8/8/2019 Load Cells DP Cells

1/4

Load Cells

8/8/2019 Load Cells DP Cells

2/4

Introduction

What is Load Cell?

It is a transducer which takes input as (force) mechanical signal and converts into an

output as electrical signal. The other names of Load Cells are Load Transducer or Load

Sensors.[1][2][3]

There are different types of Load Cell; most common type is Strain Gauge based Load

Cell.[2]

Strain Gauges are the

one of fundamental sensing

element used in many types of

sensors i. e., pressure sensors,

load cells, torque sensors,

position sensors, etc. It is usually found in foil types. It

consists of a resistive foil which is attached with the

backing material. When a force (Stress) is applied to the

foil the foil is either stretched or compressed, due to

which its resistance changes in a definite manner which

is calculated using Wheatstone bridge to evaluate the force (stress). [4]

History

The oldest type of weighing instrument was the equal arm balance which is

afterwards replaced by the lever technology. These mechanical levers were used for weighing

purpose for a long time. In 1843, the British Physicist Charles Wheatstone developed a bridge

like circuit which can measure the electrical resistance. This circuit was the best suited

technique used for measuring the resistance changes produced while using the strain gauges.

8/8/2019 Load Cells DP Cells

3/4

The first strain gauge was developed in 1940. It is used in the construction of Load Cell as

the primary sensing element. After that Load Cell replaces the use of mechanical levers for

weighing purpose.[5]

General Working Principle

A load cell is made by bonding

strain gauges to an elastic material. For

accurate measurement, strain gauges are

bonded to the position on the Elastic

material where the impact of the stress will

be the largest. The strain gauge utilizes this principle and detects a strain by changes in

electrical resistance.

When the stress caused by external force to an object is below the proportional limit

(elastic limit of strain gauge wire material), the strain varies linearly with the stress. In

addition, when stress is applied to a load cell and its Elastic material is deformed (strained),

the resistance value of the strain gauge varies linearly with the deformation.[6]

Advantages and Disadvantages of Load Cells[7]

Advantages

Rugged and compact construction No moving parts and negligible construction under load. Highly Accurate Wide range of measurement, can be used for static and dynamic loading

Disadvantages

Mounting is difficult Calibration is a tedious procedure

8/8/2019 Load Cells DP Cells

4/4

Types of Load Cells

There are two main types of Load Cells

Mechanical Load Cells Strain Gauge Load Cells

Mechanical Load Cells