Stanford Research Systems SR860 Operation Manual page 209

Appendix G
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} (press [Save Recall], then touch {Recall default}. Touch {Confirm})
2) Set the frequency synthesizer to a frequency of 9.9990 kHz.
3) Use the front panel to make the following adjustments
Press [Ref/chop]
Select External reference mode.
Press External [Trig]
Select Pos TTL.
Press [Config]
Touch {Data1 Display} to highlight the green data source.
Touch {Fext} to choose external reference frequency for Data1.
Touch {Close}
Press [Screen Layout] multiple times to set the screen to show half-screen strip chart
Touch the green vertical tile for Fe, and touch autoscale
Touch the white horizontal scale tile {Time} to display the horizontal scale palette,
and touch
Touch {Cursor MinMaxMean} to set the cursor mode
and touch {Cursor Width} to select wide mode
4) The lock-in should be locked to the external reference. Wait at least 45 seconds locked to the
external synthesizer. Then touch {Pause}
hand end of the chart. Record the average value of Fe (external frequency) from the cursor
display.
5) This completes the frequency accuracy test. Enter the results of this test in the test record at the
end of this section.
repeatedly to zoom out to 10 s/div.
, and move the cursor to 30 seconds from the right-
Performance Tests
to expand the trace.
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SR860 DSP Lock-in Amplifier
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