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Lock in Amplifiers

Lock in Amplifiers
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SR530 Lock-In Amplifier Sine Wave Mixing The SR510 and SR530 have differential inputs with 7 nV/ > √ Hz of input noise and 100 M Ω input impedance. Theinput can be configured as a voltage input, or as a current input with 10 The core of the SR510/SR530 is a precision analog sine-wavemultiplier. Lock-ins use a multiplier (demodulator) to translate the input signal (at the reference frequency) down to DC where it can be filtered and amplified. Many lock-ins use square wave multipliers which introduce spurious harmonic responses. The SR510/SR530 use clean sine-wave multiplierswhich are inherently free of unwanted harmonics. Signal Input > The SR510 and SR530 are analog lock-in amplifiers whichcan measure AC signals as small as nanovolts in the presence of much larger noise levels. Both the single phase SR510 and the dual phase SR530 have low-noise voltage and current inputs, high dynamic reserve, two stages of time constants, and an internal oscillator. In addition, both lock-ins come equipped with a variety of features designed to make them simple to use. > (U.S. list) 6 V/Again and an input impedance of 1 k Ω tovirtual ground. Full-scale sensitivities from 500 mVdown to 100 nVare available.Three input prefilters can be selected. The first is a line notchfilter providing 50 dB of rejection at the line frequency. The >

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Two stages of filtering follow the phase sensitive detector.Time constants can be chosen as long as 100 seconds formaximum noise reduction, or as short as 1 ms (20 second filter similarly provides 50 dB of rejection at thesecond harmonic of the line frequency. The third filter is a band pass filter which automatically tracks the reference frequency. These three filters can eliminate much of the noise in the signal before it is amplified. Reference Input Output Time Constants The dynamic reserve of a lock-in amplifier, at a given full-scale input voltage, is the ratio (in dB) of the largest...

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An RS-232 computer interface is standard on both the SR510and SR530. An optional GPIB interface is also available. All features of the instruments can be queried and set via the computer interfaces.  right at the detector, before the signal-to-noise ratio is permanently degraded by cable noise and pickup. The SR550 FET-input preamplifier, the SR552 bipolar-input preamplifier, and the SR554 transformer-inputpreamplifier are ideally suited for use with the SR510/SR530lock-ins. These preamplifiers are especially useful when measuring extremely low-level signals. Although the SR510 and SR530...

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