Triboelectric Noise in Medical Cables and Wires
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). 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 cable itself. Noise generated within a cable is often called handling noise or cable noise, but this type of unwanted signal is more accurately described as triboelectric noise.
What is Triboelectric Noise?
The triboelectric effect is a 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. 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.
Meeting ANSI/AAMI EC53 noise requirements for medical wires and cables requires careful material selection and design. 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 for use in critical medical applications.
Testing for Triboelectric Noise
Diagram of test set-up used at Affinity to
test for triboelectric noise in cable and wire
One of the capabilities of Affinity 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 to “test a representative sample of cable material….” Customers occasionally question why finished cables are not tested. Besides the directive to test cable material, 7’ 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
wire for triboelectric noise drop test
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 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 allowing 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.
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 also detailed in the standard. Voltage generated by the movement of the cable or wire is measured using a digital oscilloscope.
displayed on 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. Our design process begins with establishing a clear performance specification with our clients. Low noise requirements are but one design consideration. Strength, flexibility, durability and the ability to withstand common cleaning solutions are considered along with noise requirements. The best design is often a compromise which is reached in consultation with the device manufacturer.
Most diagnostic devices incorporate noise filtration or compensation; however, reducing noise at the source typically improves signal 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 pins or sockets.
Let the Affinity engineering team assist with your projects that require low noise cable assemblies or leadwires. We have the knowledge and experience to make your interconnect project successful.
Every company relies on their accounting team to keep on top of financial matters and keep the business running. At Affinity Medical, one of those that we rely heavily on is Syeda Meherunnisa.
Syeda joined Affinity Medical a little over two years ago. Her previous position was with a major software company where she managed accounts payable, accounts receivable and conducted internal audits.
Reporting directly to our President and CEO, Mary Phillipp, Syeda adapted quickly to Affinity. She immediately took charge of customer and vendor accounts, helping reduce past due receivables. She also helped implement more efficient procedures within her department.
Syeda proved she is a “multi-tasker” by getting married, earning her degree in Accounting, having her first child and completing her Masters degree in a very short time. In addition, she has qualified for and is considering taking the CPA exam in the future.
Syeda works hard to keep
Affinity accounts up-to-date
While Syeda describes herself as a “bookkeeper”, her many tasks at Affinity Medical include accounts payable, accounts receivable, financial statements, hourly payroll and internal audits. Syeda takes full responsibility for her job and personally delivers any last minute checks to the post office to be sure our vendors receive payment on time.
Syeda often steps out of her accounting role at Affinity to help out wherever needed. She is one of our trained Internal Auditors, has gone through Lean Manufacturing training and is a member of one of our process improvement teams.
When asked what she likes about her job at Affinity Medical, Syeda said, “I enjoy the variety in my daily activities and appreciate the flexible hours. All of the people at Affinity Medical are easy to work with which makes it nice to be here.”
Syeda works closely with
Affinity’s President Mary Phillipp
Syeda came to the United States in 1992 and graduated from Mathar High School while living in Chicago with her family. She returned to her native India in 1994 to complete her university studies. After earning her degree, she moved back to the states in 2000 with her new family. Syeda now lives in Orange County with her husband and two children: a 9 year old son, Ahmed, and a 2 ½ year old daughter, Aysha.
Syeda is dedicated to her family and every weekend takes her son to religious school and his many soccer and basketball games. She is an avid reader of biographies and financial magazines including Business Week. Every other weekend, Syeda and her extended family have dinner and watch movies together during “family night”.
Everyone at Affinity appreciates Syeda, not only for the great job she does in accounting but also for her cheery disposition.
Occasionally, it may be desirable to update cables in the field with a new style connector. This can happen when a manufacturer introduces a new device yet has a large installed base of cables with an incompatible connector. One option is to replace all the cables in use: another is to modify the legacy cables in the field.
Field assembled connector has the
look and feel of a molded connector
Affinity has designed a number of Field Termination Kits. Each is designed to be installed by either the manufacturer’s service team or a biomedical engineer. The field installed connector is designed so that once terminated to the cable and assembled, it is difficult to remove or disassemble. The finished assembly has the look, feel and performance of an overmolded connector.
If you would like more information or a sample of a Field Termination Kit, contact the Affinity Customer Care team at 1+ 949-477-9495 or via email at Customercare2@affinitymed.com.
Visit Affinity at MEDICA 2008
Affinity Medical Technologies will be exhibiting once again at MEDICA 2008, the world’s largest medical exhibition and trade fair, November 19th – 22nd, in Dusseldorf, Germany. Visit us in Hall 9, Row C, Stand 74.
The Pilgrims arrived in North America in December 1620 so the first Thanksgiving was celebrated in the fall of 1621.
The first Thanksgiving dinner was held in Plymouth Massachusetts with about 90 Wampanoag Indians joining the Pilgrims for their feast.
Thanksgiving Holiday Schedule
Affinity Medical will be closed Thursday, November
27th and Friday, November 28th to celebrate the Thanksgiving Holiday.
May you and your family have a very happy and
Connect with people who care:
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 Monday through Friday, except National Holidays. You may reach all Affinity team members by phone at +1 949 477 9495 or by email. Email addresses are first initial followed by last name @affinitymed.com.
Affinity Medical Technologies
1732 Reynolds Ave
Irvine, CA 92614 USA
Phone: +1 949 477 9495
Fax: +1 949 477 9499