NF FRA51615, Instruction Manual

Page: 226 / 306

5.13 External reference clock
5
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FRA 51615
5.13 External reference clock
This instrument uses an internal crystal oscillator as the reference clock, but an external 10 MHz clock
signal can also be used.
Generally, an external reference clock is used for the following purposes.
• To increase accuracy by using a reference clock that is more accurate than the internal clock (a
rubidium frequency standard for example)
• To establish a common frequency accuracy by using a reference clock that is shared by multiple
devices
■ Inputting an external 10 MHz reference clock signal
Connect an external 10 MHz reference clock signal to the
10 MHz REF IN
connector on the rear panel
of the instrument. For the specification of signals that can be input and points of caution, refer to "
■ 10
MHz REF IN
" in "
3.2 Input and output connectors
".
To enable the external reference clock, set
【
OSC
】 –
[10 MHz REF]
–
[IN] to [ENABLE] . When the
instrument is operating on an external reference clock, the status display in at the top of the screen is
[EXT]
.
10 MHz
Operating
on an external clock
Operating
on the internal clock