Reference
Flow Measurement Glossary
A comprehensive reference of technical terms and definitions for flow measurement. Covers electromagnetic, ultrasonic, vortex, and Coriolis flow meter terminology.
Accuracy
The degree of conformity of a measured value to the true value. Flow meter accuracy is typically expressed as a percentage of reading (% of rate) or percentage of full scale (% FS). R&B electromagnetic meters achieve ±0.2% of reading.
Calibration
The process of comparing a flow meter's output against a known reference standard. R&B performs factory calibration using traceable master meters under ISO 9001 quality management.
Conductivity
A measure of a fluid's ability to conduct electricity. Electromagnetic flow meters require a minimum fluid conductivity (typically ≥5 μS/cm) to generate a measurable signal.
Coriolis Flow Meter
A mass flow meter that measures flow by detecting the Coriolis force generated by fluid passing through vibrating tubes. Provides direct mass flow, density, and temperature measurement. R&B Coriolis meters achieve ±0.1% accuracy.
Custody Transfer
The metering point where ownership of a fluid (oil, gas, water) changes hands. Custody transfer meters require the highest accuracy (±0.2% or better) and regulatory certification.
DN (Diameter Nominal)
European standard designation for pipe size in millimeters. DN50 = 50mm nominal diameter. Common flow meter sizes range from DN3 (micro-flow) to DN2000 (large water mains).
Electromagnetic Flow Meter
A flow meter that uses Faraday's Law of electromagnetic induction to measure the velocity of conductive fluids. No moving parts, no pressure drop, handles slurries and corrosive liquids. R&B's core product line.
Empty Pipe Detection
A feature that detects when the flow tube is not full, preventing measurement errors. R&B electromagnetic meters include conductivity-based empty pipe detection.
Flow Range / Turndown Ratio
The ratio of maximum to minimum flow rate a meter can measure within its accuracy specification. A turndown ratio of 100:1 means the meter can measure from 1% to 100% of its maximum flow. Electromagnetic meters typically offer 100:1, vortex meters 20:1.
IP Rating
Ingress Protection rating defined by IEC 60529. IP67 = dust-tight + temporary immersion. IP68 = dust-tight + continuous submersion. R&B offers IP67 and IP68 rated flow meters for harsh environments.
Liner (Flow Tube Liner)
The insulating material lining the inside of an electromagnetic flow meter tube. Common materials: PTFE (chemical resistance), hard rubber (abrasion resistance), PFA (high temperature). Selection depends on fluid chemistry and temperature.
NIST Traceable
Calibration that can be traced back to the National Institute of Standards and Technology (USA) or equivalent national standards body. R&B calibration certificates are traceable to national standards.
Output Signal
The electrical signal a flow meter produces for integration with control systems. Common types: 4-20mA analog, pulse/frequency, RS-485 Modbus, HART protocol. R&B meters support multiple output options.
Reynolds Number
A dimensionless number that predicts flow regime (laminar vs. turbulent). Below 2300 = laminar, above 4000 = turbulent. Vortex flow meters require turbulent flow (Re > 10,000) for stable vortex shedding.
Sanitary Flow Meter
A flow meter designed for food, beverage, and pharmaceutical applications. Features: 3-A / EHEDG compliance, crevice-free design, CIP/SIP compatible, electropolished surface finish. R&B sanitary meters meet FDA requirements.
Turndown Ratio
See Flow Range. The ratio of maximum to minimum measurable flow rate. Higher turndown = wider measurement range. Critical for applications with variable flow rates.
Ultrasonic Flow Meter
A flow meter that uses ultrasonic sound waves to measure flow velocity. Two types: transit-time (clean liquids) and Doppler (particle-laden fluids). Clamp-on versions allow non-invasive installation without cutting pipes.
Vortex Flow Meter
A flow meter that measures flow by detecting the frequency of vortices shed from a bluff body in the flow stream. Works with steam, gas, and liquids. No moving parts, wide temperature range. R&B vortex meters handle up to 350°C.
Wetted Parts
The components of a flow meter that come into direct contact with the measured fluid. Material selection (316L stainless steel, Hastelloy, PTFE, etc.) is critical for chemical compatibility and service life.
Zero Stability
The stability of a flow meter's output at zero flow. Important for Coriolis meters where small zero drift can affect low-flow accuracy. R&B Coriolis meters feature automatic zero calibration.
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