Feature: Connectors
Guide to specifying medical connectors
By David Phillips, Managing Director, Binder M
edical devices based on electronic technology range from disposable, one-time-use devices to
handheld diagnostics and bedside patient monitoring and large CT and MRI scanning systems. Whilst specifying electronic connectors
for medical applications requires the same consideration as for other applications, there are some factors unique to this market. Some basic choices concerning the electrical and physical attributes are both directly related and fundamental to connector choice. Current, voltage and the number of contacts, together with the cable diameter and level of shielding required, all have a direct infl uence on 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 T e connector’s rated and impulse voltages are defi ned 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, and the expected degree of pollution. T ese factors determine the physical dimensions of the connector. T e current-carrying capacity of a
connector denotes the current that can be carried continuously and simultaneously through all its contacts, and is determined by IEC 60512-5-2. Current-carrying capacity is not fi xed and decreases with increasing ambient temperatures. Certain applications such as MRI
equipment call for shielding against electromagnetic interference (EMI), necessitating screened cable systems that require connectors with good shielding characteristics, off ered by metal-bodied or metalised plastic connectors.
28 December 2021/January 2022
www.electronicsworld.co.uk
Locking systems and ingress protection How oſt en the connector will be mated and its IP protection requirements have a major infl uence on the type of mating system; the chosen method will most likely have a big impact on connector cost. T e IP rating determines the degree of protection from 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 unmating and have excellent IP performance, but, on the downside, they are generally quite expensive, especially the metal types. Push-pull connectors can be expensive,
too. However, plastic versions have reduced costs and provide quick mating and IP67 protection, with some protection against accidental unmating. Snap-in and bayonet connectors
provide quick and simple mating and are generally the cheapest. Recent
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