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ï¾ Remote: 50 Ω Î© external source, Figure 3.13(f).
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[[Image:neoscanfig_3_13.png|thumb|center|600px|<i><b>Figure 3.13</b>: Stanford Research Systems SR844 RF Lock-In Amplifier: (a) Time constant: 24 dB/oct, (b) Signal Input: 50 Ω Low noise, (c) Sensitivity: Low noise, (d) X display: R(dBm), e) Y display: θ, (f) Remote: 50 Ω external source.</i>]]
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The signal levels at the Signal In port on the Lock-in amplifier are in the range of -100 dBm to -40 dBm or higher, depending on device one measures. It is important to set the sensitivity of the Lock-in amplifier greater than the expected input signal amplitude at the Signal Input port (from the IF Out of the optical mainframe). For example, if you expect a signal less than -67 dBm but greater than -87 dBm, set the sensitivity to -67 dBm and 100 μV (rms) setting. If the input signal is greater than the input signal setting, an OVERLOAD condition will occur and the red LED OVERLOAD indicators on the Lock-in amplifier will flash.
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[[Image:neoscanfig_3_14.png|thumb|center|600px|<i><b>Figure 3.14</b>: Optimization parameters settings in Optimization Settings Page.</i>]]
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If the optical signal is low, check to make sure: