Does JSN-SR04T need calibration/correction ?

Hi,

I was surprised to find out that if I swap a transducer on JSN-R04T with another transducer from another unit then there is difference in distance reading for the same 25cm measurement, some transducers report 26.5cm. Its repeatable and consistent.

Does it mean that some sort of calibration/correction has to be used?

Thanks and Regards,
Wonderful IOT

Those readings are indistinguishable, given that they agree within the widely accepted ranging error of +/- 1 cm for the HC-SR04.

See this thread for some tests and discussion.

But note that the sensor does not report "distance", the Arduino does, after converting pulse width information to distance.