Philips 6652C - Hints and Tips

HINTS AND TIPS
This section gives a few hints and tips about
practical procedures in operating the counter/
timers.
Measuring Time
- Low frequency signals (below 100Hz) will tend
to give unexpectedly long measuring times.
- The measuring time control for channel C mea-
surements
works in e~actly the same way as it
does for channel A.
- The measuring time potentiometer becomes a
display time control in MINIMUM/SINGLE.
For FREQ A, FREQ C, PHASE A-B and DUTY FAC-
TOR A, MINIMUM/SINGLE forces the counter to
make 1~s (PM 6652) or 2~s (PM 6654) measure-
ments
of the repetitive signal.
For PERIOD A, RATIO A/B, RATIO C/B, TIME
A-B, P WIDTH A and RISE/FALL TIME A, MINI-
MUM/SINGLE forces the counter to measure a
single complete cycle of the input signal (on
B, in the esse of RATIO A/B and RATIO C/B,
but see below).
-
For RATIO A/B and RATIO C/B, the use of MIN-
IMUM/SINGLE in conjunction with a start/stop
signal on B changes the functions to:
TOT A __fljL_ Band TOT C JljL_ B
respectively.
- MINIMUM/SINGLE has no effect in the func-
tions: TOT A/MAN, Vmax , Vmin and Vpp.
Triggering
- The AUTO trigger function will always try to
find the 50% level on signals, and will at-
tempt to offset for any DC component. If the
counter fails to trigger, because th~ AUTO
triggering feature cannot set trigger levels,
the Vmax Vmin function can be used to find
the signal's peak values. New trigger levels
can then be set via the keyboard, or estab-
lished on the potentiometers. Similarly, va-
lues found by using the potentiometers can be
examined and set as KEYBOARD levels.
- A low frequency signal (below 100Hz) will
cause problems for the AUTO feature. The
trigger levels can be set as described above.
-
If a signal contains heavy "spikes", the AUTO
feature will calculate a false Vpp. The trig-
ger levels should be set manually.
- KEYBOARD or potentiometer trigger levelset-
ting is generally recommended for:
Noisy signals < 120MHz
Burst frequencies
TIME A-B averaging
PHASE A-B
Single RISE/FALL TIME A
Single RATIO A/B
Single RATIO C/B
Single TIME A-B
Single P WIDTH A
Coupling
DC coupling is recommended for:
- Burst frequencies
- Single
RATIO A/ B
-
Single RATIO C/B
- Single TIME A-B
- Single RISE/FALL TIME A
-
ATE
Attenuation
The ATT x1 x10 control is disabled when AUTO is
in use, since AUTO selects the attenuation it-
self. The LED on the ATT control does not neces-
sarily show the attenuation in use.
In voltage measurements (Vmax Vm.in and Vpp), the
setting of the attenuator is ignored, giving the
true voltage at the input.
Use of x10 attenuation is recommended for noisy
signals, if possible.
Impedance
- When performing RISE/FALL TIME measurements,
it is important that the waveforms are as
clean as possible. Input impedances must,
therefore, be matched closely.
- The setting of the impedance control will, of
course, affect voltage measurements.
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