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TDC1000-TDC7200EVM: TOF Measurement Mode 2 - Disparity between upstream and downstream measurements

Jordan Field
Prodigy 90 points

Part Number: TDC1000-TDC7200EVM

Hi,

I am attempting to use the TDC1000-TDC7200 EVM in a flow metering application, but not in a pipe. Rather, it is to be used in an open tank environment and later in the ocean. To achieve this, I have used these pre-potted sensors: https://www.steminc.com/PZT/en/food-grade-ultrasonic-flow-sensor-1mhz. I have press fitted these into a delrin frame that my coworker created like so:

                 

   

They are flush with the edge of each "mast" and each sensor is run through a small coaxial cable to suppress EMI. The basic functionality of the board is present, however, I'm noticing a disparity between the upstream and downstream TOF causing a delta TOF of around 4 ns at zero flow. Here is a sample CSV file run in flow mode:

As you can see, there is a near-constant delay between the upstream and downstream TOF measurements. Next, I will attach screenshots of my GUI tabs, and what I read on my THS3024 Oscilloscope:

       

There is also a bit of strange ringing right before and during the START pulse for me, which I can't explain.

                          

Please let me know if you have any ideas for how I can solve this problem. I suspect it may have to do with the mounting method, but I'm not sure. Perhaps I'm overlooking some specific setting. 

Thanks,

Jordan

  • 0
    TI__Mastermind 31655 points

    Hi Jordan,

    I will look into this and get back to you as soon as I am able. In the meantime, could you please use the "Save Config" function on both the TDC1000 and TDC7200 tabs and upload the files here?

    Thank you,

  • 0 in reply to Scott Cummins
    Prodigy 90 points

    Hi Scott,

    I will not have access to the board until tomorrow (Wednesday). I will upload the config files tomorrow morning.

    Jordan

  • 0 in reply to Jordan Field
    TI__Mastermind 21685 points
    Jordan,

    You are using short time of flight. Any reason? Looks to me TOF is about 73us. Is that right? Short time of flight is for < 30us TOF. I suggest use standard time of flight. See this link below for a discussion on optimum flow settings (see the file "Interfacing a water flow sensor" especially as it shows the optimum GUI settings). There's also a config file in the posting.

    e2e.ti.com/.../1624680

    Thanks,
    Vishy
  • 0
    Prodigy 90 points

    Hi Scott and Vishy,

    Thank you for the suggestion on the FORCE_SHORT_TOF field. I was misunderstanding the parameter. This fixed my "early ringing" problem, but unfortunately, this didn't solve my main issue. I will attach images of the new scenario as well as my current config files.

       

    Also, I'm wondering why the COMPIN signal seems to be so noisy only when the STOP pulses start. Could this be crosstalk? A faulty board? Or maybe just my scope? I'm planning to switch to coax scope probes this week, like in the demo.

    Here on the GRAPH tab is

    1) Mode 2, oscillations due to upstream/downstream disparity

    2) Mode 1, Channel 1

    3) Mode 1, Channel 2

    4) Back to Mode 2

    You can see that the upstream and downstream values are directly correlated to the oscillations in Mode 2.

    The config files are attached below. If you have any more suggestions for how to fix my issue, please let me know. Of course, I am happy to answer any more questions you may have for me.

