SLOA341 October   2024 LOG300

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Description
    1. 2.1 Basics of Ultrasound Sensing
    2. 2.2 Advantages and Disadvantages of Ultrasonic Sensing
    3. 2.3 Ultrasonic Transducer
      1. 2.3.1 Transducer Construction
      2. 2.3.2 Transducer Frequencies
    4. 2.4 Transducer Topologies
    5. 2.5 Blind Zone Effect on Minimum Distance
    6. 2.6 Transducer Drive
    7. 2.7 Ultrasonic Echo and Signal Processing
      1. 2.7.1 Digital Gain or Fixed Gain
      2. 2.7.2 Time-Varying-Gain
      3. 2.7.3 Automatic Gain Control or Logarithmic Amplifier
      4. 2.7.4 Logarithmic Amplifier vs Logarithmic Detector
  6. 3LOG Detector Amplifier and the Advantages Over Conventional Opamps
  7. 4Application
    1. 4.1 Double Paper Feed and Paper Thickness Detector
      1. 4.1.1 Schematic Implementation
      2. 4.1.2 Material Thickness Detector
    2. 4.2 Bubble Detector
    3. 4.3 Material Detection
    4. 4.4 Distance or Proximity Detection
  8. 5Summary
  9. 6References

2.7.3 Automatic Gain Control or Logarithmic Amplifier

A logarithmic amplifier approach is a way to achieve automatic gain control when dealing with input signals that are both high and low in amplitude. A log amp gains an input signal based on the log scale which helps get a stronger echo response from weak signals while also appropriately gaining the strong signals but preventing saturation, similar to the time-varying-gain approach. Whereas the time-varying-gain method is dependent on where an object is in time, the logarithmic amplifier is dependent on the actual echo of the input signal with no dependency on time.