SRS Labs SR850 - Manual (Page 233)

7-15
Performance Tests
6. Frequency Accuracy
This test measures the frequency accuracy of the lock-in. This tests the accuracy of the frequency counter
inside the unit. The counter is used only in external reference mode. The internal oscillator frequency is set by
a crystal and has 25 ppm frequency accuracy.
Setup
We will use the frequency synthesizer to provide the reference signal.
Connect the TTL SYNC output of the frequency synthesizer to the Reference input of the lock-in.
Procedure
1) {PRESET} (Turn the lock-in off and on with the [
←
] key pressed)
2) Set the frequency synthesizer to a frequency of 10 kHz.
3) Press the keys in the following sequence:
[REF/PHASE]
<Ref. Source>
Use the knob to select External.
<Ref. Slope>
Select Rising edge.
4) The lock-in should be locked to the external reference. The frequency is displayed at the bottom of
the screen. Record the frequency reading.
5) This completes the frequency accuracy test. Enter the results of this test in the test record at the end
of this section.