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8
The phase difference is defined as:
)
/
(
tan
1
X
Y
.
1.2 Functional Diagram
The functional block diagram of the SE2031 DSP Lock-In Amplifier is shown in Fig.4. On the whole, the SE2031
includes signal conditioners, reference signal generators, an algorithm module and a system control module and so on.
Fig.4 Functional Block Diagram of SE2031
1.3 Reference Channel
The reference channel is used to provide control signal which is associated with the detected signal. The SE2031 reference
input can trigger on an analog signal such as a sine wave or a TTL logic signal. The input is AC coupled and the input
impedance is 1M
Ω
.
Generally, both the sine wave and the TTL signal can be used as the reference signal. However, the generator's sine output
has a small and varying amplitude. Meanwhile, many function generators provide a stable TTL SYNC output which can
be used as the reference. Therefore, for frequencies below 1Hz, a TTL reference signal is required.
The SE2031 lock-in amplifier has two reference signal modes: internal reference mode and external reference mode.
