锁相放大器的原理
锁定放大器本质上是一个频率选择交流电压表。它用于测量微弱信号（nV范围），这些信号可能被比信号高得多的背景噪声所隐藏。测量过程也称为载频法或相敏检测。锁定放大器从大多数不需要的频率的混合中选择具有特定频率和相位的信号。
Model | LIA-MV-150-S Standard | LIA-MV-150-D |
Voltage Input | BNC connector | Lemo® connector |
Single-ended | True-differential | |
Instrumentationamplifier | Instrumentationamplifier | |
Noise 12 nV/√Hz | Noise 12 nV/√Hz | |
Current Input | Lemo® connector | |
Transimpedance amplifier, gain 1kV/A | Transimpedance amplifier, gain 1kV/A | |
Noise 4 pA/√Hz | Noise 4 pA/√Hz | |
Sensitivity | Voltage: 3 µV to 100 mV, switchablein 1-3-10 | |
Current: 3 nA to 100 µA, switchablein 1-3-10 | ||
Working Frequency | 10 Hz - 45 kHz | |
Reference Input | ±100 mV to ±5 V, switchable toTTL | |
Phase | Adjustable 0° - 360° (8-bitresolution), | |
Demodulator | 50 dB max. dynamicreserve | |
Time Constants | 3 ms to 10 s, switchable in 1-3-10,slope switchable 6 dB or 12 dB/octave | |
Output | X [R · cos(angle)], ±10 V fullscale, short-circuit protected | |
Digital Control | 16 TTL, CMOS,opto-isolated | |
Power Supply | ±15 V, 100 mA typ. | |
Case | 170 x 60 x 30 mm (L x W x H),Weight 370 g | |
测量原理：生成正弦参考频率（载波频率）并将其传送到测量对象，测量对象对其进行调制。产生的调幅测量信号在锁定放大器中被放大，通过带通滤波器，*后到达同步整流器（或解调器、相敏解调器(PSD)、乘法器或混频器）。信号的整流是通过乘以参考频率来完成的。整流后的电压被均衡和再放大。
