BIPM	Bureau international des poids et mesures
EN	European Norm
CMC	Calibration and Measurement Capability
EU	European Union
MID	Measuring Instruments Directive
MM	Master meter
MPE	Maximum Permissible Error, %
WME	Weighted mean error, %
MTQ	minimum test quantity
MUT	Meter Under Test
NMI	National Metrology Institute
OIML	Organisation Internationale de Métrologie Légale
R	Resolution of the meter
DIA	Diaphragm gas meter
TM	Thermal Mass gas meter
US	Ultrasonic gas meter
H2NG	Natural gas and hydrogen mixture
NG	Natural gas
U	Expanded uncertainty
Q	flow rate, m3h−1
Qmin	minimum flow rate, m3h−1
Qt	transition flow rate, m3h−1
Qmax	maximum flow rate, m3h−1
${\overline{c}}_p$	specific heat, kJ kg−1K−1
$E_{MUT}$	measured error, %
$E_{gas}$	measured error for test in gas, %
$E_{air}$	measured error for test in gas, %
$I_{MUT}$	indication of the meter under verification
$I_{ref}$	conventional true value