Profile Operation Mode Procedures
6-12 PN: 10585-00001 Rev. P ML2437A/38A OM/PM
Range Hold may be selected to limit dynamic range and prevent small range change
disturbances on very high speed signals. Use Range Hold 1 for measurements down to -25
dBm, and Range Hold 2 up to –10 dBm. If the display update is turned off via GPIB, only the
average is updated.
Triggered Measurements
Since non-triggered measurements are of limited use in the PROFILE mode, most
applications require triggering. For example:
1. Provide a 1 kHz square wave modulated signal to sensor A, and set TRIGGER > SETUP
> MODE to Internal A (Int A). This causes the PROFILE sweep to wait until a certain
power level is present on the sensor before starting the sweep.
2. The DELAY and WIDTH parameters, as discussed above, are the positions of the two
CURSORS. These can be set to specific locations; for example, if the signal is a 1 kHz
square wave, setting the DELAY to 250 µs places the cursor in the first cycle at the
midpoint of one of the phases. Setting the WIDTH to 500 µs sets the other CURSOR to
exactly one half-cycle later, thus allowing display of the power levels in the two phases
of the signal.
3. The dynamic range in PROFILE mode is limited to the top two ranges (the DC ranges)
of the meter. The lowest measurable power is approximately –40 dBm (diode sensors
only). If the displayed range is restricted, check that RANGE HOLD is not applied.
Note
If the modulation is turned off, then the trigger conditions will not be met and the
sweep will not continue to be updated. This is useful to ‘freeze’ a display. To
display a CW signal again, re-select CONTINUOUS trigger in TRIGGER > SETUP
> MODE.
Note
In some conditions, it is useful to view triggered signals independent of signal
levels. In these cases, provide an external trigger source into the rear panel
TRIGGER input to trigger such a measurement.
Note
If RANGE HOLD 1 is applied, the lower limit will be approximately –30 dBm. If
RANGE HOLD 2 is applied, the maximum level will be limited to approximately –10
dBm. In most triggered situations, range hold should be set to AUTO.
Note
The unique method of range changing applied in this mode means that the change
between range 1 and 2 is effected in less than 2 ms. In most cases it is not
noticeable, although there may be a slight discontinuity visible when using very
small collection periods.
Note
Due to the range-change method, if a triggered signal is not repetitive the range
change may not settle instantly, and the displayed result may be in error. This is
generally true for x-axis times of less than 6 ms where it takes more than one pass
to completely update the display.
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