SLDA058 March   2021 TUSS4470

 

  1.   Trademarks
  2. 1Review of Ultrasonic Sensing Range Performance Factors
    1. 1.1 Physical Parameters
    2. 1.2 Transducer Characteristics
    3. 1.3 AFE Device Configuration
  3. 2Methods Overview
    1. 2.1 Introduction
    2. 2.2 Hardware Configuration
      1. 2.2.1 Transducers
      2. 2.2.2 Experimental Setup: Air-Coupled Level Sensing
      3. 2.2.3 Experimental Setup: Water-Coupled Level Sensing
      4. 2.2.4 TUSS4470 EVM Hardware Configuration
      5. 2.2.5 TDC1000-C2000EVM Hardware Configuration
    3. 2.3 Firmware Configuration
      1. 2.3.1 TUSS4470 Power Configuration
      2. 2.3.2 TUSS4470 220 kHz Configuration
      3. 2.3.3 TDC1000 220kHz Configuration
      4. 2.3.4 TDC1000 220kHz Configuration
      5. 2.3.5 TDC1000 1 MHz
  4. 3Short Range Air-Coupled Test Results
    1. 3.1 TUSS4470
    2. 3.2 TDC1000
  5. 4Mid-Range Air-Coupled Test Results
    1. 4.1 TUSS4470
      1. 4.1.1 Concept
      2. 4.1.2 TUSS4470 35 V Results
    2. 4.2 TDC1000
  6. 5Short Range Water-Coupled Test Results
    1. 5.1 TUSS4470
    2. 5.2 TDC1000
  7. 6Resistive Damping Device Comparison
    1. 6.1 TUSS4470
    2. 6.2 TDC1000
  8. 7Summary
  9. 8References
  10.   A Appendix A
    1.     A.1 TUSS4470: Filter Capacitor Selection
    2.     A.2 TUSS4470: Shematic
  11.   B Appendix B
    1.     B.1 TDC1000 Misc.
    2.     B.2 TDC1000-C2000EVM Schematic

6.2 TDC1000

To show the effect of the damping resistor, TX (CH1), COMPIN (CH4), START (CH2), and STOP (CH3) are shown in three ToF level measurement plots using 10 kΩ, 1250Ω, and 150Ω damping. Without damping, a 16 μs blanking period is enough to mask the ring down disturbance to COMPIN, thus an 8 μs blanking period was used to allow for an improvement in the minimum measurement range to be observed.

The noise on COMPIN matches up with the TX decay as expected, and this leads to false STOP generation just after the 8 μs blanking period ends.

GUID-20210310-CA0I-SKMS-S5J6-J1G6DR8XM7KF-low.png Figure 6-4 TDC1000 1 MHz Water Level Measurement: 10kΩ Damping

The noise is still large enough to trigger an early STOP, however the TX decay is shorter.

GUID-20210310-CA0I-QQDP-5XQ8-MDSG7HDGLZXX-low.png Figure 6-5 TDC1000 1 MHz Water Level Measurement: 1.25kΩ Damping

Here, the TX decay is truncated nicely, but the return echo is also attenuated below the threshold. In short range liquid measurements, the gain can often be increased enough to generate a STOP, yet this may only improve the short range performance if the ratio between return echo amplitude and the TX noise amplitude is greater than one. Since both and noise and echo will be attenuated similarly, the TDC1000's threshold detection method is not as conducive to this resistive damping technique.

GUID-20210310-CA0I-GQCH-ZM7K-JZHMFHC6QMBD-low.png Figure 6-6 TDC1000 1 MHz Water Level Measurement: 150Ω Damping