Measuring distance to humans wearing clothing with sonar?

Other Hardware Sensors
1

Hi,

I'm using the SR04 sonar to measure distance to different objects.

Here is my code:

#include <NewPing.h>

int trig = 4;
int echo = 5;
float distance = 0, ping = 0;
float speedOfSound = 0.34;//m/ms

//NewPing sonar(trig, echo, 100);

void setup(){
  Serial.begin(9600);
  pinMode(echo, INPUT);
  pinMode(trig, OUTPUT);
}

void loop(){
  distance = getSonar();
  Serial.print("|DISTANCE: ");
  Serial.println(distance);
  

}

float getSonar(){
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  ping = pulseIn(echo, HIGH);
  ping = ping/1000;
  ping = ping /2;
  return speedOfSound*ping*100;
}

I also used NewPing's sonar.ping_cm() function.

This works fine when measuring distances to objects like walls, but doesn't work when measuring distances to humans. The measured distance to a human is 3200 with my code and 0 with NewPing.

I'm guessing that the sensor never receives the echo because clothing absorbs the soundwaves instead of reflecting it. I didn't find any info about this on the internet, which is not what I expected. I though alot of people probably had the same issue?

Do you guys have any experience with this sonar sensor?

2

Test your theory by trying to measure the distance to a naked human.

3

jremington:
Test your theory by trying to measure the distance to a naked human.

That is exactly what I'm going to do tonight when I'm alone. It does correctly measure the distance to my naked hand by the way.