Frequency Response Curve; Measuring Probe, Directly Earthed - Philips Pm 3342 Manual

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Connect the pulser to BUl via a 1
5 attenuator
(e.g. Tektronix cat. no. 011 — 0060 — 00) and a
50-Ohm pad (e.g. XE 101.96 order no. 4822 263
60013) and apply the calibration voltage of the basic
oscilloscope (80 V) to the pulser. Adjust the pulser by
turning its knob clockwise so that its output voltage
instantly obtains the correct value.
Select C218 so that the rise time is minimum
(TIME/cm: .OS µsec/cm and "MAGN": X5, i.e.
10 nsec./cm in total) and that the overshoot does not
exceed 1%.
To check the overshoot, the time coefficient of the
basic oscilloscope should be adjusted to 1 µsec./cm.
Apply asquare-wave voltage with a frequency of
.3 Hz respectively 20 Hz and a rise time of ~ 25 nsec.
Check that in both cases the display shows no tilt.
2. Channel B
— Set the knobs mentioned below to the following
positions:
"V/cm" (SK10) to ".O1".
"V/cm" (RS) to "CAL. ".
"MODE" (SKS) and "TRIGG." (SK6) to —B".
Apply a 40-mV square-wave with a rise time of
5 25 nsec. to BU2.
Adjust the frequency to 200 Hz and the time base
to 2 msec./cm
Select C317 and R363 so that optimum squarewave
display is obtained.
Increase the frequency to
to 50 µsec./cm.
Select C315 and R355 so
display is obtained.
Increase the frequency to
to 2 µsuc./cm.
Select C311 anal R335 so
display is obtained.
Connect the pulser to BU2 via a 1 5 attenuator
and a 50-Ohm pad (see point F1) and apply the
80-V calibration voltage.
— Select C318 so that the rise time is minimum
("Time/cm": .OS µsec./cm and "MAGN." :XS, i.e.
totally 10 nsec./cm) and that the overshoot does not
exceed 1%.
To check the overshoot, the time coefficient of the
basic oscilloscope should be adjusted to 1 µsec./cm.
Apply asquare-wave voltage with a frequency of
.3 Hz resp. 20 Hz and a rise time of < 25 nsec.
Check that, in both cases, the display shows no tilt.
10 kHz and the time base
that optimum squarewave
100 kHz and the time base
that optimum squarewave
G. FREQUENCY RESPONSE CURVE
After adjusting the square-wave response of both chan-
nels (see F1-2), the —3 dB paint of the amplifier should
lie at a frequency above 50 MHz. The frequency res-
ponse curve can be measured with e.g. the PHILIPS
A.M./F.M.-generator GM 2621 and the PHILIPS
H.F.-millivoltmeter GM 6025. Check at the input of
both channels that the voltages required for the mea-
surement of the frequency response curve are equal.
For this, connect the measuring pin of the probe to the
centre contact of the A.C./D.C. switch; the casing of
the measuring probe should be directly earthed, so
without the use of the earthing cord (as in Fig. 9).
Fig. 9. Measuring probe, directly earthed
1. Channel A
— Set the knobs to the positions mentioned under Fl.
— Connect output socket H.F. II of the GM 2621 to the
input of channel A via a terminated 50-52. cable.
A 50-52 terminating plug XE 101.96 (code nr. 4822
263 60013) can be used.
— Adjust the frequency to 4.5 MHz and adjust the
generator voltage so, that a deflection of 6 cm is
obtained.
— Increase the frequency to 50 MHz.
With the same value of the input voltage, the deflec-
tion should exceed 4.2 cm.
2. Channel B
— Set the knobs to the positions mentioned under point
F2.
— Connect the generator to the input of channel B and
check the frequency response curve in the same way
as indicated for channel A.