    Best,

    Jordan

    forum7200.txt
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    TDC1000_Config0 45
    TDC1000_Config1 45
    TDC1000_Config2 12
    TDC1000_Config3 23
    TDC1000_Config4 1F
    TDC1000_TOF-1 80
    TDC1000_TOF-0 1E
    TDC1000_Error_Flags 00
    TDC1000_Timeout 33
    TDC1000_Clock_Rate 01
    TDC1000_Conts_Trigger 01
    TDC7200_Config1 82
    TDC7200_Config2 44
    TDC7200_Interrupt_Status 00
    TDC7200_Interrupt_Mask 07
    TDC7200_Coarse_Cntr_Ov_H FF
    TDC7200_Coarse_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Ov_H FF
    TDC7200_Clock_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Stop_Mask_H 00
    TDC7200_Clock_Cntr_Stop_Mask_L 00
    TRIGGER_UPDATE_FREQ 0001
    TDC_AVG/STDEV_NUM_ELEMS 000A
    SAVE_GRAPH_DATA_TO_FILE 00
    FLOW_MODE_SELECT 00
    Y-SCALE_CENTER 0032
    X-SCALE_RANGE 0032
    MEASURE_RTD1 00
    SAVE_RESULT_REGR_TO_FILE 00
    GRAPH_MULTI_STOPS 00
    TDC_SELECT 00
    TEMP_RTD_SELECT 00
    TEMP_RTD_MODE 01
    TEMP_AVG/STDEV_NUM_ELEMS 000A
    SAVE_TEMP_DATA 00
    GRAPH_YMAX_DATA 0000000000011F79
    GRAPH_YMIN_DATA 0000000000011F15
    TDC1000-HV_DRV_EN1 00
    TDC1000-HV_DRV_EN2 00
    HV_DRV_EN1_Period 001E
    HV_DRV_EN2_Period 001E
    ENABLE_POWER_CYCLE 00
    CLK_FREQ_(1-16MHz) 8.000000
    CLK_SOURCE_SEL 00
    CPU_CLK_FREQ 05
    CPU_CLK_EN 00
    TDC1000-HV_BST_PWR_EN 00
    HV_BST_PWR_EN_Period 0000
    FWD2REV_FLOW_DELAY 0000
    TDC1000-IMPE_MATCH_EN 00
    ENABLE_UART_STREAM 00
    ENABLE_MSP430TIMER_TDC 00
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    forum1000.txt
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    TDC1000_Config0 45
    TDC1000_Config1 45
    TDC1000_Config2 12
    TDC1000_Config3 23
    TDC1000_Config4 1F
    TDC1000_TOF-1 80
    TDC1000_TOF-0 1E
    TDC1000_Error_Flags 00
    TDC1000_Timeout 33
    TDC1000_Clock_Rate 01
    TDC1000_Conts_Trigger 01
    TDC7200_Config1 82
    TDC7200_Config2 44
    TDC7200_Interrupt_Status 00
    TDC7200_Interrupt_Mask 07
    TDC7200_Coarse_Cntr_Ov_H FF
    TDC7200_Coarse_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Ov_H FF
    TDC7200_Clock_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Stop_Mask_H 00
    TDC7200_Clock_Cntr_Stop_Mask_L 00
    TRIGGER_UPDATE_FREQ 0001
    TDC_AVG/STDEV_NUM_ELEMS 000A
    SAVE_GRAPH_DATA_TO_FILE 00
    FLOW_MODE_SELECT 00
    Y-SCALE_CENTER 0032
    X-SCALE_RANGE 0032
    MEASURE_RTD1 00
    SAVE_RESULT_REGR_TO_FILE 00
    GRAPH_MULTI_STOPS 00
    TDC_SELECT 00
    TEMP_RTD_SELECT 00
    TEMP_RTD_MODE 01
    TEMP_AVG/STDEV_NUM_ELEMS 000A
    SAVE_TEMP_DATA 00
    GRAPH_YMAX_DATA 0000000000011F79
    GRAPH_YMIN_DATA 0000000000011F15
    TDC1000-HV_DRV_EN1 00
    TDC1000-HV_DRV_EN2 00
    HV_DRV_EN1_Period 001E
    HV_DRV_EN2_Period 001E
    ENABLE_POWER_CYCLE 00
    CLK_FREQ_(1-16MHz) 8.000000
    CLK_SOURCE_SEL 00
    CPU_CLK_FREQ 05
    CPU_CLK_EN 00
    TDC1000-HV_BST_PWR_EN 00
    HV_BST_PWR_EN_Period 0000
    FWD2REV_FLOW_DELAY 0000
    TDC1000-IMPE_MATCH_EN 00
    ENABLE_UART_STREAM 00
    ENABLE_MSP430TIMER_TDC 00
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0 in reply to Scott Cummins
    Prodigy 90 points
    Hi Scott,

    I don't know why, but this reply keeps getting listed as a verified answer. I keep trying to reject this, but every time I refresh the page it comes back. My main problem isn't solved yet so I don't want this thread to be closed!

    Thanks,
    Jordan
  • 0 in reply to Jordan Field
    TI__Mastermind 31655 points
    Hi Jordan,

    I'm not sure how that happened, but I was able to remove the verified answer on my end. I am looking into this at the moment and will post back with an answer when I have found something.

    Thanks,
  • 0 in reply to Scott Cummins
    Prodigy 90 points
    Hi all,

    As a quick update, I switched to BNC scope probes and the COMPIN noise is now gone. However, the upstream/downstream discrepancy remains.

    I look forward to hearing back from you when you know more.

    Thanks,
    Jordan
  • 0 in reply to Jordan Field
    TI__Mastermind 21685 points
    Hi,

    Please check the following app note

    www.ti.com/.../snia020

    If I understand right, I think you are seeing a zero flow offset. Section 6.1 discusses possible cause of zero flow offset and method to handle. We see zero flow offset even in off the shelf complete flow sensor pipe from manufacturers. In your case you are using individual potted sensors and I wonder if there may significant mismatch between the two sensors.

