The lock-in amplifier measures the amplitude and phase of an AC signal by combining a PSD (phase sensitive detector) and LPF (low-pass filter). Enter an AC “reference signal” and measure only signals of the same frequency. Even if the measurement signal contains AC noise, it is possible to remove the noise and measure the wanted signal only at the specific target frequency.
What is “DR” ?
“DR” is known to represent the performance of a lock-in amplifier. Because the noise reduction capability of a lock-in amplifier is specified by DR (Dynamic Reserve).
The DR specification of NF’s lock-in amplifier is 100 dB or above, which means even with a noise of 1 Vp-p superimposed on a 10 µV AC signal, the signal is still measurable. In other words, lock-in amplifiers have really high capability of removing noises.
What kind of measurement is a lock-in amplifier suitable for?
1: Small Signal Measurement
In a general measurement environment, it is difficult to measure an amplitude signal smaller than the overwhelming background noise because there is residual noise of around mV for voltage and µA for current. However, lock-in amplifiers have excellent noise reduction capability, so they can measure very small noises.
And this is the minimum range of the measurement signal of NF’s lock-in amplifier.
- • Minimum Voltage Range: 10 nV (LI5660 / LI5655 / LI5650 / LI5645)
- • Minimum Current Range: 10 fA* (LI5660 / LI5655 / LI5650)
*”f” is femto = 10-15
2: Phase Measurement
It is possible to measure the phase difference between the measurement signal and the reference signal. The minimum resolution for phase measurement is 0.001°. It is possible to measure the phase difference between two signals, which also means the small time difference between two signals.