Factors For Selecting a Variable Area Flow Meter (Rotameter)

Three of many configurations of
variable area flow meters.
Courtesy Brooks Instrument

Industrial processes have many instances where fluid product components, liquid or gaseous, are moving within pipes. Processing is about control, so it follows that an input to the control, measurement, or data logging centers of the facility will answer the question, "How much is flowing through that pipe?".

There are numerous methods employed for quantifying flow in the industrial process measurement and control field, each with particular attributes that may be considered advantageous under  certain operating conditions. All flow measurement methods are indirect, as their actual measurement is of a property that is impacted in a predictable manner by a change in the flow. Flow measurement is an essential element that, combined with other fluid attributes, is used to calculate the total mass of a fluid that has traversed the measurement point.

One time tested method of measuring flow is the variable area meter, also called a rotameter.

Operation of the variable area meter (also referred to as a VA meter) is based upon creating an equilibrium between an upward force, produced by the fluid motion, and a downward force, gravity. The device includes a tapered glass or metal tube that encases a specially shaped float, often referred to as a shaped weight. VA meters must be installed vertically, with the media flowing from the bottom upward, so that the gravitational force necessary for operation is properly aligned with the flow direction. As fluid flows upward through the specially tapered tube, it creates drag on the float contained within the tube, lifting it upward. As the float rises, the free area between the float and the tube wall increases, causing a reduction in the fluid velocity and drag force. For any given flow volume, the flow velocity within the tube will cause the weight to rise until the drag force created by the flow reaches equilibrium with the countervailing force of gravity on the float. Proper design of the tube and the float allow for direct indication of flow volume.

Some of the attributes of variable area meters include:

• No external power or fuel required for operation
• Must be installed vertically, with flow entering bottom
• Meters are characterized to a specific substance, at a specific temperature
• Operation is stable, with low pressure drop
• Requires constant gravity for operation
• Direct local readout of flow rate with meter or scale imprinted on tube
• Glass tube based unit flow readings require visibility of float through the medium
• Accuracy is comparatively low for an industrial flow measurement device
• Generally low maintenance, simple construction, low comparative cost

Brooks Instrument, a world renowned manufacturer of flow, pressure, and level measurement instruments, has produced a concise and compact white paper that summarizes the factors to consider when specifying a VA meter, as well as how each factor impacts operation of the unit. The description is practical and easily understood. It is recommended reading for all process stakeholders to build their flow measurement knowledge.

I have included the paper below. Browse the paper. Contact the flow instrumentation specialists to discuss your application requirements and challenges. Combining your process know-how with their product application knowledge will produce a good solution.

Selecting Variable Area Flow Meters for Process Measurement from Miller Energy, Inc.

Digital Sensor Technology: An Uptick in Measurement Performance

Silicon Resonant Sensor
Courtesy Yokogawa

Industrial process control, as a field of endeavor, is a continuous quest for better, safer, and higher output. The road of progress is paved with new technologies that deliver higher accuracy and reliability in measurement. A recently commercialized advance is the silicon resonant sensor used to measure pressure in industrial process settings. One manufacturer, Yokogawa, applies this technology throughout their DPharp line of differential pressure transmitters, with numerous industrial applications.

Some of the positive attributes of this latest generation of digital pressure sensor include:

• Simultaneous measurement of differential and static pressure.

• Superior digital precision

• No A/D conversion needed

• High performance 

• Temperature effects limited to 10 ppm/deg Celsius, yielding highly stable performance

• High signal to noise ratio

• Output level increase of more than four times over previous generation piezoresistance silicon sensor

The features all add up to a substantial improvement over previous technology, delivering an incremental step up in measurement performance and confidence. You can quickly boost your understanding of how the sensor technology works by viewing the short video below. To explore how the Yokogawa DPharp sensor equipped transmitters can provide better performance to your process, contact a product specialist and share your process measurement challenges.

Multivariable Transmitter Delivers Mass Flow Rate and More

Model EJX 910A Multivariable Transmitter
Courtesy of Yokogawa

Industrial process measurement and control is charged with continually producing better, faster, and cheaper results with increasing levels of safety. For applications requiring mass flow rate measurement of fluids or tank level, a multivariable transmitter has much to offer when it comes to improving outcomes throughout your industrial process operation.

The EJX 910 series from Yokogawa provides the latest generation of digital sensing and processing to provide fast and accurate process measurement of temperature, static pressure, differential pressure, and dynamically compensated mass flow. Flow accuracy as high as +/-1.0% is achievable, along with:

±0.04% Differential Pressure Accuracy
±0.1% Static Pressure Accuracy
±0.9°F External Temperature Accuracy

Some other highlights include:

• Industry leading fast response time for safe and accurate process control.
• Yokogawa's specially developed DPharp digital sensor providing simultaneous static and differential pressure measurement, digital accuracy, and no A/D conversion error.
• LCD display can be rotated in 90 degree increments. External zero adjustment screw and range setting switch enhance field setup.
• Improved mass flow accuracy of +/- 1% from multivariable operation in one device with dynamic compensation.
• Signal characterizer for measuring level in irregular shaped tanks.
• Utilizes industry recognized open communication protocols for easy integration into existing installations.

