ADVANCING FLOW CALIBRATION FOR PRECISION FLOWMETER DEVELOPMENT


Neil Hannay reports on the investigation and resolution of calibration limitations experienced during flowmeter development for ultra-low flow applications.


When developing any type of flow meter, the ability to verify its performance is key. Titan’s current range of flowmeters can operate accurately down to 2ml/min, meeting the limit of their own traceable calibration capabilities. With an R&D drive to push the flow measure- ment boundaries into the realms of ultra-low flow, Titan investigated the advancement of its own calibration tools to achieve this objective.


Titan Enterprises supplies precision flow meters globally and operates three certified flow calibration systems to support production. These calibration rigs cover flow ranges from 2 ml/ min to 200 l/min with a manufacturer’s uncertainty of ±0.05%. The systems are based on piston provers, with linear encoder measurement of piston displacement under hydraulic or pneumatic operation. While robust and reliable for production use, these rigs are manually operated and inherently limited in versatility. Their primary purpose being the calibration of devices through production and prior to shipment to customers.


This technical report reviews the investigation of flow rig limitations when embarking on ultra-low flow measurement and how this was overcome through the in-house development of specific calibration tools to meet R&D requirements. Titan’s portfolio of meters currently operate accurately down to 2 ml/min, matching the traceable calibration capability of its certified rigs. Recent advances in electronics and signal-processing algorithms provide the potential to extend Titan’s ultrasonic technology to flows significantly below this limit. To develop flowmeters in this regime, Titan needed equally advanced calibration tools.


Current Position: Calibration Capabilities and Investment in R&D


Titan’s three state-of-the-art piston prover flow calibration tools for production calibration of their meters have an overall uncertainty of ±0.25% (95% CL). The equipment installed provide accurate calibration with water from 2 millilitres per minute up to 200 litres per minute. Annual calibration checks against certified weigh scales mean all flow meter calibrations are traceable to national standards. The production rigs are almost entirely manual in operation, being operated by our trained staff to produce 6-point flow calibration certification for each of Titan’s 10 to 15 thousand meters calibrated each year.


The calibrators use a piston within a smooth bore tube to act as a moving barrier between the pressurising control medium and the displaced test water. As the piston travels it is monitored by a linear encoder generating a continuous train of electrical pulses to indicate its position and rate. Each pulse represents an extremely small but very precise volume of fluid, and this volumetric dispensing is then correlated to the meter under test output to calibrate its performance.


These production rigs are expensive, require continual manual operation and are being operated almost continuously during the working day. Although the certified calibration systems are ideal for production, the limited availability due to such production demands, constrains the ability to conduct experimental work, and they also lack the flexibility required for early-stage product development.


Titan consistently invests approximately 10% of revenue in research and development, recognising that the ability to verify flowmeter performance is central to innovation. Over the years, Titan has designed a number of small developmental calibration systems. These initially included a transfer standard system using a high-accuracy Coriolis reference meter and a small piston prover operated by a ball screw and drive motor. These rigs enabled rapid performance assessment of prototype flowmeters and investigation of thermal effects. Absolute accuracy or stability of flow were less critical for the development of early designs of flow meter, but versatility was always a key requirement. However, as Titan’s flowmeter technology advances, particularly in the ultrasonic range, more accurate and versatile calibration systems are essential in the assessment of new flowmeter designs.


Aim: Development Projects Driving Calibration Requirements


Two major development programmes within the scope of Titan’s ultrasonic flow measurement technology created the demand for ultra-low flow calibration: 1. Extending the Atrato®


Ultrasonic Flowmeter Range – Targeting flows >10× lower than the


current minimum flow rate, with measurement capability down to 0.2 ml/min or below. This would offer a competitive volumetric alternative to existing thermal low-flow devices.


2. Clamp-On Ultrasonic Flowmeter with Disposable Tubing – Designed to measure small batches of medical-grade fluids in a low-cost disposable tube. Potential applications include dialysis equipment and bolus delivery monitoring, where accuracy, sterility, and affordability are critical.


Both projects required calibration systems capable of extremely smooth, stable, and repeatable flow delivery. Direct integration of calibrator feedback into the control system was also essential. Full automation would also allow the rigs to perform complex flow profiles and transient tests while logging detailed performance data.


Summary of Conclusion


For these development projects, the team designed hardware and software to produce smooth-flow, fully automatic calibration rigs, with a total flow range of 0.0054ml/min to 4l/min calibration capability and calculated uncertainty of 0.1%. The software allows for multiple scenarios of operation, from long-term flow stability to short batch dispensing to be assessed with new meter designs.


With the newly designed calibration rigs we were able to take concept designs for very low flow measurement using current ultrasonic knowledge and prove the effectiveness for flows down to 0.1ml/min at accuracies of ±1% + 0.02ml/min.


4 | AET NOVEMBER 2025 | ENVIROTECH-ONLINE.COM


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36