While flow meters and load cells are two very different technologies, their paths may sometimes overlap, making it a challenge to decide which technology would be best suited for a certain application. A flow meter may come in many forms, but it is usually an in-line device that measures the rate or flow of a fluid—either in volume or mass. A load cell is a device that allows for the contents of mass to be weighed accurately. Flow meters work at their best when measuring continuous flow, rather than frequent starts and stops, and they are great for bulk receiving by weight or volume (depending on the meter). Flow meters may not always be accurate as the viscosity of the water may affect the reading. Liquids with entrained air bubbles or variations in viscosity may give flow meters trouble giving accurate readings, but this is no problem for load cells. For example – clean fresh water will have a different mass to dirty water or saltwater. The flow meter measures flow and cannot take into account the viscosity or density of the water. A load cell measures the weight of the mass under load, so delays are minimized and readings are accurate at all times, provided the load cell is calibrated. A load
cell is required to be calibrated regularly to verify their accuracy. Load cells offer a particular benefit when dealing with mass. Since the sensor is not placed under direct load, there is never a deflection or deformation of the sensing device, thus providing accurate measurements time after time. A load cell system is a good solution for precise measurement of mass. One must conclude that in the load testing application that a load cell will be better suited to accurately
measure the applied load to ensure that the test is carried out to legal standards and within 1% of the rated capacity of the lifting machine. Flow meters have proven not to be very effective and accurate and are not permitted to be used in Europe and the United Kingdom.
World Wide Load Testing Specialist, +27 (0) 31 572 4940, ops@wwlts.co.za, www.wwlts.co.za
Lifting Africa - Mar/Apr 2020
23
PRODUCTS & SERVICES
Flow meters vs. Load cells: How do they measure up?
