Driving the future of technology : Original solution in measurement and control

 Lecture for Measurement

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.
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