Load Cell &DP Cell

tobascothwackUrban and Civil

Nov 15, 2013 (4 years and 6 months ago)



Load Cell &DP Cell

Load Cell

A load cell is a transducer that converts a load
acting on it into an analog electrical signal. This
conversion is achieved by the physical deformation
of strain gages which are bonded into the load cell
beam and wired into a Wheatstone bridge

A load cell is a type of transducer and this
transducer is used for converting forces into
electrical signals. For example, changes in pressure
or weight may be converted into signals which can
then be used within an electronic

Load Cell Operating Principles

Load cell designs can be distinguished according to
the type of output signal generated (pneumatic,
hydraulic, electric) or according to the way they
detect weight (bending, shear, compression, tension,

Types of Load cell

Load cell consist of two basic types

Mechanical Load Cells

Strain Gauge Load Cells

Mechanical Load Cell

This load cell consist of two major



Hydraulic Load Cell

It is force
balance devices, measuring weight as
a change in pressure of the internal filling fluid.
In a rolling diaphragm type hydraulic load cell, a
load or force acting on a loading head is
transferred to a piston that in turn compresses a
fluid confined within an elastomeric diaphragm
chamber. As force increases, the pressure of the
hydraulic fluid increases

This pressure can be locally displayed or
transmitted for remote indication or control.

Hydraulic Load Cell

Pneumatic Load Cell

Pneumatic load cell also operate on the force
principle. These devices use multiple dampener
chambers to give higher accuracy than can a hydraulic

The advantages of this type of load cell is that they are
explosion proof and not sensitive to temperature
variations. Additionally, they contain no fluids like
hydraulic type that might contaminate the process if the

Disadvantages of this type is that they are relatively
slow speed of response and the need for clean, dry,
regulated air or

Pneumatic Load cell

Strain Gauge Load Cells

This converts the load acting on them into electrical
signals. The gauges themselves are bonded onto a
beam or structural member that deforms when the
weight or force is

force or weight is applied, the strain changes
the electrical resistance of the gauges in proportion
to the load

Other load cells are fading into obscurity, as strain
gage load cells continue to increase their accuracy
and lower their unit

Strain Gauge Load cells

Strain gauge load cell further classified


Bending beam load cell

Shear beam load cell

Canister load cell

Ring and pancake load cell

Button and washer load cell

Bending Beam Load Cell

Bending beam load cells
need particular care
when mounting to ensure
good load introduction
and to prevent damage
from side or non axial
forces. Fully weld
stainless steel low
capacity beams down to
5kg are now available
offering excellent
solutions to low capacity
weighing in hostile

Shear Beam
oad Cell

Single Ended Shear


Provide the ideal solution
for medium capacity

Their ability to withstand
100% side load without
problems makes them
particularly suitable for
weighing systems with
mixers and agitators.

However these units
become costly

Shear beam Load Cell

ended shear

For medium to high
capacity applications,
the double ended
shear beam offers a
number of advantages
over other designs.

Canister load cell

Traditional canister
load cells have stood
the test of time and
provide a compact and
cost effective solution
for many high capacity
weighing systems.

Canister load cells can
be fully weld sealed
and stainless steel
construction is now an
industry standard.

Selection of Load cells

Basic type and mode of operation.

The Number of load cells.


Accuracy level related to system requirements.

Method of mounting.

Approval requirements (metrological, safety,

Sealing level and construction material.


Applications of Load Cell

Tank/ silo

Tank dispensing

Wind tower

Dual tank level controller

Bag filling machine

Differential Pressure Cell

It is a device that measures the differential
pressure between two inputs.


we have a pressure container where we connect the
side (high) of the DP
cell, L
side (low) leave in the
atmosphere (open air). The DP
cell will tell us the
pressure in the pressure container relative to
atmosphere pressure. Depending on what class the
cell is, it will give you feedback with a current
signal. Normal in Europe is 4
20 m A, where 4 is
lowest and 20 is highest.

Types of DP Cells

DP cell has the following types.

Diaphragm capsules DP cell

Pneumatic DP cell

Electronic DP cell

Diaphragm Capsules DP Cell

It consist of 2 circular
metallic diaphragms

Diaphragm capsule act as

Diaphragms have
concentric corrugations to
optimize their flexibility and

Space between backing
plate and diaphragms is
filled with silicone oil

Pneumatic DP cell

In this type of cell
capsule is held between two

which form
chambers on either side as
high and low pressure sides of
dp cells

Electronic DP Cell

These cells are much
the same as pneumatic

Convert the deflection
of diaphragms into a
change in resistance,
inductance or


Level measurement

Density measurement

interface measurement