Author Topic: suggestions for high-resolution tiltmeter (inclinometer) sensor?  (Read 51378 times)

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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #50 on: May 25, 2018, 07:09:48 pm »
I also see various sellers of "Glass Inclinometer Tubular Bubble Level Cylindrical Spirit Vial High Accuracy" around $25 on ebay.  Looks to be a glass tube 100mm long and 14 mm diameter.  Who knows but for the price, it might be worth a shot.
 

Offline branadic

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #51 on: May 25, 2018, 07:23:26 pm »
Be careful, sometimes they state "organic glass" which is nothing but a plastic ;)

-branadic-
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #52 on: May 25, 2018, 08:19:11 pm »
For those vials, what does this spec mean?

Accuracy: 4"/2mm

 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #53 on: May 25, 2018, 08:53:31 pm »
I also see various sellers of "Glass Inclinometer Tubular Bubble Level Cylindrical Spirit Vial High Accuracy" around $25 on ebay.  Looks to be a glass tube 100mm long and 14 mm diameter.  Who knows but for the price, it might be worth a shot.

 :-+  Thanks   I think this will solve my "problem" (a tilting building).  Over 25 years I have jacked up the building over 3 feet  (it was built on a compost pile  |O) ,  Once I dropped it 12 inches (a really loud noise).  Once it leaned 15 degrees  (it is 15 feet high).   I have not jacked it during the last 3 years because it "looks" OK.  It is very heavy, a 12 ton jack will not even budge it. It takes 2-20 ton jacks on one end to jack it up.   It is framed with  4x6s and sheathed with 1 1/2 in of 13 ply plywood and 1 inch of stucco.  It can be easily moved around on steel rollers.

FYI If you ever move a house do not put rollers under the whole thing.  The building may roll by itself, mine did.  After that I saw a 3,000 sq ft house move.  To move it the last 2 feet, they put rollers under one end, lifted the other with jacks and pushed it off the jacks.

This looks to be the same thing:

https://www.aliexpress.com/item/Size-14-96mm-Accuracy-4-2mm-Glass-High-Accuracy-inclinometer-Tubular-Bubble-Level-Cylindrical-spirit-level/32558917931.html

They include a spec chart.   I ordered 3 and now I have to figure out how to mount them.  I cannot find anything about "organic".  Since they sell plastic vials, I think it is safe to assume these are glass.   In my case I want to prove the building has stopped moving.  So after it is mounted, I will take one picture each month.

The dimension that would lean the most is 12 feet.   Can someone help me read this.   The accuracy is 4"/2mm   What does this mean?

First if the accuracy is correct - how would I see it?  One division?  (there are 9 divisions on each end)

How many inches of drop over 12 feet would one division be?   At 12 feet and one division, what would the degree be?  In the mean time I will look on YT to see how to read a vial.  :-DD

Thanks
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #54 on: May 25, 2018, 09:12:09 pm »
The accuracy is 4"/2mm   What does this mean?

I just asked that question and was thinking about it. I copied a picture of the vial and pasted it into my drawing program, scaled it to 100mm, and I measured 2mm between graduations.

I suspect the accuracy spec is that the bubble moves 2mm with 4 seconds of tilt. I will put that into other units... But each line is 4 seconds.

and... it's looking like 76 millionths over 4 inches...
« Last Edit: May 26, 2018, 09:59:40 am by metrologist »
 
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #55 on: May 25, 2018, 09:25:53 pm »
How many inches of drop over 12 feet would one division be?   At 12 feet and one division, what would the degree be?  In the mean time I will look on YT to see how to read a vial.  :-DD

Thanks

If one division is 4 seconds, that is just tan(0.0011) x 12 feet = 0.003 inches drop.
 
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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #56 on: May 25, 2018, 09:39:14 pm »
For something like leveling a house a water level is the way to go.  My Dad did that to a two story town house in Brooklyn Heights that was built in 1807.  Among Dad's papers we found the elevations Dad had taken with Mother's help on her birthday a month before I was born.

