Reference

The Reference tab lets you configure the frequency reference for the instrument.

For Option 1ER, the user interface appears and behaves differently as shown in the sample screens below.

Reference Source

Sets the source for the frequency reference. Choices include the following:

INTernal: Internal reference oscillator
EXTernal: External reference oscillator. Requires a signal present at the REF IN connector

The reference indicator field in the notifications bar at the bottom of the GUI displays the currently selected Reference Source and its current state.

When set to External, the frequency of the external signal can be specified with the External Reference Frequency setting.

If the external reference becomes unlocked or fails, after you correct the issue, toggle the Frequency Reference Source to Internal and back to External to update the Reference State status.

GUI Location	System Menu (triple bar icon) > Settings (gear icon) > Reference >Reference Source
SCPI Command	[:SOURce]:ROSCillator:SOURce INTernal\|EXTernal [:SOURce]:ROSCillator:SOURce?
SCPI Example	:ROSC:SOUR EXT :ROSC:SOUR?
Dependencies	Default value of INTernal is set by Restore System Defaults.
Notes	Changing the reference may take up to 30 seconds to regain frequency lock. For remote control operation, ensure your VISA timeout is set to 30 seconds (or more) when executing this command.
Range	Internal \| External
State Saved	Persistent, survives preset and power cycle but not saved in the instrument state.
Backwards Compatibility SCPI	E82X7D, E8663D, and N51xxB: [:SOURce]:ROSCillator:SOURce
Backwards Compatibility Notes	For N51xxB: SCPI query reports the setting’s stored value, not what is actively being applied to the hardware. This command differs from this prior behavior. To query what source is actively applied to hardware, see Current Reference Source setting.

Current Reference Source

Remote command only.

Returns the current reference source being applied to the instrument. Possible sources are:

INTernal
EXTernal - External will only be applied when a signal is actively present at the REF IN connector.

See the Reference Source setting for more information.

SCPI Command	[:SOURce]:ROSCillator:SOURce:CURRent?
SCPI Example	:ROSC:SOUR:CURR?

Reference Source Auto

Enables or disables the ability of the signal generator to automatically switch between the Internal and External reference oscillator.

ON - If Auto is enabled, a valid reference signal present at the REF IN connector triggers the reference source to automatically switch from Internal to External. When the valid reference signal is absent, the instrument automatically switches from External to Internal.

OFF - If Auto is disabled, the value that you set for the Reference Source setting is used as the frequency reference source.

GUI Location	System Menu (triple bar icon) > Settings (gear icon) > Reference > Auto
SCPI Command	[:SOURce]:ROSCillator:SOURce:AUTO ON\|OFF\|1\|0 [:SOURce]:ROSCillator:SOURce:AUTO?
SCPI Example	:ROSC:SOUR:AUTO ON :ROSC:SOUR:AUTO?
Dependencies	Default value of OFF is set by Restore System Defaults
Notes	Changing the reference may take up to 30 seconds to regain frequency lock. For remote control operation, ensure your VISA timeout is set to 30 seconds (or more) when executing this command.
State Saved	Persistent, survives preset and power cycle but not saved in the instrument state.

External Reference Frequency

External Reference Locking Range

The instrument provides two locking ranges for your externally supplied reference signal. Locking range of Wide allows your reference signal to be further away in frequency from the selected value in External Reference Frequency, with a slight compromise in the phase noise performance of the instrument. Locking range set to Narrow provides the best phase noise on the instrument. See table below.

Locking Range	External Reference Requirements	Benefits
Wide	Within approximately +/- 1.0 ppm of the selected external reference frequency	Easier to lock to external reference
Narrow	Within approximately +/- 1.0 ppm of the selected external reference frequency	Better phase noise

Reference State

Displays the current state of the frequency reference. The displayed state can help you understand whether the frequency reference is locked or if a failure occurred.

Reference Out

The Ref Out connector is controllable. The connector is normally on, providing a 10 MHz frequency reference by default. The connector can be switched off.

For N5185A/N5186A, the output frequency is selectable and can be 10 MHz or 100 MHz.

GUI Location	System Menu (triple bar icon) > Settings (gear icon) > Reference > Reference Out
SCPI Command	:ROUTe[:CONNectors]:REFerence:ROUTput OFF\|F10\|F100 :ROUTe[:CONNectors]:REFerence:ROUTput?
SCPI Example	ROUT:REF:ROUT OFF
Preset	This is unaffected by a Preset but is set to 10 MHz on a "Restore System Settings to Default Values."
Range	OFF \| 10 MHz \| 100 MHz
State Saved	Persistent, survives preset and power cycle but not saved in the instrument state.

GUI Location	System Menu (triple bar icon) > Settings (gear icon) > Reference > External Reference Frequency
SCPI Command	[:SOURce]:ROSCillator:FREQuency:EXTernal <freq> [:SOURce]:ROSCillator:FREQuency:EXTernal?
SCPI Example	:ROSC:FREQ:EXT 100 MHZ
Preset	This is unaffected by a Preset but is set to 10 MHz on a "Restore System Settings to Default Values."
State Saved	Persistent, survives preset and power cycle but not saved in the instrument state.
Notes	Changing the reference frequency may take up to 30 seconds to regain frequency lock. For remote control operation, ensure your VISA timeout is set to 30 seconds (or more) when executing this command. For N5185A/N5186A with Option 1ER: Valid input for <freq> can be from 1 MHz to 110 MHz. For N5185A/N5186A without Option 1ER: The only valid selection for <freq> is 10 MHz. Any other value will generate the error "703,Feature not supported; frequency value requires Option 1ER."
Min	Without Option 1ER: 10 MHz With Option 1ER: 1 MHz
Max	Without Option 1ER: 10 MHz With Option 1ER: 110 MHz
Resolution	Without Option 1ER: Not applicable With Option 1ER: 0.1 Hz