SUPPLEMENT MEDICAL ELECTRONICS
A quick guide to specifying medical connectors
David Phillips, managing director of Binder UK, discusses the most important aspects of connector design for medical applications to achieve optimal device performance and industry compliance
B
y their nature, medical applications are extremely diverse and cover
everything from disposable, one-time use surgical devices, through hand-held diagnostics and patient monitoring to large CT MRI scanning systems. However, while specifying electronic connectors for medical applications requires the same consideration as many other applications, there are a few that are unique to the medical market. There are some basic choices to be
made concerning the electrical and physical attributes that are both directly related and fundamental to connector choice. The current, voltage and the number of contacts, together with the cable diameter and level of shielding required all have a direct influence on the connector choice as do the physical characteristics relating to how the connector will be terminated, the method of mating and the space available both inside and outside the product.
ELECTRICAL REQUIREMENTS The connector’s rated voltage and impulse voltage are defined according to IEC60664-1 - a basic safety standard to achieve insulation coordination specifying clearances, creepage distances and solid insulation, taking into account the voltage stress and surge together with the expected degree of pollution. These factors determine the physical dimensions of the connector. The current carrying capacity of a connector denotes the current that can be carried continuously and simultaneously through all of its contacts and is determined by IEC 60512-5-2. The current carrying capacity is not fixed and decreases with increasing ambient temperatures. Certain applications as with MRI
equipment call for shielding against electromagnetic interference (EMI) and these necessitate screened cable systems that require connectors with good shielding characteristics and this can be offered with metal bodied or metalised plastic connectors.
LOCKING SYSTEMS AND INGRESS PROTECTION How often the connector will be mated and the IP protection requirements have a major influence on the type of mating system and the chosen method will necessarily have a big impact on connector cost. The IP rating determines the degree of protection to dust and liquid. Typically medical connectors are rated IP54 and above, with many being IP67 for temporary immersion in liquid. Screw connectors provide the ultimate protection against accidental un-mating and have excellent IP performance but, on the downside, they are generally the most expensive type of connector, especially in metal versions. Push-pull connectors can be expensive. However, the trend towards plastic versions has helped to reduce cost and provides a quick mating IP67 connector with some protection against accidental un-mating. Snap-in and bayonet connectors
provide quick and simple mating and are generally the lowest cost solution.
Figure 1:
Binder snap-in & bayonet medical connectors
Recent developments mean that these can now be rated up to IP67 thus providing an economic solution with high performance. New mating systems such as binder’s
just announced innovative Easy Locking Connector (ELC) provide positive mating and protection against accidental un- mating with a unique intuitive locking system featuring snap hooks. Here, the friction free connection allows for over 5000 mating cycles.
STERILISATION AND CYTOTOXICITY Medical applications are wide ranging with surgical applications requiring connectors resistant to medical sterilisation via steam autoclave, gamma radiation and gas plasma etc. However some applications require no sterilisation while others require the use of a type of material used which has been tested for Cytotoxicity (toxicity to skin) and are free of DEHP phthalates. There are a number of standards which should be considered when specifying connectors and EN 60601 is a family of standards whose scope covers the safety, essential performance and electromagnetic compatibility of Medical Electrical Equipment and Systems. It is technically equivalent to the international standard IEC 60601 and covers aspects such as vibration, shock, rough handling and finger-proofing. ISO 13485 specifies requirements for a
Figure 2:
New binder ELC medical connector
quality management system where an organisation needs to demonstrate its ability to provide medical devices and related services that consistently meet customer and applicable regulatory requirements. Naturally, medical connectors tend be expensive – but at what price is patient safety? binder offers technical and commercial assistance when it comes to specifying the right connector for medical applications.
Binder UK
www.binder-connector.co.uk T: 01442 257339
S6
FEBRUARY 2018 | ELECTRONICS
/ ELECTRONICS
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