Staying Connected - July 2007

Triboelectric Noise in Medical Cables and Wire

Noise in an ECG or other medical signal may make accurate diagnosis difficult, if not impossible.  To meet AAMI/ANSI EC53 requirements the maximum peak-to-peak noise shall be less than 50 micro-volts (µV).

Noise can come from a number of sources, including the cable itself.  Sometimes referred to as handling noise or cable noise, this type of unwanted signal is more accurately described as triboelectric noise.

What is Triboelectric Noise?

The triboelectric effect is an electrical phenomenon in which an electrical charge is generated between materials that are rubbed together.  The amount of charge generated is largely dependent on the composition of the materials and the amount of friction between materials caused by movement.  Within a medical cable random triboelectric noise is generated when the various conductors, insulation, and fillers rub against each other as the cable is flexed.

Meeting AAMI EC53 noise requirements for medical wires and cables requires careful material selection and cable design.  At Affinity Medical Technologies we use our experience, expertise and understanding of how the cable or wires will be used and work with our cable suppliers to develop raw cable that performs better than AAMI EC53 noise requirements.

Testing for Triboelectric Noise

Affinity Medical has the capability to test cable and wire to ensure compliance with AAMI/ANSI EC53 low noise requirements.  Testing is done on raw cable, not cable assemblies.  AAMI EC53 section 5.5.4 specifies “Test a representative sample of cable material….”  Customers 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 are not that long.  More significantly, movement at any connection point within the cable will typically generate a much greater amount of artifact than the noise generated by any triboelectric effect.

Test Set-Up


Diagram of test set-up used in Affinity test lab

ANSI/AAMI 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 are bolted into a concrete floor set five feet apart, center-to-center.  A 1” thick polycarbonate plate centered on the top of each post allows 5’ of cable or wire to be held firmly between clamps set 48” apart.

A weight equal to 40 times the weight of 1’ 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 detailed in the standard.  Voltage generated by the movement of the cable or wire is measured using a digital oscilloscope.  Noise levels below 50 micro volts meet the low noise requirements of EC53.


Bob Evans performing
triboelectric noise drop test


Noise signal on oscilloscope

Summary

Triboelectric noise in medical cable assemblies can be reduced to very low levels by incorporating raw cable that meets the ANSI/AAMI EC53 standard for noise.  Most diagnostic devices incorporate noise filtration; however reducing interference from cable noise can make accurate diagnosis from a medical signal more likely.

 

MEET BOB EVANS – Engineering Technician


Bob Evans leads the
Affinity test lab

Bob Evans is a popular figure at Affinity Medical Technologies. His friendly personality and witty sense of humor make daily interaction with Bob a pleasant experience for all members of the Affinity team.  For over six years, Bob Evans has run Affinity’s test lab reporting to Bob Frank, the Director of Engineering.

Bob’s primary function is to perform evaluations of new products for verification and validation to customer specifications.   However, you may see Bob on the production floor with the manager of manufacturing, in the test lab with our QA manager or meeting with the engineering team on a regular basis.  With 18 years of experience in the medical field, Bob’s expertise is a valuable asset to Affinity and our customers.

Bob performs a variety of different tests to ensure the product meets the customer’s specifications.  The test protocol is based mainly on the criteria as required by ANSI/AAMI EC-53 and IEC 60601 standards. These tests include but are not limited to: flex testing, hi-pot, tensile strength, defibrillation, triboelectric noise and connector mate/unmate force testing. Customized tests can also be performed at the request of customers.


Bob performing Hipot
testing on medical cables

The newly expanded state of the art test lab at Affinity Medical is fully equipped with a variety of equipment including pull force testers, a Cirris cable testers, two flex testers, high powered microscopes; a diamond blade saw, a hi-pot tester and other testing equipment.

Bob Evans is quoted as saying, “Our products never, I mean NEVER leave Affinity Medical until they fully comply with all specifications.”  In the rare case where a cable does not pass Affinity’s rigorous testing, Bob completes a Failure Analysis and dissects the part to locate the cause of the failure. After conferring with the engineering, manufacturing and QA teams to determine why there was a failure, these findings as well as possible solutions to the problem are reported to the customer.

When asked what he likes most about his job at Affinity, Bob replied: “The people.  I have great relationships with everyone including management and the production staff.  I really enjoy coming to work everyday.”  Bob was born in Washington State but grew up in Fairbanks, Alaska.  Bob writes poetry and enjoys the beautiful scenery of Dana Point, California (where he resides) by taking long walks and dining in Dana Point harbor with his wife, Trini.

IP67 Medical Connector

Ingress Protection is the degree of environmental protection provided by the product enclosure of electronic equipment.  In the case of medical cable connectors, the enclosure is the connector itself.

The numeric code is defined in international standard IEC 60529.  It provides users a uniform performance specification rather than ambiguous designations such as “dustproof” or “waterproof.”

The first number designates protection against solid objects, e.g. fingers or dust.  The second number refers to moisture protection.

Summary of Ingress Protection designations

1st Digit

Protection Against Solid Objects

2nd Digit

Protection Against Moisture

0

Not protected

0

Not protected

1

objects greater than 50mm (back of hand)

1

Dripping water or condensation

2

objects greater than 12mm (fingers or similar objects)

2

Dripping water when tilted up to 15° from vertical

3

objects greater than 2.5mm (tools, thick wires, etc.)

3

Dripping water when tilted up to 60° from vertical

4

objects greater than 1.0mm (most wires and screws)

4

Water splashing from all directions

5

Limited dust protection

5

Low pressure water jets

6

No ingress of dust

6

High pressure water jets

 

 

7

Immersion up to 1 meter

 

 

8

Continuous submersion



IP 67 telemetry connector with
mating bulkhead connector


Bulkhead and connector
in mating position

Affinity Medical Technologies has designed various medical connectors to meet IP67 protection standards.  One of the more challenging configurations requires IP67 performance in both the mated and unmated positions.  Careful design enabled Affinity to offer connectors that meet IP67 without the use of any o-rings or gaskets.

Our experience can help shorten your product development cycle.  We know what materials to use and how to design connectors to meet any level of ingress protection.

If you would like to see a sample of a connector that meets IP67, contact Affinity Medical Customer Care at 949-477-9495 or email to customercare2@affinitymed.com.


Announcements and Information


Independence Day (also known as "the Fourth of July" or July 4th) honors the adoption of the Declaration of Independence on July 4, 1776 declaring our independence from Great Britain.  We hope you enjoyed the day and Celebrated the USA!

Fireworks over the
Washington Monument





Suzann Sitka and Candy Golding
the Affinity Customer Care team

Affinity Customer Care - Hours of Operation

Affinity Medical Technologies customer care specialists are available from 7:00 A.M. until 4:00 P.M. Pacific time.

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Affinity Medical Technologies

1732 Reynolds Ave
Irvine, CA 92614  USA
Phone: 949-477-9495
Fax: 949-477-9499
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