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Chapter 4 - Electromagnetic Compatibility And Medical Devices: Susceptibility to Conducted Electromagnetic Interference

By David Prutchi & Michael Norris
From Design and Development of Medical Electronic Instrumentation

Susceptibility to Conducted Electromagnetic Interference

EMI susceptibility tests for medical devices conducted according to IEC-61000-4-6
involve injecting RF voltages onto the power line and bulk RF currents into other signal
cables. A current probe is clamped around the entire cable bundle, and radio-frequency

Warning!   This is a dangerous device! It produces high voltages that can cause very painful or lethal electrical shocks. In operation, the spark gap produces significant levels of ultraviolet radiation, which must be shielded to prevent eye damage. In addition, spark discharges can ignite flammable or volatile atmospheres. Finally, the EMI levels generated by this circuit are certainly above what the FCC likes to see dumped into the atmosphere. Thus, this generator should only be operated inside a properly shielded room.


Figure 4.24 In this experimental wideband generator, a push-pull oscillator drives a TV flyback to produce 15 to 20 kV dc. This high voltage is used to charge two transmission line capacitors, Z1 and Z2, which are etched on a double-sided PCB.

energy is injected. The frequency range for immunity tests is 150 kHz to 80 MHz, and the
injected RF has an amplitude of 3 V. Figure 4.26 shows a typical test setup. The device
under test is placed in the approximate center and 10 cm above a reference ground plane,
and is powered and operated in a normal configuration. Injection of RF into the ac power
leads is performed with the coupling network shown in Figure 4.27. Testing of signal input
leads is performed via a current clamp on the leads.

© 2005
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Signal Generators
Signal generators and waveform generators are used to test and align all types of transmitters and receivers, to measure frequency and to generate a signal, waveform or noise source. Signal generators can use AC energy, audio frequency (AF) and radio frequency (RF) to function.
Spectrum Analyzers and Signal Analyzers
Spectrum analyzers and signal analyzers display raw, unprocessed signal information such as voltage, power, period, wave shape, sidebands, and frequency. They can provide the user with a clear and precise window into the frequency spectrum.
Isolation Amplifiers
Isolation amplifiers electrically isolate input and output signals, often by inductive couplings. Isolation amplifiers, or iso-amps as they are sometimes called, may be used to protect components from potentially dangerous voltages or to amplify low-level analog signals in applications with multiple channels.
Medical Equipment and Supplies
Medical equipment and supplies are used in medical, dental, hospital, pharmacy, and clinical laboratories.
Topics of Interest

Susceptibility to Fast Power Line Transients IEC-61000-4-4 deals with the immunity that devices must present against repetitive fast transients that may be induced, for example, by inductive...

Susceptibility to High-Energy Power Line Transients IEC-61000-4-5 deals with large surges that may directly reach the device’s power line because of lightning. The surge pulses for this test...

10.1 Introduction 10.1.1 Transient Types Over the last 20 years traditional EMC testing has concentrated on radiated and conducted emission and susceptibility testing. This is carried out by...

Differential signaling is the primary choice for a low power RF interconnection because it provides superior immunity to noise by offering twice the signal swing for a given supply voltage. The out of...

Electromagnetic Interference in Medical Devices An overview of EMI issues can help develop suitable electromagnetic compatibility requirements and other solutions to minimize risk to patients.