Motion or Vision: Where should I start?

[Seth Bergman]

I would like to watch an altimeter dial using a camera (monochrome is fine). I would like to track the needle point as it swings and count the number of times it passes "0" cw and ccw around the dial. It will make one complete revolution in a minimum of 4 seconds. This altimeter will have have 10 numbers (0 through 9). Above each of numbers is a bold white line indicating 100 feet. In between the bold lines are 4 thiner and smaller white lines indicating 20 feet.

My Question is: What is the best hardware and software I should use to watch the needle point rotate, determine approx. how far it is from the small and bold white lines, and the approximate climb rate?



Spare no detail... Your help is much appreciated!

[Brian_Beal]

You could probably do this with IMAQ functions in Labview, but you may want to consider getting an encoding altimeter instead. You can get one with the display, or without the display, which is called a blind encoding altimeter. These have some sort of signal output that can be read, and some of them have an RS-232 output. I'm not sure of the cost, but you may be able to get one used. You can get one from a aircraft "junkyard", and not worry about the FAA regs if you are not going to use this as an altimeter in an aircraft.

If you chose to go the vision route, you may be better off looking at the digital display. You could use pattern matching to determine what digit is in what position. From there you could do the math to determine altitude and rates. For h
ardware, you would need the camera, frame grabber, lense, cable, and probably lighting. There are other options, for hardware, but they can get expensive, or not be as flexible.

[Seth Bergman]

Thanks Brian,

You're right about the encoder type and digital display type as well but the only altimeters I have access to look like the image posted.

I definitely have to do it the hard way... But I think it will work. I will check out the IMAQ functions in LabView too. What does NI classify as Vision and what as Motion. Aren't they both the same thing? Or is Motion, vision in motion? Hmmm... The reason why I ask is because NI has software designed for picking out the different shapes (i.e. lines) and contrast. I could do the pattern matching as well I think. I could have say 200 images. One corrosponding to each 5 feet on dial. The software (I don't know which one yet) could be able to match the closest one and return that result, right?

Thank
s again for your help.

[Brian_Beal]

Seth-

The digital display I was refering to was the one on your alitimeter. You will need the add-on IMAQ Vision functions to do much of anything, and Vision Assistant is really a must for development, so you will need to buy the Labview Vision Development Module.

Vision is strictly just that. Anything that has to do with images will fall into that category. Motion has to do with controlling movement of machines, for example. You will not need to do anything with motion.

For your altimeter, I would find the digital display, and mask off everything else. You will then have ten stored patterns for the digits 0-9. Then when the patterns are found in certain positions you could multiply the found digit by the position mulitplier, then add
them all up to get a final number. The biggest problem that you will encounter is when the digits are between numbers. You will have to store the last found digit(probably in a shift register) that was in that position and use it somehow in your math.

I don't know how much money and time you have to spend, but between software and hardware you are talking about probably $4500.00 plus a lot of programming.

Brian