Quality assurance for sensors at the Deutscher Wetterdienst (DWD) Quality assurance / maintenance / calibration Holger Dörschel, Dr Tilman Holfelder WMO International Conference on Automatic Weather Stations (ICAWS-2017) Offenbach am Main, Germany - 24-26 October 2017
Content 1. Introduction 2. Maintenance concept 3. First definition and further development of calibration intervals 4. Development of the quality system at the calibration laboratory 2
Regional presence throughout Germany for the collection of all kinds of weather- and climate-related data 182 main weather stations (staffed and automatic) 48 stations for measuring radioactivity around 1,784 voluntary measuring stations around 1,184 phenological observation sites 17 weather radar sites 2 meteorological observatories 2 main shipboard weather stations (staffed) 9 upper-air stations (with around 7,000 radiosonde launches every year) 3
Surface observing network ~470 stations with temperature and humidity measurement ~180 stations with pressure measurement Example of a primary observing station ~1900 stations with precipitation measurement ~280 stations with wind measurement Example of a secondary observing station 4
Measuring equipment at synoptic weather stations wind solar radiation Snow height visibility laser precipitation monitor (LNM) precipitation monitor precipitation (amount and intensity) temperature and humidity pressure cloud height 5
Actual types of automatic weather stations at DWD beginning in the nineties of last century nearly all primary and secondary observing stations were harmonized and equipped with AWS and sensors 6
Fully automated network the data for many meteorological parameters are collected automatically, even if an met. observer has been present at the station within the next years, by 2021, the DWD measuring network will be fully automated as all stations are already equipped with AWS only minor changes have to be done for automation 7
Our requirements and needs quality assurance of the measurements of meteorological data to achieve the requested high availability high quality of the meteorological data we want to obtain the specific technical know-how for the meteorological measurement systems (installation, data acquisition, operation) procurement of future AWS and sensors we want to ensure a short response time in case of technical failures especially for the weather radar network and AWOS at international airports 8
Facilities to fulfil these requirements DWD has its own technical staff for the maintenance of the meteorological observing systems DWD has the necessary specific facilities to support the technical staff like stock at each division of the department electronical and mechanical workshops calibration laboratories 9
Content 1. Introduction 2. Maintenance concept 3. First definition and further development of calibration intervals 4. Development of the quality system at the calibration laboratory 10
Maintenance concept one part of this quality assurance is an adequate maintenance concept including regular field checks local analysis and troubleshooting sensors, interfaces, data processor, wiring, power supply repair on site or at the workshops additional check via remote access regular exchange of the sensors for calibration calibration of the sensors in the (accredited) laboratory 11
Maintenance concept the preventive maintenances are planned additional information will trigger a corrective maintenance operation check via remote access post-processing of the meteorological data with the interactive data control and monitoring system QualiMET information from met. observer, forecaster 12
Maintenance concept four service and logistic divisions Hamburg Offenbach Potsdam Munich three minor service offices Essen Leipzig Stuttgart 13
Maintenance concept each division and service office is responsible for regular preventive maintenance and troubleshooting of different types of weather stations and several remote sensing systems responsible engineers for every type of weather station and sensor type are nominated they issue the necessary papers for handling, installation and maintenance of the technical equipment the technical staff is using the same procedures for maintenance 14
Maintenance concept the preventive maintenance intervals range varies from several month at primary observing stations to at least once a year 15
Maintenance concept the technical staff is using a computer based database including mainly the observing stations with their specific instrumentation documentation the database is indicating the sensors which have to be exchanged at the next inspection (calculated from date of last calibration) pressure, temperature, humidity, wind, radiation, precipitation 16
Maintenance concept calendar overview for long time planning of maintenance trips 17
Maintenance concept a view to the data set of primary weather station Angermünde (10291) 18
Maintenance concept additional check via remote access 19
Content 1. Introduction 2. Maintenance concept 3. First definition and further development of calibration intervals 4. Development of the quality system at the calibration laboratory 20
Sensor exchange: First definition and further development of calibration intervals to assure a high quality of the measurements, most of the sensors are exchanged regularly with calibrated sensors dismantled sensors are refurbished, calibrated and stocked 21
Sensor exchange: First definition and further development of calibration intervals first definition of calibration intervals started in 2006 to achieve the requirements of the ISO9001 certification regarding to the control of monitoring and measuring devices 1 DWD introduced new relevant documents, with rules for calibration and traceability rules for the achievement of valid calibration a table of the calibration intervals 1 (chapter 7.1.5 of ISO 9001:2015, old chapter 7.6 ISO9001) 22
