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TDC1000: How to improve accuracy of flow measurement using TDC1000 & TDC7200 in flow meter application

Part Number: TDC1000
Other Parts Discussed in Thread: MSP430FR6047

I am using TDC1000-TDC7200 ICs in a water flow measurement application, The Piezo used is of 1MHz frequency. I am able to sense the water flow and compared it with the standerd / caibrated flow meter. The problem is not getting consistency in the flow readings, sometimes getting below 1% error and sometimes it goes up to 9% error for the same flow rate. Also getting a lot of fluctuations in the delta TOF counts even at the zero flow rate. 

Can anybody help me out to get improved accuracy/repeatability in flow measurement?/ I have used the reference schematic and routing pattern of TDC1000-7200EVM to design a flow meter. 

 

  • Hello Kalpesh,

    Thanks for posting to sensors forum! The TDC1000-TDC7200 combination is actually not our recommended solution for flow meter applications. The problems as mentioned are the devices incorrect readings at zero and low flow, additionally the TDC1000 can miss the first STOP pulse generation at times which can vary your ToF measurement, this is what is possibly causing the 9% error that you are seeing in some of your flow measurements. One way to help reduce this error is by using the averaging function to help increase your measurement accuracy, but unfortunately there is not much that can be done at zero and low flow instances. The recommended solution for accurate flow metering using ultrasonic sensors is by using an MSP430FR6047.

    You can read more about this solution here: https://www.ti.com/tool/MSP-ULTRASONIC-DESIGN-CENTER

    Best,

    Isaac

  • Thank you Issac for the quick response,

    I am already using median filter and averaging function to eliminate unwanted ToF measurements and to improve stability of the measurements.

    Actually I have referred the technical note of TDC1000-7200EVM and it suggests that it can be used for the flow metering application, that's why I have selected the chipset for my flow meter design.

    I think there should be some twiks that can be used to improve accuracy and repeatability of the measurements, It would be great help if you can suggest some. Because my ultimate target is to have 4% accuracy.

  • Hello Kalpesh,

    Of course glad to help out, besides adding the averaging unfortunately we do not have much of a way to help improve the accuracy of the TDC1000-TDC7200EVM. This is the main reason why the EVM is no longer available on the web since this solution did not provide the necessary accuracy for most flow metering systems. I would mainly only recommend using this setup to detect binary flow, but for the last couple of years we have been suggesting customers to use the MSP solution mentioned above.

    Best,

    Isaac

  • Hi Isaac,

    Thank you for the clarification. Can you tell me the tentative accuracy level, we can achieve using above mentioned solution? That can give me the confidence to use mentioned MSP solution. Because, After couple months of R&D on TDC1000-TDC7200EVM, I have designed a custom board to finalize the design. Now, seems like it will not work. That process I don't want to repeat again. 

  • Hello Kalpesh,

    Unfortunately, I do not service the MSP430FR6047 solution, my recommendation would be to start a new thread regarding the MSP430FR6047 accuracy and one of the engineers that services this device should be able to provide more details and answer any questions you may have regarding this device. But it is definitely better to verify before you move ahead with a design, so please feel free to let me know if you have any other questions. Thank you!

    Best,

    Isaac