I use a microcontroller to turn on the transmitter and detect received signal so I can measure the time from turning on the transmitter to detecting signal after receiver. this time includes sound traveling time (between two sensors) plus circuit propagation delay time. I want to know how I can measure the sound traveling time (T1_2 and T2_1) which is my goal to be able to measure the flow with equation below. These times show the time from sensor 1 to 2 and sensor 2 to 1.
flow = (D/sin(2a))*((T1_2 - T2_1)/(T1_2*T2_1))
Hello Mohsen,
I assume that you have two different locations of sensor pairs for T1 and T2 measurements.
You can actually measure the first time period by placing your Sensor 1 as transmitter and then Sensor 2 as receiver. Treat this as T1
Then interchange the positions and measure T2.
Alternately, if your positions are fixed, it should be half of the time you start your pulse in Sensor 1 and you receive the echo from Sensor 2.
Hello Prasanna,
Thanks for your answer. I did that and I measured T1 and T2. My problem is T1 and T2 are not the actual sound delay time. They are sound delay time plus circuit propagation delay time. I want to extract propagation delay time and subtract it from T1 and T2 to access to real sound delay time.
Dear Mohsen,
This problem can be resolved by making the propagation distance zero, in this way one can measure the processing delay time in the transmitter and the receiver T21p processing and from T2 to T1 , T12p.If the transmitter and receivers at both sides are same then one can measure the propagation delay by loop back where one connects the output of the transmitter to the input of its receiver. Or alternatively one makes the the propagation distance equal zero. One can also double the distance and measure the delay times, then the difference will be the propagation delay time among the medium.
Best wishes
Dear Abdelhalim,
Thanks for your answer. I just want to know that I should connect transmitter to the receiver once or in each cycle before sending to the sensor.
best,
Dear Mohsen,
If your processing delay time is fixed with time that is your data rate is constant, then you may need need to measure the processing delay once. Other wise you have to measure it in every running. I would advice you to investigate this issue to get out how far is he processing time constant.
wish you success
Dear Abdelhalim,
Thanks for your help. I will do that.
best regards,
Mohsen,
I really wonder what this propagation delay within your circuit would be!
With the flow measurement say of a pipe or tube, the diameter may not be longer than 30 cm ( or 300mm) and in that case, what is your echo time? I know for sure this figure is very small. Then if your so called propagation time is not actually the travel time of the U/S wave but might be a process delay in your software algorithm.
Scrutinize your code with a magnifying lense (literally take account of every instruction cycle of your code) to analyze the time consumed. I suspect not the hardware problem but with your code.
Just have a look and let me know!
Dear Prasanna,
I am sure that it is not processing delay time because I probe it by oscilloscope and I saw that the delay was around 2 milliseconds that is not true for sensors on an iron pipe with 3 cm distance. I also use interrupt on my code so because of MCU clock I think that it is much faster than sound velocity.
MOhsen,
Can I ask you a simple but may be stupid question?
What is your code written in, C, C++ or Pure Assembly?
To measure circuit propagation delay use conditions with substance flow equal to zero.
What substance flow do You measure? Liquid or gas?
May be syncronous phase detector is more suitable for Your's task? It is more sensitive. DOI: 10.13140/RG.2.2.27763.53283
I want to measure water flow. I perused some articles about other flow meters and I just use their method to measure water flow. I did not read anything about synchronous phase detector method for this measurement. Could you send me an article that explain this method?
The simplest way to study synchronous phase detector is to play with it's model.
The synchronous phase detection is close to stroboscope detection. It is like Fizeau instrument used to measure the speed of light.
https://www.ijsr.net/archive/v4i1/SUB157.pdf
https://en.wikipedia.org/wiki/Fizeau%E2%80%93Foucault_apparatus
Mohsen, why are you use microcontroller to measure delay time for ultrasonic flow meter? I think better will be use ready-made solution, like TDC-GP22 (from Acam).
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