Dad would jack in the basement with 25 ton screw jacks on 3 corners and Mother ran from sight glass to sight glass checking and calling out the reading to Dad.

BTW Using a hydraulic jack to raise something like a house is a bad idea.  Screw jacks are much safer as they cannot suddenly drop the load the way a hydraulic jack can.

The bare vials for $25 sounds about right with levels going for $55 - $85 depending on length.  I have an ominous feeling that I'm about to start Yet Another  Project.  Please post when you get the vials.  Capacitance sensing should allow reading them to ridiculous resolution and accuracy.


Edit:  $11.28 with free shipping?  I'm doomed!
« Last Edit: May 25, 2018, 09:44:20 pm by rhb »
 
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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #57 on: May 25, 2018, 09:45:46 pm »
I'm interested in ...

JBeale since you are looking into glass vials and I assume you are doing something electronic.  Maybe I could fund your work if you make me one.  In my case I am not interested in wireless.  I would like to install a 100 foot wire and set up an alarm that would be a light.  If this might be possible PM me.  A CVS record of movement would be nice.  I am flexible.

thanks
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #58 on: May 25, 2018, 10:11:18 pm »
Edit:  $11.28 with free shipping?  I'm doomed!

Misery loves company, or I will be entertained  :-DD
 

Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #59 on: May 25, 2018, 11:12:42 pm »
$11.28 is impressively cheap, if the vial does resolve 4 seconds of arc per 2 mm division.  Indeed my application is long-term monitoring of a structure due to questions about the ground stability, and I wanted to find something with enough resolution to pick up very slow creep in a reasonable time, and cheap enough so I could use several sensors, because I would not trust just one device at one measurement location.  Adding some electrodes for capacitive readout should give plenty of resolution.  It will be at least a month before I even start on that project though, so I won't have any results to report for a while.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #60 on: May 25, 2018, 11:20:18 pm »
If one division is 4 seconds, that is just tan(0.0011) x 12 feet = 0.003 inches drop.

That is crazy.  Where did 0.0011 come from?  Yikes  maybe it is too sensitive!   Darn I already ordered them.

Here is something - at least now I know what the 2mm means (distance between lines)

https://www.leveldevelopments.com/sensitivity-explained/

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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #61 on: May 25, 2018, 11:40:57 pm »
If you look at the table in your link https://www.leveldevelopments.com/sensitivity-explained/ at the bottom you see that 0 deg 0 min 4 sec = 0.0011 degrees.  That is where tan(0.0011) came from, which is 1.92E-5 which means a rise/run slope of 19.2 um/m, which is also 0.0027 inches over 12 feet. 

With a sensor like that on a typical structure, I think you'll see a day/night change as soil humidity and temperature changes around the foundation; maybe also seasonal changes, very likely shifts due to soil moisture when it rains, etc.  Resting on the concrete slab of a garage, I'm sure it would record the change in tilt depending on whether a car is parked there or not.

EDIT: 4"/2mm is a standard format for reporting the sensitivity of level vials, and matches the most sensitive commonly available type, and those are generally about the size, shape and appearance of the ebay/alibaba photos for this unit. A few years ago I got one that looks similar to this from ebay but housed in a square aluminum shell, and I think it does have roughly that sensitivity (just leaning on my shimmed and solid workbench moves it offscale). Of course online as everywhere else, buyer beware.
« Last Edit: May 25, 2018, 11:59:41 pm by JBeale »
 
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Offline StillTrying

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #62 on: May 25, 2018, 11:42:55 pm »
Are you sure the 4" isn't just the length in inches = 100mm.
.  That took much longer than I thought it would.
 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #63 on: May 26, 2018, 01:01:16 am »
If one division is 4 seconds, that is just tan(0.0011) x 12 feet = 0.003 inches drop.

That is crazy.  Where did 0.0011 come from?  Yikes  maybe it is too sensitive!   Darn I already ordered them.

Here is something - at least now I know what the 2mm means (distance between lines)

https://www.leveldevelopments.com/sensitivity-explained/

Not to worry.  I'm sure someone here will be happy to buy them.  I tried to order one, but AliExpress did some things which made me uncomfortable when I tried to pay using PayPal. So I decided to punt for now.  As interested as I am, I have far too many projects already.

