MSP430FR6043: Transducer Length Calibration

Marvn Arcangel

Hi Experts,

I need your comments on the inquiry below.

A customer developed a custom firmware integrating the GSM state machine to run alongside the measurement process.

The main challenge is implementing the TI calibration procedure in the actual setup without using the USS GUI/Design Center.

At the moment, the setup consists of a pump and the water meter under calibration. But currently do not have a reference flow meter or a system for controlling the water temperature. Therefore, they are looking for guidance on how to establish a practical calibration setup and methodology under these constraints.

The target is to achieve approximately ±5% measurement accuracy. Would you kindly assist on the following?

The correct procedure for transducer-length calibration without the GUI.
Which USS parameters and calibration coefficients need to be determined or modified directly in the source code.
How the calibration coefficients generated by the GUI can be reproduced without using the GUI.
What reference flow measurement method TI recommends for calibrating the meter.
How water temperature should be measured or controlled during calibration, and how temperature variation should be handled if temperature control is not available.
The minimum calibration points and conditions required to target approximately ±5% accuracy.

Any application notes, source-code examples, or recommendations for implementing the calibration procedure without the GUI would be greatly appreciated.

Thanks!

Marvin

24 days ago

0 Peter Jiang 11 days ago

TI__Expert 7515 points

Hi Marvin,

We don't have official app notes for the calibration without GUI, but based on the principle, customers can obtain the actual flow rate and then use linear fitting method to match the reference flow rate to achieve this by themselves. Please take below two documents for related information.

MSP Ultrasonic Sensing Library Users Guide 02_40_00_00 "Volume Flow Rate Flow Calibration" section.

USS Water Flow Rate Calibration

For the test environments setup, please refer to the below two documents.

Ultrasonic Water Flow Meter Design and Testing

MSP430FR6047 and Ultrasonic Software Based Water Flow Meter Measurement Results

Regarding your questions:

1. We don't have the step by step procedure for it, but according to the principle, you can use the absTOF and the sound speed in this specific temperature to calculate and calibrate the actual transducer-length.

2. If you refer to the calibration related parameters modification, please refer to the MSP Ultrasonic Sensing Library Users Guide 02_40_00_00 "Volume Flow Rate Flow Calibration" section.

3. As mentioned, you need to implement the common linear fitting algorithm by your own if not using the GUI.

4. Please refer to the MSP430FR6047 and Ultrasonic Software Based Water Flow Meter Measurement Results for the environment set up.

5. Typically, customers will have equipment such as heaters and water baths for controlling and measuring the temperature of liquids.

6. I would say it depends on multiple factors to achieve the target ±5% accuracy but I think you can take the defaut 3 calibration points for each range as the starting point to perform the test.

Best Regards,
Peter

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MSP430FR6043: Transducer Length Calibration