Network isolator

Network Isolators form a galvanic separation point with an increased dielectric strength within a copper -run Ethernet data line. Here high-frequency AC voltages in the used for the data transmission frequency band is transmitted with minimal losses on the principle of electromagnetic induction. Due to this transfer principle require network isolators not have its own power supply. Network Isolators currently allow transfer rates of up to 1000 Mbit / s

Areas of application

Medical

Network Isolators are used in the medical field to protect the patient from leakage currents. The network connection between an active medical device and an Ethernet network or a non- medical device such as an office PC or laptop, is thereby placed in accordance with standard IEC EN 60601-1 ( third edition ) for medical electrical equipment and systems as a potential source of danger, the cause as a result of voltage differences between the Erdpotenzialen the connected network components for a patient may be hazardous leakage current. Such voltage differences may be caused within the cable management but also by a faulty installation eg in case of wrong assignment or case of metallic contact between the screen and data lines of a damaged cord and live parts.

Network Isolators can be used as an accessory or part of a medical electrical device or system. Network Isolators are themselves subject in the medical electrical system, although the requirements of EN 60601-1 and EN 60601-1-2, but are not medical devices according to the Medical Device Directive 93/42/EEC, in themselves as they fulfill no therapeutic or diagnostic purpose. However, the manufacturer of the network isolator can display it as a general accessory of a medical device on the market. He would also be a medical device under the Medical Devices Act. They are as individual units normally not the obligation to conduct a safety inspection ( STK), unless this is consisting requested by the manufacturer of the network insulator or the medical electrical system from network isolator and active medical device in the accompanying documents.

However, if the network isolator has been brought as a medical product on the market, this will facilitate the manufacturer of the medical system, the determination of compliance. This, only 10 MPG, Section 1 must be reviewed in accordance with § whether all sub-systems of the medical device system are used according to their purpose, and they influence each other and do not adversely from the outside. This is recorded in writing by a simple statement.

However, the Medical Devices Act allows the operator of an active medical device, pursuant to § 12 MPG, the so-called in-house production to produce a medical electrical system itself. After passing through the simplified conformity assessment procedure, the risk assessment of the new system, measurements of electrical safety and clinical evaluation by a physician, the operator is allowed to use the system for their own needs in their own premises. For the use of a network isolator, this means that compliance with the limit values ​​according to EN 60601-1 and EN 60601-1-2 must be ensured in the current version. This is usually possible only by demonstrating a standard audit by an accredited testing laboratory. However, this method is much more responsibility in the " self- producers " as in the above variant, since in the former case he must only verify that all medical devices are operated and used in the area of ​​intended use.

Network isolators should be placed as close to the medical device. They are often used in the medical field, together with isolation transformers, which also serve to protect the patient, but should be protected from excessive currents from the power supply system in the event of an insulation fault.

Other areas of application

Network isolators are also used in many other technical equipment in order to achieve electrical isolation between the connected devices, such as:

• For measuring and monitoring devices in electrical test bays, which are over Ethernet with a control center in conjunction
• For redundant server systems, which are connected over distances of up to 100 meters using copper cabling
• For copper- based network connections in the private or commercial sector, which are vulnerable to inevitable differences in potential between buildings or parts of buildings, but in which a connection via fiber-optic cables appears to expensive
• In general, as the sheath flow filter for Ethernet connections

Technical Requirements

From the international standard IEC 60601-1 ( 3rd edition ) for medical electrical equipment and systems and their national counterparts such as DIN EN 60601-1, OEVE / OENORM EN 60601-1 arise for network isolators high demands on the technical design of isolation. There, much higher demands are made, as in the applicable in non-medical standard IEC 60950 ( Information technology), as is assumed, may be that a patient is unconscious, anesthetized or immobilized and thus there is an increased need for protection for him.

For medical devices or systems have two independent means of protection for patient protection (English Means Of Patient Protection = MOP ) required by the IEC 60601-1 (3rd edition). A network isolator can form from its insulation structure one or two protective measures for patient protection depends. In the case of only one MOPP a second protective measure for the unit concerned must be taken, for example by a fixed equipotential bonding conductor.

Compliance with the requirements of the applicable standards and guidelines, in particular the IEC 60601-1 confirm producers through their own CE statements and / or by independent testing laboratories test certificates. Whether a network isolator on one or two mops does not go under the Certificates, however, generally produced and depends on the combination of realized clearances and creepage distances, the structure of the insulation and dielectric strength. From the dielectric strength alone - required 1.5 KV (AC ) for a MOPP 4 and KV (AC ) for two MOP - can not provide information about the number of realized mops are derived.

Unshielded cable connections that are sometimes given as an alternative to the use of network isolators, unfold according to IEC 60601-1 not sufficient protection, as well as the data lines themselves can cause hazardous voltages.

The galvanic isolator elements used to network cards and other according to IEC 60950 -built active network components do not meet the requirements of a galvanic isolation device as defined in IEC 60601-1, both because the shield is connected and all the other, the insulation structure is usually not the strict requirements of corresponds to IEC 60601-1 and can therefore in the medical field network isolators do not replace.

The transmission quality of a network isolator can be obtained with the standard in the networking parameters for cabling links determine (eg insertion loss, return loss, near-end crosstalk ).

The determination of a network isolator is to prevent any direct electrical connection between the connected devices. Therefore, only the data lines and the cable shield must be electrically isolated.

Designs

Network Isolators are available in different designs, as an external device in its own housing, as built-in versions for device manufacturers and integrated into wall outlets for networks.

Swell

• Hospital IT Journal issue 05 /2008
• DeviceMed Edition 10/2008
• Meditronic Journal, Issue