Frequency (Internal Timebase) Adjustment
Frequency (Internal Timebase) Adjustment
The instrument stores a calibration constant that sets the crystal oscillator to put out exactly 10 MHz. The instrument
should have been running continuously for 30 minutes prior to this calibration adjustment to ensure timebase sta-
bility.
1. Set the frequency counter resolution to better than 0.01 ppm and the input termination to 50 Ω (if your
frequency counter does not have a 50 Ω input termination, you must provide an external termination). Make the
connections shown below.
2. Use the frequency counter to measure the output frequency for each setup in the following table.
Nominal Signal
Setup
Frequency
Amplitude
2
<10 MHz
~1 Vpp
Output frequency is slightly less than 10 MHz
3
>10 MHz
~1 Vpp
Output frequency is slightly more than 10 MHz
4
~10 MHz
~1 Vpp
Output frequency is should be near 10 MHz
5*
10 MHz
~1 Vpp
Output frequency should be 10 MHz ± 1 ppm
* Constants are stored after completing this setup.
3. Using the numerical keypad or knob, adjust the displayed frequency at each setup to match the measured
frequency. Select
ENTER VALUE
.
4. After performing setup 5:
a. If your calibration procedures require you to verify the adjustment just made, exit the calibration menu and
perform
Internal Timebase Verification
b. If you are making all of the adjustments and then verifying the instrument’s performance, continue with the
next procedure in this section.
Agilent 33500 Series Operating and Service Guide
389
