan Nakaasa Instruments .±. 0.2 K .:!:. 0.2 R Every 2 years y" Netherlands Degussa, for soil Temperature .±. 0.003 K I Degussa, for Psychrometer .±. 0.1102 K .±. 0.005 K Every 2 years y" Ethanol bath '"I Hew Zealand Yellow Springs lnstrullent Co. .±. 0.04 K Sensor: Every 5 years Y" Oil filled calibration bath lod. 7111 and 703X .:!:. 0.09 K .±. 0.06 K Instrulll:Every 2 years (Friedr. lod. B221.1) Philips 5 sets of readings Republic of Ishikawa, lod. IEH-B6j) .:!:. 0.01 K Every year Y" Alcoholic bath Korea Spain Thies .to.OlB K.:!:.0.15 [p.a below O'C: .:!:. 11.01 K .:!:. 0.015 K .±.O .01 K above O·C: .±. 0.003 K .±. 1!.015 K Every 3 month '0 Calibration in a bath Sweden Heraeus .:!:. 0.02 K .±. 0.02 K .!. 0.04 K Y" No Calibration in a bath, Computer aided calculation and comparison S,iherland leteolabor A6 .:!:. 0.01 K .±. I!. 002 K .±. 0.05 .K Every 3-4 years No Rosemount lIod. 'JIOAC Ventilated Therm.ometer VHT-l Variable Temp. oil Bath Venti lated Therlllohygrometer Uni ted Kingdom Rosem.ount, Mod. M4a ,±,O.OOH! .!. 0.002 K .to.0035K Every 2 years Y" Measuring the resistance at stabilised tem.peratures TYPE OF IMSTRUIEKT: TRERIOIEIERS COUNTRY ItANUFACTURER/J(ODEL PRINCIPLE OF MEASURElENT I.IMITS OF CALIBRATION RANGE OF NUMBER OF TYPE OF fORKING STANDARD liPERATION RANGE ERROR INTERVAL CALIBRATIOlf CAL. POINTS Argentina Mercury, alcohol, ~7U ...+55'( 3 years -7U ... +55·C Every 5 K Fuess mercury thermometer, toluol, Mere-thallium -25 ...+55'(, 1955 lfegretti & Zambra toluol thermometer, -BU ...+I0U·C, 1950 Austria Hemetsberger ~inimum Ih Toluol -40 ...+30'( .:!:. 0.3 K Not regularly caL br . -35 ...+30'( 14 Bassecker, Hg- Ii-Thermometer, 1942 Hemetsberger Maximum Ih Mercury -15 ..+45'( .:!:. 0.2 K Not regularly cal br . -15 ... +45·C 12 lIellletsberger Ordinary th lertilry -35 ..+50'( .:!:. 0.1 K Not regularly cal br. -30 .. +40'C IS Bangladesh Mod. 85T692 Ordinary th Mercury 0...+50'C .:!:. 0.1 K 1 year 0... +50·C 6 Ilercury therllometer, Zeal (Engl.) lod. BS-TaZ Botswana Casella Ordinary th -10 ..+65"C 1 year -10 ... +65·C Every 5 K laximum th -10 ..+65'C -10 ..