Hioki BT3554-50, Instruction Manual, Page: 174 / 188

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Synchronous Detection
11.5 Synchronous Detection
The figure below provides an equivalent circuit for a battery. If an
object under measurement include other components other than
pure resistance component, as shown in this figure, synchronous
detection can be used to obtain the effective resistance of the object
under measurement. The synchronous detection is also used to
separate faint signals from noise.
E
L
R
1
R
2
C
The synchronous detection is a detection method that can separate
the signal component having the same frequency as the reference
signal’s frequency from a signal. The figure below illustrates a
simplified schematic diagram of the synchronous detection method.
The system consists of the multiply circuit, which multiplies two
signals, and the low-pass filter (LPF), which allows only DC
components of the multiply circuit output to pass.
+1
−1
Non-inversion
amplifier
Inversion
amplifier
LPF
Low-pass filter
Multiplier circuit
Reference
signal
HIOKI BT3554F961-00 HIOKI BT3554F961-00