Stanford Research Systems SR844, User Manual

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Performance Tests 5-11
SR844 RF Lock-In Amplifier
4. Frequency Accuracy
This test measures the frequency accuracy of the SR844. This tests the accuracy of the frequency counter
inside the unit. The counter is used only in External Reference mode.
Setup
We will use the RF synthesizer (Marconi 2023 or equivalent) to provide the external reference signal.
Connect the synthesizer output to REF IN.
Set the RF synthesizer to:
Frequency: 1.9993 MHz
Amplitude: 0.0 dBm
Modulation: OFF
Procedure
1) Press
Shift
then
Recall
to restore the factory preset instrument settings.
2) Press the keys in the following sequence:
Source
Switch to
EXTERNAL
Reference mode.
Shift
then
Freq (Precise Freq)
Display the Precise Frequency on the CH2 and Reference displays.
3) For each frequency in the table below, repeat steps 3.1 through 3.3.
Test Frequencies
1.9993 MHz
1.9997 MHz
3.1) Set the RF synthesizer to the frequency in the table.
3.2) Wait a few until the SR844
UNLOCK
indicator is off.
3.3) Record the frequency reading shown on the CH1 and Reference displays. The most
significant 3 digits are on the CH1 display. The least significant 3 digits are on the
Reference display. There are a total of 6 digits in the frequency reading.
4) This completes the Frequency Accuracy test. Enter the results of this test in the test record at the
end of this chapter.