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TDC1000: TDC1000: The D-value of the AB and BA flight time is sometimes 1us in the still water. The center frequency of transducer is 1MHZ.

user3697981
Prodigy 30 points
Part Number: TDC1000

HI,I have some problems about the d-value in flow velocity measurement of water with tdc1000.

1、The d-value of the AB and BA flight time is mostly 1ns.But sometimes it becomes 1us.

2、The temperature measurement is sometimes error ,three times in fourteen hours.

I am confusing about the reason of Periodic translation.

Could you tell me the most important reason affecting it?

Does it relate to the capcity in the transducer or the length of the wire connecting the transducer?

Thanks .

  • 0
    TI__Mastermind 27950 points

    user3697981,

    The time-of-flight delta of 1us is likely due to the threshold level missing the first cycle of the captured echo. If the ECHO_QUAL_THLD value is not set to have sufficient margin, then in the case of a 1MHz, a single cycle (period) is the equivalent of 1us in time, which would explain the difference.

    In the figure below, the dark blue line (threshold) barely intersects the peak of the echo (COMP_IN). If there is any fluctuation or attenuation of the echo peak, it is possible that the first STOP pulse is offset by one period to the next peak.

    Try decreasing the Echo qualification DAC threshold level with respect to VCOM (ECHO_QUAL_THLD) or increasing the PGA gain level (PGA_GAIN) for more robust echo detection.

    For very accurate ultrasonic flow metering, please consider using the MSP430FR6047 instead of the TDC1000. The TDC1000 was designed for level sensing and concentration measurements.