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Technical Description
Chapter 3
3-1
3.1 Introduction
The model 7220 lock-in amplifier is capable of outstandingly good signal recovery
performance, provided that it is operated correctly. This chapter describes the design
of the instrument, enabling the best use to be made of its facilities. Of particular
importance is the correct adjustment of the AC Gain parameter, described in section
3.2.04.
3.2 Principles of Operation
3.2.01 Block Diagram
The model 7220 utilizes two digital signal processors, a microprocessor and a
dedicated digital waveform synthesizer, together with very low-noise analog
circuitry to achieve its specifications. A block diagram of the instrument is shown in
figure 3-1, and the sections that follow describe how each functional block operates
and the effect it has on the instrument’s performance.
Figure 3-1, Model 7220 - Block Diagram