Assessor, Consultant and Trainer for WeACT! (2017-)
Freelance consultant in the field of calibration, metrology and accreditation of measuring laboratories (2017 -)
Trainer at Kelvin Training in the field of weighing instruments (NAWI), mass, pressure, force and volume measurement (2017 -)
Metrology employee VSL Dutch Metrology Institute, Delft, the Netherlands (1990 - 2018)
Quality manager VSL Dutch Metrology Institute, Delft, the Netherlands (2014 - 2018)
Member of the Technical Committee Pressure Measurement (TCDM, 1991 -)
Participant of the Mirror group of NEN with regard to the revision of ISO / IEC 17025: 2005 (2016)
Member of the FENELAB Accreditation Committee (2014-2017).
Member of the European Technical Commission for Quality (TC-Q, EURAMET, 2014-2018).
Technical expert / assessor for and at RvA (NL), BELAC (BE) and some other foreign accreditation bodies for calibration laboratories in accordance with ISO / IEC 17025, 1990 -)
Contact Person for EURAMET TC Mass and Derived Quantities (2000-2008).
Member of the CCM Medium Pressure Working Group (2000-2014)
Member of the CCM High Pressure Working Group (2000-2014)
Observer of the CCM Mass standards Working Group and the CCM Force Working Group (2000-2008)
Co-author of various articles on ring comparisons in the field of pressure and mass measurement (1995 - 2018).

Teaching Assistent physics, Univ Botswana (1982)
Grade I qualified teacher in physics (1985-)
Technical responsible scientist for temperature and humidity standards of NMi/VSL (1986-2004)
Teacher at and writer of courses of NMi/VSL (1989 -2005)
Representing NMi/VSL at the CCT (1996-2003) and rapporteur for CCT-meetings of 2000 and 2001. Chairman  CCT Werkgroep 8 (2002-2004)
Chairman EUROMET TC-Therm (2001-2004)
Owner MartinDeGroot Consultancy (2004-2005 & 2008-)
Project- and quality manager Contell-IKS (2005-2007)
Teacher for Kelvin-Training (2004-)

ISO/IEC 17025 Technical assessor for RvA (1987-),UKAS (1995-),SANAS (2003), PCA (2005), ISRAC (2004-2006), INAB (2010-2011) and BELAC (2004-)
ISO/IEC 17025 lead assessor for RvA (2008-) and INAB (2010-2011)
Many of the afore-mentioned Conformity Assessment Bodies (CAB's) are members of European Accreditation and all are signatories to the ILAC  MRA

Author of some 100 publications on thermometry, humidity and uncertainty

consultant for Wemea (2007-):
- Advise on weighing and measurement in practice;
- Internal and external audits (also for certification);
- adapt your quality manual  to terminology of legal metrology;
- advice when seeking accreditation to ISO/IEC 17025 or certification to legal requirements.
- Sales rights of EMeTAS (registration system of admission).

auditor Verispect (2000-2006)
technical expert/assessor at RvA, INAB and Belac (2006-)
teacher for Wemea and Kelvin-Training (2006-)

With over forty years of experience for Nederlands Meetinstituut (previously Dienst van het IJkwezen) and
Verispect, the legal authority for the Metrologiewet (legal metrology previously IJkwet) Ruud Elving held many different positions between 1966 and 2006. Still not tired of metrology and working Ruud is now owner of  Wemea consultancy(2006-).

Secondary teacher training Mathemathics and Physics (PTHN 1989-1993)
Teacher at C+B advice and expertice, telematics and lighting technique (1993-1997)
Teacher VSO/LOM De Stolberg Eindhoven maths and physics (1997-1999)
VSO Physics teacher and teachertrainer Katsina State Nigeria (1999-2001)
Teacher at Stebo Utrecht maths and physics (2002-2005)
Teacher at Gymnasium Beekvliet St. Michielsgestel maths (2007-2011)
Developer for e-learning courses at Kelvin-trainingen (2013-)

Courses for QAducation Vof are in collaboratorion with  dr. Ir. Jo H.M van der Berg and drs. Ad. G. Snijders