Offset Calculation; Figure 5-1. Oscillator Adjustment Setup - HP 10811A Operating & Service Manual

b. Connect oscillator output to Channel A of the oscilloscope. Adjust sweep speed so pattern
movement can be seen.
c. Adjust oscillator frequency adjustment (FREQ AD) on 10811A/B Crystal Oscillator unit) for
minimum sideways movement of the 10 MHz displayed signal. Increase oscilloscope sweep
speed for greater resolution.

5-13. Offset Calculation:

a. By timing the sideways movement (divisions per second on the oscilloscope), the approximate offset
can be determined based on the oscilloscope sweep speed as shown below.
b. For example, if the trace moves 5 divisions in 10 seconds and the sweep speed is 0.01 μs/div., the
oscillators signal is within 5 X 10-9 of the reference frequency. The calculation can also be made as
follows:
Where:
Δf/f is the normalized frequency difference between the 10811A/B and the reference signal
Δt is the change observed in the oscilloscope
t is the time required for Δt to occur.
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Figure 5-1. Oscillator Adjustment Setup

Model 10811A/B