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TDC1000: quality of water

HARINI KRISHNA
Expert 1905 points
Part Number: TDC1000
Other Parts Discussed in Thread: TUSS4470

Hi,

I have an application where i need to measure quality of drinking water. 

I read from the datasheet that TDC1000 can be used for fluid identification/concentration. 

Can I use TDC1000 for this application?

Thankyou 

Warm Regards

Harini Krishna

  • 0
    TI__Mastermind 27780 points

    Hi Harini ,

    Though the TDC1000 can be used for fluid identification/concentration measurements, we recommend the TUSS4470 device instead.

    Refer to the ultrasonic application table of the Ultrasonic Sensing FAQ page for an explanation on this use-case: https://e2e.ti.com/support/sensors/f/1023/t/748143

    The fluid ID/concentration implementation of the TUSS4470 will be similar to that of the TDC1000.

  • 0 in reply to Akeem Whitehead
    Expert 1905 points

    Hi Akeem,

    Thank-you for the suggestion

    Can TUSS4470 measure both soluble and insoluble contaminants in water?

    Thankyou 

    Regards

    Harini Krishna

  • 0 in reply to HARINI KRISHNA
    TI__Mastermind 27780 points

    Harini,

    The concept of ultrasonic concentration measurement is primarily used to determine if a soluble impurity exists in the water.

    Large insoluble contaminants may create multiple points of returning or scattered reflections, so it may be possible to detect these also, but identifying the exact type of contaminant may not be possible.

  • 0 in reply to Akeem Whitehead
    Expert 1905 points

    Hi Akeem,

    Thankyou for the information. 

    As a part of study i found out that the contaminants in tap water are chlorine, chloroamines, fluorides, Copper and lead.

    The recommended value for the following are

    Chlorine : 4mg/L

    Chloroamine : 4mg/L

    Florides : 0.5mg/L

    Copper : 0.005mg/L

    Lead : 1.3 mg/L.

    Can all these impurities be measured using ultrasonic sensor?

    As you said, it is not possible to determine the exact type of contaminant. Can we determine i water is contamination if the concentrations of the given contaminants are above the recommended value by observing the change in speed of sound in water?

    Thankyou

    Regards

    Harini Krishna

  • 0 in reply to Akeem Whitehead
    Expert 1905 points

    Hi Akeem,

    I want to know the speed of light when water is contaminated with different contaminants to specify limits for my application. I am finding difficulty in calculating the speed of light for different contaminants. 

    Can you help me in measuring the speed of light for different contaminants Can you share any resources which would be helpful?

    Thank you

    Warm Regards

    Harini Krishna

  • 0 in reply to HARINI KRISHNA
    TI__Mastermind 27780 points

    Hi Harini,

    The only relevant resources we have on this topic are as follows:

    Though the device discussed in the content is TDC1000, the same principles apply to the TUSS4470. I do not believe you will be able to distinguish the amount of each impurity in the water. You will only be able to determine that the water contains an abnormal amount of impurities or not. If the recommended amount in impurities is lacking or exceeded, you should observe this a change in the speed of sound.

    Note: we are using speed of sound (ultrasound) in these measurements, not speed of light (optical).

  • 0 in reply to Akeem Whitehead
    Expert 1905 points

    Hi Akeem,

    Thank you for sharing the resources.

    We calculated the speed of sound in fresh water , water containing 4mg/l of chlorine and water containing 10mg/l of contaminants and got the speed to be 

    speed of sound in fresh water = 1440.916204 m/s

    speed of sound in water containing 4mg/l of chlorine= 1440.916207 m/s

    Speed of sound with a10mg/l the contaminants =1440.9688 m/s.

    I found the values to be very close and observed that  addition of 10mg would not change the density much.

    Is it possible to differentiate between fresh water and water with 10mg of contaminants? 

    Regards

    Harini Krishna 

  • 0 in reply to HARINI KRISHNA
    Expert 1905 points

    Hi Akeem,

    Is it possible to differentiate between 

    1440.9688 m/s and 1440.916204 m/s?

    Thankyou

    Warm regards

    Harini Krishna

  • 0 in reply to HARINI KRISHNA
    TI__Mastermind 27780 points

    Harini,

    The ability to differentiate between various speeds of sound will ultimately depend on the sample rate of your ADC, and the fixed distance of your container.

    In your case, you need to be able to differentiate down to the hundredths decimal place (two digit resolution) in meters per second in the case of 1440.9688 m/s and 1440.916204 m/s.

    Here is how to calculate the minimum required ADC sample rate given a fixed distance and two speed of sound values.

    Minimum Required ADC Sample Rate when the one way distance is 1m and the speed of sounds are 1440.9688 m/s and 1440.916204 m/s

    = 1 /  (distanceFixed / speedOfSound1) - (distanceFixed / speedOfSound2)

    = 1 / (1m / 1440.9688m/s ) - (1m / 1440.916204 m/s )

    = 40 MSPS

    As the fixed distance decreases, the sample rate of your ADC will need to increase:

    Fixed Distance (m) Speed of Sound A (m/s) Speed of Sound B (m/s) One Way ToF A (s) One Way ToF B (s) TOF Difference (s) Minimum Required ADC Sample Rate (MSPS)
    1 1440.9688 1440.916204 0.000693978 0.000694003 2.53314E-08 39.47667681
    0.1 1440.9688 1440.916204 6.93978E-05 6.94003E-05 2.53314E-09 394.7667681
    0.01 1440.9688 1440.916204 6.93978E-06 6.94003E-06 2.53314E-10 3947.667681

    For round trip measurements using one sensor, divide the ADC sample rate by 2.

    You can also post your question to the TI E2E ADC forum for a specific part recommendation.