3
3-15
IM 701830-01E
Before Starting Observation and Measurement of Waveforms
3.10 Compensating the Probe (Phase Correction)
When making measurements using the probe on the High-Speed Isolation Module or High-
Speed Module, make sure to phase correct the probe, first.
CAUTION
Never apply an external voltage to the COMP terminal, as damage to the instrument
may result.
Operating Procedure
1.
Turn ON the power switch.
2.
Connect the probe to the input terminal to which the signal is to be applied.
3.
Touch the probe’s tip against the COMP output terminal and connect the earth wire to the
functional earth terminal.
4.
Perform auto set-up using the procedure described on page 4-4.
5.
Insert a screwdriver into the trimmer adjusting hole in the probe and turn the trimmer so that
the displayed waveform becomes square.
Phase adjusting hole
COMP signal output
terminal
Functional earth
terminal
Explanation
Reason for probe compensation
If the probe’s input capacitance is outside the specified range, the gain will not be constant
across different frequencies, preventing display of the correct waveforms. The input capacitance
varies depending on the probe used, so the variable capacitor (trimmer) provided on the probe
must be adjusted.
Probe compensation must be performed when the probe is to be used for the first time.
Moreover, the appropriate input capacitance varies according to which channel is used, so probe
compensation is required when the probe is switched from one channel to another.
Compensation signal
A COMP signal (square waveform) of the following characteristics is output from the COMP
terminal on the front panel.
Frequency : 1 kHz
±
10%
Amplitude : 1 V
±
10%
Waveform differences
Correct waveform
Over-compensated
(gain is too high at high
frequency)
Under-compensated
(gain is too low at high
frequency)