The manufacturer's white paper, describing precisely how the unit works and how it can be applied, is below. Browse the white paper for some additional detail, but consult with a product specialist to explore how to improve your process measurement and control performance. They have even more information than is provided here which, when combined with your process knowledge, is sure to generate a positive solution to any challenge.

Yokogawa Multivariable Transmitter EJX910 from Miller Energy, Inc.

Connecting Modbus Transmitter to USB Converter

EJX910 Multivariable Transmitter
Courtesy Yokogawa

Industrial process measurement and control utilizes transmitters in abundance. There may be instances where, for convenience or due to equipment changes, the output signal from the transmitter will need to be converted to a different protocol or format. Yokogawa has produced an instructional video showing, in a clear and understandable way, how to install a signal converter on their EJX910 Multivariable Transmitter. While the instructional video shows a conversion from Modbus to USB, the knowledge and understanding gathered from the short video will help you to meet other signal conversion challenges that may arise in your facility.

Your investment of five minutes to watch the video will generate returns by increasing your understanding and allowing you to move forward with confidence when a signal conversion task inevitably comes up. More information on signal conversion products, as well as process measurement transmitters, is available from an application specialist. Enlisting their help to generate solutions to your industrial measurement and control requirements is also a good investment of your time.

Liquid Density Measurement for Industrial Process Control

DM8 Liquid Density Meter
Courtesy Yokogawa

Density is certainly a fundamental physical attribute of any liquid that is the subject of a process control operation. The ability to accurately measure liquid density in a process application is achievable using specially applied technology from Yokogawa.

The company's latest version, the model DM8, is a vibration type liquid density analyzer with reliable, multi-function operation. It is the culmination of manufacturing and density measurement technology experience extending back over 40 years. The DM8 employs a converter with an incorporated microprocessor to directly convert sensor frequency signals into displayed density values. One touch calibration, internal diagnositics, and digital communications are also provided.


The DM8 liquid density analyzer measures liquid density of general process liquids with high sensitivity and excellent stability. It has a measuring density range of 0 to 2.0 g/cm3, and is unaffected by flow rate and viscosity. Sensor options include general-purpose, sanitary, and explosion proof versions.

The brochure below provides additional detail on application configuration, product specifications, and operating principle. Share your process process measurement challenges with a product specialist to achieve the best solution for your application.

Yokogawa Vibration Type Density Meter from Miller Energy, Inc.

Improve Process Safety Compliance With Safety Transmitters

Oil Refinery

Industrial processes often are characterized by substantial hazard through their operation. As operators, engineers, and designers, we are responsible for keeping those actual and potential hazardous conditions and occurrences in check. I recently wrote about safety transmitters that can be used to enhance safe industrial process operation and provide compliance with applicable standards.

I located a single sheet document that summarizes the features, benefits, cost savings, and compliance ratings for the safety transmitters from United Electric. You can get more detailed information on these devices and how to properly apply them in your process control scheme by contacting a product specialist. Combining you process expertise with their product application knowledge will generate a solid solution.

United Electric One Series Safety Transmitter from Miller Energy, Inc.

Safety Transmitter for Temperature and Pressure in Industrial Processes

One Series Safety Transmitters
Courtesy United Electric Controls

United Electric Controls has developed a safety transmitter that combines transmitter, safety switch, and display gauge in a single, easily deployed device. The One Series Safety Transmitter includes the manufacturer's patented self diagnostics, along with diverse and redundant signal processing that feed algorithms to detect and respond to internal faults and process abnormalities.

The safety transmitter provides a local switch that can be used for rapid emergency shutdown at the point of measurement or detection, eliminating the need to communicate with other safety controllers and await a response. The safety relay output is programmable and can handle high voltages and currents associated with shutting down control valves, compressors, and other industrial equipment.

In addition to the safety relay output, the One Series Safety Transmitter provides logic outputs that can be employed in voting logic schemes often used to produce warnings prior to a shutdown. For reliability, the unit employs no moving parts and includes self diagnostics with a local display of device status.

There is a whole lot more to learn about these "Safety right out of the box" industrial pressure and temperature transmitters. The product brochure is provided below, but you can get the latest and most detailed product and application information from a specialist in industrial process measurement and control.

United Electric One Series Safety Transmitter from Miller Energy, Inc.