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Introduction to Load Cells

AUTHOR : Date : 8/17/2012 10:01:09 PM


Day-in and day-out we have been using electronic scales or weighing machines. You go to any grocery store or a jewellery shop; the items are weighed using electronic weighing machines (Weighing balances are also used in situations where very high accuracy is not of paramount importance). But, have we ever given a thought on the mechanism of the electronic scales?

At the heart of electronic scales or weighing machines is a sensor called load cell. These sensors sense the force (or weight) of the items and the electronic circuitry processes the sensors’ output and displays it on the indicator. Load cells are highly accurate transducers which provide the user with information not generally obtainable by other technology due to commercial factors. Usage of load cell is not limited to electronics scales; they are used load testing machines, industrial scales, flow-meters, etc., though we hardly ever come in direct contact with the load cells. In short, load cell can be used wherever there is a requirement of “force measurement”.
Subsequent sections will discuss in-outs of the load cells.
What is Load Cell
As per dictionary, a load cell is described as a “weight measurement device necessary for electronic scales that display weights in digits.” However, load cell is not restricted to weight measurement in electronic scales.
Load cell is a passive transducer or sensor which converts applied force into electrical signals. They are also referred to as “Load transducers”. 
Load cells use different operating principles, viz.,
·         Load Cells based on fluid pressure
·         Load Cells based on elasticity
·         Load Cells based on magnetostriction effect or piezoelectric effect
However, the only load cells which are prevalent are the load cells based on strain gages. Hence, the term ‘load cell’ means ‘strain gage-based load cells’. The reason behind the wide adoption of strain gage-based load cells is their characteristics
1.  Highly precise and linear measurements
2.  Little influence due to temperature changes.
3.  Small size compared with other types of load cells.
4.  Long operating life due to lack of moving parts or any parts that generate friction.
5.  Ease in production due to small number of components.
6. Excellent fatigue characteristics