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TDC7200: Tdc7200 + tdc1000 as gas meter scheme, the time obtained by TDC is not accurate. In a closed environment, the time of each measurement changes a lot. There are hundreds of NS. What factors will affect this time?

kevin.huang_FJXM
Expert 2925 points
Part Number: TDC7200
Other Parts Discussed in Thread: TDC1000

Tdc7200 + tdc1000 as gas meter scheme, the time obtained by TDC is not accurate. In a closed environment, the time of each measurement changes a lot. There are hundreds of NS. What factors will affect this time?

Scenario: (gas meter application)

Installation: transducer (200kHz) opposed mode

Calculation: obtain the sending and receiving time through tdc7200 + tdc1000. (calculate velocity using time difference method)

To configure:

Uint8? Tdc7200? Reg? Local? Copy [10] = {0x02, 0x44, 0x07, 0x07, 0xff, 0xff, 0xff, 0xff, 0x0, 0x0};

Uint8? Tdc1000? Reg? Local? Copy [10] = {0x25, 0x00, 0x01, 0x00, 0x00, 0xe0, 0x00, 0x00, 0x23, 0x00};

Main problems:

TDC time acquisition time is not accurate. In the closed environment, the time of no measurement changes greatly, with hundreds of NS

报错

  • 0
    TI__Genius 11015 points

    Kevin,

    I have received this question and will get back with you by next week Wednesday.

  • 0
    TI__Genius 11015 points

    Kevin,

    There are few different or combinations of scenarios that can affect the variations in the accuracy of the gas flow metering:

    1. Mismatch between transducers will cause the delta TOF to drift away from zero in a zero flow condition. I am linking two application notes that address this issue and provide some examples of analog interface circuits that can mitigate this problem. One is based mostly on gas flow sensing, but both have pertinent information on this topic.

    2. Whenever there is any disturbance in the water/gas in the pipe can cause the device to report ToF which is not accurate.

    3. The Rx pulse may have some noise/ringing associated with it and that could be either from the wall sides/burst energy of the Tx signal that the Rx senses and this can give unstable ToF readings.

    In case you require a very high precision flow metering with good resolution, we recommend that you use the MSP430FR6047 device:

    http://www.ti.com/tool/MSP-ULTRASONIC-DESIGN-CENTER