UWE Bristol Engineering showcase 2015

Louis Fixsen
MEng Electrical and Electronic Engineering
Material and Distance Analysis Using Static Eliminators
In conjunction with Fraser Anti-Static Techniques Ltd.
Static eliminators have a variety of applications
such as in the production of plastics, paper,
clothes and micro-electronics. Static electricity can
be dangerous to personnel, damaging to
components or simply affect a garment’s
appearance.
Over the past summer I worked for Fraser Anti-
Static Techniques Ltd, a company that produces a
wide range of equipment that controls static
electricity. I was involved in the production of a
piece of testing equipment for their newest series
of static eliminator bars, the B-series.
The new series has an adaptive controller inside
the bar – this provides feedback that could be
used for a variety of measurements. Fraser Anti-
Static wanted someone who could investigate the
uses for this additional functionality but could not
dedicate the time to a possibly fruitless pursuit
themselves.
The research involved studying electrostatics and
the processes involved in static elimination, the
construction of a test rig, establishment of a
methodology for experimentation and large
amounts of programming in MATLab in order to
automate the entire process.
The initial phase of the investigation consisted of
developing a method for obtaining results, with
the goal of constructing a test rig that meant
reliable measurements with a fixed material and
distance could be obtained.
A list of parameters that could be varied on the
bar and in the environment was created. The
charging voltage is the primary parameter that can
be changed, affecting the amount of charge that
will be deposited on the material.
Electrical eliminator bars have small metal pins -
commonly made of tungsten or similarly robust
metals - called emitters that produce positively
and negatively charged ions in a corona around
each pin. They operate at high voltages up to and
in excess of 30 kilovolts. The ions are charged air
particles that have either gained or lost electrons
from interacting with the emitters.
How long it takes for the charge to dissipate and
the voltage at the surface of the material to drop
to certain level is the charge decay. Different
materials show different charge decay
characteristics, meaning that through
measurement and analysis a material might be
able to be identified based on an observed decay.
The static eliminator was used to charge and
discharge the material, with the voltage from the
current measurement ‘C-SENSE’ module giving a
relative measure of the current at the bar’s pins.
Measurements were obtained using a PicoScope
digital oscilloscope connected to debug outputs
from the bar. The bar was controlled using a
MATLab script that also controlled the
oscilloscope. The material beneath the bar was
charged and discharged whilst the oscilloscope
gathered data.
Distance estimation using the B12 bar appears to
be possible. If the material is known then the peak
value of the charging and discharging decays give a
good indication of the distance – within a certain
range.
Curve fitting tools would allow for accurate
material and distance estimation. Individual
parameters cannot be used to differentiate
between different curves, each material was found
to have an identifiable decay curve with noticeable
characteristics. Use of curve fitting would allow
these to be stored and compared against new
data.
Project Supervisor
Nigel Gunton
Project summary
The aim of this research investigation was to discover
how effectively an electrical static eliminator bar
could be used for material and distance analysis.
Initial work included a literature survey and research
into static eliminators, charge decay and other topics.
A test rig was designed and constructed in order to
produce repeatable measurements to assess the
reliability results. MATLab scripts that handled bar
control and data acquisition were written. Data was
analysed and used to write a script that could
estimate what material was beneath the bar or the
distance between the bar and material, which was
partially successful
Project Objectives
• Construct a test rig that allowed for repeatable
measurements.
• Obtain reliable results using the bar to charge and
discharge a material.
• Conduct large scale data acquisition with multiple
materials and distances.
• Find parameters that varied with material and
distance.
• Use these in script to estimate material or
distance.
Project Conclusion
The investigation was mostly success. Measureable
changes in voltage from the C-SENSE module were
recorded relative to the current draw at the pins of
the static eliminator bar with changes in distance and
material. It was not possible to create a script that
could estimate using simple parameters, more
complex data analysis is needed. It is significant that
through analysing feedback from the bars the type of
plastic that is beneath the bar, or the distance
between the bar and material can be given. It means
that development of even more ‘intelligent’ bars is
possible.