Original question:
Hello form,
i need the explanation for default value of meter constant here set as 61.why 61 is fixed for gas demo ....whenever i tried to calculate for meter constant M2(new meter constant),their formula is M1*(Y/X).where flow rate of x and y ,hence X and Y is calculated from volume flow rate graph or not ??? where i can take the value of x and y???
About the absTOF,
In the USS SW Library used in this reference design, the absToF is determined by computing the envelope of the received signal through Hilbert transform. A maximum of the envelope for each capture is first computed. The envelope crossing as a given ratio of this maximum is then determined. The absToF offset is then calculated by the two envelope points crossing the threshold and the threshold line. In the below figure, the red points are ADC capture data, raw signal. And the yellow points are the envelop data of the receive signal.
That is all we can share about how we calculate the absTOF in gas meter application.
Best regards,
Cash Hao
Hi,
There are huge noise showed in your ADC capture. The noise could cause spikes in the results.
I would reduce the noise in the ADC capture first. Could you use a standalone power supply for the MCU. Like using a battery to power up the board. It could reduce the noise coming from the power line. And could give a better result.
You can supply the power from block 1. And turn the switch to EXT in block 2. Then remove the VCC jumpers in block 3.
Best regards,
Cash Hao
Hello Cash Hao,
i had tried with airflow in 5000 rpm it graph as
in above graph is with airflow ....how can i change for further it is good or not
for 15000 rpm my adc capture is like
kindly check my graph in forum_new.zip and above mentioned graph
Hi,
These data looks good to me.
One question, why you set these two parameters? Because usually they are set to 0 unless particularly use case.
Best regards,
Cash Hao
Hello Cash Hao,
had set these two parameters as zero ....hence the graph is good ...so i need to calibrate the time of flight,absolute time of flight and volume ....by API in uss algorithm where it is mentioned in a document ...
i didnt understand how the values are calculated ....I need a detailed explanation for how the graph is generated and the value in the graph is calibrated pls give a example graph with their calibration of abs tof,volume and time of flight ....help me to get the graph with mean value..i need the explanation for how mean min ,max values are calculated...needed calibration wise example and explanation needed sir...
Hello Cash,
will u pls give a formula to find absTOF ....here in datasheet where used formula is 
what is meant of Tprop,Tups and dns thresh ,Toffset values are calculated how it is found it ??
Hi,
You can find the explanation of these parameters below that equation.
The Toffset can be considered as 0 for easy understanding. You don not need to consider about it.
Best regards,
Cash Hao
Hello Cash,
will u pls explain abt TI's Ultrasonic Sensing Subsystem... i didn't understand from document where block diagram is mentioned in below....will u pls explain about subsystem pls ...den also how the hilbert transform is used for envelope a signal ....because basically hilbert transform is for changing the phase ...how it is used to apply in an adc capture
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