I’d like to welcome guest blogger Dara McLain, who is the EMC engineer, Program Manager Interference Investigations for Philips Healthcare. Dara has extensive experience and some excellent “Best Practices.” After reading her blog below, please click on "comments" and let us know what you think. 

Power Is More Than Just Plugging Into an Outlet
Hospital power isn’t something that everyone views as an EMC issue. I can assure you it is.

Surges and sags in voltage, 60Hz jitter, and high transient spikes can cause burned out power supplies, spontaneous reboots, and malfunction of programmed operations. Large conduits of high voltage wires can produce magnetic fields that will interfere with all kinds of devices, even when enclosed in ceilings, or walls.

Managing your facility for the prevention of interference should include power quality surveys, especially in very old hospitals, where electrical wiring has been kludged and large portions were added via the “spaghetti method,” Much of this wiring was installed with very old electrical standards; the wire gauge is too small for the circuits they power, there are no ground wires back to the panel, etc.


When a new large system is purchased, is the electrical upgraded to handle the load? What else in the area will suffer? Where is this new equipment being installed? Will it generate EM disturbances that can interfere with ultrasound? Telemetry? Other systems?

If the equipment is not rated as medical equipment, such as a UPS, or HVAC equipment, I can assure you that it is not tested to the same standards as medical equipment. What type of guarantee does the manufacturer give you that it won’t interfere? You should be asking this question.

Electrical work is more than likely done in the ceilings. Are these workmen aware of the critical wiring up there, such as telemetry networking? Biomeds are responsible for the continued performance of medical devices and systems. You would not allow just anyone to work inside an expensive device without assuring they did not damage it—why would you allow it around your 1.5 mil telemetry system?

Your hospital’s power distribution is generally the facility department’s responsibility. Help them understand how they can avoid causing problems within your realm of keeping medical equipment in good running order.

Surveys cost around $2,500. You could spend far more in replacement parts or devices, and/or investigative services.

By Dara McLain, EMC engineer, Program Manager Interference Investigations, Philips Healthcare. E-mail: [email protected]

You can also read Dara's "Fine-Tuning Your Environment" article in the February 2006 issue of 24×7.


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