Author Topic: suggestions for high-resolution tiltmeter (inclinometer) sensor?  (Read 15096 times)

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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #275 on: May 20, 2019, 10:33:18 am »
I make high resolution inclinometers mainly for marine use https://www.jmsensors.fi

Resolution is 0.001 degrees (RMS at 10 Hz, much lower after averaging). Accuracy 0.005 degrees + 0.5%. Long term stability (years) better than the accuracy. Measuring range +-17 degrees. The basic model is 1 k€ (USB connection, Windows software and IP68 aluminium enclosure). I don't think you can find cheaper ones with similar specs.

I also make an OEM model, which can be temperature calibrated for very good offset stability (typical +-0.01 and max +-0.02 degrees -20C - 80C).

I use a MEMS sensor and calibrate each sensors at 1 degree intervals.

I'd have to rate this as blatant advertising. It shows no knowledge of the thread.   The discussion in this thread is at least two orders of magnitude (100x!) more sensitive than your product.

Please behave better.  A tutorial series on applications for your product are, I'm confident, most welcome.  But, you are in nerdland.  You do not want to discover what nerds will do to sales puppies.  It's really quite appalling.

So, either step up to the plate and blow us away with what you know about measuring small angles, or please, go away quietly and don't do this again.

Or to put it another way:

If you can quote chapter and verse, I'll listen.  If not, I think you should move one.

Nobody in particular,
Reg
 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #276 on: May 20, 2019, 10:52:26 am »
Who was the UK supplier of vials?    I need at least four 2"/2 mm vials.   @ez24 gave me a couple (I broke one :-(

I may get some more Chinese, but I want to compare with UK for my application.

But I *do* have my CA3039s! So once I recover from my gratuitous folly, I'll get a bridge going.

Many thanks to those who have been tracking down the theory via the patents.

When I calculate the theoretical possibilities and look at the cost I am blown away by what a very low BoM cost design can do.
 

Offline jmaja

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #277 on: May 20, 2019, 07:06:25 pm »
I make high resolution inclinometers mainly for marine use https://www.jmsensors.fi

Resolution is 0.001 degrees (RMS at 10 Hz, much lower after averaging). Accuracy 0.005 degrees + 0.5%. Long term stability (years) better than the accuracy. Measuring range +-17 degrees. The basic model is 1 k€ (USB connection, Windows software and IP68 aluminium enclosure). I don't think you can find cheaper ones with similar specs.

I also make an OEM model, which can be temperature calibrated for very good offset stability (typical +-0.01 and max +-0.02 degrees -20C - 80C).

I use a MEMS sensor and calibrate each sensors at 1 degree intervals.

I'd have to rate this as blatant advertising. It shows no knowledge of the thread.   The discussion in this thread is at least two orders of magnitude (100x!) more sensitive than your product.

Please behave better.  A tutorial series on applications for your product are, I'm confident, most welcome.  But, you are in nerdland.  You do not want to discover what nerds will do to sales puppies.  It's really quite appalling.

So, either step up to the plate and blow us away with what you know about measuring small angles, or please, go away quietly and don't do this again.

Or to put it another way:

If you can quote chapter and verse, I'll listen.  If not, I think you should move one.

Nobody in particular,
Reg

I'm sorry you feel that way. I just noticed this thread a few days ago. I read all of it before replying. The original question was about long term measurement and 0.001 or better resolution for which just a module was said to cost more than 1 k. I felt my inclinometer might be a solution for the original problem. Then the conversation went to very high resolution reading of a bubble in a vial. But was decent long term stability or temperature stability achieved? Not much point doing long term measurements without good stability. Of course very high resolution may have some other applications even without stability.

I can see my post regarded as marketing or even spam. I don't really do that. It must have been more than a year since the last time I linked my homepage to any forum.

I don't really know what is the resolution limit of my inclinometer with averaging, since it has not been used for applications needing sub 0.001 degrees resolution. It's dynamic response is quite fast, about 10 Hz. So it's quite different from the vial bubble one. As I said I get 0.001 RMS at 10 Hz and averaging reduces it with SQRT(n) as long as the stability effects come into play or noise can no longer be averaged out. I do know it's clearly better than 0.001 degrees, but I haven't really had any need to measure very long term. With one minute averaging you would get 600 samples and 0.001/SQRT(600)= 4e-5 degrees RMS in theory, but then you don't need much of a temperature change to cause more even with temperature calibrated ones.
 

