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TDC1000-TDC7200 EVM LabVIEW Code and Measurement Error

Gert Mema
Intellectual 305 points
Other Parts Discussed in Thread: TDC1000

Hello,

I am using the TDC1000-TDC7200EVM for distance measurment with the included 1MHz transducer.

The medium is air. When I start the graph in the GUI, the measurement starts and it displays a TOF. When I change the distance from the sensor to the object, the TOF doesn´t change. Is this a known problem? What am I doing wrong?

Is the LabVIEW-Code of this program avaiable anywhere?

Thank you.

  • 0
    TI__Mastermind 21685 points
    Gert,

    The 1MHz transducer is for liquid level measurement.

    Please check the following documents

    www.ti.com/.../snaa266

    www.ti.com/.../snaa270

    For short distance meaurements in air, please check the following posting

    e2e.ti.com/.../498792

    For getting started with TDC1000-TDC7200 firmware, please check the following

    e2e.ti.com/.../520659

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points

    Dear Vishy,

    Thank you for your reply.

    I need to do a level measurement from the top of a tank. I have a circuit which boosts the voltage up and can use an other sensor which has a lower resonant freq. 

    As far as I can see, the only difference to the GASEVM is that it can boost the voltage up to 30 V, right? So it should be possible to use the TDC1000-TDC7200EVM for distance measurement in air?

    When I want to use measurement Mode1, do I have to connect TX1 and Rx1 to my Sensor, so I have 3 wires connected to my Sensor (Tx1, Rx1, Gnd)?

  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points
    Gert,

    >>>As far as I can see, the only difference to the GASEVM is that it can boost the voltage up to 30 V, right? So it should be possible to use the TDC1000-TDC7200EVM for distance measurement in air?

    That's correct, GASEVM includes a boost circuitry (BSTEVM) to boost the TX excitation pulses to 30V. You can use your own circuitry to do that instead of BSTEVM. Only thing to remember when using TDC1000-TDC7200EVM is to make sure the bandpass filter on the receive path is modified to suit the transducer resonant freq you are using. By default bandpass filter is setup for 1MHz transducers.

    >>>When I want to use measurement Mode1, do I have to connect TX1 and Rx1 to my Sensor, so I have 3 wires connected to my Sensor (Tx1, Rx1, Gnd)?

    For level application, you use TDC1000 Mode 0. You send on TX1 and receive on RX2. In mode 0, TDC1000 groups TX1/RX2 as 1 channel and you connect TX1/RX2 together as shown in the TDC1000-TDC7200 EVM schematic. Transducer is connected between TX1/RX2 and GND.

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points

    Dear Vishy,

    Thank you for your reply.

    how do I need to setup the Mode/Registers in the GUI to use one channel for TX and one channel for RX? Is this even possible? How do I have to wire the sensor with Rx, Tx and Ground?

  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points
    Hello Gert,
    I am not sure if I fully understand you. If you want separate channel for TX and separate channel for RX, then is it correct to assume you are going to use 2 transducers? If that's correct, then you can select "Mode 1" in the "TOF_MEAS_MODE" field of CONFIG2 register of the TDC1000. In Mode 1, as explained in the TDC1000 Data Sheet, you can send on the transducer connected to TX1 and receive on RX1 connected to the second transducer.
    Please check the following references

    www.ti.com/.../tdc1000

    www.ti.com/.../snaa266

    www.ti.com/.../snaa220

    www.ti.com/.../snia020

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points

    Hello Vishy,

    No, I want to use only one transducer. I have to seperate Tx from Rx because the Voltage needed for my sensor is about 140V. The START-signal is not high enough, so I have to use my extra boost circuitry. The echo is also passed through my extra circuitry and is limited to a 5V-Signal, so it is suitable as Rx signal. 

    My question is:

    1.) Is it possible to seperate the Tx and Rx channel using only one sensor?

    2.) If I am using a frequency lower than 1 MHz, do I have to change R34, R31, C32 and C27 to modify the bandpass?

    Thank you.

  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points
    >>>1.) Is it possible to seperate the Tx and Rx channel using only one sensor?

    I don't think you need to separate Tx and Rx channel as the TDC1000 device takes care of making sure TX excitation pulses or the ringing after the excitation is not coupled into the RX circuit. As explained in the data sheet section 8.4.6, after the TX excitation pulses, blanking is used to decide when TDC1000 starts to look for echo in its RX channel. Only after this period, the mux is switched to the correct RX path. This helps prevent TX burst or ringing noise from being amplified in the RX path.

    Let me know if this answers your concern.

    >>>2.) If I am using a frequency lower than 1 MHz, do I have to change R34, R31, C32 and C27 to modify the bandpass?

    For 58kHz to 300kHz transducers, you have to make the following changes in TDC1000-TDC7200EVM to match the GASEVM main board. Please check the posting below
    e2e.ti.com/.../1866054

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points

    Hello Vishy,

    Thank you for your reply.

    Actually this didn´t answer my question. Isn´t it possible to seperate Tx channel from Rx channel using mode 1 instead of mode 0?

    How can I calculate the value for C36? 

  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points

    >>>Isn´t it possible to seperate Tx channel from Rx channel using mode 1 instead of mode 0?

    Always Tx and Rx channel are separate and they are 4 separate pins TX1,RX1, TX2, RX2. In Mode 0, the internal state m/c assigns TX1/RX2 as channel1 and TX2/RX1 as channnel 2 and these channel pairs are independent. Meaning, you can connect transducer1 to TX1/RX2 to measure level and TX2/RX1 to transducer2 to measure concentration. Whereas in mode 1, TDC1000 internal state machine asssigns TX1/RX1 as channel1 and TX2/RX2 as channel2. In this case, the channels are not really independent. Meaning when you connect transducer1 to TX1/RX2 and transducer2 to TX2/RX1, they work together. You send on Channel1 TX1 to transducer1 and receive on transducer2 to RX1 for measuring forward flow. They you send on Channel2 TX2 to transducer2 and receive on transducer1 to RX2.

    Now if you want to use mode1 with a single transducer, then you have to make sure the transducer pin is switched to RX1 at the time you want to receive. This is something you have to setup and experiment.

    >>>How can I calculate the value for C36?

    Please check the following document Figure 5 and Table 1

    www.ti.com/.../snaa284

    Thanks,
    Vishy

  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points

    Thank you Vishy.

    I am still not sure about this:  So I have to use J5 Pin 8 to Receive and J5 Pin 10 to Transmit, right? (Mode 0) I don´t want to do a flow measurement, I just want to measure the distance with one sensor using one pin for Tx and another pin for Rx!

  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points
    Assuming you are using the TDC1000-TDC7200EVM (without modifications) then you connect one pin of the transducer to J5.10 and the other J5.9 (GND). The transducer will send TX excitation pulse on J5.10. It will receive the echo on J5.8 and process.
    You can hear this webinar to understand how TDC1000 works

    e2e.ti.com/.../504584

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Intellectual 305 points
    Vishy,

    Pin 10 and Pin 8 are connected, so the TX excitation pulse can be measured on both, J5.10 and J5.8 . I want to use J5.8 just as an Receiver Pin, without being connected to the Transmit pin. Can I just remove the 0 Ohm R42 for this purpose?

    Thank you.
  • 0 in reply to Gert Mema
    TI__Mastermind 21685 points
    Gert,

    Yes, you can try that. I am not sure if removing R42 and connecting transducer between J5.10 and J5.8 is going to work.

    Thanks,
    Vishy