SR04M ultrasonic sensor time

ESPHome
1

Can someone tell me how to get the travel time instead of distance from and SC04M ultrasonic sensor, please?

New to ESPHome and Home Assistant so apologies if this is a daft question!

Using the sensor to measure oil level in a plastic storage tank. But the oil level is varying with temperature throughout the day. Could be a mixture of the plastic tank expanding and contracting plus the speed of sound changing due to temperature

2

The ESPHome code uses the following function to convert the measured time (which is the time it took for the sensor to hear its echo) to a distance:

float UltrasonicSensorComponent::us_to_m(uint32_t us) {
  const float speed_sound_m_per_s = 343.0f;
  const float time_s = us / 1e6f;
  const float total_dist = time_s * speed_sound_m_per_s;
  return total_dist / 2.0f;
}

So to get back the number of microseconds it took, taking the distance as an input:

(distance * 2) / 343 * 1000000

It doesn’t look like there’s a way to get the travel time directly.

3

Thanks! @robertklep