Offline branadic

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #278 on: May 20, 2019, 08:09:43 pm »
MEMS based inclinometers suffer from drift due to a mixture of different materials with different t.c. forming the sensor element. Even burn-in can only reduce initial drift, but not fully eliminate it. Thus, MEMS-based inclinometers with capacitive principle are limited by physical constrains. Discussions with companies like murata confirmed that. In most cases their noise figure is defined by FFT, since their main use is vibration detection.
The only way to come across with this limitation, which is not given by the silicon itself, is to use a different methode of measuring the displacment of the seismic mass instead of capacitive measurement. The capacitive measurement also adds an additional portion of displacement due to electrostatic forces. Thus, longterm stability of current MEMS inclinometers is not that great, limiting the use of them for arcsec accuracy and resolution. But I can tell you, there is work in progress to overcome this limitation.

Vial based or fluid based inclinometers are a very simple approach with very good longterm stability. In most cases the readout circuitry or the mounting of the sensing element inside a package are the limiting factors on longterm stability, not the sensing element itself. The fluid defines the dynamic of the sensor. With such elements resolution in the arcsec and sub-arcsec range can be achieved, while having very big measurement range of several angular degree.

-branadic-
Fluke 8050A | Prema 5000 | Prema 5017 SC | Advantest R6581D | GenRad 1434-G | Datron 4000A | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, Keithley 2182A, HDO6054, Keysight 53230A and other goodies at work
 

Offline jmaja

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #279 on: May 20, 2019, 10:42:13 pm »
I have used this MEMS chip since 2007 and had a lot of discussion with chip designers way before the company was bought by Murata. They still have the factory in Finland and all the designers I have been contact with are Finnish.

All the data I have given is based on my own measurements. I haven't really measured very long time stability, but my sensors have been used years in applications were 0.01 degrees long term drift would be noticed and I haven't heard any problems with that. Humidity and temperature will have an effect on long term stability rate. I still haven't found one needing recalibration to achive the specs I gave earlier. What kind of stability has been achieved with vial reading discussed in this thread?

Unfortunately they are discontinuing the chip I'm using due to subcontractor ASIC process change. They are developing a new one with about the same specs. I'm just ordering the current one hopefully lasting long enough for the new chip to be available. The discontinued chip seems to be totally unique. I haven't seen any other with comparable specs.
 

Offline smithnerd

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #280 on: May 20, 2019, 10:46:36 pm »
Who was the UK supplier of vials?    I need at least four 2"/2 mm vials.   @ez24 gave me a couple (I broke one :-(

Level Developments:

https://www.leveldevelopments.com/products/vials/

For the UK manufactured vials.

The chap on ebay.co.uk trading as 'caterpiller_red' is (I believe) selling imported Indian manufactured vials. The photos show them marked 'PIE', which seems to stand for 'Paragon Instrumentation Engineers'.

 

Online RoGeorge

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #281 on: May 20, 2019, 11:27:09 pm »
My question is, why do a bubble vial is even needed, in the first place?

A bubble vial makes sense for a passive device, read by reading the marks with naked eye, but when reading the tilt electronically, why?

A simple bowl (or some other type of container) with some electrodes around it will do it just fine, maybe even better then the vial, with it's hysteresis in bubble's move because of the not so well polished interior of the glass.  The fluid itself can be the ground electrode, and two piece of Al adhesive tape on top would make the two measuring capacitor electrodes.

 :D

Later edit:
To go a little further, maybe having some liquid is also not a good idea, because of its inertia.  But capacitors are the simplest possible component to manufacture in a DIY regime.  Literally everything is a capacitor.  Easy to make 2 capacitors and connect them to that measuring bridge.

Maybe a simple ball bearing, suspended with a metallic wire inside a jar will be enough as a tiltmeter or even as a seismometer.  The jar is fixed to the earth, the ballbearing ball's inertia will act as a reference.  Two Al foil stick on the jar will make the capacitors.  Eventually 4 foils to make X-Y axes measurements and find the direction were the shake/wave is coming from.  A 3rd sensor for the Z axis would be harder to imagine, but not impossible.  Maybe a ball bearing suspended with a metallic resort.  I bet the exact waveform in 3D can be deduced by knowing the elasticity constants of the spring and the weight of the inertial ball.
« Last Edit: May 20, 2019, 11:44:48 pm by RoGeorge »
 

Offline jmaja

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #282 on: May 21, 2019, 12:25:58 am »
A bubble vial makes sense for a passive device, read by reading the marks with naked eye, but when reading the tilt electronically, why?

