Configuring PLL (Phase-locked loop) Demodulation with Python API
Written by Dylan Perez
Updated at April 1st, 2026
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The Moku Lock-In Amplifier has four demodulation options; None, Internal, External, or External PLL (phase-locked loop). The External PLL option will track the frequency of the second input signal and use the resulting signal as the demodulation signal. This can be easily configured in the Moku app by navigating to the ‘Settings’ drawer on the top right and selecting ‘External (PLL)’ as the demodulation source.
The PLL settings such as tracking frequency, PLL bandwidth, and harmonic multiplier can be adjusted by clicking on the PLL block.
To configure this in the API takes a few more steps. Below is a code snippet for setting up the PLL demodulation and configuring the PLL parameters. More API documentation can be found here.
from moku.instruments import LockInAmp
lia=LockInAmp('192.xx.xx.xx', force_connect=True)
# Relative phase can be adjusted here
lia.set_demodulation(mode='ExternalPLL', phase=10)
# auto_acquire must be explicity set False if manually entering reference frequency, default is True
lia.set_pll(auto_acquire=False, frequency=2e6, frequency_multiplier=1, bandwidth='100kHz')
lia.relinquish_ownership()