Philips PM 6670 Operating Manual page 17

19
Count measurements
There are three different count modes:
Manual
Gated by B
_J L_
Start - stop by B
The counter totalizes events
during the time interval
between realising and
depressing the DISPL HOLD
pushbutton. An event is
defined as a positive-going
slope.
The counter totalizes events
at input A, between the
leading and trailing edge
(SLOPE released) of the
input B signal.
The counter totalizes events
at input A, between the
start and stop event at
input B.
1 .Make the preliminary settings.
2.Select the appropriate COUNT mode.
3.Connect the signal to be counted to input A.
4.Depending on the shape of the input signal, use
either AC mode or push the trigger level control
for input A (DC mode) and set the trigger level
approx to half the amplitude of the signal to be
counted.
5.Connect the control signal (if used) to input B.
6.Set the trigger level/sensitivity control for input B
to suit the control signal (if used).
7.At 10® counted events, the display is full. When
further events are totalized, truncation of the LSD
starts and the unit indicator now indicates
exponents. If the ps/kHz indicator glows read 10®
pulses, for ms/MHz read 10® pulses and for
s/GHz read 10® pulses.
Hold-Off (PM 6671 only)
To avoid false stop triggering on spurious or unwanted
signals, the hold-off function could be used. To display
the set hold-off time, select TIME INT SINGLE A-B
and push CHECK.
Ratio measurements
1 .Make the preliminary settings.
2.Select RATIO A/B.
3.Connect the signals to input A and input B. The
frequency range is 0...1 OMHz.
4.Decrease the sensitivity until no triggering at all
occurs.
5.Increase the sensitivity again, until a stable
reading is obtained.
6.Set the measuring time to give optimum resolution
and measurement speed.
To obtain full frequency range on PM 6671...72,
a ratio measurement can be made in the FREQ A or
C mode:
1 .Make the preliminary settings.
2.Select FREQ A or C.
3.Connect the signal with the highest frequency to
input A or input C (PM6672).
4.Connect the other signal to input D and set the
switch to EXT STD IN. Note that the frequency
range at input D is 50kHz...10MHz.
5.Set the sensitivity for channel A.
6.Set the measuring time to give optimum reso
lution and measurement speed.
7.Divide the displayed value by 10^ (10MHz) to
obtain the correct ratio.
Time Interval measurements
There are two modes for measuring time intervals.
Single: The counter measures the time interval
between a start event at input A and a
stop event at input B.
Average: The counter measures the time interval
average of a repetitive signal that is not
synchronized with the used time-base.
I.Make the preliminary settings.
2.Select TIME INT single A-B or average A-B.
3.Connect the signals to input A and input B.
4.When measuring time intervals on a single channel,
connect the signal to input A and push COM via A.
5.Push the trigger level control (DC mode) and select
correct trigger level, e.g. 50% of the signal
amplitude for measuring pulse width or 10% and
90% for measuring rise-time.
6.Select correct trigger slopes.
7.Time interval average only:
Set the measuring time to give optimum resolution
and measurement speed.
Phase delay measurements
1 .Make the preliminary settings.
2.Select PHASE A-B.
3.Connect the signals to input A and input B.
4.The input voltages must exceed lOOmVRMS
5.If any of the input voltages exceeds . Push
ATT x10 for the appropriate channel.
6.Do not change the sensitivity setting.
7.Try to obtain approx the same signal amplitude
to both inputs. Use ATT xlO or an external
attenuator (preferable resistive) if necessary.
8.Do not use oscilloscope probes as they introduce
extra phase delays.
9.Invert the trigger slope for channel B when measur
ing phase angles around 0° , thus 180° will be
added. Unstable readings caused by phase-jitter are
now avoided.
lO.Set the measuring time to give optimum reso
lution and measurement speed.