324 6000 Series Oscilloscope User’s Guide
8 Reference
Using the 10 MHz reference clock
The 10 MHz REF BNC connector on the rear panel is provided so
you can:
• Supply a more accurate sample clock signal to the
oscilloscope, or
• Synchronize the timebase of two or more instruments.
Sample clock and frequency counter accuracy
The oscilloscope’s timebase uses a built-in reference that has an
accuracy of 15 ppm. This is sufficient for most uses. However, if
you are looking at a window that is very narrow compared to
the selected delay (for example, looking at a 15 ns pulse with
the delay set to 1 ms), significant error can be introduced.
Using the built-in sample clock, the oscilloscope’s hardware
frequency counter is a 5-digit counter.
Supplying an external timebase reference
When you supply an external timebase reference, the hardware
frequency counter is automatically changed to an 8-digit
counter. In this case, the frequency counter (Quick
Meas
&Select&Counter) is as accurate as the external clock.
For more information on the hardware frequency counter,
see “Counter” on page 237.
To supply a sample clock to the oscilloscope
1 Connect a 10 MHz square or sine wave to the BNC connector
labeled 10 MHz REF. The amplitude must be between 180 mV
and 1 V, with an offset of between 0 V and 2 V.
CAUTION
Do not apply more than ±15 V at the 10 MHz REF BNC connector on
the rear panel or damage to the instrument may occur.
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