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Chapter 3 193
Instrument Functions: M - O
Marker Fctn
Instrument Functions: M - O
To guarantee accurate data for noise-like signals, a correction for equivalent noise
bandwidth is made by the analyzer. The Marker Noise function accuracy is best when the
detector is set to Average or Sample, because neither of these detectors will peak-bias the
noise. The trade off between sweep time and variance of the result is best when
Avg/VBW
Type
is set to Power Averaging. Auto coupling, therefore, normally chooses the Average
detector and Power Averaging. The Marker Noise function works with all settings of detector
and Avg/VBW Type, but using the positive or negative peak detectors does not gives less
accurate measurement results.
Note that the value when the Y-axis units are watts is the square of the value when the
Y-axis units are volts. For example, when the percent ratio with Y-axis units in volts is 20%
(0.2), the percent ratio with Y-axis units in watts will be 4% (0.2
2
= 0.04). When you read
the value out remotely you have to know whether you are in log (dB) or linear (percent),
and if linear, whether volts or watts.
Key Path:
Marker Fctn
Dependencies/
Couplings: Video triggering is not available when the detector is Average,therefore
marker functions that would set the detector to Average, and thus conflict
withvideotriggering,arenotavailablewhentheVideo trigger is On.
Remote Command:
See
“Marker Fctn” on page 191 for the command to select a function.
Example: CALC:MARK:FUNC NOIS turns on marker 1 as a noise marker.
CALC:MARK:FUNC? returns the current setting of marker function for the
marker specified. In this case it returns the string: NOIS.
CALC:MARK:Y? returns the y-axis value of the
Marker Noise function for
marker 1 (if Marker Noise isONformarker1).
3.2.3 Band/Intvl Power
Measures the power in a bandwidth (non-zero span) or time interval (zero span) specified
by the user. If no marker is on, this key activates the delta pair marker mode. If the
detector mode is set to Auto, the average detector is selected. If the Avg/VBW type is set to
Auto, Power Averaging is selected, other choices of detector and Avg/VBW type will usually
cause measurement inaccuracy. The active marker pair indicate the edges of the band.
Only
Delta Pair and Span Pair marker control modes can be used while in this function,
selecting any other mode (for example,
Normal or Delta) turns off this function.
Key Path:
Marker Fctn
Dependencies/
Couplings:
Video triggering is not available when the detector is Average,therefore,
marker functions that would set the detector to Average, and thus conflict
withvideotriggering,arenotavailablewhentheVideo trigger is On.
Selecting
Band/Intvl Power when the marker control function is off, normal,
or delta will set the marker control function to delta pair.