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

2.3.5 TDC1000 1 MHz

The default settings listed in Table 2-5 are a good starting point for water-coupled ToF applications. It is recommended to perform a simple tank test with these settings for first time evaluation of the TDC1000. For comments on measurement timing below, T0 = 125 ns (1/8 MHz).

Table 2-5 TDC1000 Water-Coupled Suggested Evaluation FW Setup
GUI Setting GUI Value Comments
TOF_MEAS_MODE 0 Measurement mode 0 for mono-static ToF measurements
Recieve Mode Single or Multi-Echo
CLOCKIN_DIV Div by 1 Set T0 with CLOCKIN_DIV
FORCE_SHORT_TOF Disabled Standard ToF measurement mode
TOF_TIMEOUT_CTRL 1024 ✕ T0 (128 μs) This allows a maximum echo listen period.
NUM_TX 4- 15 pulses This is a good starting point for producing a strong return echo.
NUM_RX 1 STOP With a higher threshold allowed, and stronger return pulse expected, only one STOP is necessary.
PGA_GAIN 6dB 0 - 6dB should be sufficient
ECHO_QUAL_THLD -220mV Default value
LNA_FB Capacitive Required for transducers in this frequency range.
AUTOZERO_PERIOD 128✕ To (16 μs) In the standard ToF measurement mode, this period occurs just before the listen period.
TIMING_REG 30 For more information, see [7].
FORCE_SHORT_TOF Disabled Standard measurement mode

Evaluation Notes:

Details on procedure can be found in the TDC1000-C2000EVM TDC1000-C2000EVM User’s Guide and in How to Select and Mount Transducers in Ultrasonic Sensing for Level Sensing and Fluid ID.

A suitable tank size for this evaluation can be determined based on the timeline diagram (Appendix B) for the standard ToF measurement. Assuming 10 TX pulses and the settings in Table 2-5, the measurement range may be determined from this timing table - (T0 = 125 ns, T1 = 1 μs).

Table 2-6 TDC1000 Air-Coupled Measurement Timeline Example
TRANSMIT WAIT COMMON-MODE AUTOZERO ECHO LISTEN
NUM_TX ✕ T1 (TIMING_REG-30) ✕ 8 ✕ T0 128 ✕ T0 128 ✕ T0 1024 ✕ T0
10 μs 0 μs 16 μs 16 μs 128 μs

Minimum ToF: (10 + 0 + 16 + 16) = 42 μs

Maximum ToF: 42 μs + 128 μs = 170 μs

Assuming c = 1480m/s in water, the water level in the evaluation tank should be between about 3.2cm and 12.5cm. The WAIT time period should be adjusted to shift the echo-listen period as needed.