What type of sensor needed to indicate plumb?

Don M

I know nothing about any of the angular sensors that Parallax sells. If I wanted to attach something to a pole to measure (indicate) whether a pole's vertical level position is leaning too far left or right and too far to and fro would I use this one - http://www.parallax.com/Store/Sensors/AccelerationTilt/tabid/172/CategoryID/47/List/0/SortField/0/Level/a/ProductID/93/Default.aspx ?

Thanks.

Don

W9GFO

An accelerometer would be good but I think it would need to be a very sensitive one if you need it to be very accurate.

Another way is to use mercury switches.

Rich H

kwinn

Don M wrote: »

I know nothing about any of the angular sensors that Parallax sells. If I wanted to attach something to a pole to measure (indicate) whether a pole's vertical level position is leaning too far left or right and too far to and fro would I use this one - http://www.parallax.com/Store/Sensors/AccelerationTilt/tabid/172/CategoryID/47/List/0/SortField/0/Level/a/ProductID/93/Default.aspx ?

Thanks.

Don

Two potentiometers with pendulums as shown in the attached diagram would work. If greater accuracy is required 4 pots wired as 2 Wheatstone bridges would provide greater accuracy.

erco

IMHO electronics won't save the day here. It comes down to mechanical repeatability. You need a long coupler to accurately reference the pole's position, and you might as well build plumb arrows along its length. Check the sketch attached. A 90-degree channel will fit a wide variety of pole diameters and self-locate very accurately. Make some free-pivoted pendulums (one per face) to hang down and indicate vertical.

Dave Hein

The datasheet for the Memsic 2125 claims to have "less than 1mg resolution". If this means better than 1/1000th g resolution then I think the it would have about 0.1 degree of accuracy. That seems pretty good. If a $30 part is within your budget give it a try and see if it works for you. Note that this sensor is essentially a bubble level that measures the position of a hot bubble. It seems like the sensor would need to be mounted horizontally, and could not be mounted vertically. I've never used it, so I don't know for sure. I think you would need a different sensor if you want to mount it vertically instead of horizontally.

Ron Czapala

If you could find out what type of device is used in a digital protractor, you'd have a posibble solution.

Dave Hein

You could use the Hitachi H48C Tri-Axis Accelerometer Module, which goes for $25. It should give you 0.2 degree accuracy, and you can mount it horizontally or vertically.

kwinn

I like erco's idea. Simple, accurate, and inexpensive. With a conductive pendulum and nails in place of the indicator marks it could even provide an electronic plumb indication.

Mark_T

With an accelerometer chip there will always be a need to calibrate the vertical position due to the small size of the sensor and the difficulty of mounting it precisely. So at some stage a plumb-bob will be needed to do this calibration, might as well just use the plumb-bob in the first place?

(Well actually that's a bit flippant, in windy conditions a plumb-bob is not the right solution!)

kwinn

Mark_T wrote: »

With an accelerometer chip there will always be a need to calibrate the vertical position due to the small size of the sensor and the difficulty of mounting it precisely. So at some stage a plumb-bob will be needed to do this calibration, might as well just use the plumb-bob in the first place?

(Well actually that's a bit flippant, in windy conditions a plumb-bob is not the right solution!)

Actually, if you mounted the plumb bob inside a length of pvc pipe it would not be affected by wind and could provide a reasonably accurate plumb indication.