I am looking for a non-mechanical means to measure the descension of a plate within a container about 3cm by 15cm by 7cm. The plate is not terribly well guided so there is a need for a lot of room for error, our resolution does not need to be high at all. We are measuring descension and ascension of about 3/4cm over the span of 15cm. Any thoughts on a sensor that could be good for my needs? it also needs to be rated to -20F and about 120F and be able to withstand fast acceleration and deceleration and shock. If you can help I will be very appreciative!

  • \$\begingroup\$ What's your budget? Many of the solutions that meet your environmental requirements aren't cheap. \$\endgroup\$ – HikeOnPast Nov 30 '12 at 20:56
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    \$\begingroup\$ Isn't that temp range just industrial spec? As well, what kind of G-Force are you looking at in the accel/decel and shock range, what I think is very fast, and you think are very fast is subjective. A numerical range would be better. As for noise, it's probably more appropriate to either find a sensor with a built in kalman filter or combine it with a microprocessor and implementing a filter/state estimator. \$\endgroup\$ – Jeff Langemeier Nov 30 '12 at 21:21
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    \$\begingroup\$ You need to provide a lot more detail about the application. What is the container made of? What is the plate made of? What is the container filled with? What makes the plate move up and down? \$\endgroup\$ – Dave Tweed Nov 30 '12 at 22:07
  • \$\begingroup\$ @okay sorry for the lack of detail, I am under a non-disclosure agreement so i'm trying to reveal as little as possible to get some suggestions. It is a stamped steel container, the plate is also steel. The plate will be forced down by cylinders about 1 1/2cm each being inserted via a pneumatic motorized system into the container. A spring under the plate will be the force for ejecting the cylinders into the next system. I'm sorry this has to be so vague, I hope some suggestions could still be made! \$\endgroup\$ – EncoderGuy Nov 30 '12 at 22:21
  • \$\begingroup\$ @JeffLangemeier the G forces are somewhat hard to guess because I do not have a prototype produced yet unfortunately. I'm just looking for a type of sensor or ideas of things to look into. \$\endgroup\$ – EncoderGuy Nov 30 '12 at 22:24

many rang finding options exist .. take your pick

  1. Ultrasonic (cheap, easy works over temperature accuracy is an issue)
  2. Laser range finder (expensive, accurate, works over temperature)
  3. inductive/capactive (depends on details of your application is this will be suitable)
  4. 77 GHz radar - for example has great resolution and is being used in automotive collision avoidance and cruise control as well as depth sensing of grain silos)
  5. Pressure sensor ?? - not sure if there will be a pressure change due to your environment
  6. many other possibilities: it really depends on your specific application requirement
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