Boonton 52000 Series USB CW Power Sensor User Manual
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Other Information
Other useful information
The following sections provide some useful information about power
measurement and your USB sensor.
What is zeroing?
Zeroing is a measurement process that ensures that the sensor
indicates as close as possible to 0 watts when no power is applied.
This ensures that the sensor gives the best possible linearity.
Due to the very low voltages that are measured by the analogue to
digital converter in the sensor, some averaging is necessary and the
process takes about eleven seconds. The zero should be re-measured
periodically for best accuracy at low power levels. It should also be
re-measured after connecting the sensor directly to equipment that
is at a significantly different temperature than the sensor, when the
sensor has reached operating temperature.
It is only necessary to re-zero if the power indicated when no power
is applied to the sensor is worse than -55 dBm. A poor zero affects
lower power measurements more than larger ones. Excessive zeroing
in automatic measurement programs is not recommended as it can
significantly increase program run times.
Pulse measurement and setting the duty cycle
The duty cycle facility is used to measure the ‘pulse power’. This is the
power measurement while an RF burst is present, when the signal is
a gated burst of a sinusoidal RF signal - for example a radar pulse.
The sensor is calibrated to measure average power, and provided the
pulse repetition rate is sufficiently high, a measurement of the pulse
power can be obtained from the average power.
Certain assumptions are made about the RF burst, and these must be
met if the measurement is to be accurate. The burst is assumed to be
either on or off, in other words it does not take a finite time to ramp
up or down.
The ramp up and down times should be small in relation to the
on time of the signal generator. The burst is also assumed to have
constant amplitude when on. The amplitude does not ring, droop
or overshoot. If the pulse does not have these attributes, then the
accuracy of the result is not valid.