Norm Dresner
Aug23-04, 04:05 AM
<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no, location=no,scrollbars=yes,resizable=yes,status=no ,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nSurfing the www one day I came across a design for a tilt-meter (technically\nan inclinometer, I guess) which used an almost full vial of liquid and a\npair of electrodes to create a capacitance between the electrodes that\nchanged as the vial was tilted. It can be seen here:\nhttp://www.designnotes.com/CIRCUITS/tiltmeter.htm\n\nIt\'s been decades (literally) since I studied any fluid mechanics -- and\neven then it was purely theoretical, elementary stuff in a senior Applied\nMath course so I started to imagine the physics involved in this sensor.\nCertainly for large changes in attitude (say even 10 degrees), the bubble\nmoves a considerable amount and the capacitance changes significantly. But\nfor very small displacements, say a few milliradians, it\'s my physical\nintuition that there are surface forces that will prevent the bubble from\nmoving at all and would make this design impractical, if not useless, as,\nsay, a seismic sensor.\n\n1. Is my intuition correct?\n\n2. How could one go about actually computing -- predicting -- the\nconfigurational change as a function of attitude [for simplicity, assume a\nsingle rotational degree of freedom, at least initially]?\n\n3. Is the math & physics involved in the theoretical analysis of this\ndevice beyond a casual approach by a mathematical physicist who\'s been doing\nelectronics and computer hardware and software for the last few decades?\n\n4. Are there any published results that are relevant to this problem?\n\nTIA\nNorm\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>Surfing the www one day I came across a design for a tilt-meter (technically
an inclinometer, I guess) which used an almost full vial of liquid and a
pair of electrodes to create a capacitance between the electrodes that
changed as the vial was tilted. It can be seen here:
http://www.designnotes.com/CIRCUITS/tiltmeter.htm
It's been decades (literally) since I studied any fluid mechanics -- and
even then it was purely theoretical, elementary stuff in a senior Applied
Math course so I started to imagine the physics involved in this sensor.
Certainly for large changes in attitude (say even 10 degrees), the bubble
moves a considerable amount and the capacitance changes significantly. But
for very small displacements, say a few milliradians, it's my physical
intuition that there are surface forces that will prevent the bubble from
moving at all and would make this design impractical, if not useless, as,
say, a seismic sensor.
1. Is my intuition correct?
2. How could one go about actually computing -- predicting -- the
configurational change as a function of attitude [for simplicity, assume a
single rotational degree of freedom, at least initially]?
3. Is the math & physics involved in the theoretical analysis of this
device beyond a casual approach by a mathematical physicist who's been doing
electronics and computer hardware and software for the last few decades?
4. Are there any published results that are relevant to this problem?
TIA
Norm
an inclinometer, I guess) which used an almost full vial of liquid and a
pair of electrodes to create a capacitance between the electrodes that
changed as the vial was tilted. It can be seen here:
http://www.designnotes.com/CIRCUITS/tiltmeter.htm
It's been decades (literally) since I studied any fluid mechanics -- and
even then it was purely theoretical, elementary stuff in a senior Applied
Math course so I started to imagine the physics involved in this sensor.
Certainly for large changes in attitude (say even 10 degrees), the bubble
moves a considerable amount and the capacitance changes significantly. But
for very small displacements, say a few milliradians, it's my physical
intuition that there are surface forces that will prevent the bubble from
moving at all and would make this design impractical, if not useless, as,
say, a seismic sensor.
1. Is my intuition correct?
2. How could one go about actually computing -- predicting -- the
configurational change as a function of attitude [for simplicity, assume a
single rotational degree of freedom, at least initially]?
3. Is the math & physics involved in the theoretical analysis of this
device beyond a casual approach by a mathematical physicist who's been doing
electronics and computer hardware and software for the last few decades?
4. Are there any published results that are relevant to this problem?
TIA
Norm