Measure Distance Using a Transmitter and a Receiving Unit

[AndyTM]

Does anyone know of a devise that uses a sending unit/transmitter and a separate receiving unit to measure distance? I know there are several inferred, ultrasonic and laser devises out there, but I need to find something that will monitor the variable distance between two specific points (two steel beams). The problem is that these steel beams can become coated with dirt, mud and/or ice. I do not want those elements to alter the measurement reading. The distance I need to monitor is between 5” and 20”, and I want to be able to identify changes as small as 0.05” (if possible). Also, cost is a factor.

 

[IRstuff]

What are the available references or markers? Is it always the same two beams? How much money?

TTFN

 

[AndyTM]

Yes, it is always the same two beams. Ya see, the two beams are apart of a larger structure. Basically, beam # 1 is attached to the ground (or base structure) and beam # 2 (located above beam #1) is attached to a piece of industrial machinery. The two beams are connected through a series of supports similar to leaf springs. These springs help support and stabilize the machinery through its operational cycles. I want to measure the variable distance between the two beams during various periods of the machines operation, and I want to be able to repeat the measurement process a few times a day over several months or more. Ideally, I would like the measurement device to be under a few hundred dollars or less.

 

[Skogsgurra]

Mud, dirt, ice. 0.05" resolution. A few hundred dollars.
Not much in that corner.

Take mud and ice away, then a simple potentiometer with a string can be used.

Take 0.05" away, then (perhaps) a sturdy chain or a toothed rod and sprocket can be used.

Acceleration? High speeds? Then forget what I said.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[IRstuff]

Laser distance measurement system --> ~$500 to ~$2500

http://testproducts.com/safecart/pr...d/508?osCsid=f5d46df5a268b1185f99d18f7a349f65

Ultrasonic:

http://mysick.com/partnerPortal/ProductCatalog/datasheet.aspx?ProductID=7400

TTFN

 

[Comcokid]

Also might try a magnetostrictive sensor as made by MTS and others. But again, these are more expensive than your price range.

 

[logbook]

I don't think it is possible (or if it is then it's hard) to have a separate transmitter and receiver as you have asked for. Measuring transit time differences requires a time reference. Unless both units are sync'ed to an external clock the time difference information would not be available.

You are not asking for much resolution, 0.05 in 15= 1 in 300. I would think the string and optical shaft encoder would be a good bet. You can’t afford the laser thing and in any case the mud/dirt would stop the reflections. They would also attenuate any acoustic or EM waves as well. You would just have to put the string in a plastic case to stop it getting gunged up.

 

[bmnet]

why not try using a sonar? But then you'll need a detector, not sure how much those cost but should be cheap...

Bmnet

 

[VisiGoth]

Broadband radar methods could be used. Snow ice and precision could be met. Absolute accuracy by calibrating at initial setup with some external measurement method. After that two very high cost units could keep track of changes in distance. This would be an awful lot of money, so there has to be a more cost effective method. If you could add some telemetry bandwidth you could do the calculations on a PC much cheaper, so your costs could get down to a few k Euro for material.
Good luck!


jsolar

 

[biff44]

Do you have a single use, or volume application? These types of products are being developed for low cost applications.

 

[Higgler]

What about a simple capacitance meter measurement. If you can take a distance and capacitance reading between the two beams at low frequency, then move the beams and see the change in the meter. Granted the water and ice would change things a bit, but using a very low frequency like kHz may negate that.
If you had a meter that produced an output based on measurements, you could analyze it with a microprocessore to look for min and max readings and interpret them.

If the beams themselves are too difficult to add a meter to, then you could add simple mechanical extensions to the beams and get two parallel plates near each other in which to measure the capacitance. The Fluke muliti meters can output a graph to your computer and you can analyze the data

http://assets.fluke.com/AppNotes/Multimeters/gmm-app3.pdf.

The meters are typically around $300. Not a full solution, but a low cost approach. Tolerance issues, and calibration etc.

Did you need to measure distance constantly, or only if a certain distance is exceeded? May make or break this multimeter approach.

kchiggins

http://www.toyon.com