programming with MaxBotics ultrasonic sensor

Technical NI LabVIEW
1

I am trying to get some help for one of our programmers to get the MaxBotix ultrasonic sensor working. Unfortunately, I normally work on the hardware and I am not familiar with LabView and there is no one else available who is. A search of CD has not turned up any threads where someone had similar symptoms.

What we are seeing is that the value returned is very different from the actual distance. As the distance is increased, the distance measured goes up and down (i.e. 39 inches at 3ft, 32 inches at 4ft). He has been using the software with the following settings: Bit Average of 3 and 10, Sample Rate of 100 samples/second, Scaling of 0.0098 V/in. He was aiming the sensor at a large piece of cardboard (2.5 ft x 5 ft). He did notice that how he held the sensor in his hand had some influence on the distance measured.

I noticed on the AndyMark website that the sensor has a “reading rate” of 10Hz. Am I correct in thinking that we should sample the output of the ultrasonic sensor at something closer to it’s reading rate, say 5 to 20 samples/second?

Is there a recommended value for the bit averaging? Am I correct in thinking that this value determines the number of sample values that are used to compute a running average?

Are there any recommendations for how to mount the sensor other than what is discussed on the MaxBotix website?

2

I don’t have one of the sensors to experiment with, but the data sheet implies your read rate is high and you may be averaging good and bogus values. I searched and people don’t seem to give detailed instructions. That implies it should be pretty easy and something like the sample rate may be the primary issue.

Greg McKaskle

3

Thanks for your input. We only only had enough time to try 100 samples/sec. It was originally up at 1000 samples/second. I will get him to try different sample rates next time.