Inches per second to Mills
Inches per second to Mills
(OP)
I understand the simple inches per second measurement, but what exactly is a Mill? I am talking axial vibration of a shaft. What does a Mill stand for? Millimeters per second? Thanks for your help in advance folks...





RE: Inches per second to Mills
Or... 1000 mils = 1 inch.
RE: Inches per second to Mills
IPS is vibration usually expressed in the US as pk/0 value.
If displacement is sinusoidal x(t)=X0*sin(w*t)
then velocity will be
v(t)=d/dt (x(t))= w*X0*cos(w*t).
Hence the conversion between mils and ips is frequency-depdendent.
The conversion I use to convert between displacement magnitude in mils pk/pk (X) and velocity magnitude in ips pk/0 (V) assuming single frequency sinusoid at frequency F (cpm) is follows:
X = V * (18,000/F)
V = X * (F/18,000)
Those are round numbers... it's actually closer to 19,000 but 18,000 is a good round number when you are converting to speeds like 3600, 1800, 1200 etc.
You can verify the result for yourself using first principles v(t)=d/dt (x(t))= w*X0*cos(w*t) taking using suitable unit conversions and the fact that V is expressed as PK/0 while X is expressed as PK/PK (in the US).
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RE: Inches per second to Mills
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Eng-tips forums: The best place on the web for engineering discussions.
RE: Inches per second to Mills
"IPS is velocity usually expressed in the US as pk/0 value."
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Inches per second to Mills
If you are measuring mils peak to peak (pp), then it is vibration, and the measurement is thousandths of an inch from the maximum positive excursion to the maximum negative excursion in the signal. Mils pp can be obtained either with a proximity probe directly measuring the displacment of a shaft, or with a casing transducer where the signal has been integrated from acceleration to velocity, and then integrated again to displacement.
When you say you are measuring axially, I suspect that you are looking at thrust position. What kind of measurement device are you using for this?
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RE: Inches per second to Mills
http://www.reliabilitydirect.com/appnotes/cvr.html