User manual

In Detail
P6015A Instruction Manual
1-9
Probe Placement
CAUTION. Probe placement can be critical in some applications.
To minimize Device-Under-Test circuit loading, the P6015A input
resistance is very la rge and input ca pacit ance is very smal l. Small
changes in capacitance near the i nput resistor will affect the
accuracy of the measurement. These changes can result from placing
the probe tip near conductive surfaces. Changes in the input
capacitance will change the probe compensation, causing the leading
edge of pulses to overshoot or undershoot the true pulse amplitude.
The time constant will not be visible on shorter pulses where the
entire top of the m easured waveform will appear to be the wrong
amplitude. Surfaces connected to the input signal will peak the
response, resulting in overshoot, while those that are static or
grounded will dampen the response, resulting in an undershoot.
To minimize the chance of changing the probe compensation, do not
allow the conductor, to which the probe is attac hed, to pass along the
side of the probe body. Keep the probe perpendi cular to the at tached
conductor or at the end of a dedi cated test lead. If the test configura-
tion does not allow this, minimize the error by readjusting the probe
compensation by connecting the probe to the calibra tion generator
that closely duplicates the physical configuration used in the ac tual
measurement.