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TDC1000-C2000EVM: Flow detection performed by TDC1000-C2000EVM

Satoshi OKAFUJI
Prodigy 30 points
Part Number: TDC1000-C2000EVM
Other Parts Discussed in Thread: TDC1000, MSP430FR6043, TDC7200

Hello all, I have a question.

I would like to use a TDC1000-C2000EVM and two 2 MHz transducers to detect the flow rate of tap water flowing through a PVC pipe in a non-contact manner (by placing the transducers outside the pipe).

The transducers are fixed on the outside of a 20mm PVC pipe, each side by side at a 45 degree angle.
For now, I would like to try to detect when the water in the pipe is standing still and when it is flowing before measuring the exact flow rate.

We started the TDC1000_C2000_EVM software, configured and connected the transducer, and turned on the START GRAPH button in the GRAPH tab.

In this state, TDC AVE VALUE displays a value of about 43us and the graph is updated.
The graph appears to be almost straight and stable at around 43us.

When water flows through the pipe at this point, the graph initially swings violently up and down by 1 to 2 us around 43 us.
However, if the water continues to flow for about 30 seconds, the graph will hardly change at all and stabilize around 43us.
(There is no difference between the graph and the graph without water flow.)

What should the display look like when Mode 2 measurement is made with TDC1000_C2000_EVM software?
Also, do you have any kind of example settings?

I was originally thinking of getting TDC1000-TDC7200EVM, but it seems to have been discontinued and was not available.
If I wanted to try to do the same thing with TDC1000_C2000_EVM as with TDC1000-TDC7200EVM, how would I go about it?

Thank you in advance.

---.

1) What settings should I make?

For many items, we do not have criteria to determine how they should be set.
The following is a list of items that have been explicitly changed.

CONFIG0
The design frequency of the transducer is 2MHz, so the internal 8MHz clock is selected and TX_FREQ_DIV is set to 4.
CONFIG2
Mode 2 was selected for flow measurement.
TOF-1
PGA_GAIN was set to 21dB, otherwise echoes were not detected.

For the other values, I think the settings are the same as when I started the TDC1000_C2000_EVM software.
Are there any problematic settings?

Here are the values for all current settings.

[CONFIG0]

TX_FREQ_DIV: Divide by 4
NUM_TX: 8Pulses

[CONFIG1]

NUM_AVE: 1Cycle
NUM_RX: 1STOP

[CONFIG2]

VCOM_SEL: Internal
MEAS_MODE: TOF
DAMPING: Disable
CH_SWP: Enable
EXT_CHSEL: Disable
CH_SEL: CH1
TOF_MEAS_MODE: Mode2

[CONFIG3]

TEMP_MODE: REF_RTD1_RDT2
TEMP_RTD_SEL: Pt1000
TEMP_CLK_DIV: Divide by 8
BLANKING: Disable
ECHO_QUAL_THLD: -220mV

[CONFIG4]

RECEIVE_MODE: Multi Echo
TRIG_EDGE_POL: Rising
TX_PH_SHIFT_POS: 31

[TOF-1] PGA_GAIN: 21dB

PGA_GAIN: 21dB
PGA_CTRL: Active
LNA_CTRL: Active
LNA_FB: Capacitive
TIMING_REG: 3

[TOF-0]

TIMING_REG: 255

[ERROR FLAGS]

ERR_SIG_WEAK: 0
ERR_NO_SIG: 0
ERR_SIG_HIGH: 0

[TIMEOUT]

FORCE_SHORT_TOF: Disable
SHRT_TOF_BLNK_PRD: 128 x T0
ECHO_TIMEOUT: Enabled
TOF_TIMEOUT_CTRL: 1024 x T0

[CLOCK RATE]

CLOCKIN_DIV: Divide by 1
AUTOZERO_PERIOD: 128 x T0


2) How should transducers be connected?

For the two transducers, I have connected them to TX1 and GND and TX2 and GND of J5, is this correct?
The 0 ohm resistors R80 and R81 are still connected.

  • 0
    TI__Mastermind 22120 points

    Hello Satoshi,

    Thank you for posting to the sensors forum! Just as a preface we no longer recommend the TDC1000 for ultrasonic flow measurements. The recommended device is the MSP430FR6043: https://www.ti.com/tool/EVM430-FR6043

    This is due to a bug in the TDC1000 that causes a reduction in accuracy. The EVMs are essentially the same the main difference is that the C2000 is used as the timer instead of a TDC7200. The timer on the TDC7200 is much better than the timer on the C2000 so there may be some issues with the accuracy there.

    1) One of the main problematic configurations that I noticed were the timming configurations for the echo pulses. Essentially if the timing window for echo qualification is not setup correctly then the device will not generate any pulses for the C2000 to measure. I am not sure what the distance/ToF is but I assume it should be relatively small and a fast speed of sound so you should most likely enable the FORCE_SHORT_TOF and change the values in the TIMING_REG registers. I usually like to start with a known target to help ensure the setup is correct.

    2) The configuration of your transducers sounds correct, although the R80 and R81 resistors should be depolpulated. The R80 and R81 resistors connect TX1 with RX2 and TX2 with RX1, while mode operates TX1 with RX1 and TX2 with RX2. You will also need to connect these the RX channels to the TX channels to ensure the echo signal is getting to the TDC1000.

    Best,

    Isaac