TechArchive

Original article date: May 1998

The stringent demands of building medical equipment need special consideration. Lemo’s range of plastic electrical connectors encompass special design features to meet these untypical requirements.

The modular construction of Lemo connectors is combined with a self-latching push-pull design. This construction means that new connector specifications can often be satisfied by developing only one or two additional components.

For example in the 3P range of medical plastic connectors the plastic shell rated to IP61 (IEC529) has been designed for all applications requiring minimum weight and maximum electrical isolation as well as for steam or gas sterilisation.

In addition the insert polarisation can be determined at the time of cable assembly giving 11 options from the same identical shell. Eight different colour code rings assist with identification of the specific connector for safety purposes in addition to the insert and housing keying.

For catheter and other applications such as urological probes plastic shell connectors are combined with gold-plated contacts and the latching system. The range includes a number of shell configurations and up to 14 contacts. Shell styles include in-line plugs in-line sockets and panel and disposable sockets.

While the standard shell material (polysulfone PS) is suitable for steam sterilisation (20 cycles) others such as polyetherimide (Ultem PEI) can be substituted where more aggressive chemicals and extended steam sterilisation cycles are likely to be encountered.

A new range of connectors has been developed to provide complete electrical isolation of patients while giving full EMC screening for the protection of sensitive electrical signals. Here a metal inner shell is used and together with an earthing crown and collet system it gives 360deg screening through the connector pair. The outer shell and collet nut are made from steam-sterilisable polysulfone though other materials such as Radel polyphenylsulfone (PPSU) are available. Contact types can be coaxial triaxial multi-pole and high voltage.

The new range is compatible with the original self-latching keyed B series range of connectors which are widely used in medical applications due to the combination of the metal shell with full EMC screening. Typical applications include patient dosing systems portable patient monitoring systems and Doppler systems for cardiac peripheral vascular carotid and transcranial patient monitoring. Other applications include endoscopes depilation laser controls biometric monitoring sleep apnea analysis heat stress monitoring and scanner controls.

The standard and plug/panel socket combination throughout the size range has UL recognition. Options include:

• Multiple keys for improved security
• Crimp or solder contacts
• Reverse contacts for isolation where required
• Range of coloured strain reliefs for identification
• Range of collets to suit all cables
• Semi-latching or lanyard versions for auto-release and safety
• Coloured washers for socket identification.

This range can be supplied with plastic titanium or stainless steel outer shell. Contact options include solder PCB and crimp for low voltage (2 to 64 contact) mixed coaxial or triaxial with low voltage and mixed high voltage or fibre optic with low voltage all within the same connector. Other contact types include thermocouple contacts for temperature measurement and non-magnetic contacts.

Whilst fibre optics offer many advantages over copper conductors and a full range is available there remain many existing and potential applications where both are required. These include the combination of laser light with electrical sensor signals in blood perfusion monitoring systems.

High voltages are used in many medical applications such as ECG machines medical laser sources and general power supplies. These can be either single connectors or with multi-HT contacts.

A new 3kV DC (9kV test) connector which is only 6.5 in diameter has just been introduced. This pencil-thin connector provides space savings over HT connectors of similar rating and has its own built-in locking ring for additional safety.

Standard HT connectors are DC rated to 5 10 15 and 30kV with safety locking rings and microswitch cuts-off also available. HT contacts for mixed HT/LV connectors are rated up to 5.6kV DC.

• Lemo
• 01903 234543

May 1998