D-8
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6482-901-01 Rev. A / August 2012
Appendix D: Measurement Considerations
Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual
Electromagnetic interference (EMI)
The electromagnetic interference characteristics of the Model 6482 comply with the
electromagnetic 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:
•
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.
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 different
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.
Summary of Contents for 6482
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