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BS EN 837-3:1998
Pressure gauges. Diaphragm and capsule pressure gauges. Dimensions, metrology, requirements and testing (British Standard)
This European Standard specifies requirements for diaphragm and capsule (designated by D and C respectively, see clause 12) indicating pressure gauges, vacuum gauges and combined vacuum and pressure gauges (compound gauges), from 50 to 250 nominal size with ranges up to 25 bar for the measurement of gauge pressure. A reading of zero bar is atmospheric pressure.
British Standards Institution [bsi]