Commercial metering systems are ubiquitous in the commercial marketplace (to dispense liquified products, from gas and water to food products and agricultural chemicals). Customers and businesses alike rely on these meters to monitor and deliver their products consistently over time and across a range of locations.
Weights and measures officials use several well-acknowledged field test standards to measure and verify the quantity fuel dispensed and indicated by commercial metering systems. This includes retail motor-fuel dispensers, loading rack meters, and liquefied petroleum gas metering systems. However, many of the traditional field test standards pose both reliability and practical challenges. Thus, NIST Office of Weights and Measures (OWM) has been working with the State weights and measure programs to explore the use of “master meters” or Coriolis mass flow meters as the next generation of field test standards.
For meters dispensing Liquefied Propane Gas (LPG) and other liquid fuels, calibrated volumetric, neck-type provers are most often used as test standards. Compressed Natural Gas (CNG) dispensers and some larger metering systems are typically tested gravimetrically, using a scale and a receiving tank to weigh the dispensed product. What these test standards have in common is that they are much more accurate than the commercial metering system itself. NIST Handbook 44, Appendix A, 3.2 states that when a test standard is used without correction, it shall be three times more accurate than the tolerance applied to the commercial weighing or measuring device.
While volumetric neck-type standards provide a viable way to test a wide range of types and sizes of metering systems, this method can pose challenges for use in certain metering applications. For example, neck-type provers are not suitable for ..
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