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Original question:

Short distance measurements in AIR (Level from the Top)

TDC1000-GASEVM: Not detecting Echo Waveform

Nishant Sharma72
Intellectual 780 points

Part Number: TDC1000-GASEVM

Hi,

I am working on a project which requires measurement of Time of Flight in air. For accomplishing this I have bought TDC1000-GAS EVM and is using ultrasonic Transducer MA58MF14-7N from Murata. I am using single transducer for both transmission and receiving echo signal and have configured TDC1000 settigns in GUI for same. I am hereby attaching my EVM configuration file.

Fullscreen TDC1000_Config_10.5.2019.txt Download 
TDC1000_Config0                         87
TDC1000_Config1                         41
TDC1000_Config2                         25
TDC1000_Config3                         00
TDC1000_Config4                         1F
TDC1000_TOF-1                           0C
TDC1000_TOF-0                           1E
TDC1000_Error_Flags                     00
TDC1000_Timeout                         73
TDC1000_Clock_Rate                      03
TDC1000_Conts_Trigger                   01
TDC7200_Config1                         02
TDC7200_Config2                         40
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          04
TDC7200_Clock_Cntr_Stop_Mask_L          00
TRIGGER_UPDATE_FREQ                     0001
TDC_AVG/STDEV_NUM_ELEMS                 0014
SAVE_GRAPH_DATA_TO_FILE                 00
FLOW_MODE_SELECT                        00
Y-SCALE_CENTER                          C350
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                         00000000000F6FEB
GRAPH_YMIN_DATA                         00000000000DE94B
TDC1000-HV_DRV_EN1                      00
TDC1000-HV_DRV_EN2                      01
HV_DRV_EN1_Period                       00C8
HV_DRV_EN2_Period                       03E8
ENABLE_POWER_CYCLE                      00
CLK_FREQ_(1-16MHz)                      1.846200
CLK_SOURCE_SEL                          02
CPU_CLK_FREQ                            0B
CPU_CLK_EN                              01
TDC1000-HV_BST_PWR_EN                   01
HV_BST_PWR_EN_Period                    0000
FWD2REV_FLOW_DELAY                      0000
TDC1000-IMPE_MATCH_EN                   00
ENABLE_UART_STREAM                      00
ENABLE_MSP430TIMER_TDC                  00

Transducer mounting image:

I am trying to measure time of flight by bouncing ultrasonic waves from a wall at a distance of 22cm.  So according to that TOF must be around  1.27ms . The picture for setup is shown below:

The resonant frequency of transducer is 58 KHz and i am transmitting 7 pulses with same frequency which can be seen in the DSO capture below. I have also captured signal at COMP_IN pin. 

Signal on channel 1(Yellow) is Transducer input 

Signal on channel 2(Blue)is COMP_IN signal.

When i try to get Time of Flight data on the GUI it is not showing anything. Also it can be seen from the DSO captures that there is no echo. Even if I change the distance of the transducer from the wall still there is no change in the signals observed on DSO. It would be of great help if someone could point out what i am doing wrong or any suggestions for how to measure TOF in air with TDC1000.

Nishant Sharma

  • 0
    TI__Genius 11015 points
    Nishant,

    I will look into this and will respond to you by Monday.
  • 0 in reply to Bharat Aravamudhan
    Intellectual 780 points

    Bharat,

    It would be great if you could help me out on this issue. Waiting for your response.

    Nishant Sharma

  • 0 in reply to Nishant Sharma72
    TI__Genius 11015 points
    Nishant,

    The COMPIN pin signal does not look correct, please try to change the coupling in oscilloscope to DC coupling. Please check the signal at the Tx/Rx end at the transducers itself to check if the transducer itself picking up the echo post its burst.
  • 0 in reply to Bharat Aravamudhan
    Intellectual 780 points
    Bharat,

    By using DC coupling on oscilloscope fro COMPIN pin, there is addition of offset only. That's why I have used AC coupling. Regarding signal at TX/RX pin, you can clearly see in the DSO capture above that there is no echo. This is the issue i am facing that there is no echo. If you could go through my configuration file and point out what i might be doing wrong it will be really helpful.

    There is another thing I would like to know. Out of TDC1000 and PGA460 which is better suited for distance measurement in air? I have both the EVMs and would like to proceed ahead with the best suited AFE for this application.

    Thanks
    Nishant Sharma
  • 0 in reply to Nishant Sharma72
    Prodigy 130 points
    Maybe 22cm is too long(total distance will be doubled as 44cm) to make the sensor measuring the reflecting sound waves. The original amplitude I observed is about 0 ~ 10mV(even less) , in conditions that two sensors (one for transmition and another for reception) divided by 10cm. So I guess you can try it first by using a shorter distance. And the normal line to the surface of the sensor must be perpendicular to the wall. Because the sensor has a limited angle.
  • 0 in reply to JJ Martin
    Intellectual 780 points
    I have already tried by using shorter distance for reflection. I even tried to test at a distance of around 4 cm. The problem is that there was not even a slight change in the waveform observed on DSO. That's why I think there might be something which I am missing while configuring the EVM. If you have successfully configured EVM for your application, could you please share the signal on COMPIN so i can have a reference for what to expecte in echo.

    Thanks
    Nishant Sharma
  • 0 in reply to Nishant Sharma72
    TI__Genius 11015 points
    Nishant,

    I see that you do not seem to receive any signal post reflection. Please try to probe an oscilloscope at the transducer end and see you can see it wiggle at transmit & receive.

    PGA460 will work for longer distance say upto 5m, however the minimum distance that you can measure would be around 40cm.

    Please let me know the range and resolution that you would eventually like to measure.
  • 0 in reply to Bharat Aravamudhan
    Intellectual 780 points

    Bharat,

    My application requirement is to measure distance from 10cm - 30cm. The channel 1 (yellow) signal in DSO capture is at transducer end only. I also read that transducer MA58MF14-7N from Murata can only measure distance above 30cm. Which transducer does TI suggest for use with TDC1000 and distance measurement in range of 10-30 cm.

    Thanks
    Nishant Sharma

  • 0 in reply to Nishant Sharma72
    TI__Genius 11015 points
    Nishant,

    Please check with the transducer supplier to check for transducers that will be suitable for your application.
    We recommend transducer with frequency range of 40Khz to 300Khz to measure through air.
  • 0 in reply to Bharat Aravamudhan
    Intellectual 780 points
    Bharat,

    Now I am using PGA460 BOOSTXL EVM for my application. I am able to get satisfactory results with the transducer supplied with the kit. But i reasd on e2e ti threads it is suitable for distance measurement in the range of 30cm-5m . As my application demands distance measurement less than 15cm. So now i am in process of getting high frequency transducers. I will try to measure ToF on TDC1000 as well as PGA460 with new transducers.

    Thanks
    Nishant Sharma
  • 0 in reply to Nishant Sharma72
    TI__Genius 11015 points
    Nishant,

    Please try with new transducer and start a new thread with any new questions if you may have.