How gas metering is transforming

April 23, 2026 By Randy Warner 0 Comments

Gas metering has long been debated and often confused in the propane industry.

Traditionally, diaphragm (positive-displacement) meters have been the standard, known for reliable mechanical measurement. Today, ultrasonic technology has revolutionized gas measurement, providing better accuracy, reducing mechanical wear and improving monitoring.

This column offers a summary of how traditional and modern meters measure gas volume, along with a practical guide to choosing the correctly sized meter for a propane system.

▶ Traditional diaphragm meters

Diaphragm meters measure gas volume using internal compartments that fill and empty as gas flows. Diaphragms flex with pressure changes to draw gas into one chamber and push it out of another. Valves regulate flow, and linkages translate movement to the dial, recording volume in cubic feet or meters.

Because each diaphragm cycle displaces a fixed gas volume, the meter gives consistent, repeatable measurements. But it depends on mechanical parts that wear over time. Regular testing and maintenance are needed to keep accuracy.

Despite their mechanical complexity, diaphragm meters have been reliable for decades and are still common in many installations.

▶ Ultrasonic meters

Ultrasonic metering is a technological advance that uses a stationary measurement method, avoiding moving parts, friction and wear, ensuring reliable accuracy throughout the meter’s lifespan.

In an ultrasonic meter, gas flows through a smooth tube with a known diameter. Two ultrasonic sensors are positioned at angles – one facing upstream and the other downstream. Each sensor sends pulses across the tube to the opposite sensor. By comparing the time it takes each pulse to travel upstream and downstream, the meter calculates flow velocity. Because the distance remains constant, any change in transit time directly indicates a variation in flow rate.

Temperature also influences sound speed, so ultrasonic meters include temperature compensation to ensure the measured volume is adjusted to 60 degrees F. When no gas flows, the upstream and downstream pulse times are equal, indicating zero flow.

In addition to accuracy, ultrasonic meters offer operational benefits. Their electronic measurement data can be sent remotely, providing visibility into meter performance and gas usage without requiring site visits.

▶ Sizing gas meters correctly

Choosing the right meter size is crucial for providing a reliable gas supply, building customer trust and ensuring system safety. Proper sizing requires understanding total demand, diversity factors, site elevation, system line pressure and the specific characteristics of the gas being measured.

1. Calculate total demand: Start by listing the Btus-per-hour ratings of all gas appliances. If any appliance has a different rating unit than Btu/hr, convert it first.

2. Consider the meter’s capacity: Many meters are rated for use with natural gas, with a maximum capacity of 250 cu. ft. per hour (cfh) at 0.5 in. of water-column differential. Since each gas has a different specific gravity, capacity must be calculated based on the type of gas. For example, the same 250 cfh capacity meter for propane, with a specific gravity of 1.53, might have a capacity of 158 cfh, while butane, with a specific gravity of 2.00, has a capacity of 138 cfh.

3. Apply a diversity factor: Since not all appliances operate at the same time, many companies apply a diversity factor – usually 85 percent – to adjust the calculated load.

4. Factor in line pressure: Residential propane systems typically operate around 11 in. of water column, though some systems use higher-pressure service (2 pounds per sq. in.). Higher pressure increases the meter’s effective capacity.

5. Use the correct capacity formula: For natural gas: capacity = meter rating (250 cfh) × Btu/cf (natural gas 1,037) = 259,250 Btu/hr. For propane: capacity = meter rating (158 cfh) × Btu/cf (propane 2,488) = 393,104 Btu/hr.

6. Remember key conversions: Propane engineers often convert between cu. ft. and gallons. One example: gallons (liquid) = cf × 0.027.

Randy Warner is product safety manager for Cavagna North America. Reach him at randywarner@us.cavagnagroup.com.

NOTE: The opinions and viewpoints expressed herein are solely the author’s and should in no way be interpreted as those of LP Gas magazine or any of its staff members.

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