68 53220A/53230A User’s Guide
3 53220A/53230A Measurements
Specifying the External Reference Frequency
When the reference oscillator source is EXTernal as set by either
SENSe:ROSCillator:SOURce or SENSe:ROSCillator:SOURce:AUTO, the
lock frequency of the external signal (to which the internal oscillator is tuned)
must be indicated using the command:
[SENSe:]ROSCillator:EXTernal:FREQuency {1E6|5E6|10E6|
MINimum|MAXimum|DEFault}
[SENSe:]ROSCillator:EXTernal:FREQuency? [{MINimum|MAXimum|
DEFault}] (query form)
The external reference frequency setting is 10 MHz when the counter is
shipped from the factory or following the SYSTem:SECure:IMMediate com-
mand. The setting is stored in non-volatile memory and is not changed after a
reset (*RST) or instrument preset (SYSTem:PREset or Preset key).
External Reference Example
The following example configures the counter to tune to an external reference
if present, and the expected external frequency is 10 MHz.
SENS:ROSC:SOUR:AUTO ON // tune to external ref if present
SENS:ROSC:EXT:FREQ 10E6 // signal will be 10 MHz
Detecting a Valid External Reference Signal
ExtRef will appear in the top, right corner of the display when a valid (external)
reference is present. If a valid frequency is not present or was not specified,
the message “No valid external timebase” is displayed. The error is also logged in
the error queue.
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