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TDC1000: Application Water Level measurement - Echo Timeout error

Velmurugan Ekambanathan
Prodigy 140 points
Part Number: TDC1000
Other Parts Discussed in Thread: TUSS4470

We have developed the water level measurement to measure tank water level up to 150cm, Device able to measure the level well most of the time. But some time we dot get echo (software) for the same water level.

We are dynamically in the software adjusting the threshold 35, 50, 75 mV and pulses from 8, 10,12,14,16 in all combination possible to get the water level (echo). If we are not getting this echo with in 4ms ( software time out) we show level cannot be measured error. When we see this error, if we move the sensor or change the water level, then error goes off. We are not able find why this error comes.  We see this issue in tank close to empty and full level say (20cm to 150cm). As our sensor is floating device we are not able probe the signal in the real time.

Can a ultrasonic sensor expert help us on this. Water temperature is between 24C to 40C.

To know how our product works you can have look of our product in www.ezztank.com

  • 0
    TI__Expert 3450 points

    Hello,

    What is the transducer resonant frequency?

    At first glance, it sounds like you may be operating the sensor near the limits of the transducer. Transducer ringing picked up by the receive signal path can block out a short range ultrasonic received pulse. Long range operation can cause signal loss when the SNR of the received pulse is too low for the TDC1000 filters and LNA. The minimum and maximum range of the sensor system can be characterized by probing the START and COMPIN pin received signal. Are you able to remove the transducer + sensor system to probe the TDC1000?

    Since the transducer is floating, waves could also cause the transducer to transmit on an angle to the tank bottom and miss the return pulse due to the reflection. 

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 140 points

    Resonant frequency of the transducer is 1Mhz, and we drive with 1 MHZ signal.  We connect the sensor to J8 Conn.

    Below I have given the snap shot of schematics and the waveforms. We have tested up to 203cm, we could able to get water level but some time we get time out and the time out timer value is 2708 uS.  We have taken the waveform from the actual product when it is floating in the water.

  • 0 in reply to Velmurugan Ekambanathan
    TI__Expert 3450 points

    Hi, 

    TX and RX waveforms look okay. It looks like the schematic did not upload correctly. 

    As seen below in the standard ToF diagram, the TIMING_REG and TOF_TIMEOUT_CTRL control the echo-listen period. In these tests, is your device set to stop listening around 2708 us? That is very close to the expected ToF from a 203cm test. What is the recorded ToF when the 203cm test is successful?

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 140 points

    Our software time out interval is 5ms after we initiate the start pulse. For 203cm the time was 2740 us.  

    Even though we use software time out of 5ms, we get hardware time out before software time out ,from TDC1000, the calculated time out for the the TDC was around 4596us.

    Above 150cm water level, we see many time the TDC timeout.  For now we are limiting the product range to 150cm and releasing the product to market.

    Any possibility to measure the water level above 3m reliably?

  • 0 in reply to Velmurugan Ekambanathan
    TI__Expert 7599 points

    Hello,

    Very glad to hear that you are releasing the product with our product.

    For measurements above 3m the return signal can degrade and will need you to look for a high performance high gain solution. The TDC1000 AFE gain of 40dB will be the limitation here. 

    We do have a newer part TUSS4470 that we released that has an integrated log amp and can provide a gain up to 96dB. This would be the preferred part for application above 3m. 

    Here is the information on the part and an App note on the integrated log amp. The TUSS4470 also has a high voltage driver support which will provide additional flexibility in driving higher voltage for longer distance measurements. 

    Please reach out to us if you have any specific questions on the TUSS4470.