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ASME B40.1 Accuracy for Pressure Indicating Dial Type, Elastic Element Gauges

The following tables define the ASME B40.1 accuracy grades. Accuracy of a pressure gauge may be expressed as percent of span or percent of indicated reading. Percent of span is the most common method. Percent of indicated reading is usually limited to precision test gauges and unless specifically spelled out, it may be assumed that an accuracy of ±½% means ±½% of span.

Permissible Error % of Span (Excluding Friction) Minimum Recommended
Number of Test Points (Note)
Grade Lower 25% Middle 50% Upper 25%
4A <------------±0.1------------> 10
3A <------------±0.25------------> 5
2A <------------±0.5------------> 5
1A <------------±1.0------------> 5
A ±2 ±1 ±2 5
B ±3 ±2 ±3 3
Note: The test points shall be distributed over the dial range and shall include points within 10% of the ends of the dial range.

ASME B40.7 Accuracy for Pressure Indicating Digital Gauges
Grade Permissible Error Recommended
Number of Test Points (Note)
5A ±0.05% of span 15
4A ±0.1% of span 10
3A ±0.25% of span 5
2A ±0.5% of span 5
A ±1.0% of span 5
B ±2.0% of span 3
5AR ±0.05% of reading 15
4AR ±0.1% of reading 10
3AR ±0.25% of reading 5
2AR ±0.5% of reading 5
AR ±1.0% of reading 5
BR ±2.0% of reading 3
Note: The test points shall be distributed over the dial range and shall include points within 10% of the ends of the dial range.

The information above is derived from B40.1 & B40.7 contained in ASME B40.100. Printed copies are available from ASME, Three Park Ave, New York NY 10016. You can visit their website at www.asme.org.

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