Pendulum CNT-90 Series User Manual

Measuring Functions
■ How Does the Sync Delay Work?
The sync delay works as an internal start arm-
ing delay: it prevents the start of a new mea-
surement until the set sync delay has expired.
See Fig. 4-5.
After the set measurement time has started,
the counter synchronizes the start of the mea-
surement with the second trigger event in the
burst. This means that the measurement does
not start erroneously during the Burst Off
du-ration or inside the burst.
Fig. 4-5
Measuring the frequency of the
carrier wave signal in a burst.
■ Possible Errors
Before the measurement has been synchronized
with the burst signal, the first measurement(s)
could start accidentally during the presence of
a burst. If this would happen and if the
remaining burst duration is shorter than the set
measurement time, the readout of the first
measurement will be wrong. However, after
this first measurement, a properly set
start-arming sync delay time will synchronize
the next measurements.
In manually operated applications, this is not a
problem. In automated test systems where the
result of a single measurement sample must be
reliable, at
least two measurements must be
made, the first to synchronize the measurement
and the second from which the measurement
result can be read out.
Frequency
Modulated Signals
A frequency modulated signal is a carrier
wave signal (CW frequency = f
0
) that changes
in frequency to values higher and lower than
the frequency f0. It is the modulation signal
that changes the frequency of the carrier
wave.
The counter can measure:
f0 = Carrier frequency.
fmax = Maximum frequency.
fmin = Minimum frequency.
Δf = Frequency swing = fmax -f0.
Carrier Wave Frequency f
0
To determine the carrier wave frequency
measure f
mean which is a close approximation
of f
0.
Press STAT/PLOT to get an overview of all
the statistical parameters.
Select the measurement time so that the coun-
ter measures an integral number of
modulation periods. This way the positive
frequency deviations will compensate the
negative deviations during the measurement.
Example: If the modulation frequency is 50
Hz, the measurement time 200 ms will make
the counter measure 10 complete modulation
cycles.
If the modulation is non-continuous, like a
voice signal, it is not possible to fully
compensate positive deviations with
negative deviations.
Here, part of a
modulation
swing
may
remain
uncompensated for,
and lead to a
USER MANUAL ● CNT 9x Series ● Rev.22 February 2020
4-6

Pendulum CNT-90 Series Specifications

General

Brand	Pendulum
Model	CNT-90 Series
Category	Measuring Instruments
Language	English