Power Meter NRVS
Power, level and voltage measurements from DC to 40 GHz
• Accurate, general-purpose,
easy-to-use
• Intelligent measuring heads:
just plug them in and measure
• DC frequency input for tracking
frequency response correction
•Analog output
• Remote control of all functions
via IEC/IEEE bus
Uncompromizing technology and
ease of operation make the NRVS an
ideal instrument for any kind of power
measurement in manifold laboratory
and system applications. Thanks to its
unique measuring heads with calibration data memory and temperature
sensor, which make adjustments by
the user superfluous, the NRVS measures at all times with high accuracy
and free of operator’s errors.
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The range of measuring heads includes thermal power sensors as well as highly sensitive diode power sensors, peak power
sensors, probes and insertion units for voltage measurements. The NRVS covers a power span from 100 pW up to the
kW range. In addition to the power sensors, all voltage probes of the URV5-Z series can be used.
Readout
Measurement results, units and various
items of information are displayed on a
large 41/2-digit LC display in three
steps of resolution.
All standard units of measurement or
relative modes can be selected. A highresolution bargraph indicator with selectable scaling or autoscaling permits
quasi-analog display of measured values with any unit or resolution.
The characters „PEP“ or „PUL“
preceding the numerical value denote the maximum envelope power (measured with a
Peak Power Sensor of the
NRV-Z3x series) or the pulse
power, respectively. The pulse
power is a calculated peak
value for RF bursts with rectangular envelope. It is based on
the duty factor and the average power value. Pulse power measurements can be
made using thermocouple
sensors as well as diode power sensors operated in the
square-law region.
Operation
Operation of the power meter is to a
great extent via selfexplanatory menus
so that the user will hardly ever have to
refer to the manual. For setting the instrument rapidly to a specific status, 20
complete setups can be stored. A selectable write protection prevents inadvertent alteration of stored setup data.
Measurement rate
The attainable measurement rate not
only depends on the type of measuring
head used but also on the setting of the
averaging filter, which must be
matched to the measurement conditions. Taking into account the connected measuring head, the NRVS automatically selects the appropriate measurement rate by determining the optimum
averaging time required for a steady
readout as a function of level and selected resolution. This automatic selection
may be disabled and an averaging
time of between 4 ms and 25 s may be
set manually to measure faster than in
automatic operation or to further reduce the noise.
Measuring heads
Power meters cover a wide range of applications and a great variety of frequency and power ranges. Since suitable measuring heads are available for
the various applications and ranges,
the only factors to influence the selec-
2 Power Meter NRVS
tion of a power meter are versatility,
system compatibility and ease of operation. In these aspects the NRVS is a
top-class unit. NRVS measuring heads
are not type-specific and may therefore
be used with any unit of the R&S power
and voltmeter families.
Thermal power sensors measure the average power irrespective of the signal
shape and meet the highest demands on
accuracy. Diode power sensors are more
sensitive – they are able to measure pow-
er down to the pW range – but their
measurement accuracy is impaired when
high-level, non-sinusoidal signals are to
be measured. In the medium sensitivity
range it is recommended to use diode
power sensors with integrated attenuator, eg NRV-Z2. This combination not
only allows considerably faster level
measurements in the range between 10
and 100 µW than a thermal power sensor, it also offers better matching than a
highly sensitive diode detector and still
measures true rms power.
The maximum envelope power of modulated signals can be measured by
means of a Peak Power Sensor of the
NRV-Z3x series. These sensors are suitable for sync peak power measurements on TV transmitters and transmitter
power measurements on TDMA radio
equipment or for general applications.
Peak Power Sensors, which consist of a
fast diode detector followed by a peakhold circuit, are calibrated individually
like all Rohde&Schwarz power sensors.
Besides the NRV-Z power sensors, all
voltage probes of the URV5-Z series
can be used with the NRVS.
WF 40 103
NRVS in use:
on-site meas-
urement on TV
transmitter
Measurement accuracy
The accuracy of an RF power measurement essentially depends on the characteristics of the power sensor. Errors
encountered in this case are a function
of level, temperature and frequency
and cannot be eliminated completely
by design. Error sources of power sensors:
• Non-linearity
• Level-dependent temperature effect
• Frequency response
To be able to measure correctly under
any conditions, deviations from the ideal must be registered numerically and
considered in the measurement result.
The usual way to obtain accurate results
is to calibrate the sensors with the aid of
a generator prior to their use. The disadvantages of this method are obvious:
a calibration has to be performed before each measurement, for each individual sensor and even at intervals during a measurement (in the case of tem-
perature variations). For this reason,
Rohde&Schwarz has for years been
producing sensors that offer great convenience to the user, although at a higher expenditure to the manufacturer. This
technique can be summarized as: plug
in and go!
All relevant parameters are measured
in the factory individually for each
measuring head and then stored in the
head. The level-dependent temperature
effect is represented as a two-dimensional characteristic with a great
number of measurement points.
Each measuring head comprises a temperature sensor, the signal of which is
evaluated in the power meter at regular
intervals. From the measured temperature and level values, the stored characteristic yields the correction values for
the output voltage of the measuring
head. The input power is then calculated from this corrected voltage with the
aid of a transfer function which is also
stored in the head.
Power Meter NRVS 3
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