But I did laugh when I read your post, as i t was clear you didn't realize what 2 seconds of arc meant. Actually, in most houses you could use them as a burglar alarm.  The bad guy would have to be able to fly to get by one.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #64 on: May 26, 2018, 01:03:05 am »
Are you sure the 4" isn't just the length in inches = 100mm.

I am pretty sure 4"  is  4 seconds  and 100mm is the length

Refresher course:



Now I have to find a arc-tan refresher course.  Good mental exercise.  The least "accurate"  is 90"  and I have to work the math to figure the change in 12 feet.   Just doing a ratio calc I come up with 0.06 inches per division ?  (I have to find a scientific calculator)
Quote
very likely shifts due to soil moisture when it rains,

This is a really big deal.  Every winter I surround the area with at least 8 - 12x16' tarps.  If I can get these levels working, next winter I will not use tarps and check what soil moisture does.  I expect mounting on a wall will be hard.   I must be able to re-level the level so when it goes off scale I can get it back reading.  I need to look at change not the absolute angle.  I have a good digital level for that.  Going to start looking for thin shims.  whew
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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #65 on: May 26, 2018, 01:10:43 am »
During a drought in Dallas I noticed a 3/8" gap in the brick work of my garage.  I moved the soaker hose from the outer perimeter of the patio to the gap in the concrete slab next to the garage.  After a couple of days the gap closed.

4"/2mm levels will move when you walk up to read them.  For your application less sensitive vials would be better.
 
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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #66 on: May 26, 2018, 01:13:52 am »
But I did laugh when I read your post, as i t was clear you didn't realize what 2 seconds of arc meant.

True  :-DD

Actually, in most houses you could use them as a burglar alarm.  The bad guy would have to be able to fly to get by one.

This is still shocking to me that a liquid level could measure these small angles  :-DD

I ordered a couple of these:

https://www.aliexpress.com/store/product/High-Precision-spirit-level-90-2mm-10-41mm-water-level-tool-bevel-protractor-Accessories-for-measuring/1960842_32560066552.html

In case I cannot work with the other ones.
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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #67 on: May 26, 2018, 04:13:43 am »
I am sure this action-packed video will be the hit of Youtube:  https://youtu.be/9ocW3byVysI

It shows the level linked below, resting on the concrete slab floor of my garage, as I walk past it. It is sped up 4x to make the shift easier to see.
The red marks are 2 mm apart. Looks to me like my weight tilts the slab about 1 arc-second, at a rough estimate.
If instead I put the level in the house on the wood floor, my weight affects it much more.

https://www.aliexpress.com/item/Free-shipping-Mechanical-equipment-dedicated-bar-level-tooling-with-mounting-holes-level-level-142X21X20MM/32827782884.html
« Last Edit: May 26, 2018, 03:36:21 pm by JBeale »
 
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Offline ez24

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Offline ChunkyPastaSauce

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #69 on: May 26, 2018, 06:07:09 am »
I am sure this action-packed video will be the hit of Youtube

That's nuts, had no idea

For very large spans, just a tube and liquid
https://en.wikipedia.org/wiki/Water_level_(device)
« Last Edit: May 26, 2018, 07:04:41 am by ChunkyPastaSauce »
 

Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #70 on: May 26, 2018, 05:21:28 pm »
Here is another video to compare to the first. This time, the level is resting on the kitchen counter, which tilts as the floor underneath flexes (house is typical wood-frame construction; wood floor supported by wood joists).  First my 7-yo walks past (53 lbs). Then I walk past (170 lbs) so that is about a 3:1 weight ratio, and the total deflection of the level is also roughly in that ratio.  We walked very slowly, and the video is sped up 4x to make it less tedious, because the level takes several seconds to respond. In fact I probably didn't walk slowly enough for it to quite show the full deflection.

