Other than the tongue-in-cheek request to remind me of the Allegro sensors when I need them, I was sincere. The tubular shape and lead orientation of normal prox sensors often makes them difficult to fit into a design, prox's in flat packages are an expensive compromise, and I wasn't aware of self-contained zero-speed Hall sensors.
Karl emailed me that you were helping him choose an appropriate device.
Ned
I think he's going to go with opto. I agree with you that opto is the best choice where indexing repeatability is an issue. There's no such thing as a "sharp edge" with magnetic flux, while .010" of shutter motion can completely interrupt a beam of light. That's about 0.4 deg of rotation with a 3" dia disc.
Don Foreman wrote in news: snipped-for-privacy@4ax.com:
Thier fiber optic sensors are truely world class, and they have a lot of new stuff, especially laser sensors. The only thing they haven't done very well at yet is vision. It was a miserable failure in our application, even after they had supposedly proved it worked for our application. Cognex and DVT have the big upper hand in that segment.
Doing some research for a customer recently I was surprised to find that Cognex purchased DVT.
My experience with DVT several years ago was mixed. Very impressive products, dismal support. Their support model seemed to be to put the clueless new hires in tech support to insulate anyone knowledgeable from customers. Which wouldn't be so bad if when after a couple tries the new guy can't answer a question, he can connect you to someone who can. In my case, I had a question about the function of a single option for one of the inspection tools. It took almost 3 weeks to to find out that the checkbox in question had *no* function, it was there to "maintain a consistent look to the interface."
Ned Simmons
Ned Simmons wrote in news: snipped-for-privacy@news.suscom-maine.net:
Yes, they did that to get the line scan technology. DVT is _the_ deal when you need line scan ability, Cognex never could compete on that. But, from my experience, if you do not need line scan ability, Cognex is the leader hands down. The new 5000 series cameras are really, really good, as is the software. We use cameras for several different applications, part orientation, part marking inspection, actual part visual defect detection, and part location in conjunction with robotic loading, (i.e. the camera tells the robot where the part is located, so the robot can pick it up).
I've never heard DVT's technology described as line scan, which I understand to mean capturing an image as a series of one dimensional pixel arrays. My dim recollection is that DVT's innovation was to integrate the image sensor and memory onto a single semiconductor die. The captured image is transferred to memory via a very fast bus and processed there. Or something like that. I used DVT's stuff for the high speed capability this technology allowed.
We were inspecting the wooden pieces of spring-type clothespins travelling at
15-20 feet/second. I still find the occasional clothespin half wedged in some odd place in my shop 7 years later.Ned Simmons
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