Electromagnetic Interference (Emi) - Keithley 6430 Instruction Manual

F-16 Measurement Considerations

Electromagnetic Interference (EMI)

The electromagnetic interference characteristics of the Model 6430 comply with the electro-
magnetic compatibility (EMC) requirements of the European Union as denoted by the CE
mark. However, it is still possible for sensitive measurements to be affected by external
sources. In these instances, special precautions may be required in the measurement setup.
Sources of EMI include:
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The effect on instrument performance can be considerable if enough of the unwanted signal
is present. The effects of EMI can be seen as an unusually large offset, or, in the case of
impulse sources, erratic variations in the displayed reading.
The instrument and experiment should be kept as far away as possible from any EMI
sources. Additional shielding of the instrument, experiment and test leads will often reduce
EMI to an acceptable level. In extreme cases, a specially constructed screen room may be
required to sufficiently attenuate the troublesome signal.
External filtering of the input signal path may be required. In some cases, a simple one-pole
filter may be sufficient. In more difficult situations, multiple notch or band-stop filters, tuned to
the offending frequency range, may be required. Connecting multiple capacitors of widely dif-
ferent values in parallel will maintain a low impedance across a wide frequency range. Keep in
mind, however, that such filtering may have detrimental effects (such as increased response
time) on the measurement.
Radio and TV broadcast transmitters.
Communications transmitters, including cellular phones and handheld radios.
Devices incorporating microprocessors and high-speed digital circuits.
Impulse sources as in the case of arcing in high-voltage environments.