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.RC.
12-17-2012, 04:59 AM
Came across what appears to be cheap level sensors... specs as follows.. With the discrimination being 0.01 arc seconds would that mean with a suitable driver and reader they could be used as something similar to a talyvel? And thus used as a very sensitive talyvel type machine?





AS A TILT TRANSDUCER

Linear Range (typical)

Linearity Error (max)

Asymmetry Error (max)

Unambiguous Range

Discrimination

Datum Change
for 5 Tilt about Cross Axis (max)

Temperature coefficient
with Matched Detector
-10C to 25C
+25C to + 60C

Datum Temperature Drift (max)

AS AN ACCELEROMETER

Linear Range

Unambiguous Range

Equivalent Pendulum length

Undamped Natural Frequency

Damping Factor at 25C

PHYSICAL PROPERTIES

Datum Stability Long Term

Datum Stability Short Term

Settling Time to <1%


Value



0.5

1.0

2.0

2.0

0.01


1




0.2
-0.1

0.3



0.01

0.1

305

1

0.6



10

1

5
Units



Degrees

%

%

Degrees

arc-seconds


arc-mins




%/C (max)
%/C (max)

arc sec/C



g Units

g Units

mm

Hz





arc-sec/month

arc sec/hour

seconds

oldtiffie
12-17-2012, 05:36 AM
Good question.

Here is the web page:

http://www.taylor-hobson.com/electronic-levels-and-clinometers.html

The report/specs from the web site for the better electronic version is:


Digital Clinometer

Digital Inclinometer Is a robustly constructed instrument designed for clear simple reading, the system is ideal where precision angle is required over a large range.

All four quadrants of the system are precision machined making it possible to measure angle from any side.

The system has the ability to work from absolute or relative modes through a simple push button operation.


The battery power, sturdy design and compact construction make it ideal for almost any situation, features include;
•Built in calibration program ensuring measurement integrity
•Direct reading to 4 arc secs
•Accuracy to 2 minutes of arc
•Large measurement range +/- 45 degrees


1 minute of arc = 1/3600 degrees

2 minutes of arc = 2/3600 = 0.000055555 degrees the sine of which is: 0.0000097 the inverse of which is 103,132 which is 1mm per 103,132mm or 0.001mm per 1,031 meters which is very good.

As surface plate calibration (even USA-made ones) are metric where the units are in metres and um (aka microns = 1 millionth of a meter = 0.00004" (ie 0.4 "tenths" of and inch)).

That on the face of it is very good indeed.

I wonder what the cost is?

I'd like someone to check my maths though - just in case I've got it wrong.

ikdor
12-17-2012, 06:38 AM
I think one minute of arc is 1/60th of a degree. And you added an extra zero in the 0.000555 figure.

Igor

Barrington
12-17-2012, 07:10 AM
Came across what appears to be cheap level sensors...

Found here: http://www.tilt-measurement.com/dsheets/htmlfiles/elh100.html

How it works: http://www.tilt-measurement.com/appnotes/htmlfiles/anim1.html

Other products: http://www.tilt-measurement.com/sfc.html

The sensor looks deceptively(?) simple, but the spec (discrimination of 0.01 arc seconds) doesn't sound cheap to me !!

Cheers

.

Jaakko Fagerlund
12-17-2012, 10:20 AM
Sure it may have that resolution, but notice that it is not so linear on all the scale length. But same can be said for a dial test indicator: very good at showing runout, but doesn't actually measure how much exactly.

oldtiffie
12-17-2012, 06:38 PM
I think one minute of arc is 1/60th of a degree. And you added an extra zero in the 0.000555 figure.

Igor

Thanks Igor - it was a silly mistake.

oldtiffie
12-17-2012, 06:43 PM
The Talyvel resolution of 2 arc seconds is fine and as Barrington says is probably quite (very?) expensive too.

Compare it with the Starret 199Z Master Precision level (with 10 second accuracy) the features of which are:


Specially designed to set up, check and test machinery of all types
At-a-glance reading of the exact variation of machinery levelness
Auxiliary level vial shows lateral position and assists in horizontal setting
Level vials are positioned so breakage is reduced to a minimum
Fool-proof adjustment
Seasoned, machined castings
Finished wood case
Groove has a special involute design, permitting better centering and greater capacity to handle larger rounds
Groove and bearing flats are machined together for maximum accuracy
Ground and graduated main vial of 10-second accuracy; one division equals 1/2 thousandth (0.0005) of an inch per foot, or 0.04mm per meter
Main vials have seven graduations on each side of the bubble
Special alloy iron used to obtain freedom from thermal effects
All level bases are made from the finest quality seasoned cast iron and are precision-machined on the reference surface
Scraped reference surface

http://www.starrett.com/metrology/product-detail/Precision-Measuring-Tools/Precision-Hand-Tools/Machinsts-Levels/Levels/199Z

.RC.
12-17-2012, 10:51 PM
I guess you could say this thread has been tiffified..

LKeithR
12-18-2012, 12:03 AM
OK, I'll bite. Here's my allotted silly question for the day. What the H*ll is a a Talyvel?:confused:

oldtiffie
12-18-2012, 02:10 AM
http://www.taylor-hobson.com/electronic-levels-and-clinometers.html

A pretty accurate and probably quite expensive up-market levelling machine and a vertical angle (inclinometer) measuring device.

LKeithR
12-18-2012, 05:53 AM
http://www.taylor-hobson.com/electronic-levels-and-clinometers.html

A pretty accurate and probably quite expensive up-market levelling machine and a vertical angle (inclinometer) measuring device.

Thanks. I are now officially enlightened...:o

Mark Rand
12-19-2012, 08:07 PM
The sensor looks quite simple. It's be nice to know if the price matched the simplicity.

I was toying with the idea of making a Talyvel clone using a pendulum and differential capactors coupled to a Blumlein bridge and a lock-in amplifier (rather than the inductive proximity probe that T&H used). In fact a Bentley Nevada proximity probe and a 2" pendulum will give 2mV/Second of arc for a reasonable price.

This all became superfluous when I eventually picked up a Taylor & Hobson 0.2sec autocollimator. Still got to make the mirror mounts to use with that though...

oldtiffie
12-20-2012, 01:11 AM
That's quite a machine:

http://en.wikipedia.org/wiki/Autocollimator

http://www.google.com.au/search?q=g&rls=com.microsoft:en-au:IE-Address&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7IRFC_enAU360&redir_esc=&ei=0p3SUOj6M6ihigfzxIHIBw#hl=en&sugexp=les%3B&gs_rn=1&gs_ri=serp&pq=g&cp=37&gs_id=7&xhr=t&q=Taylor+%26+Hobson+0.2sec+autocollimator&pf=p&tbo=d&rls=com.microsoft:en-au%3AIE-Address&rlz=1I7IRFC_enAU360&sclient=psy-ab&oq=Taylor+%26+Hobson+0.2sec+autocollimator&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.1355534169,d.aGc&fp=def9f3f538eb70d&bpcl=40096503&biw=1920&bih=846