I guess it is because it is possible to manufacture a bubble vial, which amplifies the extremely small movement of the vial into much bigger movement of the bubble and the fluid. 0.001 degrees is less than 2 um on a 10 cm vial length. How would you detect that small movements? Any bearing will cause problems. One problem of a vial is very limited scale. But it's quite a task to get a wide scale together with very high resolution.
 

Offline tomato

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #283 on: May 21, 2019, 01:48:36 am »
I'd have to rate this as blatant advertising. It shows no knowledge of the thread.   The discussion in this thread is at least two orders of magnitude (100x!) more sensitive than your product.

Please behave better.  A tutorial series on applications for your product are, I'm confident, most welcome.  But, you are in nerdland.  You do not want to discover what nerds will do to sales puppies.  It's really quite appalling.

So, either step up to the plate and blow us away with what you know about measuring small angles, or please, go away quietly and don't do this again.

Or to put it another way:

If you can quote chapter and verse, I'll listen.  If not, I think you should move one.

Nobody in particular,
Reg

Maybe the moderator(s) will let you preview all posts in the future to ensure they are of sufficient interest to you and meet your standards.
 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #284 on: May 21, 2019, 04:17:58 am »
The bubble vial has the virtue that high sensitivity is easily attained.  It's pretty hard to beat for simplicity and cost.

A pendulum and LVDT as used in a Talyvan is a lot more complex.

The NASA Tech Brief noted that the application did not require the sensitivity of a commercial inclinometer.  Given that the NASA design was reading 0.05 seconds and a change of vial would result in 0.01 arc seconds should give some idea of how sensitive the commercial tiltmeters are.
 

Offline IDEngineer

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #285 on: May 21, 2019, 04:49:57 am »
A bubble vial makes sense for a passive device, read by reading the marks with naked eye, but when reading the tilt electronically, why?

I guess it is because it is possible to manufacture a bubble vial, which amplifies the extremely small movement of the vial into much bigger movement of the bubble and the fluid. 0.001 degrees is less than 2 um on a 10 cm vial length. How would you detect that small movements? Any bearing will cause problems. One problem of a vial is very limited scale. But it's quite a task to get a wide scale together with very high resolution.
And capacitance is straightforward with fluids. Water has an incredibly high dielectric constant, way more than traditional "high DE" materials like tantalum.  I haven't looked into the DE of oils such as are commonly used in vials like these but the point is that basing an inclinometer on the movement of a bubble in fluid has several advantages that are hard to replicate in other ways. It's hard to imagine a mechanism simpler than a bubble in a sealed glass vessel.
My political litmus test: I will vote for any candidate, regardless of party affiliation or positions on other issues, who promises to abolish the TSA.
 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #286 on: May 21, 2019, 12:36:56 pm »
The "spirit" in a spirit vial is *not* alcohol.  It feels like acetone, but smells different. 

I'd like to know what it is. 

In the meantime I suggest that if you break one, or think you might have, you place it outdoors until the contents evaporate.
 

Offline branadic

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #287 on: May 23, 2019, 09:29:23 pm »
Quote
My question is, why do a bubble vial is even needed, in the first place?
A bubble vial makes sense for a passive device, read by reading the marks with naked eye, but when reading the tilt electronically, why?

I can tell that 1µm/m stability over 24h is achivable with a capacitive, temperature compensated readout approach of a spirit vial. It's even harder to separate stability of the sensor from movements of the ground, even with high resolution inclinometers such as Leica Nivel or Wyler Zerotronic as reference.

Quote
I'd like to know what it is.

Well, some companies claim it's alcohol or hydrocarbonate.

-branadic-
Fluke 8050A | Prema 5000 | Prema 5017 SC | Advantest R6581D | GenRad 1434-G | Datron 4000A | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, Keithley 2182A, HDO6054, Keysight 53230A and other goodies at work
 


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