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home > Products > Measurement Instruments > Lock-in Amplifier/Preamplifier > Lock-in Amplifier > LI5660/LI5655/LI5650/LI5645 > Features
Product Information
Lock-in Amplifier/Preamplifier
Digital Lock-in Amplifier
High-response and High-stability

High-response and High-stability
Time Constant Time Constant Setting
Time Constant

The minimum time constant is 1 μs for LI5660/LI5655 (5 μs for LI5650/LI5645).
Our newest lock-in amplifiers have achieved high-frequency and high speed response.

Synchronous Filter

This is an integer-period moving-average filter. Ripple caused by detection is greatly reduced, and the output is nearly settled in the averaging interval (integer period), so the time constant can be reduced (to obtain faster response)

High-speed Locking Even at Low Frequencies

  It takes just about two cycles to lock on to the reference signal even at low frequencies. Furthermore, a moving average filter synchronized with the signal cycle obtains a high-speed response with a small ripple.
Outstanding Dynamic Reserve

Phase detection and subsequent processing are performed digitally. Output zero drift at high gains is smaller than the analog system, and up to 100 dB dynamic reserve can be obtained (measurement can be performed with a noise 100,000 times larger than the sensitivity, namely the signal full scale).

Up to 11 MHz with the wide-band, high-frequency input terminal (LI5660)
Voltage measurements can be made with a single end (A) or differential (A-B) input, as well as 10 Vrms input (C) and high-frequency input (HF) terminals with the LI5660. The HF input terminals can be used to measure up to 11 MHz.

Fractional Harmonic Measurements
Measurements can be made at submultiple frequencies of the fundamental wave (1 to 63) / (1 to 63).
Provide measurement of fractional times frequency of the fundamental wave. In 2-frequnecy measurement mode of LI5660/LI5655/LI5645, each primary PSD and secondary PSD individual frequency setting available. For example, primary PSD set as n/m times with reference signal frequency, and secondary PSD set as n times with reference signal frequency or set as different frequency from primary frequency.
Fractional Harmonic Setting
Fractional Harmonic
Harmonic measurements are made at integral multiples between two measurement frequencies (f2 = (f1 x n) ). In this case, distortion in thef1 side signal results in an integral multiple frequency (harmonic), which cannot be distinguished from the f2 signal. With subharmonic measurements, measurements can be conducted with the f2 = f1 x n/m relationship, which means that even if distorted harmonics are generated with f1, the frequency can be set so that it does not affect f2. f2 harmonic measurements are possible without being affected by f1 harmonics.
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Dual-frequency Simultaneous Measurements
2-phase (Rcosθ, Rsinθ), 2 PSDs (Primary PSD, Secondary PSD)
LI5660/LI5655/LI5650 come with 2-phase sensitive detectors (PSD), allowing simultaneous measurement of two frequency components that are included in a single input signal. Measurements that previously required two lock-in amplifiers using the dual beam method can now be made with a single lock-in amplifier.
Ratio calculations can be made by determining the ratio between the measured value and reference value, and the secondary PSD can be connected in cascade to the primary PSD, to run detection using the secondary PSD after detecting the signal with the primary PSD.
Detection Mode (Dual 1)
Detection Mode (Dual 1)
Detection Mode
Primary PSD
Secondary PSD
SINGLE* Fundamental / Fractional Harmonic None 2-phase detection is at one frequency.
DUAL1 Fundamental / Fractional Harmonic Fundamental / Harmonic Simultaneous measurement of the fundamental wave and its harmonic components included in a single input signal
DUAL2 Primary Frequency Secondary Frequency
Simultaneous measurement of two individual harmonic components included in a single input signal
CASCADE Primary Frequency Secondary Frequency The secondary PSD is connected in cascade to the primary PSD.
*The detection mode of LI5645 is "SINGLE" mode only.

External 10 MHz Synchronization
Synchronizing operation of other devices such as a signal generator and the LI5600 series using a 10 MHz frequency source allows synchronization to any frequency (can be configured) without having to use an external reference signal (REF IN). External 10 MHz Reference Input Setting
External 10 MHz Reference Input

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Wide Range of Functions in a Thin, Compact Body
Front Panel of LI5660
Rear panel of LI5660

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