R&S SMJ100A, Operating Manual

Page: 253 / 874

Instrument Function
R&S
®
SMJ100A
237 Operating Manual 1403.7458.32 ─ 14
Zeroing calibrates the external power sensor by adjusting its reading at zero signal
power. For this purpose, the RF power source must be switched off or disconnected
from the sensor (see tips below). R&S power sensors automatically detect the pres-
ence of any significant input power. This aborts zeroing and generates an error mes-
sage. Zeroing can take a few seconds, depending on the sensor model; refer to the
documentation of your external power sensor for more information.
Tips for zeroing
Zeroing should be performed:
●
During warm-up after switching on or connecting the instrument
●
After a substantial change of the ambient temperature
●
After fastening the power sensor module to an RF connector at high temperature
●
After several hours of operation
●
When very low-power signals are to be measured, e.g. less than 10 dB above the
lower measurement limit.
●
Switch off the RF power source for zeroing; do not disconnect it from the power
sensor. In this way you will maintain the thermal equilibrium, and zeroing will also
compensate for the noise superimposed on the measured signal (e.g. from a
broadband amplifier).
Remote command:
:SENSe<ch>[:POWer]:ZERO
on page 567
Source
Selects the source for measurement.
"RF" Measurement source is the RF signal of the generator. The RF fre-
quency is used as the measurement frequency of the sensor and the
corresponding correction factor is used.
In this mode the RF frequency of the generator is send to the sensor
automatically if changed.
"User" Measurements source is any freely selectable source. The frequency
is entered manually under frequency (e.g. for measurement of ampli-
fier gain with 2 sensors).
Remote command:
:SENSe<ch>[:POWer]:SOURce
on page 566
Frequency
Source User only
Enters the frequency for measurement source "User".
Remote command:
:SENSe<ch>[:POWer]:FREQuency
on page 564
Level Offset
Activates and defines a level offset which is added to the measured value. This allows
e.g. an attenuator in the signal path to be considered. The offset is always entered in
dB, irrespective of the selected unit for result display.
Remote command:
:SENSe<ch>[:POWer]:OFFSet:STATe
on page 565
:SENSe<ch>[:POWer]:OFFSet
on page 565
RF Signal and Analog Modulations - RF Block