vne147
Member
Hello, it's nice to meet everyone. I spend a fair amount of time in General Electronics Chat and Electronics Project Design/Ideas/Reviews but have never posted in here before. This forum seemed most fitting for my question though. I've searched a little for an answer but haven't really found a good one. Hopefully, someone here can help me out.
What I'm trying to do:
I’m working on a project where I need to measure distance with an accuracy of ± 1mm (~ .04") at the most. Better accuracy is obviously preferred if possible. The distances I will be measuring will be in the range 150mm - 750mm (~ 6" - 30").
Solutions considered:
I have worked with several of the Sharp IR distance sensors before but I recently learned that they have a built in 8bit DAC that provides the analog output. Unfortunately, 8 bit resolution would not provide the accuracy I require. I have also thought about laser range finders but I'm on a budget. That pretty much brings me to ultrasonic sensors.
I haven't used one before and after doing some searching on the web, I didn't have much luck finding accuracy specs on many of the pre-made ultrasonic sensors. I think the sensor that might work best is the PING from Parallax. The data sheet says that it outputs a pulse of a duration dependent on the distance that was measured. I could easily feed that into a PIC and measure the duration of the pulse. If I clock the PIC at 20 MHz and I can measure the pulse with and accuracy of ± 2 - 3 µs, that would give me the accuracy I need.
My questions:
I hope my ideas and questions are clear. Thanks in advance for the help and I'm looking forward to your responses.
What I'm trying to do:
I’m working on a project where I need to measure distance with an accuracy of ± 1mm (~ .04") at the most. Better accuracy is obviously preferred if possible. The distances I will be measuring will be in the range 150mm - 750mm (~ 6" - 30").
Solutions considered:
I have worked with several of the Sharp IR distance sensors before but I recently learned that they have a built in 8bit DAC that provides the analog output. Unfortunately, 8 bit resolution would not provide the accuracy I require. I have also thought about laser range finders but I'm on a budget. That pretty much brings me to ultrasonic sensors.
I haven't used one before and after doing some searching on the web, I didn't have much luck finding accuracy specs on many of the pre-made ultrasonic sensors. I think the sensor that might work best is the PING from Parallax. The data sheet says that it outputs a pulse of a duration dependent on the distance that was measured. I could easily feed that into a PIC and measure the duration of the pulse. If I clock the PIC at 20 MHz and I can measure the pulse with and accuracy of ± 2 - 3 µs, that would give me the accuracy I need.
My questions:
- Does anyone have experience using a distance sensor to obtain this level of accuracy?
- Is there anything inherent in the design of the PING sensor that would limit the accuracy I could obtain?
- Does my idea seem feasible?
- If you were doing the project, how would you do it?
I hope my ideas and questions are clear. Thanks in advance for the help and I'm looking forward to your responses.