Boonton 4240 RF Power Meter - Manual (Page 13)

Boonton 4240 Series RF Power Meter
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ual Independent Channels. When equipped with the optional second measurement channel, the
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• optimized through the use of
lectable filtering. Filter times can be adjusted up to 20 seconds maximum in 50 millisecond
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ne-third of the sensor's dynamic
range are valid only for non-modulated signals. In the RMS region, linearity is excellent, and any
overload headroom of more than 5 dB for continuous signals. The dynamic range in the RMS
detecting, they provide true RMS response over their entire range. Very high peak powers (15 to
be stored in the instrument's non-volatile
correction
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D
instrument can display two CW signals simultaneously. Each channel is calibrated and all channel
parameters are channel-independent.
Selectable Ranging. Any of seven measurement ranges, or autoranging, can be selected during
instrument setup. The selection will be held until it is changed, or until the instrument is turned
off. When measuring signals with levels that fall within a narrow range, selecting one specific
instrument range may reduce measurement time. Autoranging is useful if the RF signal level is
unknown, or if RF signals with widely varying levels are to be measured.
Selectable Filtering. Measurement speed and display stability can be
se
increments.
Zeroing. Automatic zeroing (nulling of offsets for the sensor and input channel) is done
independently on each range to eliminate zero carryovers.
Power Sensors.
A wide range of diode and thermocouple power sensors for both coaxial and
waveguide applications are available for use with the Model 4240. Frequency Calibration factors
traceable to NIST standards are stored in each power sensor’s EEPROM and downloaded to the
instrument. Data sensor adapters are supplied with the Model 4240, however, the power sensor
must be ordered separately.
Diode sensors measure the voltage across a precision resistor, using specially selected diodes.
Detection is square law (true RMS) over approximately the lower two-thirds of the sensor's
dynamic range, and peak detecting over the upper portion. Because the instrument is calibrated
for sine waves over the entire range, measurements at the top o
signal type can be measured. The diode range has been extended into the peak detecting region
with the use of real time shaping for the diode curve. When coupled with the high sensitivity of
the diode, such shaping allows a dynamic range of 90 dB. Diode sensors are rugged and have an
region can be extended further through use of an external attenuator.
Thermal sensors measure the voltage developed across a dissimilar metal junction caused by the
thermal gradient generated by the RF power being measured. Because these sensors are heat
30 watts) can be accommodated for very short duty cycles and still provide valid results. The
dynamic range is 50 dB. Thermal sensors are not as sensitive as diode sensors.
The data sensor adapter contains non-volatile memory for storage of the calibration data. In
ddition, calibration data for up to four sensors can a
memory. The user can enter both the linearity and high frequency sensor calibration correction
data which are supplied with each sensor. For sensors ordered with the Model 4240, the
calibration data is loaded into the data sensor adapter prior to shipment. When the frequency of
the RF signal to be measured by one of these sensors is entered, the instrument looks up the
ppropriate calibration factors, interpolates as necessary, and automatically applies the a
to the measured value. Calibration factors for sensors ordered with the instrument are stored in the
plastic pouch attached to the inside of the instrument's top cover.
Built-In Precision Calibrator. A 50 MHz step calibrator, traceable to NIST, enhances
measurement accuracy and reliability. The user-selectable automatic calibration routine calibrates
most sensors and the instrument in steps over the full dynamic range.
General Information
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