Measuring fluid levels with load cells

Measuring fluid levels is something we do every day, from checking the oil level in our cars with a dip stick to assessing much milk is left in the carton (followed by the obligatory, precautionary sniff of course!).

Recording levels by eye

Most fluid level testing we do for ourselves at home is purely by eye, and remarkably the same applies for many industrial situations, often with the use of a gauge or consistency of reading. Other methods include hydrostatic devices such as floats which rely on a consistent specific gravity of the liquid being measured.

However, readings from such methods and devices are not reliable or accurate, and require a person to note and record levels. In situation where companies want to closely monitor tank contents, with the aim to reduce costs and waste, the old-fashioned sight glass is too restrictive. Add in the safety issues of sight glasses leaking or getting clogged with debris, and it’s time to replace this weak link in any system with something more robust, reliable and accurate.

 

Load cells in fluid level measurements

Needless to say, that ‘something’ is a load cell. Load cells work in fluid measurement by effectively weighing the liquid to a high degree of accuracy. The load cells sit under or within the supports for the fluid’s container, and simply detects the changes in force as the vessel fills or empties.

With some fluids, the weight of the container and associated pipework will be considerably more than the weight of the contents. This is where the accuracy and continual monitoring by load cells comes into its own, detecting even the slightest change in the container contents.

Unlike sight glasses and other floating devices, the load cell never comes into contain with the fluid itself, so it remains separate, dry and free from possible contamination. Its output can be relayed wirelessly to a processor and onwards to monitoring and inventory software. Compared to new technologies that use radar, ultrasound or laser to monitor fluid levels, load cells are proven technology that’s reliable, relatively cheap, easily calibrated and readily available.

 

Load cells and flow meters

Measuring the amount of liquid transferred from a storage container to a transporter or similar is fairly straightforward. However, the same cannot be said for bulk solids when they need to be loaded into another container, truck or vessel. This is especially true if contents from various containers are to be mixed at point of exit from their original container. The answer is to use a flow meter, as an article in “Powder and Bulk Solids” magazine explains:

“A flow meter can be used to obtain a master rate that different feeders can be ratioed off of. This is a common application in large plastic and food extrusion processes. The flow meter feeds in the base material acquiring a master rate to which the additive feeder(s) can be ratioed.”

 

The four types of flow meter

Load cells are used in the four main types of flow meter:

• Impact flow meters

The material comes into contact with a plate that has a load cell attached to measure the force on the plate.

• Deflection flow meters

With this type of meter, the materials slide down a chute that is attached to the load cell. A data processor converts the weight of the material into a rate of flow.

• Combination flow meter

A combination of an impact and a deflection flow meter in one unit.

• Coriolis flow meter

This includes a rotating wheel fitted with vanes through which the materials pass. The wheel is turned by a motor attached to a load cell. The processor calculates the rate of flow by measuring the force exerted on the load cell by the motor, as defined by the Coriolis force. This is “an inertial force that acts on objects that are in motion relative to a rotating reference frame.”

 

Load cells at your service

Load cells are a remarkably versatile technology, with a proven track record of reliability in even the most challenging of environments. We design, manufacture and distribute our own load cells all over Britain and beyond.

So, whatever the task, we have a load cell to suit and if not, we can design and make one to your precise requirements.

Give us a call to discuss your next project – we’re always happy to talk techie!