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TDC1000-TDC7200EVM: TDC1000-TDC7200 concentration measurement

a a81
Intellectual 390 points

Part Number: TDC1000-TDC7200EVM

Hello. I want to ask a question TDC1000-TDC7200 EVM. I want to do concentration measurement with TOF. But when i take a measure, i saw a lot of change in the TOF Value and i do any change in the my container. What can be its reason? (i attached my piezo with glue.)

And my second question if i do concentration measurement for liquids (like drop alcohol to water and then find water density) what is the best settings for my application(ı use 1MHz piezo)? I m waiting your suggestions. Thanks.

  • 0
    TI__Mastermind 31655 points
    Hello,

    Small changes in TOF are normal, but if you are seeing large changes these can be due to a few things. It could be poor coupling between the transducer and the container, air bubbles in the fluid, or any disturbance in the fluid among other things.

    Can you provide more information about your setup? The optimal settings will depend on the distance over which you will be measuring the concentration. What is the distance between the transducer and the reflector, and what medium is it being transmitted through (I assume water)?

    Regards,
  • 0 in reply to Scott Cummins
    Intellectual 390 points

    The distance is 7.2 cm between the transducer and the reflector. And the medium is water.

    And i am using plastic container. What is the best configuration for this situation. And you said "small changes". what is small changes. For example  4000 ns is convenient? What is the tolerance value?  Thanks.

  • 0 in reply to a a81
    TI__Mastermind 31655 points

    Hello,

    I've attached some settings that should work for a setup with that distance in water. Keep in mind the threshold may need to be adjusted if this is a noisy environment or the echo return isn't very strong.

    Fullscreen TDC1000_Setup_concentration.txt Download 
    TDC1000_Config0                         44
TDC1000_Config1                         41
TDC1000_Config2                         04
TDC1000_Config3                         05
TDC1000_Config4                         5F
TDC1000_TOF-1                           40
TDC1000_TOF-0                           1E
TDC1000_Error_Flags                     00
TDC1000_Timeout                         23
TDC1000_Clock_Rate                      01
TDC1000_Conts_Trigger                   00
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          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                         000000000001259B
GRAPH_YMIN_DATA                         0000000000012537
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

    Note the active channel is CH2. You may need to change it to CH1 if that is how your board is set up.

    For concentration measurements, small changes should be in the 1ns range. Large disturbances in the medium can cause spikes of around 1us in the time of flight, but it is not normal for it to be fluctuating continuously by those wide margins.


    Regards,

  • 0 in reply to Scott Cummins
    Intellectual 390 points

    I measure concentration( not level) in small plastic container. And i saw changes approximately 50ns and it happened everytime. And sometimes i start programme again and i see different TOF value and it was changing too. Do you have configuration for my concentration application. Thanks.

  • 0 in reply to a a81
    TI__Mastermind 31655 points

    The setup attached in my previous post is for your concentration application.

  • 0 in reply to Scott Cummins
    Intellectual 390 points

    I will try it. Do you have any idea what should i do for this changing value ? I need to determine liquids destiny value and ı think to use TOF value for it. But value is changing very much. I will try attached piezo again but i did it like in your datasheet. Do you have another different reason for this changing ? 

  • 0 in reply to a a81
    Intellectual 390 points

    Hello. I have a question. When i measure the concentration TOF AVG is not very changing(maybe+/- 2ns). But TOF AVG is changing if i measure the concentration maybe 3 or 4 minutes later. And the new TOF is not very changing too. For example when i measure concentration first time, the TOF AVG 85314 ns and after 200 sample it can be 85312 ns but then the TOF AVG is starting 85300 ns and after 200 sample it can be 85298 ns. What are those different values reason? Thanks.

  • 0 in reply to Scott Cummins
    Intellectual 390 points
    I used your configuration for concentration measurement. Programme is normal first but then it is changing. For example TOF AVG is 95227 first and it can be 95226 or 95228 but it is changing maybe 3000 sample later 3ns(not 1ns). What can i do ? I couldnt understand its reasons. And i read tdc1000 datasheet but i couldnt understand configuration value's meaning. Can you explain its meaning and effect. Thanks.