TDC1000: TDC1000

chao zhong

Part Number: TDC1000
Other Parts Discussed in Thread: TDC7200

Tool/software:

The TDC1000 specification states that the TOF at 0 flow rate is a few nanoseconds, but we actually tested that the TOF at 0 flow rate is a few microseconds？

Our testing environment is as follows：

The distance between two transducers is about 35cm。

The schematic diagram is as follows：

The TDC1000 (left) and TDC7200‘s （right） Register configuration：

3 months ago

0 Eddie LaCost 3 months ago

TI__Mastermind 43500 points

Hello Chao,

35cm between transducers seems quite large for a flow application. In the figure 59 data that you shared, the distance is 6cm. Your zero flow drift still seems pretty large.

Are you using 1MHz transducers?

Also, please see the note below regarding TDC1000 in flow applications. It is possible that the first stop pulse is not generated causing an impact on the accuracy.

Note: The TDC1000 is no longer recommended for flow applications, only level sensing or static concentration/identification applications. The TDC1000 flow meter configuration is known to have issues in repeatability and accuracy when there is no flow (with or without water present). The TDC1000 is no longer recommended for flow applications, only level sensing or static concentration/identification applications. You can continue to use the TDC1000+TDC72000/+C2000 combination for water flow measurement, but you are taking a risk a inconsistent accuracy due to a device bug whereby the first stop pulse is occasionally missed (does not toggle STOP pin on TDC1000). Considering flow metering relies heavily on nano to pico-second timing accuracy, missing the stop pulse can have a significant impact on the flow rate measurement. As a workaround, it is possible to perform multi-cycle averaging to compensate for the occasionally missed first stop pulse.

Due to the potential issues of the TDC1000, we recommend the specialized MSP430 devices for flow metering applications: http://www.ti.com/microcontrollers/msp430-ultra-low-power-mcus/ultrasonic-performance-sensing-mcus-overview.html

0 chao zhong 3 months ago in reply to Eddie LaCost

Prodigy 100 points

The distance between our transducers is 35cm,We are using two 1MHz transducers.

Under what conditions is the TOF measured at a few nanoseconds in 0 flow water as stated in the specification sheet?In our application scenario, the distance between transducers is 30cm to 200cm。

“The TDC1000 is no longer recommended for flow applications”，Where can I find a detailed explanation of this issue？

0 Eddie LaCost 3 months ago in reply to chao zhong

TI__Mastermind 43500 points

Chao,

Please see the FAQ below. There is information under section 3.9 and I have also included it below.

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/724028/faq-tdc1000-everything-you-need-to-know-for-ultrasonic-tof-liquid-coupled-collateral-tools-designs-faq

1. Please use MSP430 based ultrasonic solution for any high accurate & resolution solutions for flow metering. The link for MSP430 device for this purpose is http://www.ti.com/microcontrollers/msp430-ultra-low-power-mcus/ultrasonic-performance-sensing-mcus-overview.html
2. In case you would like to use the TDC1000-TDC7200 based solution for flow metering, please refer to the documents below while you design your solution:

i. http://www.ti.com/lit/an/snia020/snia020.pdf

ii. http://www.ti.com/lit/an/snaa284a/snaa284a.pdf

3. TDC1000 device misses the first STOP pulse at times:

1. TDC1000 is known to miss the first STOP pulse generation at times; this can vary the ToF measurements in the range of ps.
2. In case you encounter the above issue, we recommend that you try to use the averaging function in the device and that will increase your accuracy of measurement.

0 Eddie LaCost 3 months ago in reply to Eddie LaCost

TI__Mastermind 43500 points

Also, see section 6.1.2 of the app note below regarding improving zero flow drift.

https://www.ti.com/lit/an/snia020/snia020.pdf

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