Staying Connected - August 2010

Triboelectric Noise in Medical Cables and Wires


AAMI EC53 requires maximum cable
noise not exceed 50 micro-volts

Noise can make diagnosis of an ECG or other medical signal difficult, if not impossible.  To meet AAMI/ANSI EC53: 1995/(R) 2008 requirements the maximum peak-to-peak noise shall be less than 50 micro-volts (µV).  Many device manufacturers specify even lower noise limits for their cables and leadwires.

Noise can come from many sources external to the cable but also from the within the cable itself.  Noise generated within a cable is often called handling noise or motion noise, but this type of unwanted signal is more accurately described as triboelectric noise.

What is Triboelectric Noise?


The same forces that causes the
child’s hair to be attracted to the
plastic basket can cause unwanted
noise in medical cables

The triboelectric effect is a phenomenon in which an electrical charge is generated by materials coming together then separating.  Friction is a form of materials coming together and then separating and can produce a large electrical charge.  Almost everyone has experienced the triboelectric effect when, after shuffling their feet on a carpet and touching metal, experience an electrical “shock.”  This same effect can produce an unwanted charge within wire and cable which is seen by monitors as noise.

The amount of the charge generated is largely dependent on the composition of the materials and the amount of friction between the materials.  Within medical cable assemblies and leadwires, random triboelectric noise is generated when the various conductors, insulation, and fillers rub against each other as the cable is flexed or moved.

Meeting ANSI/AAMI EC53 noise requirements for medical wires and cables requires careful cable design and material selection.  Affinity Medical Technologies does not extrude cable or wire, but works closely with trusted suppliers to develop proprietary low noise cable and wire material.  Affinity has developed a variety of ultra low noise cable and wire constructions for use in critical medical applications.


Diagram of test set-up used at Affinity to
test for triboelectric noise in cable and wire

Testing for Triboelectric noise

One of the capabilities of the Affinity lab is to test cable and wire to ensure compliance to our customers’ specifications and AAMI/ANSI EC53 triboelectric noise requirements.  Testing is done on raw cable or wire, not cable assemblies.  AAMI EC53 section 5.5.4 specifies “Test a representative sample of cable material….”

Our OEM partners occasionally question why finished cables are not tested.  Besides the directive to test cable material, 7 feet of cable is needed for the test and most cables assemblies do not have that long of an uninterrupted span of cable material.  More significantly, movement at any termination point within the connector or cable assembly will typically generate a much greater amount of artifact than the noise generated by the triboelectric effect.


Detail of stand and clamp to
hold cable or wire for triboelectric
noise drop test

Noise Testing Set-Up

ANSI/AAMI EC53 details the test setup in section 5.5.4 and in Figure 8 of the EC53 standard.  At Affinity, 36” high heavy gauge steel posts have been bolted into a concrete floor set five feet apart, center-to-center.  A one-half inch thick steel plate is centered on the top of each post allows 5’ of cable or wire to be held firmly between clamps set 48” apart.  Care must be taken in locating the test area away from interference from electrical panels or large electrical motors and away from vibration of equipment or vehicles.  The Affinity test set-up assures accurate, consistent and repeatable results.


Performing triboelectric
noise drop test


Triboelectric noise displayed
on oscilloscope

A weight equal to 40 times the weight of one-foot of cable or wire is attached at the center, held at the level of the clamps, and dropped.  Electrical connections for both ends of the cable are also detailed in the standard.  Voltage generated by the movement of the cable or wire is measured using a digital oscilloscope.

Designing to Reduce Triboelectric Noise

Within multi-conductor cable the greater the number of conductors and surrounding material, the greater the opportunity to generate triboelectric noise.  Selecting materials that slip on each other easily increases flexibility, however care must be taken to select materials that when rubbed together do not produce unwanted noise.

At Affinity, we understand both the regulatory issues and performance requirements associated with low-noise cable assemblies and leadwires.  We also understand how cable design can impact manufacturing efficiencies.

Our design process begins with establishing a clear performance specification with the device manufacturer.  Low noise requirements are but one design consideration.  Strength, flexibility, durability and the ability to withstand cleaning and disinfection are considered along with noise requirements.  The best design is often a compromise which is reached in consultation with the device manufacturer. 


Low noise cable and wire
are an Affinity specialty

Summary

Most diagnostic devices incorporate noise filtration or compensation, however reducing noise at the source improves signal integrity and overall performance.  Triboelectric noise can be reduced to very low levels by incorporating low-noise cable and wire material and designing connectors and strain reliefs to prevent any movement at the termination of conductors to contacts.

Let the Affinity engineering team assist with your projects that require low noise cable assemblies or leadwires.  We have the knowledge and experience to offer low noise cable and wire solutions and to make your interconnect project successful.

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Meet Erick Kelsen – Affinity Buyer and Planner


Erick Kelsen

Joining the company as Buyer/Production Planner a little over three months ago, Erick Kelsen is one of Affinity Medical’s newest team members.