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    TI__Mastermind 21685 points
    Please check these debugging tips as well by Bahram

    e2e.ti.com/.../1548429

    Thanks,
    Vishy
  • 0 in reply to Vishy Viswanathan
    Prodigy 90 points

    Vishy, 

    I am starting to think that it could indeed be a sensor-mismatch issue like you have suggested. I will try shortening my sensor cables and making better connectors.

    In the meantime, I was wondering about something. In the document you linked in your first reply, there are several mentions to a "Texas Instruments sensor interfacing circuit" and then a picture with this schematic.

    Excuse me if this is a bad question, but is this circuit included on the EVM? I saw no reference to the switching chip shown here. If it is not already on the EVM board, can I assume that this circuit may solve my problem if it is indeed due to some sensor mismatch? 

    I look forward to your reply,

    Jordan

  • 0 in reply to Jordan Field
    TI__Mastermind 21685 points

    >>>Excuse me if this is a bad question, but is this circuit included on the EVM? I saw no reference to the switching chip shown here. If it is not already on the EVM board, can I assume that this circuit may solve my problem if it is indeed due to some sensor mismatch?

    That circuit is not on the EVM. I enclose a document that summarizes our experiments with such a board to improve performance when using audiowell flow sensor pipe. As you can see the setup we have used to test with is different. I also enclose the config file used. 

    Thanks,

    Vishy

    Interfacing a water flow sesnor to TDC1000-TDC7200EVM-020716.pdf

    TDC1000-CONFIG-EXT-Sensor-Interface.txt
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    TDC1000_Config0 42
    TDC1000_Config1 45
    TDC1000_Config2 12
    TDC1000_Config3 08
    TDC1000_Config4 1F
    TDC1000_TOF-1 80
    TDC1000_TOF-0 28
    TDC1000_Error_Flags 00
    TDC1000_Timeout 6A
    TDC1000_Clock_Rate 03
    TDC1000_Conts_Trigger 01
    TDC7200_Config1 02
    TDC7200_Config2 44
    TDC7200_Interrupt_Status 07
    TDC7200_Interrupt_Mask 07
    TDC7200_Coarse_Cntr_Ov_H FF
    TDC7200_Coarse_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Ov_H FF
    TDC7200_Clock_Cntr_Ov_L FF
    TDC7200_Clock_Cntr_Stop_Mask_H 00
    TDC7200_Clock_Cntr_Stop_Mask_L 00
    TRIGGER_UPDATE_FREQ 0002
    TDC_AVG/STDEV_NUM_ELEMS 0064
    SAVE_GRAPH_DATA_TO_FILE 00
    FLOW_MODE_SELECT 01
    Y-SCALE_CENTER 0000
    X-SCALE_RANGE 0000
    MEASURE_RTD1 00
    SAVE_RESULT_REGR_TO_FILE 00
    GRAPH_MULTI_STOPS 00
    TDC_SELECT 04
    TEMP_RTD_SELECT 00
    TEMP_RTD_MODE 01
    TEMP_AVG/STDEV_NUM_ELEMS 000A
    SAVE_TEMP_DATA 00
    GRAPH_YMAX_DATA 000000008CCCCCCC
    GRAPH_YMIN_DATA 000000007FFFFFFF
    TDC1000-HV_DRV_EN1 00
    TDC1000-HV_DRV_EN2 00
    HV_DRV_EN1_Period 001E
    HV_DRV_EN2_Period 001E
    ENABLE_POWER_CYCLE 00
    CLK_FREQ_(1-16MHz) 8.000000
    CLK_SOURCE_SEL 00
    CPU_CLK_FREQ 05
    CPU_CLK_EN 00
    TDC1000-HV_BST_PWR_EN 00
    HV_BST_PWR_EN_Period 000F
    FWD2REV_FLOW_DELAY 0000
    TDC1000-IMPE_MATCH_EN 01
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0 in reply to Vishy Viswanathan
    Prodigy 90 points

    Hi Vishy,

    Thanks for those documents. If my sensor mismatch problems continue, I may be interested in using the sensor interfacing board mentioned in the first document. Within, it says "The sensor interfacing board is only available through special request from the ISC marketing team."

    I was wondering: could you could help me find a contact for them so that I may place a special order for the add-on board? I can't seem to find any mention of that team from a Google search.

    Thanks, 

    Jordan

  • 0 in reply to Jordan Field
    Prodigy 90 points
    Vishy,

    Still hoping to special order that sensor interfacing board. Let me know if there's a way I could do that!

    Jordan
  • 0 in reply to Jordan Field
    TI__Mastermind 31655 points

    Hi Jordan,

    Unfortunately we are not able to supply these boards any more directly from TI. I have attached the Altium design files so that you can have them built by a PCB manufacturer of your choice.

    1108.Impedance Matching (12-29-2015 2-45-49 PM).zip

    Regards,