原创 the Use of a Lock-in Amplifier

Today, noise measurements have become an essential factor in the characterization of signals. This is easy to understand when one realizes that it is phase noise that ^[23]:<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

- limits the operating range of radar

- degrades the quality of television pictures

- limits the precision of satellite positioning

- spoils the quality of data transmission

So how can you measure signals partially or completely buried in noise? For example, how can you extract a 50 mV sine wave from a white noise signal with 5 V amplitude.

In its most basic form a Lock-in amplifier is an instrument with dual capability. It can recover signals in the presence of an overwhelming noise background or, alternatively, it can provide high resolution measurements of relatively clean signals over several orders of magnitude and frequency. However, modern instruments offer far more than these two basic functions and these increase capability have led to their acceptance, in many scientific disciplines, as units which can provide the optimum solution to a large range of measurement problems. For example, the modern lock-in amplifier will function as:

-an AC Signal Recovery Instrument

-a Phase Meter

-a Noise Measurement Unit

-a Spectrum Analyzer

-…and much more