Agilent Technologies 3458A Calibration Manual page 35

turn off sources of high EMI. It may be necessary to test in a shielded
room.
•
Ground Loops: Ground loops arise when the multimeter and the circuit
under test are grounded at physically different points. A typical example
of this is when a number of instruments are plugged into a power strip
in an equipment rack. If there is a potential difference between the
ground points, a current will flow through this ground loop. This
generates an unwanted voltage in series with the circuit under test. To
eliminate ground loops, ground all equipment/circuits at the same
physical point.
•
Internal Temperature: The internal temperature of the 3458A
under test must be within 5
If the multimeter's temperature is not within 5
multimeter's fan operation and clean the filter. Also, make sure
that you adjust the operating environment such that the ambient
temperature is at or very near 25
results if you maintain your environment close to 25
choose to verify performance when the temperature is not within
°
5 C, you must recalculate all test limits based on the temperature
variation beyond the 5
calculated without additional temperature coefficient errors added.
°
C of its temperature when last adjusted.
°
C. You will achieve the best
°
C limitation. The published test limits were
Chapter 4 Performance Verification Tests
°
C first check the
°
C. If you
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