The three primary differences between the ASME B40.100 and the EN-837-1 are their preferred units of measure, accuracy and dial sizes.
1. Preferred units of measure.
ASME B40.1 preferred units of pressure are psi, size in inches and process connections with NPT threads.
EN837-1 preferred units of pressure are bar, size in millimeters and process connections with metric threads.
2. Accuracy.
ASME B40.100 uses accuracy grades from 4A to D.
For Grades 1A through 4A, the accuracy is defined as a ± % of span over the entire span of the gauge.
For Grades A through D, the accuracy is defined as ± % of span in 3 different sections of the span: the lower 1/4 scale, the middle 1/2 of the scale and the upper 1/4 of the scale.
EN837-1 accuracy classes are defined as a ± % of span over the entire span of the gauge.
3. Gauge size.
Gauge size will determine your operator's ability to read the gauge at a specified distance. The larger the dial size the easier it is to read.
AMSE B40.100 defines gauge size by the diameter of the dial size in inches.
EN837-1 defines gauge size by the diameter of the case.
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