Sensor exchange: First definition and further development of calibration intervals the decision for the individual calibration interval depends on the type of sensor the experiences (stability, maintenance) manufacturer s instructions guidelines from National Metrological Institute of Germany (PTB) other guidelines for example the German Calibration Service (DKD) the capacity of the calibration laboratories, workshops, technicians 23
Sensor exchange: First definition and further development of calibration intervals for example some calibration intervals Type calibration interval in month value in 2006 actual value (2017) Pt100 air thermometer 60 60 Pt100 soil thermometer 120 not regularly Cup anemometer 24 24 Ultrasonic anemometer 24 36 Pressure gauge 18 24 Humidity transmitter 18 18 Weighing rain gauge 48 48 / 60 minor changes were made to these intervals 24
Sensor exchange: First definition and further development of calibration intervals; example 1 in 2013 the calibration interval for the soil thermometers was investigated an exchange of soil thermometers has an impact on the surrounding soil and in consequence on the homogeneity of the measurement data this effect might be larger than the possible drift of the sensor itself after the originally defined calibration interval of 10 years as high class Pt 100 sensors have in general a very good long time stability 25
Sensor exchange: First definition and further development of calibration intervals; example 1 26
Sensor exchange: First definition and further development of calibration intervals; example 2 in 2014 the calibration interval for pressure gauges was investigated DWDs first calibration interval was set to 18 month with a few exceptions all pressure gauges were within the accepted tolerance of ±0.15 hpa in the relevant pressure range (700-1050 hpa) so DWD decided to increase the interval to 24 month 27
Sensor exchange: First definition and further development of calibration intervals; example 3 28
Sensor exchange: First definition and further development of calibration intervals; example 2 after improving the equipment in the laboratories a review of the calibration interval was carried out in September 2017 all pressure gauges of Vaisala PTB220 type were within the accepted tolerance 29
Sensor exchange: First definition and further development of calibration intervals; example 2 30
Sensor exchange: First definition and further development of calibration intervals; future activities in 2017 DWD started in September 2017 with the replacement of weighing rain gauge with a new sensor type (weighing tipping bucket) based on the manufacturers proposal, the calibration interval has been defined to 48 month this proposal will be investigated in the future, because DWD has only limited experiences with the stability of this rain gauge to prove this interval the calibration laboratories will calibrate a sample from different locations after an operation period of 12, 24, 36 and of course 48 month hopefully the calibration interval of 48 month can be confirmed 31
Content 1. Introduction 2. Maintenance concept 3. First definition and further development of calibration intervals 4. Development of the quality system at the calibration laboratory 32
Development of the quality system at the calibration laboratory to achieve best results of the measurements, the calibration laboratory was subjected the accreditation process according to DIN EN ISO/IEC 17025:2005 with the status as a testing laboratory (2007-2016) in 2015 DWD decided to become accredited as a calibration laboratory according to DIN EN ISO/IEC 17025:2005 accredited calibration laboratory since September 2017 traceable measurements 33
Development of the quality system at the calibration laboratory temperature humidity pressure wind speed wind direction 34
Development of the quality system at the calibration laboratory parallel the accreditation process the standards and facilities at the calibration laboratories are renewed for example Laser Doppler Anemometers Piston Gauges Humidity Generators + Dew Point Mirrors 2018: new calibration bathes and reference thermometers (tender 11/2017) 35
Development of the quality system at the calibration laboratory Instrument Undergoing Calibration Calibration Range Reference wind speed sensors 0,5 50 ms -1 anemometer 2D laser doppler burst spectrum analyzer Calibration and Measurement Capability (CMC) 1,2 % of reference but not smaller than 0,1 ms -1 wind direction sensors 0 360 precision turntable 0,9 Pt100-30 +40 C temperature transmitter -30 +40 C special selected IPRT or SPRT IPRT with electronic thermometer 50 mk 60 mk heated and unheated humidity transmitters and probes 15 95 % of relative humidity chilled mirror dewpoint meter 0,1 + 0.006 x U in % of reference but not smaller than 0,4 % absolute pressure transmitters 100 2500 hpa piston gauge, vacuum gauge 0,0025 hpa + 0,00002 x P + uncertainty of the reference vacuum measurement 36
Thank you very much for listening! WMO International Conference on Automatic Weather Stations (ICAWS-2017) Offenbach am Main, Germany - 24-26 October 2017
Your contact person: Deutscher Wetterdienst Mr Holger Dörschel Head of Calibration Laboratory Division Service and Logistics north Frahmredder 95 22393 Hamburg E-Mail: holger.doerschel@dwd.de Tel.: +49 (0) 69 8062 / 6688 Fax: +49 (0) 69 8062 / 6699 38
Your contact person: Deutscher Wetterdienst Dr Tilman Holfelder Vice-Chair ET Operational Metrology Head of Department Service and Logistics Frankfurter Straße 135 63067 Offenbach E-Mail: tilman.holfelder@dwd.de Tel.: +49 (0) 69 8062 / 2843 Fax: +49 (0) 69 8062 / 11922 39