HP 83480A User Manual

Increasing Measurement Accuracy
and Time-Interval Measurement
If the output of the circuit under test is current-limited, the slew rate is
determined by equation 2. An example of this slew rate limit caused by the
eect of probe capacitance is shown in Figure 9-9.
Equation 2 dV =dt = I=C
Figure
9-9.
Eect
of
probe
capacitance.
P
erhaps
you
have
connected
an
instrument
to
a
circuit
for
troubleshooting,
only
to have
the
circuit
operate
correctly
after
connecting
the
probes
.
The
capacitive
loading of
the
probes
can
attenuate
a
glitch,
remove
ringing
or
overshoot,
or slow
an
edge
just
enough
that
a
setup
or
hold
time
violation
no
longer
occurs.
Summary Minimize the eects of transient response on time-interval measurements by
following these guidelines.
 Choose an instrument and probe with a combined rise time of less than 1/3
the fastest rise time or pulse width to be measured.

Consider
probe
loading
eects
,
particularly capacitive
loading.
The
RC
time
constant
of
the
output
impedance
of the
circuit
under
test
and
the
capacitance of the probe should be very small compared to the signal rise
time
.
9-19

HP 83480A Specifications

General

Brand	HP
Model	83480A
Category	Measuring Instruments
Language	English