So as long as your burglars move slowly, it seems you actually could use an arcsecond tiltmeter as an home intruder alarm, at least in this kind of timber-frame house.  I read about a case recently where some guys low-crawled along a hallway to avoid tripping the active PIR motion-sensor alarm. Even with a ~3 second time constant, a high-resolution tilt sensor might have detected that situation.

https://youtu.be/_0OUdvOpVwQ
« Last Edit: May 26, 2018, 09:23:23 pm by JBeale »
 
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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #71 on: May 26, 2018, 06:24:42 pm »
Watching your videos (thanks by the way), I realize I probably will not be able to use the vials I ordered.  So I am looking at round levels on their store.  They can sense 1 degree and if I did my trig right,  that works out to be 0.2 inches in 12 feet.   (can someone check my math)

This is more reasonable.   

Here is their store:

https://haccury.aliexpress.com/store/1960842/search?spm=2114.12010615.0.0.62c072ddjIZxAA&SearchText=bubble&origin=n&SortType=price_desc

Here is their most expensive one:

https://www.aliexpress.com/store/product/HACCURY-Metal-Level-Bubble-Universal-Flange-Bubble-Level-for-Loader-Crane-Four-Colors-Size-100-75/1960842_32865653759.html


It has "5/1000"  on it, whatever that means

Here is a better place to learn about them:

https://www.leveldevelopments.com/products/circular-levels/surface-mounted-circular-levels/

So today I will learn about circular levels   :-+













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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #72 on: May 26, 2018, 09:38:34 pm »
I recalled that I had a 1.5" long bare vial ("new old stock" from ebay) with good sensitivity. Seemed almost a shame to break open the box noticing the date mark from 1944, anyway this does work. I used some copper foil tape and the 4-diode bridge circuit shown in the NASA Tech Brief (ARC-11344) linked earlier.  Input was 5 Vpp 300 kHz sine wave.  The recommended matched set of low-capacitance diodes I'm sure would be better, my random 1N34 discrete diodes have much more capacitance, and it varies with DC bias, so as my cheap function generator output amplitude changes, so does the output offset.  But I can still see the result is quite sensitive. As I roll my chair around even slightly on the wood floor of my office/workshop, the output shifts 0.1 mV or more.  With the whole thing sitting open on the workbench it is of course also very sensitive to my hand waving over it,  I can get 10 mV or more of shift just moving my hand near one electrode, so you certainly want this in a shielded box.
« Last Edit: May 26, 2018, 09:48:05 pm by JBeale »
 
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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #73 on: May 27, 2018, 05:14:49 pm »
Update: I put the tilt vial + diode bridge in a metal box, and set three ball-bearings on the bottom so it could sit on just three well-defined points, and not wobble uncertainly.
Having done that, I'm prepared to believe all the visible variations in the output voltage are real tilt measurements, and not some kind of noise. There is a slowly rising background curve, in this case just under 1 mV per hour, likely from humidity changes affecting the wood frame of the house. On top of that, a sharp step change whenever I walk into the room and sit at the desk with my weight flexing the floor, which returns to the previous curve when I leave the room.  There are also some much smaller wobbles, which might well correspond to activity elsewhere in the house.

It's interesting to make such a sensitive measurement with a simple all-passive circuit, no transistors or opamps (apart from the Keithley 196 DVM measuring the output, of course).

EDIT: Seems I could certainly clean up the layout, for example that long red wire going to the smaller copper electrode on the right will shift the output many 10s of mV, just with a small bend towards or away from the ground plane. Looks like we are measuring femto-farads of capacitance change here, so the wires to sense electrodes should be an absolute minimum length.
« Last Edit: May 27, 2018, 07:07:31 pm by JBeale »
 
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Offline ChunkyPastaSauce

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #74 on: May 27, 2018, 05:21:02 pm »
That's pretty awesome

Having done that, I'm prepared to believe all the visible variations in the output voltage are real tilt measurements, and not some kind of noise. There is a slowly rising background curve, likely from humidity changes affecting the wood frame of the house, and a sharp step change whenever I walk into the room and sit at the desk with my weight flexing the floor. 

You can largely confirm by rotating box 180 to point other direction, should decrease in similar way
 


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