TDC7200EVM: TOF change

Hsiao victor

Part Number: TDC7200EVM

Using TDC1000-7200EVM to test the concentration, the temperature and concentration did not change. Why did the TOF value change from 125348 to 125051 after 3 hours?

over 2 years ago

0 Eddie LaCost over 2 years ago

TI__Mastermind 46505 points

Hello Hsiao,

Can you please provide some more information about the configuration? Are you using 1Mhz transducer with water as the medium? Do you have a log of the data? I would like to see if this was a sudden shift or slowly changing over time. Last, can you provide your GUI configuration?

0 Hsiao victor over 2 years ago in reply to Eddie LaCost

Prodigy 10 points

	TIME	TOF	Temperature
1	09:58	125348	19.99
2	10:15	125337	20.14
3	10:58	125319	20.24
4	11:30	125278	20.45
5	12:08	125194	21.09
6	13:33	125015	21.14
7	14:14	124947	21.15
8
	transducer	1MHZ	15mm*1mm
	water

The distance from Transducer to reflector is 90mm
The medium is water

Transducer 1MHZ diameter15mm*thickness1mmm

0 Hsiao victor over 2 years ago in reply to Hsiao victor

Prodigy 10 points

Another test record TOF will also decrease.

	TIME	TOF	Temperature
1	13:40	124834	20.87
2	14:31	124823	21.9
3	15:16	124802	21.1
4	15:44	124790	21.07
5	16:08	124782	20.94
6	17:02	124755	20.88
7
8
	transducer	1MHZ	15mm*1mm
	water

0 Eddie LaCost over 2 years ago in reply to Hsiao victor

TI__Mastermind 46505 points

Hsiao,

Thanks for the information. This ToF decrease seems to be related to the temperature. In the first data set, the temperature increase by 1.15C. As the temperature increases, the speed of sound in water will increase resulting in a shorter time of flight. The link below shows a chart of speed of sound vs. temperature. You could consider using the temperature of the medium to adjust your ToF calculation.

https://www.engineeringtoolbox.com/sound-speed-water-d_598.html

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TDC7200EVM: TOF change