Measuring Distance Between PC and User

Hi everyone.

Im new in the world of Arduino and Electronic Components.

I have a little project, the objetive of this is like a virtual supervisor, check if a person is working in a PC. Im using two sensors, PIR move sensor and the ultrasonic sensor (HC-SR04), with this last one I want to know if is a persons sitdown in front of the pc, is it, with the PIR sensor now monitoring moves, if the user doesnt move, is not working or the person fall as sleep.

But I facing some problems. The ultrasonic sensor can detect a objetc, like a box or the pc cabinet, but when I put it in front of the chest of a person, the distance is not corrrect, the sensor return values like 2800cm (2m), when the aprox distance it is bewtween 60-70cm.

The question is, The clothes of the person can be the problem or I missing something?

Greetings.

teotl:
But I facing some problems. The ultrasonic sensor can detect a objetc, like a box or the pc cabinet, but when I put it in front of the chest of a person, the distance is not corrrect, the sensor return values like 2800cm (2m), when the aprox distance it is bewtween 60-70cm.

The question is, The clothes of the person can be the problem or I missing something?

Greetings.

A quick and easy test would be to put a piece of clothing over the sensor and see if it still detects the box or PC cabinet.

Paul

Ultrasonic detectors like a hard surface to produce a definite reflection, but if sensitive enough should detect a
person (that's how car reversing sensors work).