When asked what attracted you to Affinity, Erick replied, “I worked at a large medical device company before coming to Affinity so when the chance to work at a small but fast growing company opened up, I jumped at it.  The opportunity to become an integral part of the manufacturing process from beginning to end really appealed to me.”

Erick reports to Affinity Material Supervisor, Sue Alessi, giving her much needed help in purchasing and planning.  Affinity Business Development Manager, Hank Mancini, commented, “Erick has had an immediate positive impact since joining Affinity.  He is persistent, which is often needed when trying to expedite deliveries from our suppliers.”

Asking Erick what are his impressions about Affinity so far, he replied: “It has been great.  Affinity is made up of really wonderful and knowledgeable people that are great to work with. I’ve learned a great deal in my short time here.”


Erick and Affinity Material
Supervisor, Sue Alessi

“My short term goals at Affinity are to develop a good rapport with our many suppliers and reduce downtime due to material/supply issues,” said Erick.  In the longer term, I want to become Affinity’s product knowledge expert and help Affinity continue on its Lean journey.”

Erick brings an open mind and a strong work ethic to his position.  He said that his biggest challenge so far has been just keeping up.  “Affinity is a fast paced, dynamic company and very responsive to the needs of its customers.  It takes a lot of work to stay on top of everything, everyday.”

Erick grew up in Orange County, California, attending El Toro High School and graduated from UCLA with a Bachelors Degree in History in 2002.  He and his wife live in Murrieta which is about sixty miles from the Affinity plant.

Erick’s wife, Dana, is a grad student studying Library and Information Science.  She also coaches Volleyball and teaches at a local high school.   Erick’s father is a photographer for the Los Angeles Times and lives in Mission Viejo and his mother is a realtor living in Dana Point, California.
 
When not working, Erick says, “I love to read: I especially enjoy American history, presidential biographies as well as science-fiction and fantasy books.  The last book I read was “The Wilderness Warrior” by Douglas Brinkley.  I’m an avid movie-goer and when we go on vacation, we try to avoid the tourist traps and go to places that the locals enjoy.”

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Custom Connector Integrated Into Case


Custom connector designed
by Affinity engineering team

The Affinity engineering team is often asked to design a custom connector for one of our OEM partners.  Occasionally, we are asked to integrate the connector design into the device case.  Unlike many connector manufacturers, Affinity engineers are not tied to any particular connector design and have the freedom to offer a true custom solution.

In this example, one of the important design considerations was integrating the connector into the side of the case for an ambulatory monitoring device.  Eight contacts were used to provide a variety of ECG lead configurations.  The desired retention force of the non-locking connector was achieved by selecting pins and sockets with specific retention force and careful design of the plastic interface.


Custom connector integrated into case
of ambulatory monitoring device

If you are considering a custom connector, let the Affinity engineering team help you.  We have the experience and expertise to design and manufacture a connector that meets your exact requirements.

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Announcements, Information, and Trivia

Labor Day Holiday

Affinity will be closed Monday, September 6th to observe Labor Day

Labor Day is a federal holiday in the United States nd is observed on the first Monday in September (September 6 in 2010).

The first Labor Day in the United States was celebrated on September 5, 1882 in New York City.  In the aftermath of workers deaths at the hands of the US military and US Marshals during the 1894 Pullman Strike, President Grover Cleveland made reconciliation with Labor a top priority. Fearing further conflict, legislation making Labor Day a national holiday was rushed through Congress unanimously and signed into law a mere six days after the end of the strike.

For most Americans, Labor Day traditionally marks the end of summer and the start of fall, even though fall actually begins a few weeks later.

Chocolate

At Affinity Medical, there are a lot of fans of Chocolate, especially dark chocolate.  Dark chocolate is produced by adding fat and sugar to a cacao mixture.  Because of its high cocoa content, dark chocolate is a rich source of epicatechin and gallic acids, which are believed to offer cardio-protective properties.  Some believe that dark chocolate may reduce the possibility of a heart attack when consumed regularly and in small amounts.

Hawaii is the only US state that grows cacao beans to produce chocolate.

The melting point of cocoa butter is just below the human body temperature -- which is why it literally melts in your mouth.

The botanical name of the chocolate plant is Theobramba cacao, which means "Food of the Gods."



Suzann Sitka, Cesar Jara and Candy Golding
- the Affinity Customer Care Team

Affinity Customer Care -
Hours of Operation

At Affinity Medical, we don’t have a customer service department.  In place of customer service, we have Customer Care Coordinators.  While our Customer Care Coordinators perform many of the same functions that customer service representative would, we strive to offer our OEM partners more than that.  The job of our Customer Care Coordinators is to take care of our OEM customer partners.

Affinity Medical Technologies Customer Care specialists are available to assist you from 7:00 A.M. until 4:00 P.M., Monday through Friday U.S. Pacific Time, except holidays.

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: +1 949 477 9495
Fax: +1 949 477 9499
Email: CustomerCare2@affinitymed.com
Website: www.affinitymed.com