4 Input/Output Functions
Input/Output
Preset Empty after Restore Input/Output Defaults. Survives shutdown/restart of analyzer application
(including power cycle)
Min Freq: 0 Hz
Amptd: –1000 dBm
Max Freq: 1 THz
Amptd: +1000 dBm
Initial S/W Revision A.02.00
Modified at S/W Revision A.14.00
Freq Ref In
Specifies the frequency reference as being the internal reference at the rear panel input labeled EXT REF
IN, a 1 pulse per second signal at the EXT REF IN input,, external reference or sensing the presence of a
signal at the EXT REF IN input.
When the frequency reference is set to internal, the internal 10MHz reference is used even if an external
reference is connected.
When the frequency reference is set to external, the instrument will use the external reference. However, if
there is no external signal present, or it is not within the proper amplitude range, a condition error message
is generated. When the external signal becomes valid, the error is cleared.
When the frequency reference is set to Pulse, the instrument expects a 1 pulse per second signal at the
EXT REF IN input. The instrument uses this signal to adjust the frequency of the internal reference.
If Sense is selected, the instrument checks whether a signal is present at the external reference connector.
If it senses a signal within 5 ppm of the External Ref Freq (as set on the External Ref Freq softkey), it will
automatically switch to the external reference. If it senses a 1 pulse per second signal, it enters Pulse
mode, wherein the signal is used to adjust the internal reference. When no signal is present, it
automatically switches to the internal reference. No message is generated as the reference switches
between pulse, external and internal. The monitoring of the external reference occurs approximately on 1
millisecond intervals, and never occurs in the middle of a measurement acquisition, only at the end of the
measurement (end of the request).
If for any reason the instrument’s frequency reference is not able to obtain lock, Status bit 1 in the
Questionable Frequency register will be true and a condition error message is generated. When lock is
regained, Status bit 1 in the Questionable Frequency register will be cleared and the condition error will be
cleared.
If an external frequency reference is being used, you must enter the frequency of the external reference if it
is not exactly 10MHz. The External Ref Freq key is provided for this purpose.
Key Path
Input/Output
Remote Command
[:SENSe]:ROSCillator:SOURce:TYPE INTernal | EXTernal | SENSe | PULSe
[:SENSe]:ROSCillator:SOURce:TYPE?
Dependencies The PULSe parameter, and support of the 1 pps signal at the EXT REF IN input, are not available in
firmware prior to A.13.00. They are also not available in some model numbers. If not available, the
EMI Receiver Mode Reference 195
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