The watts calculation is simply the voltage squared divided by the
given impedance.
The calculation of dBm is slightly more complicated, according to the
following formula:
where V is the measured voltage, R is the programmable impedance,
and Pr is 1 milliwatt. The log calculation is to the base 10.
The impedance used for watt calculations is remembered separately
from the impedance used for dBm calculations. To set the impedance
references, go to the Analyzer Only panel and select dBm or Ω for the
main measurement units using the upper left soft key. Then the
reference impedance for the selected unit will be shown across the
center of the display and the AMPLITUDE controls may be used to
change it.
Time and Frequency units
.
Hz – hertz, basic unit of frequency (1/sec)
.
s or sec – seconds, basic unit of time
.
% - percentage variation in frequency
.
∆% - percentage deviation from ideal frequency
Hertz (abbreviated Hz) is the basic unit of frequency. It is a count of
the number of cycles a waveform goes through in a second. It is the
reciprocal of the number of seconds required for one cycle of a
waveform.
The % (percent) unit is used in the Wow and Flutter measurement
function to measure the variation in frequency. The Wow and Flutter
detector measures the frequency variation and reduces it to a number
in hertz, according to the selected detector and statistical choices. This
variation is then calculated as a percentage of the 3 kHz or 3.15 kHz
intended frequency using the following formula:
where D is the frequency deviation and F is the intended frequency.
dBm = 10 log
V
2
/R
Pr
()
% = abs
D
F
()
100
& For
information
about the dBm
and dBu units, see
page 3-29.
& For information
on moving among
the panels, see
page 4-1.
3 Operation
Operational Overview Units
ATS-1 Dual Domain User's Manual 3-31
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