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82
RF
Figure
1.
82RF
High
Frequency Probe
5.
Connect
the probe's
ground
lead
to signal
common.
CAUTION
To
avoid short
circuit
damage,
never
connect
the
probe
ground
lead to a potential
other than
ground
unless the voltmeter
is
equipped
with a
floating
low
Input
(i.e.,
not grounded).
6.
Contact
the
measurement
point with
the
probe
tip
and
read the
rms
voltage
level
directly
from
the
voltmeter.
Measurements above
100
MHz
require
the
use of the
BNC
adapter
and
a
terminated
system.
CAUTION
To
avoid
probe
damage
the
dc
components
or
the input signal
must
not
exceed 200
volts,
including
transients.
30V
ac
rms and 200V dc
are the
maximum
inputs
to
the probe.
These
specifications
allow
measurements
of
an ac
signal riding
on
a
dc
voltage
of
up
to
200V.
When
this
type
of
measurement
is
being
made,
the input capacitor
will
charge
to
the
peak
value
of
ac
plus dc.
If
the
dc
level
is
then
changed
by
more
than 200V, the
resulting
transient
may damage
the probe.
The chance
of
damage
can be minimized by
discharging
the input
capacitor
at
the
end
of
each
measurement.
This
is
done by
momentarily
touching
the
probe
tip
to
the
ground
clip.
THEORY
OF OPERATION
Circuitry within the
82RF
consists
of
a capacitor-coupled
rectifier circuit
which
responds
to the
peak
value of the
input
waveform.
The
output
is
positive polarity
dc
voltage
which
is
calibrated
to
be equivalent
to
the
rms
value of
a
sine
wave
input.
See Figure
2.
Resistors,
R
1
,
R2
and
R3
are selected to
properly
scale
the
dc output
when
connected
across a
dc voltmeter having a
10
MH
input
resistance.
Figure
2.
82RF
Simplified
Circuit
Diagram
2
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