Inconsistent reads on ultrasonic range sensor?

Hi there, I've recently started playing around with Netduino and some sensors - specifically the ultrasonic range sensor (seed studio). I've connected it to my digital pin. If I aim it at the same place, I get fluctuations of about 20cm sometimes... usually from 85cm -> 120cm at the same place? Any ideas? Here are some environmental situations: The 5V range sensor is on the breadboard with a LED and a resistor (330ohm) Code: while (true) { outPort.Active = true; // Put port in write mode outPort.Write(true); // Pulse pin outPort.Write(false); outPort.Active = false;// Put port in read mode; bool lineState = false; // Wait for the line to go high, for start of pulse. while (lineState == false) lineState = outPort.Read(); long startOfPulseAt = System.DateTime.Now.Ticks; // Save start ticks. // Wait for line to go low. while (lineState) lineState = outPort.Read(); long endOfPulse = System.DateTime.Now.Ticks; // Save end ticks. int ticks = (int)(endOfPulse - startOfPulseAt); lastReading = ticks / 580; Debug.Print(lastReading.ToString() + " cm");

Hello Reactive, and welcome to the forum. Could you specify a link with the sensor specs? Cheers

The busy-loop method is not very accurate as a single read can take pretty long - i've used an InterruptPort to detect the edges (you'll need another port or some piece of circuitry with e.g. a 555 to trigger the sensor reading, since there's no tristate for interrupt ports ...). Mario, it's at http://www.seeedstud...surement_module - it's basically the same as the Parallax Ping))) which already has some threads here.