Posted 2020/5/20
Measurement of Small AC Signals Superimposed on Large DC Signals
Preamplifier with DC Signal Removal and Low Noise
2. Waveform measurement: AC Signal and Noise
(1) The Small Sine-wave Superimposed on the DC Signal
Measurement signal: 100 µVp-p, 100 kHz sine wave superimposed on 8.5 V DC
Measuring instruments
-
a) Oscilloscope
-
b) Preamplifier "CMP61102" and oscilloscope
|
|
a) The oscilloscope is unable to measure because the measurement range includes DC
signal.
|
b) A small AC signal can be measured by utilizing the preamplifier
|
(2) Output Noise of DC Power Supply
The output noise of the power supply can be measured with the DC voltage output.
-
Linear DC Power Supply
When measuring the output of the linear DC power supply, electric hum noise caused by
commercial power frequency was observed.
-
DC-to-DC Converter (Switching Power Supply)
Switching noise of 0.5 ms period was observed at the output of the 5V DC to DC converter.
-
High Voltage Amplifier (40V DC)
When measuring the output of a 40V DC voltage amplifier, a 1 mV noise was observed.
